PETROLEUM fuel burners for the generation of RADIANT ENERGY FOR FROST CONTROL By F ra n c is J e ffe rs o n H a ssle r A THESIS S u b m itte d t o t h e S c h o o l o f G ra d u a te S t u d i e s o f M ic h ig an S t a t e C o l le g e o f A g r i c u l t u r e an d A p p lie d S c ie n c e i n p a r t i a l f u l f i l l m e n t o f t h e r e q u ir e m e n ts f o r th e degree of DOCTOR OF PHILOSOPHY D e p a rtm e n t o f A g r i c u l t u r a l E n g in e e rin g 1950 ii TABLE OF CONTENTS Page INTR QDUGTI Q 'J-------------------------------- ---------- - ................................- 1 Review o f t h e Weed and Ile th o d s f o r F r o s t C o n t r o l - 2 W ature o f t h e p r o b l e m ------------------------------------- 2 R a d i a t i o n - t y p e f r o s t --------------------------------------- 2 ile th o d s u s e d f o r t h e p r o t e c t i o n o f v e g e t a t i o n from f r o s t damage ------------------------- 5 P r e l i m i n a r y t e s t s a t M ic h ig a n S t a t e C o l le g e - 7 Theory o f t h e E m is s io n , T r a n s m is s io n , and A b s o r p tio n o f I n f r a r e d o r Therm al R a d i a t i o n -------- 11 Q u a n t i t a t i v e lav/s f o r b la c k b o d y r a d i a t i o n — 14 T r a n s m is s io n o f i n f r a r e d r a d i a t i o n --------------- 20 A b s o r p t i o n o f r a d i a t i o n by v e g e t a t i o n ---------- 22 P r e v io u s Work and P r e s e n t S t a t u s o f t h e U t i l i z a t i o n o f I n f r a r e d R a d ia n t E nergy f o r t h e P r o t e c t i o n o f V e g e t a t i o n from F r o s t Damage ---------- 24 O r i g i n a l i n v e s t i g a t i o n s ---------------------------------- 24 S t u d i e s t o d e v e lo p a h i g h c a p a c i t y n o n ­ powered l i q u i d p e tro le u m f u e l b u r n e r ----------- 27 R e f l e c t o r s t u d i e s -------------------------------------------- 29 EXPERIMENTAL WORK — --------------- 33 S t u d i e s t o Im prove t h e F r o s t g u a r d ------------------------- 34 A s tu d y o f l i q u i d p e t r o le u m f u e l s ----------------- 34 I iii Page An a n a l y s i s o f t h e b u r n in g c h a r a c t e r i s t i c s o f t h e F r o s t g u a r d -------------------------------------------- 41 E x p e r im e n ta l t r i a l s t o im prove t h e F r o s t g u a r d ------------------------------------------------- 45 The o r i g i n a l b u r n e r — ----------------------------- 45 F i r s t m o d i f i c a t i o n ---------------------------------- 48 Second m o d i f i c a t i o n -------------------------------- 50 T h ir d m o d i f i c a t i o n ---------------------------------- 52 D i s c u s s i o n o f r e s u l t s ------------------------------------- 55 S t u d i e s t o D evelop a High C a p a c ity Nonpowered L iq u id P e tro le u m F u e l B u rn e r ---------------------- 58 O b j e c t i v e ---------------------------------------------------------- 59 P r o c e d u r e ---------------------------------------------------------- 61 E x i s t i n g non-pow ered l i q u i d p e tro le u m f u e l b u r n e r s — --------------------------------- 66 F i r s t t r i a l b u r n e r ------------------------------------------- 68 Second t r i a l b u r n e r ----------------------------------------- 76 T h ird t r i a l b u r n e r ------------------------------------------- 79 D i s c u s s i o n of r e s u l t s ------------------------------------- 81 Developm ent o f a L i q u i f i e d P e tro le u m Gas B u rn e r f o r t h e G e n e r a tio n o f R a d ia n t E nergy f o r F r o s t C o n t r o l ------------------------------------------------------------ 83 O b j e c t i v e ---------------------------------------------------------- 35 P r o c e d u r e ---------------------------------------------------------- 86 I iv Page D i s c u s s i o n o f r e s u l t s ------------------------------------- 89 S u m m ary ----------------------------------------------------------------------- 97 C o n c l u s i o n s ----------------------------------------------------------------- 101 LITERATURE CITED -------------------------------------ACKWCWLEDGIaENTS - ------------- 103 -1 0 6 V LIST OF FIGURES Page F ig . 1 A co m p ariso n o f t h e r a d i a n t en e rg y d i s t r i b u t i o n from a n o x i d i z e d s t e e l s u r f a c e w ith a t h e o r e t i c a l b l a c k b o d y --------------------------- F ig . 2 15 S p e c t r a l en erg y d i s t r i b u t i o n a s a f u n c t i o n o f t e m p e r a t u r e --------------------------------------------------- 17 19 F ig . 3 T o t a l r a d i a t i o n a s a f u n c t i o n o f t e m p e r a tu r e - F ig . 4 D iagram showing t h e p r i n c i p l e o f t h e i n v e r s e s q u a re lav; o f r a d i a t i o n d i s t r i b u t i o n from a p o i n t s o u r c e o f o r i g i n ------------------------------------- F ig . 5 21 The e f f e c t o f c o m p a r a tiv e ly l a r g e r e f l e c t o r s on t h e d i s t r i b u t i o n o f r a d i a t i o n fro m a s t r a i g h t s u r f a c e ------------------------------------------------ F ig . 6 30 R a d ia n t energy d i s t r i b u t i o n from t h e F r o s t g u a r d ---------------------------------------------------------- 31 F ig . 7 The Evans F r o s t g u a r d ----------------------------------------- 55 F ig . 8 P re s s u re h e a t-v a p o riz in g ty p e k ero sen e b u rn e r 42 F ig . 9 The a rra n g e m e n t o f t h e b u r n e r and com b u stio n chamber o f t h e E vans F r o s t g u a r d ---------------------- F ig . 10 I l l u s t r a t i n g t h e f i r s t m o d i f i c a t i o n o f t h e F r o s t g u a r d ---------------------------------------------------------- F ig . 46 49 11 I l l u s t r a t i n g t h e second m o d i f i c a t i o n o f t h e F r o s t g u a r d ---------------------------------------------------------- 51 vi Page F ig . 12 Showing t h e p o s i t i o n o f t h e ce ra m ic m a t e r i a l to s t a b i l i z e th e b u rn e r f o r th e F ro stg u ard — F ig . 13 A rrang em en t f o r t e s t i n g n o n -p o w e re d l i q u i d p e t r o le u m b u r n e r s ---------------------------------------------- F ig . 54 63 14- A p p a r a tu s f o r m e a s u r in g t h e r a d i a n t en erg y d i s t r i b u t i o n from h e a t e r u n i t s ------------------------ 65 F ig . 15 Open p o t b u r n e r s ------------------------------------------------ 67 F ig . 16 B u rn in g c h a r a c t e r i s t i c s and r a d i a n t en e rg y d i s t r i b u t i o n f o r t h e U n ite d S to v e Company O rch ard H e a te r --------------------------------------------------- F ig . 17 B u rn in g c h a r a c t e r i s t i c s an d r a d i a n t en e rg y d i s t r i b u t i o n f o r an o p e n - to p p e d c o n t a i n e r ---- F ig . 70 18 The R e t u r n - s t a c k O rchard H e a te r d e v e lo p e d a t t h e U n i v e r s i t y o f C a l i f o r n i a --------------------------- F ig . 69 71 19 B u rn in g c h a r a c t e r i s t i c s and r a d i a n t en ergy d i s t r i b u t i o n f o r t h e R e t u r n - s t a c k O rchard H e a t e r ----------------------------------------------------------------- 72 F ig . 20 F i r s t T r i a l B u r n e r -------------------------------------------- 73 F ig . 21 B u r n in g c h a r a c t e r i s t i c s an d r a d i a n t en erg y d i s t r i b u t i o n f o r t h e F i r s t T r i a l B u r n e r -------- 75 F ig . 22 S econd T r i a l B u r n e r ------------------------------------------ 76 F ig . 23 B u rn in g c h a r a c t e r i s t i c s an d r a d i a n t e n e rg y F ig . d i s t r i b u t i o n f o r t h e Second T r i a l B u r n e r ------ 78 24 T h ir d T r i a l B u r n e r -------------------------------------------- 80 v ii Page F i g . 25 E x p e r im e n ta l p ro p a n e b u r n e r u n i t s - - --------------- F i g . 26 B u rn in g c h a r a c t e r i s t i c s and r a d i a n t en erg y d i s t r i b u t i o n f o r t h e 60° t y p e p r o p a n e b u r n e r - F i g . 27 90 91 B u rn in g c h a r a c t e r i s t i c s and r a d i a n t en e rg y d i s t r i b u t i o n f o r t h e 3 2° t y p e p ro p a n e b u r n e r - 92 1 INTRODUCTION 2 Review o f Reed and M ethods o f F r o s t Conti o l N a tu re o f t h e p rob lem One o f t h e m ain h a z a r d s t o f r u i t and t r u c k ci ops i s r a d i a t i o n - t y p e f r o s t damage ( 2 6 ) . T h is damage i n ckludes l a t e m a t u r i t y o f c r o p s (due t o l a t e p l a n t i n g ) , p o o r qu a l i t y and q u a n t i t y , and i n some i n s t a n c e s a t o t a l l o s s o f pi oduce. I n t h e U n ite d S t a t e s , l o s s e s b e c a u s e o f f r o s t dam g e a r e more p ro n o u n c e d i n s t a t e s such a s F l o r i d a and Cal i f o r n i a w here t h e c i t r u s c ro p makes up i n t e n s i v e o r h ig h ly - v a lu e d a g ric u ltu re . The same i s t r u e f o r s t a t e s t h a t grccw t r u c k c r o p s and f r u i t o r c h a r d s e x t e n s i v e l y . M ic h ig a n r e p r e s e n t s t h i s t y p e o f a g r i c u l t u r e and t h e a n n u a l f r o s t damsjge i n t h e S t a t e o f M ic h ig a n i s e s t i m a t e d t o ra n g e from t e n \ o tw e n ty m illio n d o lla r s (6 ). R a d ia tio n -ty p e f r o s t The e a r t h r e c e i v e s i t s h e a t from t h e sun i n t h e form o f r a d ia n t en erg y . T h is en e rg y i s a b s o rb e d by plad n t s and tr a n s f o r m e d i n t o s e n s i b l e h e a t . At t h e same tim e t h a t h e a t i s b e in g r e c e i v e d , p l a n t s a r e r a d i a t i n g a p a r t o f t h i s h e a t b a c k to w ard t h e sk y . However, t h e r e i s a n e t g a i r l on th e p a r t of th e p la n ts d u rin g a tw e n ty -fo u r hour p e ric d . T h is c o n d i t i o n i s b r o u g h t a b o u t by t h e b l a n k e t i n g e f f e ctt o f t h e 3 a tm o sp h e re on t h e e a r t h , f o r t h e en e rg y o f t h e sun i s e m i t t e d i n s h o r t w a v e - le n g th r a d i a t i o n w hich p e n e t r a t e s th e a tm o sp h e re o f t h e e a r t h w ith l i t t l e l o s s , w h ile t h e p l a n t s , h a v in g ab ­ so rb e d t h i s e n e rg y , em it i t i n lo n g w a v e - le n g th r a d i a t i o n w hich i s r e a d i l y a b s o rb e d by t h e a tm o sp h e re and t h e r e b y r e s u l t s i n h e a t b e in g added t o t h e a tm o s p h e re ; w hich a t t h e same tim e d e c r e a s e s t h e n e t l o s s from t h e e a r t h and p l a n t s . T h is i m p l i e s t h a t , v o id o f i t s a tm o s p h e r e , t h e e a r t h would become e x tre m e ly h o t d u r in g t h e day and e x tre m e ly c o ld d u r in g t h e n i g h t w h ich c o r r e s p o n d s t o t h e te a c h i n g o f p h y s i c i s t s i n g e n e ra l. T h e r e f o r e , t h e a tm o sp h e re s e r v e s a s a t r a p w hereby t h e e a r t h r e t a i n s s u f f i c i e n t h e a t t o c a r r y i t th r o u g h t h e n ig h t. The c o n d i t i o n o f t h e a tm o s p h e re , t h e n , w i l l g r e a t l y i n f l u e n c e t h e n e t amount o f h e a t g a i n e d by p l a n t s i n any one p e r i o d o f tim e . F or exam ple, t h e a b s o r b in g c h a r a c t e r i s t i c s o f t h e a i r become more p ro n o u n ced a s t h e a b s o l u t e h u m id ity in c re ase s. C o n v e rs e ly , i f t h e r e i s l i t t l e h u m id ity i n t h e a i r , a s on a c l e a r n i g h t , t h e p l a n t s r a p i d l y l o s e t h e i r h e a t . R a d i a t i o n - t y p e f r o s t i s common d u r in g t h e e a r l y and l a t e p a r t s o f t h e grow ing s e a s o n . I t s f o r m a t i o n can b e ex­ p l a i n e d a s f o llo w s on t h e t h e o r y o f h e a t t r a n s f e r . To s e t t h e s t a g e f o r t h i s ty p e o f f r e e z e , i t i s r e q u i r e d t h a t t h e r e 4 b e a p r e l i m i n a r y i n f l u x o f c o o l t o c o ld a i r , f o llo w e d by a calm, c l e a r n i g h t . S in c e t h e p l a n t s u n d e r t h e s e c o n d i t i o n s a re r a d ia tin g h e a t to th e o u te r space, th e n e t h e a t t r a n s ­ m i s s i o n i s away from t h e p l a n t s . by c o n d u c tio n t o t h e s e p l a n t s . The a i r w i l l become c o o le d As t h e a i r becomes c o o l e d , g r a v i t y p u l l s i t down t o s e t t l e c l o s e t o t h e g ro u n d . When t h e p l a n t s have l o s t s u f f i c i e n t h e a t by r a d i a t i o n and h a v e co o le d t h e s u rro u n d in g a i r t o a low t e m p e r a t u r e , t h e i r te m p e ra tu re s w i l l approach th e f r e e z in g p o in t. I f th e p la n t t e m p e r a t u r e f a l l s b elo w t h e dev/ p o i n t o f t h e s u r ro u n d in g a i r , m o is tu r e w i l l condense on t h e v e g e t a t i o n , and when s u b s e ­ q u e n tly fro z e n t o ic e , w i l l g iv e th e f a m il ia r f r o s t appearance. Not a l l f r e e z i n g , ho w ev er, i s v i s i b l e . F o r exam ple, when t h e w ind v e l o c i t y i s i n t h e m a g n itu d e o f f i v e m i l e s p e r h o u r , t h e c o n d e n s a te i s c a r r i e d o f f t h e v e g e t a t i o n , l e a v i n g no m o i s t u r e t o form v i s i b l e f r o s t . A n o th e r c o n d i t i o n o c c u rs when t h e dev/ p o i n t i s lo w e r t h a n t h e minimum p l a n t t e m p e r a t u r e fo r th a t fre e z e . T h is f r e e z i n g w ith o u t v i s i b l e f r o s t i s commonly known a s " b la c k f r o s t " . E x c e p t f o r e x tre m e ly c o ld c o n d i t i o n s , a f o u r - m i l e p e r h o u r wind w i l l c a u s e s u f f i c i e n t t u r b u l e n c e t o p r e v e n t t h e a i r fro m c o l l e c t i n g i n s t r a t a . The moving a i r a l s o c o n v e c ts h e a t t o t h e p l a n t s , k e e p in g t h e i r t e m p e r a t u r e s above t h e 5 fre e z in g p o in t. However, when t h e p r e l i m i n a r y i n f l u x o f a i r i s r e l a t i v e l y c o l d , f r e e z i n g i s l i k e l y t o o c c u r even i f t h e r e i s a b r i s k w ind, b e c a u s e t h i s c o ld a i r ca n n o t c o n v e c t enough h e a t t o t h e p l a n t s t o o f f s e t t h e h e a t t h a t i s l o s t by ra d ia tio n . M ethods u s e d f o r t h e p r o t e c t i o n o f v e g e t a t i o n from f r o s t damage The b a s i c p r i n c i p l e i n v o l v e d i n t h e p ro b lem o f k e e p in g v e g e t a t i o n from f r e e z i n g i s t o m a i n t a i n t h e t e m p e r a t u r e o f t h e v e g e t a t i o n s a f e l y above i t s f r e e z i n g p o i n t . a p p ro a c h e s t o t h i s problem a r e : The t h r e e (1) c o n s e rv e t h e e x i s t i n g h e a t p o s s e s s e d by t h e p l a n t s and t h e g ro u n d ; (2) u t i l i z e t h e h e a t i n t h e s u r ro u n d in g a i r th r o u g h s t i r r i n g ; an d , (5) add a d d i t i o n a l h e a t from a s o - c a l l e d a r t i f i c i a l s o u r c e . Numerous a t t e m p t s h av e b e e n made t o g a i n t h e s e t h r e e o b j e c t i v e s , b u t t h e m ethods t r i e d h a v e b e e n e i t h e r t o o ex­ p e n s i v e , r e q u i r e d to o much l a b o r t o i n s t a l l an d o p e r a t e , o r w ere n o t e n t i r e l y s u c c e s s f u l . F o r exam ple; g l a s s c o v e r i n g s , o r a c o v e rin g o f c l o t h and l a t h s c r e e n s , a r e e x c e l l e n t p r o ­ t e c t i o n , b u t f a r to o e x p e n s iv e f o r t h e a v e r a g e c ro p . I r r i g a t i o n has been used s u c c e s s fu lly , b u t i t , t o o , i s ex­ p e n s iv e t o i n s t a l l and p ro m o tes f e r t i l i t y l o s s th r o u g h le a c h in g . F lo o d in g i s e f f e c t i v e , b u t o f t e n c a u s e s w a t e r damage. E f f o r t s t o make a r t i f i c i a l c lo u d s h a v e n o t b een su c c e ssfu l. L a rg e m o t o r - d r i v e n p r o p e l l o r s have b e e n u s e d t o s t i r t h e a i r , w hich i n t u r n c o n v e c ts h e a t t o p l a n t s , b u t to p o g r a p h y , c l i m a t e , and t h e v a l u e o f cro p l i m i t t h i s a p p l i ­ c a tio n . The most w i d e l y - u s e d and s u c c e s s f u l means o f com bating f r o s t damage h a s b e e n t h e u s e o f o r c h a r d h e a t e r s i n t h e c itr u s groves. The o r i g i n a l i d e a was t o b l a n k e t t h e a r e a w ith d e n s e smoke i n o r d e r t o c u t down r a d i a t i o n l o s s . From t h i s p r a c t i c e t h e b u r n e r s came t o b e c a l l e d "smudge p o t s " . The i n d i v i d u a l u n i t s c o s t l i t t l e , b u t one p e r t r e e , h u n d re d p e r a c r e , a r e r e q u i r e d t o b e e f f e c t i v e . o r two The damage from t h e smoke and t h e n u i s a n c e th e y c a u s e h a v e l e d u r b a n com m unities t o p a s s o r d in a n c e s r e s t r i c t i n g t h e u s e o f t h i s ty p e o f h e a t e r . A l a r g e r o r c h a r d h e a t e r was t h e n d e s ig n e d t o h e a t t h e groves. W hile t h e s e u n i t s a r e more e x p e n s iv e , o n ly a b o u t f i f t y p er ac re are re q u ire d . In a d d itio n to ra d ia tin g a p a r t o f t h e l i b e r a t e d h e a t , t h i s h e a t e r t a k e s a d v a n ta g e o f t h e f a c t t h a t on a c l e a r , calm n i g h t t h e r e i s a t h i n l a y e r o f c o ld a i r n e a r t h e g ro u n d , w h ile t h e a i r t e m p e r a t u r e i n ­ c r e a s e s w ith e l e v a t i o n t o a c e r t a i n p o i n t , above w hich t h e t e m p e r a tu r e a g a i n d e c r e a s e s . T h is phenomenon i s c a l l e d 7 " te m p e r a t u r e i n v e r s i o n " . The p rim a ry p u rp o se o f t h e s e h e a t e r s i s t o warm t h e a i r u n d e r th e i n v e r s i o n p o i n t t o t h e n e c e s s a r y degree. I t i s m ost e f f e c t i v e i f t h e day t e m p e r a tu r e h a s been h ig h an d , t h e r e f o r e , i t i s n e c e s s a r y t o h e a t l e s s a i r . Even th o u g h t h e s e h e a t e r s a r e e f f e c t i v e f o r t h e c o n t r o l o f r a d i a t i o n - t y p e f r o s t , th e y a r e e x p e n s iv e n o t only b e c a u s e o f t h e i n i t i a l c o s t and t h e f u e l c o s t , b u t b e c a u s e much l a b o r i s r e q u i r e d f o r i n s t a l l a t i o n and m a in te n a n c e . T hese f a c t s have c a u s e d t h e c i t r u s i n d u s t r y t o lo o k f o r b e t t e r means f o r p r e v e n t i n g f r o s t damage. P r e l i m i n a r y t e s t s made a t M ic h ig an S t a t e C o lle g e The f a r m e r s o f M ic h ig an r e a l i z e t h e n e e d f o r p r o t e c t i o n a g a i n s t f r o s t damage, a s a l a r g e p a r t o f t h e i r a g r i c u l t u r a l i n d u s t r y i s d e v o te d t o t r u c k g a r d e n in g and com m ercial f lo w e r and f r u i t g ro w in g ; a l a r g e p a r t o f w hich ca n n o t b e co n ta m i­ n a t e d a s would r e s u l t from t h e p r e s e n t o r c h a r d h e a t e r s . The prob lem o f f r o s t damage, w h i l e alw ay s i m p o r t a n t , became more so d u r in g World War I I when t h e c ro p v a l u e s i n c r e a s e d . By 1945 t h e problem o f f r o s t p r o t e c t i o n h a d become so a c u t e t h a t t h e M ic h ig an A g r i c u l t u r a l E x p erim e n t S t a t i o n was a sk e d t o d e v e lo p a p r a c t i c a l means f o r c o n t r o l l i n g f r o s t fo rm a tio n . The p ro b lem was s u b s e q u e n tly r e f e r r e d t o t h e A g r i c u l t u r a l E n g in e e rin g D e p a rtm e n t. 8 As a f i r s t s t e p , an i n t e n s i v e stu d y was made t o d e­ te r m i n e t h e r e l a t i v e a d v a n ta g e s and d i s a d v a n t a g e s o f a l l known a t t e m p t s t o c o n t r o l f r o s t , Methods t h a t a p p e a re d t o b e p r a c t i c a l w ere g iv e n c a r e f u l c o n s i d e r a t i o n , and some o f t h e s e m ethods w ere t e s t e d by t h e A g r i c u l t u r a l E n g in e e rin g D e p a rtm e n t. I n one i n s t a n c e t h e U n ite d S t a t e s Army A ir F o r c e s s e n t a h e l i c o p t e r t o t h e C o lle g e t o b e u s e d i n c i r ­ c u l a t i n g t h e a i r by f l y i n g a t low a l t i t u d e s o v e r t h e a r e a s to be p ro te c te d . I t was co n c lu d e d t h a t w h ile some o f t h e s e p r a c t i c e s w ere e f f e c t i v e u n d e r s e l e c t e d c o n d i t i o n s , th e y vjould be i m p r a c t i c a l f o r t h e c o n d i t i o n s s u r r o u n d in g M ichigan a g ric u ltu re . C a r e f u l s tu d y showed t h a t c o n v e c te d h e a t was l i m i t e d i n t h a t i t i s d e p e n d e n t upon t h e a t m o s p h e r ic c o n d i t i o n s . I n th e f a l l o f 19 45 , A. W. F a r r a l l , Head o f t h e D epartm ent o f A g r i c u l t u r a l E n g in e e r in g a t M ic h ig a n S t a t e C o l l e g e , p ro p o se d t h e u s e o f i n f r a r e d r a d i a n t en e rg y a s t h e p r i n c i p a l s o u rc e o f a d d i t i o n a l h e a t f o r a s o l u t i o n t o t h i s p ro b le m . I n o r d e r t o t e s t t h i s m ethod, an e l e c t r i c a l l y - p o w e r e d r a d i a n t - t y p e u n i t was d e s ig n e d and c o n s t r u c t e d a t M ic h ig an S t a t e C o lle g e i n t h e s p r i n g o f 1946 w i t h t h e c o o p e r a t i o n o f t h e R esearch' Committee o f t h e D e t r o i t B oard of.- Commerce. I n f o r m a t i o n was n e e d e d a s t o t h e e f f e c t i v e n e s s , o f r a d i a n t 9 h e a t i n p r e v e n t i n g f r o s t damage, t h e r a d i a t i o n i n t e n s i t y r e q u i r e d p e r u n i t s u r f a c e a r e a , and t h e c o s t o f c o n s t r u c t i n g and o p e r a t i n g a p r a c t i c a l u n i t . T h is u n i t was d e s ig n e d t o co v e r a p l o t f o r t y f e e t s q u a r e .. The h e a t i n g u n i t c o n s i s t e d o f r o d - t y p e chrom olox e le m e n ts w i t h an i n p u t o f tw e n ty K.W.. W ith t h e u s e o f s t a n d a r d r e f l e c t o r d e s i g n t e c h n i q u e s , t h i s u n i t was so c o n s t r u c t e d t h a t p r a c t i ­ c a l l y a l l o f t h e h e a t b e in g r a d i a t e d was u n if o r m ly d i s t r i b u t e d o v er t h e d e s i g n a t e d a r e a ( 9 ) . T e s t s were made d u r in g n a t u r a l r a d i a t i o n - t y p e f r o s t s (7 ) . A lth o u g h a c t u a l t e m p e r a t u r e s o f t h e v e g e t a t i o n and su rro u n d in g a i r w ere n o t r e c o r d e d , t h e t e s t s i n d i c a t e d t h a t a r a d i a t i o n i n t e n s i t y o f t h r e e w a t t s p e r s q u a r e f o o t would a d e q u a te ly p r o t e c t v e g e t a t i o n from f r o s t u n d e r t h e c o n d i t i o n s m ost l i k e l y t o o c c u r d u r in g t h e s p r in g and e a r l y f a l l (1 0 ). A lth o u g h t h i s e l e c t r i c a l l y h e a t e d u n i t was e x c e l l e n t f o r t e s t i n g p u r p o s e s , and s u p p l i e d t h e n e c e s s a r y b a s i c d a t a , i t would b e t o o c o s t l y t o be c o m m e rc ia lly f e a s i b l e . F u rth e rm o re , p r e s e n t e l e c t r i c l i n e s a r e o f i n s u f f i c i e n t c a p a c i t y t o p ro ­ v id e p r o t e c t i o n f o r a p p re c ia b le a r e a s . The n e x t s t e p was t o d e v e lo p a r a d i a n t h e a t s o u r c e t h a t would be p r a c t i c a l . 10 Two f a c t o r s l e d t o t h e u s e o f o i l - b u r n i n g e q u ip m e n t. F irs t, on a BTU b a s i s o i l i s i n e x p e n s i v e ; s e c o n d , i t was f e l t t h a t o i l - h e a t e d r a d i a t i o n u n i t s c o u ld b e c o n s t r u c t e d a t a re a so n a b le c o s t. The a v e r a g e n e t h e a t l o s s from t h e s u r f a c e o f t h e e a r t h by r a d i a t i o n a t n i g h t h a s b e e n fo u n d t o b e a t t h e r a t e o f a p p r o x im a te ly one m i l l i o n BTU p e r h o u r p e r a c r e ( 8 ) . U sing t h i s a s a b a s i s from w hich t o s t a r t , a n o i l - b u r n i n g u n i t was c o n s t r u c t e d t h a t w ould b u r n f u e l a t t h e r a t e o f a p p r o x im a te ly s e v e n g a l l o n s p e r h o u r . The r a d i a t i n g s u r f a c e was made o f t h r e e s t e e l o i l drums w eld e d end t o en d . Aluminum r e f l e c t o r s were p o s i t i o n e d aro u n d t h e b a r r e l s i n an a t t e m p t t o d i r e c t t h e r a d i a t i o n downward. v a p o r i z i n g b u r n e r was u s e d . A c o m m e r c ia l- ty p e p r e s s u r e T h is u n i t was t e s t e d d u r in g t h e f a l l o f 1946 u n d e r n a t u r a l f r o s t i n g c o n d i t i o n s . The r e s u l t s were c o n c l u s i v e i n e s t a b l i s h i n g t h e e f f e c t i v e n e s s o f t h e p r i n c i p l e o f f r o s t c o n t r o l th r o u g h t h e u se o f r a d i a n t h e a t . The a r e a c o v e re d was g r e a t l y expanded and t h e o r i g i n a l f i g u r e o f t h r e e v /a tts p e r s q u a re f o o t was foun d t o b e t h e a v e r a g e i n t e n s i t y r e q u i r e m e n t s f o r p r o t e c t i o n a g a i n s t n o rm al f r o s t i n g c o n d i t i o n s d u r in g t h e f a l l . 11 T h eo iy o f t h e E m is s io n , T r a n s m is s io n , and A b s o r p tio n o f I n f r a r e d o r Thermal R a d i a t i o n T here a r e t h r e e v/ell-know n means by w hich h e a t i s t r a n s ­ f e r r e d from a h o t t o a c o l d e r bo d y . They a r e c o n v e c ti o n , c o n d u c tio n , and r a d i a t i o n , and a l l t h r e e a r e g e n e r a l l y i n ­ v o lv e d o r a s s o c i a t e d i n any one p r o c e s s . The t h i r d method, r a d i a t i o n , i s u n iq u e i n t h a t i t i n v o l v e s no m a t e r i a l means o f t r a n s f e r , and f o r t h i s r e a s o n t h e r e a p p a r e n t l y a r e a d v a n ta g e s and j u s t i f i c a t i o n f o r e x p e r i m e n ta l work i n e v a lu ­ a t i n g t h i s means a s a f r o s t c o n t r o l m e a su re . R a d ia n t en e rg y i s t r a n s f e r r e d a s e l e c t r o m a g n e t i c r a d i a t i o n and i s fo un d t o t r a v e r s e a vacuum w i t h o u t a t t e n u a t i o n , b u t w i l l be a b s o rb e d t o some e x t e n t by g a s e s o r v a p o r s . As t o t h e s o u r c e o f th e r m a l r a d i a t i o n , i t was f i r s t ad v a n ce d by P r e v o s t , i n 1792, t h a t a l l m a t t e r above a b s o l u t e z e r o t e m p e r a t u r e e m itte d en e rg y i n t h e form o f r a d i a t i o n . S in c e a l l m a t t e r a b s o r b s such e l e c t r o m a g n e t i c r a d i a t i o n a t some wave l e n g t h , i t would seem t h a t t h e second la w had b e e n i n v a l i d a t e d by t h i s h y p o t h e s i s ; how ever, even though a h o t body may r e c e i v e en e rg y from a c o l d e r body, t h e r e i s e x p e r i m e n ta l e v id e n c e t o t h e f a c t t h a t t h e n e t exchange w i l l i n v a r i a b l y show a g a i n f o r t h e c o l d e r bod y. T h is i s b e s t i l l u s t r a t e d by p l a c i n g o b j e c t s a t v a r y in g te m p e r a tu r e s 12 w i t h i n an i n s u l a t e d v a c u a t e d c o n t a i n e r and n o t i n g t h a t t h e o b j e c t s a p p ro a c h a n e q u a l t e m p e r a t u r e , t h e t e m p e r a t u r e o f th e c o n ta in e r. Q u a n t i t a t i v e lav/s f o r "b la ck b o d y " r a d i a t i o n f o l l o w ; h ow ever, a few e x p l a n a t o r y rem a rk s a b o u t t h i s s p e c i a l c l a s s i ­ f ic a t io n of r a d ia tio n i s in o rd er. T h e re a r e s e v e r a l d e f i n i n g f e a t u r e s w h ich c h a r a c t e r i z e " b la c k b o d y " r a d i a t i o n . im p o r t a n t f e a t u r e s a r e : The (1) a b la c k b o d y a b s o r b s a l l t h e r a d i a n t e n e rg y w hich f a l l s upon i t ; (2 ) no body p o s s e s s e s a r a d i a n c y g r e a t e r t h a n t h a t o f a b la c k b o d y ; a n d , (5 ) b la c k - b o d i e s obey L a m b e r t 's C o sin e Law w h ile n o n - b la c k b o d ie s do n o t , w hich means t h a t t h e i n t e n s i t y a t any d i r e c t i o n from t h e n o rm al e q u a l s t h e p r o d u c t o f t h e n o rm al i n t e n s i t y tim e s t h e c o s i n e o f t h e a n g l e t h a t t h e d i r e c t i o n i n q u e s t i o n makes w ith t h e n o r m a l. As a c o n seq u en c e o f ( 3 ) , t h e s t e r a d i a n c y o r b r i g h t n e s s o f a s u r f a c e i s t h e same from a l l d i r e c t i o n s o f v ie w . These t h r e e c o n d i t i o n s o r c h a r a c t e r i s t i c s h o ld f o r s p e c t r a l v a l u e s a s w e l l a s t o t a l e m is s iv e v a l u e s . As p r e v i o u s l y s t a t e d , t h e d e r i v a t i o n s o f q u a n t i t a t i v e la w s a r e b a s e d on " b la c k b o d y " r a d i a t i o n and s in c e i t i s a d m itte d t h a t t h e r e a r e no s u r f a c e s o f m a t t e r w h ich c o rre s p o n d p e r f e c t l y t o a b la c k b o d y (even th o u g h such m a t e r i a l s a s ca rb o n b l a c k , p la tin u m b l a c k , z i n c b l a c k , and carborundum a r e 13 among t h e b e s t a p p r o x i m a t i o n s ) , t h e r e seems l i t t l e ju sti­ f i c a t i o n o r e x p e r i m e n t a l p r o o f t o w a r r a n t such d e r i v a t i o n s . However, f o r t h e o r e t i c a l c o n s i d e r a t i o n s and c a l i b r a t i o n p u r p o s e s , a t r u e s o u rc e o f "b la c k b o d y " r a d i a t i o n i s a t t a i n e d sim p ly by s tu d y in g s o - c a l l e d c a v i t y r a d i a t i o n . T h is i s t h e r a d i a t i o n e m i t t e d from a s m a ll a p e r t u r e i n t h e s i d e o f a u n if o r m ly h e a t e d e n c l o s u r e o f opaque w a l l s . I t i s under­ s t a n d a b l e t h a t t h i s a p e r t u r e w i l l a b s o r b a l l t h e im p in g in g r a d i a t i o n , f o r once i t g e t s w i t h i n t h e c a v i t y t h e r e i s o n ly a rem o te p r o b a b i l i t y t h a t i t w i l l come o u t a g a i n . The second c o n d itio n i s s a t i s f i e d sin c e th e r a d i a t i o n d e n s ity i s a maximum (which can be shown t h e o r e t i c a l l y ) f o r t h e g iv e n e n c l o s u r e t e m p e r a t u r e , and s i n c e t h e a p e r t u r e i s e s s e n t i a l l y th e i n s i d e s u r f a c e , t h i s c o n s i d e r a t i o n g i v e s t h e r a d i a t i o n i n t e n s i t y f o r t h e a p e r t u r e a maximum v a l u e f o r t h a t t e m p e r a t u r e . As t h e r a d i a t i o n from t h e a p e r t u r e i s u n if o r m i n a l l d i ­ re c tio n s ( i n t h e o utw ard h e m is p h e r e ) , t h e i n t e n s i t y w i l l v a ry a s t h e c o s in e o f t h e a n g l e w i t h t h e n o r m a l; t h u s s a t i s ­ fy in g th e t h i r d c o n d itio n . I n t h i s s tu d y o x id iz e d s h e e t s t e e l was g e n e r a l l y u s e d f o r th e ra d ia tin g su rfa c e . T h is s u r f a c e h a s t o t a l e m i s s i v i t y v a l u e s r a n g in g from .8 t o .95 (18) w h ich i s t h e r a t i o o f i t s t o t a l e m i s s i v e power t o t h a t o f a b la c k b o d y a t t h e same te m p e ra tu re . A ls o , t h e v a r i a t i o n o f t h i s s u r f a c e from L a m b e r t 's 14 C osine Law i s i l l u s t r a t e d i n F i g . 1 , and i t i s n o te d t o compare v e r y c l o s e l y w i t h a b la c k b o d y e m i t t i n g s u r f a c e . S in c e t h e t o t a l e m is s iv e power and h e m i s p h e r i c a l d i s t r i b u t i o n a l c h a r a c t e r i s t i c s a p p ro a c h t h a t o f a b la c k b o d y t h e q u a n t i t a t i v e r e l a t i o n s h i p s f o r b la c k b o d y c o n d i t i o n s a r e a p p l i c a b l e t o a f i r s t o r d e r o f a p p r o x im a tio n f o r t h e r e a l s u r f a c e s . T here­ f o r e , th e fo llo w in g r e l a t i o n s h i p s a re in c lu d e d to f u r t h e r an u n d e r s t a n d i n g o f t h e a p p l i c a t i o n t o b e made. Q u a n t i t a t i v e la w s f o r b la c k b o d y r a d i a t i o n (24) A t t e n t i o n i s f i r s t d i r e c t e d t o t h e s p e c t r a l e n e rg y d i s t r i b u t i o n o r s p e c t r a l e m i s s i v e power o f t h e r a d i a t i o n a s a f u n c t i o n o f wave l e n g t h and t e m p e r a t u r e ( F ig . 2 ) . T h is p l o t i s p o s s i b l e th r o u g h t h e a p p l i c a t i o n o f P l a n c k ’ s a n a ­ l y t i c a l e x p r e s s i o n f o r t h e s p e c t r a l en e rg y d i s t r i b u t i o n o f "b la ck b o d y " r a d i a t i o n . P la n c k was a b l e t o d e r i v e t h i s r e l a t i o n s h i p , w h ich i s i n a g re e m e n t w ith e x p e r i m e n t a l r e s u l t s , by i n t r o d u c i n g t h e quantum t h e o r y i n c o n j u n c t i o n w i t h t h e c l a s s i c a l s t a t i s t i c a l th e o ry v ib ra tio n s). ( th e o r y o f e l a s t i c o r e l e c t r o n i c E i n s t e i n and B ose ea ch h a v e s u b s e q u e n tly d e r i v e d t h e same r e l a t i o n s h i p t h r o u g h t h e u s e o f s t a t i s t i c a l m e c h a n ic s . W ith o u t c a r r y i n g th r o u g h t h e d e r i v a t i o n , t h e r e s u l t i s g iv e n i n t h e f o llo w in g e q u a t i o n : = 3.740*/Q~s Sec. I— _/7 J 20 3.0 "30 ^ 6d 40 ^ > // J E ^ R E T t/A tsg L /} OD EM/TTWO Si .70 20 Sul 8d 70 60 40 40 50 50 F i g u r e 1 , A co m p ariso n o f t h e r a d i a n t e n e rg y d i s t r i b u t i o n frnra an o n id in a d s t e e l s u r f a c e vjith a t n a o r e t i c a l from an b la c k b o d y . d 16 B ased on t h i s r e l a t i o n s h i p t h e c u rv e s ( f o r 1000°F. and 1 5 0 0 ° F .) i n F i g . S w ere d e v e lo p e d . F o llo w in g P l a n c k 's d e r i v a t i o n o f t h e s p e c t r a l en e rg y d i s t r i b u t i o n f o r "blackb od y " r a d i a t i o n , t h r e e im p o r ta n t r e l a t i o n s h i p s w ere d i r e c t l y d e r i v a b l e . The f i r s t t o b e in c lu d e d h e r e g i v e s an e x p r e s s i o n f o r t h e t o t a l e m is s iv e p ow er. T h is i s fo u n d by i n t e g r a t i n g t h e s p e c t r a l e n e rg y e q u a tio n b e tw e e n t h e wave l e n g t h l i m i t s o f 0 and o o , g iv in g 9\ O —S = S . 6 7 Z X /& «y« ^ £ £ 2 2 .-------2 o ? , * S ee. •/? * 7 F o r a 1 5 00°F . e m i t t i n g s u r f a c e (assum ing "b lack b o d y " r a d i a t i o n ) t h i s e q u a t i o n g i v e s a t o t a l e m is s iv e power e q u a l t o 2 5 ,6 0 0 B T U /H r ./f t2 . As a co m p ariso n t h e a r e a u n d e r t h e c u rv e was m easured w ith a p l a n i m e t e r from w hich t h e t o t a l e m is s iv e power was c a l c u l a t e d a s 2 9 ,0 0 0 B T U / H r ./ f t 2 . i t i s p o ssib le th a t a b e t t e r ag re e m e n t would b e o b ta in e d by p l o t t i n g t h e en e rg y d is trib u tio n to a la rg e r sc a le . 17 30 X 10' 20 X 10 I0 0 0 ° F RAO I A NT INTENSITY - Ea Oa = BT U / (H R.) ( SQ. FT.) (C M .) 70 X 10’ 5 1*0 15 20 F igu re 2. S p e c t r a l energy d i s t r i b u t i o n as a f u n c t i o n o f temperature. 18 A g r a p h o f t h e t o t a l e m is s iv e power a s a f u n c t i o n o f te m p e ra tu re i s i l l u s t r a t e d i n F ig . 3. A n o th e r d e r i v a t i o n b a s e d on P l a n c k 's s p e c t r a l en e rg y d i s t r i b u t i o n g i v e s t h e r e l a t i o n t h a t t h e modal wave l e n g t h of th e r a d ia tio n ( th e wave l e n g t h f o r w hich t h e monochromatic, e m is s iv e power o f t h e b la ck b o d y i s a maximum) i s i n v e r s e l y p r o p o r t i o n a l t o t h e a b s o l u t e t e m p e r a tu r e o f t h e b la c k b o d y . T h is i s fo u n d by d i f f e r e n t i a t i n g P l a n c k 's e q u a t i o n w ith r e s p e c t t o t h e wave l e n g t h , and s o lv i n g f o r t h e wave l e n g t h w hich makes t h e r e s u l t i n g e x p r e s s i o n e q u a l t o z e r o , T h is e x p r e s s i o n i s known a s W ie n 's D is p la c e m e n t Lav; s i n c e h e h ad r e a l i z e d t h e r e l a t i o n s h i p and d e te r m in e d t h e c o n s t a n t , e x p e r i m e n t a l l y , a t an e a r l i e r d a t e . From t h i s e q u a t i o n t h e wave l e n g t h a t w hich t h e mono­ c h r o m a tic e m is s iv e power i s a maximum f o r a 1500°F. t e m p e r a t u r e s o u r c e i s 2 .6 5 8 m ic r o n s . 32X10 . I6X BTU / (HRJ (SQ.FT.) 24X10' ex u u ✓ 800' 900' 1300 1200 1100' 1000 T E M P E R A T U R E - 0 E 6 R E E S FAHRENHEI T ' F igu re 3. T o t a l r a d i a t i o n as a f u n c t i o n o f temperature. 14 00 1500 1600' 20 The t h i r d d e p e n d e n t r e l a t i o n s h i p s t a t e s t h a t t h e maximum m onochrom atic e m is s iv e power o f a b la c k b o d y , v i z ..,, t h a t w ith in , t h e w a v e - le n g th i n t e r v a l d N a t t h e modal wave l e n g t h A/», i s p r o p o r t i o n a l t o t h e f i f t h power o f i t s a b s o ­ l u t e te m p e ra tu re . The d e r i v a t i o n sim p ly r e q u i r e s t h e s u b s t itu ti o n of th e v alu e o f i n t o P l a n c k 's e q u a t i o n , g iv in g 0 -t* T r a n s m is s io n o f i n f r a r e d r a d i a t i o n The q u a n t i t a t i v e lav/s d e a l w ith t h e s o u r c e o f r a d i a t i o n o n ly and t h e r e a r e o t h e r i m p o r t a n t f a c t o r s w h ich i n f l u e n c e t h e amount o f e n e rg y t h a t i s t r a n s m i t t e d . One o f t h e s e f a c t o r s , w hich i s by f a r t h e m ost i m p o r ta n t, i s t h a t r e s u l t i n g from t h e s o - c a l l e d I n v e r s e S q u are Law o f R a d ia tio n . T h is lav/ i s i l l u s t r a t e d i n F i g . 4 from w hich i t i s n o te d t h a t t h e r a d i a t i o n from a p o i n t s o u r c e c o v e rs f o u r t i m e s a s much a r e a a t two f e e t a s compared t o t h e a r e a a t one f o o t ; g i v i n g t h e r e l a t i o n s h i p t h a t t h e i n t e n s i t y i s in v e rs e ly p r o p o r tio n a l to th e sq u are of th e d is t a n c e . ) Figure 4 . Diagram showing the p r i n c i p l e o f the in v e r s e square law o f r a d i a t i o n d i s t r i b u t i o n from a p o in t source o f o r i g i n . The o t h e r f a c t o r t o b e c o n s i d e r e d i s t h e a b s o r p t i o n o f t h e r a d i a n t en e rg y by t h e atm o sp h ere o r t h e a t t e n u a t i o n o f t h e i n t e n s i t y a s t h e r a d i a t i o n t r a v e r s e s t h e d i s t a n c e from source to p l a n t . T h ere fo re , i t i s e rro n eo u s to ac c la im t h a t t h i s form o f h e a t i n g can b e t r a n s f e r r e d d i r e c t l y t o t h e v e g e t a t i o n in d e p e n d e n t o f t h e i n t e r v e n i n g medium. The e x t e n t o f t h i s f a c t o r on t h e i n t e n s i t y o f r a d i a t i o n from a g iv e n s o u r c e a t a chosen p o i n t i s d e p e n d e n t on t h e com ponents o f t h e a tm o s p h e r e . S in c e w a te r v a p o r i s e s s e n t i a l l y t h e only v a r i a b l e com ponent, i t i s l o g i c a l t o assum e t h a t t h e r e l a t i v e h u m id ity i s a f a c t o r i n d e te r m in in g t h e e f f i c i e n c y o f r a d i a n t en e rg y tr a n s m is s io n . The B e e r-L a m b e rt Law o f A b s o rp tio n w hich e x p r e s s e s t h e fo llo w in g r e l a t i o n s h i p i s a p p l i c a b l e f o r c a l c u l a t i n g th e re s u ltin g in te n s ity ( 2 5 ): I / I 0 = e“k x , w here I s i n t e n s i t y a t x , I 0 - i n i t i a l i n t e n s i t y , x = d i s t a n c e th ro u g h a b s o rb in g medium, k = a b s o r p ti o n c o e f f i c i e n t , and i s a f u n c t i o n o f b o th wave l e n g t h and d e n s i t y o f w a te r v a p o r. I t h a s b e e n o b se rv e d s p e c t r o s c o p i c a l l y t h a t t h e r e a r e w ide ra n g e s o f wave l e n g t h s w hich a r e n o t a f f e c t e d by th e atm o sp h ere w h ile o th e r s a r e a b s o r b te d a t v a r y in g d e g r e e s ; some wave l e n g t h s a r e t o t a l l y a b s o r b te d by a s h o r t d i s t a n c e o f t r a v e l i n t h e a tm o s p h e re . T h is f a c t o r h a s n o t b e e n g iv e n s u f f i c i e n t stu d y t o w a r r a n t f u r t h e r d i s c u s s i o n i n t h i s p a p e r; how ever, s in c e t h e d a t a a r e a v a i l a b l e i n p h y s i c s ' j o u r n a l s , f u t u r e i n v e s t i g a t i o n o f t h i s p ro b lem sh o u ld p ro v e s i g n i f i c a n t i n c o n n e c tio n w ith t h e u s e o f r a d i a n t en e rg y f o r f r o s t c o n t r o l . A b s o r p tio n o f r a d i a t i o n by v e g e t a t i o n A f t e r th e e le c tr o m a g n e tic r a d i a t i o n o f i n f r a r e d en erg y im p in g e s upon t h e s u r f a c e o f v e g e t a t i o n o r o th e r m a t t e r , 23 t h e r e i s th e phenomenon o f t r a n s f o r m a ti o n t o s e n s i b l e h e a t . To form an a n a lo g y w ith e le c tr o m a g n e tic r a d i a t i o n o f r a d io f r e q u e n c y , t h e v e g e t a t i o n m ust a c t a s a " r a d io r e c e i v e r " . As would be e x p e c te d from t h i s a n a lo g y , t h e v e g e t a t i o n s h o u ld e x h i b i t s e l e c t i v e a b s o r p ti v e p r o p e r t i e s o r b e m ore r e c e p t i v e t o d i f f e r e n t f r e q u e n c i e s o r wave l e n g t h s . T h is i s e x a c tly th e c a s e and th e phenomenon i s e x p la in e d e i t h e r on th e c l a s s i c a l wave th e o r y o r th e more modern quantum th e o ry w hich we w i l l n o t a tte m p t t o e x p la in i n t h i s p a p e r . H ow ever,, t h i s p r o p e r ty i s e a s i l y e v a lu a te d e x p e r im e n ta lly w ith th e s p e c tr o p h o to m e te r o r s p e c tr o g r a p h . G e n e r a lly , a s id e fro m i s o l a t e d i n t e r v a l s th r o u g h o u t th e i n f r a r e d sp e c tru m , i t h a s b e e n fo u n d t h a t tr a n s m is s io n and r e f l e c t i o n o f r a d i a t i o n by g r e e n v e g e t a t i o n i n c r e a s e s w ith wave l e n g t h i n g o in g fro m v i s i b l e l i g h t i n t o th e n e a r i n f r a r e d sp e c tru m ( 5 ) , w hich means i n f a c t t h a t th e a b s o r p ti o n o r h e a tin g e f f e c t d e c r e a s e s w ith t h i s change i n wave l e n g t h . T h is f a c t i s o f im p o rta n c e i n c o n s i d e r a t i o n o f th e e f f i c i e n c y o f a s o u r c e o f r a d i a n t en e rg y a s a f r o s t c o n t r o l m e a s u re . 24 P re v io u s Work and P r e s e n t S t a t u s o f t h e U t i l i z a t i o n o f I n f r a r e d R a d ia n t E nergy f o r t h e P r o t e c t i o n o f V e g e ta tio n fro m F r o s t Damage O r i g in a l i n v e s t i g a t i o n s As d e s c r ib e d e a r l i e r i n t h i s p a p e r, t h e i n i t i a l w ork i n th e i n v e s t i g a t i o n o f t h e a p p l i c a t i o n o f i n f r a r e d en erg y a s a f r o s t c o n t r o l m e a su re was c a r r i e d o u t w ith an e l e c t r i ­ c a l l y pow ered s o u r c e . At t h a t tim e th e m a jo r em phasis was p la c e d on th e v i s i b l e e v a l u a t i o n o f t h e e x t e n t o f p r o t e c t i o n o r a r e a t h a t was k e p t f r e e from f r o s t f o r m a tio n u n d e r f r e e z i n g te m p e r a tu r e s a t th e g ro u n d l e v e l . The te m p e r a tu r e was m easu red w ith a c h e m ic a l o r m e r c u r y - in - g la s s th e rm o m e te r. From t h i s i t was fo u n d t h a t i n f r a r e d e n e rg y , a p p lie d w ith s u f f i c i e n t i n t e n s i t y , w ould a f f o r d f r o s t p r o t e c t i o n t o v e g e ­ ta tio n . L a te r i t was fo u n d t h a t a r a d i a t i o n i n t e n s i t y o f 10 B T U / s q .f t / H r ., m easu red n o rm al t o th e d i r e c t i o n o f p ro p a ­ g a t i o n , w ould p r o t e c t a h eav y s i x - i n c h b l u e g r a s s sod u n d e r m o d e ra te t o s e v e r e f r o s t i n g c o n d i t i o n s . The i n t e n s i t y - p r o t e c t i o n r e l a t i o n s h i p was fo u n d t o h o ld t r u e f o r t e s t s u n d e r s i m i l a r c o n d itio n s w ith th e o r i g i n a l o il- b u r n in g u n i t ; th e o n ly e x c e p tio n b e in g t h a t th e i n t e n s i t y r e q u ir e d v a r i e d somewhat w ith t h e ty p e and am ount o f f o l i a g e 25 i n t h a t a lo w e r i n t e n s i t y s a f e l y p r o t e c t e d s p a r s e v e g e t a t i o n w hich w as grow ing a p p r e c ia b ly above th e g ro u n d l e v e l . L a b o ra to ry e x p e r im e n ta tio n was c a r r i e d o u t i n 1947 (11) t o i n v e s t i g a t e th e p l a n t t e m p e r a t u r e - r a d i a t i o n i n t e n s i t y re la tio n s h ip . The t e s t s w ere made a t b o th room te m p e r a tu r e and w ith in a c o ld s to r a g e w here th e am b ien t te m p e r a tu r e was h e ld a t 3 5°F . The r e s u l t s o f t h i s w ork i n d i c a t e d t h a t w ith in , th e l e a f o f a n exposed p l a n t a r a d i a t i o n i n t e n s i t y o f 10 B T U /S q .ft/H r. r a i s e d i t s te m p e r a tu r e a p p ro x im a te ly 2 °F . T h is h e ld t r u e i n b o th e n v iro n m e n ts i n d i c a t i n g t h a t , w ith in t h e te m p e r a tu r e i n t e r v a l t e s t e d , t h e p l a n t s f a i l e d t o e x h i b i t p h y s i o l o g i c a l ch an g es t o r e g u l a t e t h e i r te m p e r a tu r e when b e in g h e a te d by i n f r a r e d e n e rg y . S in c e t h e n e t g a in i n p l a n t te m p e r a tu r e i s d i r e c t l y p r o p o r t i o n a l t o th e d i f f e r e n c e i n te m p e r a tu r e b etw een t h e p l a n t and s u r ro u n d in g s , t h e o n ly f a c t o r t h a t w ould change th e i n t e r v a l o f te m p e r a tu r e i n c r e a s e w ould l o g i c a l l y b e o f p h y s io l o g ic a l o r i g i n . A ls o , i t was. f o u n d 't h a t a shaded o r s h ie ld e d l e a f , even th o u g h i t was a d j a c e n t to a n ex posed l e a f , f a i l e d t o i n d i c a t e a n a p p r e c i­ a b l e i n c r e a s e i n te m p e r a tu r e . Even th o u g h t h e r e was n o a tte m p t made t o d e te rm in e th e te m p e r a tu r e o f th e s u r f a c e w hich was i r r a d i a t e d , i t i s l o g i c a l t o assum e t h a t t h i s te m p e r a tu r e w ould h av e b ee n c o n s id e r a b ly 26 i n e x c e s s o f t h e i n t e r i o r te m p e r a tu r e . T h is i s fo u n d ed on th e h y p o th e s is t h a t th e g r e a t e r p a r t o f t h e tr a n s f o r m a tio n o f r a d i a n t en e rg y t o h e a t ta k e s p la c e i n a c o m p a ra tiv e ly th in la y e r of p la n t t i s s u e . The a s s u m p tio n t h a t th e i r r a d i a t e d s u r f a c e o f t h e p l a n t h a s a c o n s id e r a b ly g r e a t e r i n c r e a s e i n te m p e r a tu r e g iv e s e x p la n a tio n t o th e f a c t t h a t f r o s t f a i l s t o fo rm on a s u r f a c e w hich i s exposed t o a r a d i a t i o n i n t e n s i t y o f o n ly 10 BTU/Sq. f t / H r . a t an a m b ie n t a i r te m p e r a tu r e o f 25 °F . S in c e th e s u r f a c e te m p e r a tu r e i s above 5 2 °F . and i f t h e p l a n t s a r e exp o sed t o s u f f i c i e n t r a d i a t i o n i n t e n s i t y b e f o r e t h e p l a n t te m p e r a tu r e h a s f a l l e n t o 3 2 ° F ., th e n , i n v iew o f th e f a c t t h a t h e a t flo w s from a h o t t e r t o a c o o le r r e g io n , t h e te m p e r a tu r e o f th e i n t e r i o r o f th e p l a n t sh o u ld b e m ain­ t a i n e d a t a l l tim e s above t h i s c r i t i c a l te m p e r a tu r e . T h is would em p h asize th e im p o rta n c e o f ap p lj^in g th e r a d i a t i o n b e f o r e t h e p l a n t s h ad f a l l e n t o t h e c r i t i c a l te m p e r a tu r e . The above f a c t o r s a r e o f p rim a ry im p o rta n c e , e s p e c i a l l y w here p r o t e c t i o n i s c a r r i e d o u t th r o u g h th e a p p l i c a t i o n o f i n f r a r e d e n e rg y . J 27 S tu d ie s t o d e v e lo p a h ig h c a p a c ity non-pow ered l i q u i d p e tro le u m f u e l b u r n e r F o llo w in g t h e p r e lim in a r y i n v e s t i g a t i o n s w ith th e u s e o f e l e c t r i c i t y a s th e s o u rc e o f power t h e n e x t move was t o d e s ig n an o i l - b u r n i n g ‘u n i t . T h is was deemed n e c e s s a r y i f th e m ethod o f f r o s t c o n t r o l by r a d i a n t en e rg y was t o a t t a i n p r a c tic a l a p p lic a tio n . From th e s ta n d p o in t o f c o s t , a v a i l a ­ b i l i t y , and b u rn in g c h a r a c t e r i s t i c s , k e ro s e n e 7/as b e l ie v e d to be th e b e s t fu e l fo r t h i s u se . S e v e r a l e x p e rim e n ta l u n i t s w ere c o n s tr u c te d and t e s t e d on a c o m p a ra tiv e b a s i s t o e v a lu a t e th e a d v a n ta g e s o f each ( 1 2 ) . As a r e s u l t , one p a r t i c u l a r d e s ig n was s e l e c t e d w ith th e i n t e n t i o n o f i n t e r e s t i n g a m a n u fa c tu rin g company who w ould make and d i s t r i b u t e a l i m i t e d number o f su ch u n i t s f o r f u r t h e r ex­ p e r im e n ta tio n and e v a l u a t i o n o f t h e p r a c t i c a b i l i t y o f i t s use. T h is p la n was c a r r i e d th ro u g h and th e d i s t r i b u t i o n in c lu d e d n o t only M ich ig an b u t many o t h e r s t a t e s . The p r i n c i p a l a p p l i c a t i o n was on t r u c k and flo w e r c r o p s . The r e s u l t s o f th e s e o p e r a tio n s g e n e r a l l y s u b s t a n t i a t e d t h e f i n d i n g s o f t h e o r i g i n a l work a t th e A g r i c u l t u r a l E n g in e e rin g D ep artm en t o f M ich ig an S t a t e C o lle g e w hich a r e sum m arized a s f o l l o v / s : 1. F or a r a d i a t i o n - t y p e f r o s t w here t h e f r o s t l i n e 28 d id n o t e x te n d h ig h e r t h a n s i x t e e n in c h e s , e a c h u n i t p r o ­ te c te d out to n in e ty f e e t . 2. F o r th e m ost s e v e r e r a d i a t i o n - t y p e f r o s t m ost l i k e l y t o o ccu r d u r in g t h e n o rm al gro w in g s e a s o n ( a g a i n s t w hich th e u n i t must p r o t e c t t o b e p r a c t i c a l ) t h e f r o s t l i n e was a p p r o x i­ m a te ly s i x t y - f i v e f e e t from th e u n i t . 3. F or c o ld w in d -b lo w n f r e e z e s t h e u n i t s p r o t e c t e d a v e ry s m a ll a r e a . 4. U n its w ould n o t o p e r a t e s a t i s f a c t o r i l y i n wind i n e x c e s s o f f i v e m ile s p e r h o u r. 5. The b u r n e r was fo u n d e r r a c t i c i n i t s o p e r a tio n u n d e r a l l c o n d i tio n s , and co u ld be c o r r e c t e d o nly by an e x p e rie n c e d o p e ra to r. T h is l a s t f a c t o r was o f g r a v e co n se q u e n c e s in c e s a t i s ­ f a c t o r y o p e r a tio n a t a l l tim e s was e s s e n t i a l i f a cro p was t o b e a s s u r e d p r o t e c t i o n from a l l p o s s i b l e f r o s t s th r o u g h o u t t h e grow ing se a s o n . The r e s u l t s a l s o i n d i c a t e d th e l i m i t a t i o n o f a p p l i c a t i o n o f t h i s m ethod o f f r o s t c o n t r o l . I t was fo u n d t h a t o n ly th o s e c ro p s o f h ig h e r v a l u e c o u ld e c o n o m ic a lly s u p p o rt t h e i n i t i a l and o p e r a t io n a l c o s t . 29 R e fle c to r s tu d ie s E x te n s iv e e x p e rim e n ta l work an d s tu d y h a s b e e n done on r e f l e c t o r s f o r i n f r a r e d en e rg y i n c o n n e c tio n w ith t h i s a p p l i c a t i o n (13) a s r e f l e c t o r s a r e one p ro v ed m ethod o f re d u c in g t h e a d v e rs e e f f e c t o f th e i n v e r s e s q u a re lav/ o f r a d i a t i o n from a r e l a t i v e l y s m a ll s o u rc e o f r a d i a t i o n . As p r e v io u s l y p o in te d o u t, a p l o t o f t h e i n t e n s i t y from a f l a t s u r f a c e d e s c r i b e s a sp h e re ( e x a c t f o r a b la c k b o d y ) in w hich th e i n t e n s i t y i n any d i r e c t i o n e q u a ls t h e p ro d u c t o f th e n o rm al i n t e n s i t y tim e s t h e c o s in e o f th e a n g le w hich th e d i r e c t i o n i n q u e s tio n makes w ith th e norm al t o t h a t su rfa c e . F ig . 5 i l l u s t r a t e s a n a p p l i c a t i o n o f r e f l e c t o r s f o r a i d i n g i n t h e e f f e c t i v e d i s t r i b u t i o n o f r a d i a n t en e rg y f o r f r o s t c o n tro l. I n c o n t r a s t F ig . 6 b r i n g s o u t th e l i t t l e a d v a n ta g e o f u s in g a c o m p a ra tiv e ly s m a ll r e f l e c t o r i n con­ j u n c t i o n w ith a l a r g e s o u r c e o f r a d i a t i o n . . The r e f l e c t o r s t u d i e s i n c o n n e c tio n w ith t h i s problem w e re : (1 ) th e s e l e c t i o n o f t h e b e s t m a t e r i a l from th e s ta n d ­ p o in t o f c o s t , a v a i l a b i l i t y , and d u r a b i l i t y ; (2 ) th e m ost e f f e c t i v e shape and a rra n g e m e n t o f r e f l e c t o r s an d r a d i a t i n g s u r f a c e s ; an d , (3 ) an o v e r a l l v ie w p o in t to w ard k e e p in g th e m a t e r i a l and f a b r i c a t i o n c o s t t o a minimum. I N T E N S I T Y X | 0 3 B.T.U./ H R / S Q . F T . 10 15 20 25 . 30 A Y, 35 0 90 80 F igu re The e f f e c t of c o m p a r a tiv e ly l a r g e r e f l e c t o r s on tiie d i s t r i b u t i o n o f r a d i a t i o n from a straigh t surface. i Figure 32 The r e s u l t s o f th e s e s t u d i e s a r e sum m arized a s fo llo w s 1. A nodized alum inum i s p r e s e n t l y t h e b e s t m a t e r i a l . 2. The l a r g e r th e r e f l e c t o r i n r e l a t i o n t o t h e r a d i ­ a t in g s u r f a c e , t h e b e t t e r t h e d i s t r i b u t i o n . 3. I n o r d e r t o o f f s e t t h e in v e r s e s q u a re la w t o a r e a s o n a b le d e g r e e , th e p r o p e r r e f l e c t i o n o f a l a r g e p a r t o f th e r a d i a t i o n i s r e q u i r e d . 4. C urving t h e r a d i a t i n g s u r f a c e a n d / o r th e r e f l e c t o r gave p o s i t i v e e v id e n c e o f a i d in g i n th e d i s t r i b u t i o n o f t h e r a d i a t i o n , b u t t h e g a i n i n e f f e c t i v e n e s s a p p a r e n tly w ould n o t o f f s e t t h e added c o s t o f c o n s t r u c t i o n . 35 EXPERIMENTAL 34 S tu d ie s t o Im prove t h e E vans F ro s tg u a r d As s t a t e d i n th e i n t r o d u c t i o n ( P .2 7 ) , th e d e s ig n o f a p e tro le u m f u e l ( k e r o s e n e ) b u r n e r f o r t h e g e n e r a t i o n o f r a d i a n t en e rg y f o r f r o s t c o n t r o l , t h e " F r o s tg u a r d " , F ig . 7 , was r e l e a s e d t o E vans P ro d u c ts Company o f P lym outh, M ich ig an , f o r m a n u fa c tu re and d i s t r i b u t i o n on a l i m i t e d s c a l e . T h is was deemed n e c e s s a r y i n o r d e r t o g a i n f u r t h e r in f o rm a tio n a s t o i t s o p e r a t io n u n d e r v a r io u s f i e l d and f r o s t i n g con­ d itio n s . The r e s u l t s o f th e s e t e s t s p la c e d th e p r a c t i c a l u s e o f t h i s ty p e o f u n i t f o r f r o s t c o n t r o l i n a l i m i t e d c a te g o r y o r o th e rw is e r e s t r i c t e d i t s u s e t o c e r t a i n a r e a s and p a r t i c u l a r c r o p s . T here w ere two p r i n c i p a l f a c t o r s w hich l i m i t e d th e u s e of t h i s h e a te r: (1 ) i t s f a i l u r e t o o p e r a te s a t i s f a c t o r i l y a t a l l tim e s , i . e . l a c k o f d e p e n d a b i l i t y ; and (2 ) i n view o f th e i n i t i a l and o p e r a tin g c o s t s , i t was fo u n d t o b e i m p r a c t i c a l from an e c o n o m ic a l s ta n d p o in t e x c e p t f o r c ro p s o f com para­ t i v e l y h ig h v a l u e . T h e r e f o re , t h e n e x t move was to w a rd im provem ent, and th e w ork t h a t was done i n th e A g r i c u l t u r a l E n g in e e rin g D ep artm en t f o llo w s . A s tu d y o f l i q u i d p e tro le u m f u e l s o il) (k e ro se n e and No. 1 f u e l 35 B e fo re a tte m p tin g m o d if ic a ti o n s o f th e F r o s tg u a r d u n i t , i t was n e c e s s a r y t o make a f u r t h e r s tu d y o f th e p h y s i c a l and c h e m ic a l p r o p e r t i e s o f t h e f u e l u s e d , an d t o stu d y t h e fu n d a m e n ta l p r i n c i p l e s u n d e r ly in g l i q u i d p e tro le u m f u e l b u rn e rs. A b r i e f d i s c u s s i o n o f t h e fu n d a m e n ta l p r i n c i p l e s o f co m b u stio n w i l l s e rv e t o b r in g o u t th e b a s i c r e q u ir e m e n ts fo r a l l b u rn ers. C om bustion o f f u e l o i l may be d e f in e d a s t h e ch e m ic al c o m b in a tio n o f t h e component e le m e n ts ( p r im a r ily c a rb o n and h y d ro g e n ) w ith oxygen, r e s u l t i n g i n t h e e v o l u tio n o f h e a t .. The r a t e o f a n e x o th e rm ic r e a c t i o n , such a s t h e b u rn in g o f h y d ro c a rb o n s , i n c r e a s e s w ith te m p e r a tu r e . U n le ss t h e oxygen i s made a v a i l a b l e i n c lo s e p ro x im ity t o t h e e le m e n ts ca rb o n and h y d ro g e n , d e la y e d b u rn in g w i l l r e s u l t . A ls o , any p h y s ic a l b a r r i e r s , su ch a s t h e p r e s e n c e o f i n e r t g a s e s o r i f th e s e e le m e n ts a r e b u r ie d w ith in a com plex m o le c u le , w i l l c a u se d e la y e d b u r n in g . R e g ard in g te m p e r a tu r e , ea c h f u e l h a s i t s own c h a x 'a c t e r i s t i c i g n i t i o n te m p e r a tu r e — t h i s b e in g th e te m p e r a tu r e ( o f t h e oxygen and f u e l m o le c u le s ) a t w hich t h e ch e m ic a l p r o c e s s o f co m b u stio n t a k e s p l a c e . T h is i g n i t i o n te m p e r a tu r e ra n g e s from o v er 1 2 0 0 °F . f o r n a t u r a l g a s down t o a s low a s 5 5 0 °F . f o r f u e l o i l s . An e x p la n a tio n o f t h i s v a r i a t i o n i s fo u n d i n th e f a c t t h a t n a t u r a l g a s i s made up o f s a t u r a t e d h y d ro c a rb o n m o le c u le s w hich r e q u i r e g r e a t e r 37 h e a t e n e rg y t o b r e a k down t h e bond b etw een th e ca rb o n and h y d ro g en th a n t h a t f o r u n s a t u r a t e d h y d ro c a rb o n m o le c u le s — th o s e fo u n d i n k e ro s e n e and f u e l o i l s . T h e r e f o r e , a lo w e r te m p e r a tu r e w i l l c a u se b u rn in g t o s t a r t i n t h e u n s a tu r a te d h y d ro c a rb o n s , s u b s e q u e n tly r e l e a s i n g h e a t w hich p ro d u c e s t h e te m p e r a tu r e and h e a t e n e rg y t o s u p p o rt a " c h a in - r e a c tio n " f o r c o n tin u e d co m b u stio n o f a l l o th e r m o le c u le s i n t h a t f u e l . I n a d d i t i o n t o r a i s i n g t h e te m p e r a tu r e o f th e r e a c t a n t s i n th e co m b u stio n p r o c e s s t o a s h ig h a te m p e r a tu r e a s p r a c t i ­ c a l (b u t b elo w th e i g n i t i o n te m p e r a tu r e ) , any m eans o f p ro m o tin g i n t i m a t e m ix in g o f th e a i r f o r co m b u stio n w ith th e e le m e n ts t o b e o x id iz e d , c a rb o n and h y d ro g e n , w i l l enhance t h e r a t e o f th e co m b u stio n r e a c t i o n . T h is p ro v e s t o b e th e a d v a n ta g e e x h i b ite d i n t h e e a s e w ith w hich a n a t u r a l g a s e o u s f u e l can b e b u rn e d q u ic k ly and c l e a n l y , f o r , s in c e th e s e m o le c u le s a r e r e l a t i v e l y s m a ll and w id e ly s e p a r a te d , th e a i r i s e a s i l y m ixed t o p ro d u c e an a i r - v a p o r m ix tu re w hich b u m s r e a d i l y once t h e p ro p e r te m p e r a tu r e i s r e a c h e d . The d i f f e r ­ en c e b etw een g a s e o u s f u e l s and l i q u i d f u e l s i s a p p r e c ia t e d when one c o n s id e r s th e p ro b lem o f h a v in g f i r s t t o b r e a k up t h e l i q u i d f u e l i n t o i t s com ponent m o le c u le s ( to v a p o r iz e them ) b e f o r e o th e r th a n s u p e r f i c i a l m ix in g w ith t h e a i r w i l l ta k e p l a c e . A n o th e r p ro b lem e n t e r s i n t h a t , i f h e a t i s u se d t o v a p o r iz e t h e s e m o le c u le s , and i f t h e lo w e s t i g n i t i o n 38 te m p e r a tu r e f o r t h i s g ro u p o f m o le c u le s i s re a c h e d d u rin g t h i s v a p o r i z a t i o n , b u rn in g i s i n i t i a t e d w hich s p re a d s t o o th e r m o le c u le s ; t h u s , i n h i b i t i n g f u r t h e r m ixing o f a i r w ith t h e f u e l m o le c u le s . As a r e s u l t , ca rb o n atom s w i l l c o a le s c e g iv in g body t o t h e fla m e , w hich p ro d u c e a lu m in o u s flam e i f th e y b u rn o r p a s s o f f a s smoke i f th e y f a i l t o b u rn c o m p le te ly . G aseous f u e l s a r e th o u g h t o f a s i n h e r e n t l y b u rn in g w ith a n o n -lu m in o u s fla m e , and l i q u i d p e tro le u m f u e l s a s g iv in g a lu m in o u s fla m e . T h is i s p u r e ly a m easu re o f t h e com­ p l e t e n e s s o f t h e m ix in g o f th e a i r and f u e l v ap o r ( p r im a r ily b e f o r e b u rn in g s t a r t s ) . T h ere a r e i n u s e s o - c a l l e d " o i l - t o - g a s " c o n v e r t e r b u r n e r s w hich ta k e th e h e a v i e r f r a c t i o n s o f f u e l o i l and b u rn them w ith th e fla m e c h a r a c t e r i s t i c s o f g a s e o u s f u e l s ; t h i s e m p h asiz es th e im p o rta n c e o f p ro p e r a l r f u e l m ix in g . The f u e l u n d e r c o n s id e r a ti o n f o r t h i s a p p l i c a t i o n was s t r a i g h t - r u n k e r o s e n e o r No. 1 h o u s e h e a tin g f u e l o i l . S in c e t h e s e two f u e l s h a v e l i t t l e d i f f e r e n c e in t h e i r b o i l i n g p o in t te m p e r a tu r e s , th e y a r e v e ry n e a r l y i d e n t i c a l i n th e p r e s e n tday r e f i n i n g p r o c e s s . The e x i s t i n g demand r e g u l a t e s th e c l a s s i f i c a t i o n , r a t h e r th a n th e s m a ll d i f f e r e n c e i n p r o p e r t i e s . T h is same f r a c t i o n i s r e p r e s e n te d i n c ra c k e d p e tro le u m ; h o w ev er, c ra c k e d p e tro le u m y i e l d s a f r a c t i o n w hich i s con­ s id e r a b ly m ore d i f f i c u l t t o b u rn and sh o u ld n o t be u s e d i n t h i s a p p lic a tio n . A t y p i c a l f u e l u se d i n t h i s a p p l i c a t i o n i s c h a r a c t e r i z e d by t h e fo llo w in g a n a l y s i s o f r e c e n t h e a t e r o i l a s m a n u fa c tu re d by S ta n d a rd O il Company ( I n d ia n a ) ( 4 ): S ta n d a rd H e a te r O il ( S t r a i g h t r u n ) G r a v ity , °API D o c to r C o lo r F la s h S u lf u r C arbon R e sid u e on 10% B ottom s Co. s t r i p 3 h r s . © 212°F . V is . S a y b o lt Therme I n i t i a l B o ilin g P o in t °F .. 10 20 30 40 50 60 70 80 90 End P o in t W ater & S ed im en t % D ie s e l In d e x 4 0 .3 Sw eet 18 133 214 01 1 440 338 582 398 410 422 436 448 464 480 508 562 None 6 3 .8 From t h e s e d a t a i t i s p o s s i b l e t o d e te r m in e o th e r p h y s ic a l and ch e m ic al p r o p e r t i e s w hich a r e p e r t i n e n t t o t h e problem o f b u r n e r d e s ig n . B ecau se o f t h e d i f f e r e n c e i n t h e 40 cru d e p e tro le u m ( p a r a f f i n s , n a p h th e n e s , and a r o m a tic s ) and t h e w ide ra n g e o f ty p e s and s i z e s o f m o le c u le s w h ich make up any one f r a c t i o n , t h e d e r iv e d e m p ir ic a l r e l a t i o n s h i p s e x p r e s s in g t h e s e p r o p e r t i e s a r e a p p ro x im a tio n s w hich h ave p ro v ed t o b e s u f f i c i e n t l y a c c u r a te t o s a t i s f y t h e p e tro le u m i n d u s t r y and consum ers o f p e tro le u m p r o d u c ts . These r e l a t i o n ­ s h ip s a r e b a s e d on th e s p e c i f i c g r a v i t y and a v e ra g e b o ili n g p o i n t o f t h e p e tro le u m f r a c t i o n . The fo llo w in g p r o p e r t i e s o f t h e ab o v e f u e l w ere d e te rm in e d by t h e l a t e s t a c c e p te d g r a p h i c a l m ethods ( 1 5 ): S p e c i f i c G r a v ity = 0 .3 2 5 A verag e B o ilin g p o in t = 4 5 9 °F . (19) A verage M o le c u la r w e ig h t r 186 C r i t i c a l T em p e ra tu re = 7 8 0 °F . H ydrogen c o n t e n t, $ by w e ig h t = 1 3 .5 $ A verage s p e c i f i c h e a t o f l i q u i d a t c o n s ta n t p r e s s u r e (Cp ) = 0 .5 7 5 B T U /°F /lb . H eat o f v a p o r i z a t i o n (1 a tm .) = 108 B T U /lb. H ig h e r H eat v a lu e o f f u e l = 1 9 ,7 2 0 B TU /lb. T h e o r e t i c a l Amount o f a i r f o r co m b u stio n = 1 4 .5 l b s o f a ir /lb . of fu e l I g n i t i o n T e m p e ra tu re = 5 6 3 °F . (20) 41 An a n a l y s i s o f t h e b u rn in g c h a r a c t e r i s t i c s o f th e F r o s tg u a r d U sing th e f u e l d is c u s s e d i n t h e p r e v io u s s e c t i o n , t h e n e x t c o n s i d e r a t i o n was i t s u s e a s f u e l f o r t h e F r o s tg u a r d b u rn er. T h is b u r n e r , i l l u s t r a t e d i n F ig . 8 i s o f t h e p r e s s u r e h e a t- v a p o r iz in g ty p e w hich o p e r a te s on a f u e l p r e s s u r e o f from 50 t o 80 p s i g . The l i q u i d f u e l ( k e r o s e n e ) i s s e l f ­ v a p o r iz e d and t h r o t t l e d th ro u g h t h e n o z z le o r j e t , and i s i g n i t e d a s i t e n t e r s t h e co m b u stio n cham ber, t h e s u r f a c e of w hich s e r v e s a s t h e so u rc e o f r a d i a n t e n e rg y . T h is p r i n c i p l e i s t h e same a s t h a t o f a common blow t o r c h and r e q u i r e s an e x t e r n a l so u rc e o f h e a t f o r s t a r t i n g . A r e a s o n a b le tim e la g m ust b e a llo w e d b e f o r e th e b u r n e r ta k e s h o ld and becom es s e l f - g e n e r a t i n g , w hich i s a d is a d v a n ta g e i n t h i s a p p l i c a t i o n ; and i t h a s b een fo u n d g e n e r a l l y t h a t t h i s ty p e o f b u r n e r i s s u b je c t t o c o n s id e r a b le v a r i a t i o n i n i t s c a p a c i t y . I t was hoped t h a t th r o u g h c a r e f u l s tu d y , t h i s v a r i a t i o n o r l a c k of d e p e n d a b i l i t y c o u ld b e c o r r e c t e d and a t t h e same tim e d e ­ c r e a s e t h e fla m e volum e r e q u i r e d f o r th e o r i g i n a l r a t e o f b u r n in g . I f co m b u stio n co u ld b e a c c o m p lish e d w ith in a s m a lle r fla m e volum e, th e n e i t h e r o f t h e f o llo w in g tw o im provem ents co u ld b e em ployed: (1) th e r a t e o f b u rn in g c o u ld b e i n c r e a s e d f o r t h e same s i z e com bustion cham ber, th u s in c r e a s i n g t h e 42 COILS AOOED TO INCREASE CAPACITY ^ / / , standard VAPORIZING COIL S — - - - ' / . ' V :: r.T - r- '-v - - -- -j: INLET BURNER NOZZLE F ig u re S. P r e s s u r e h e a t - v a p o r i z i n g type kerosene burner. 43 s u r f a c e te m p e r a tu r e o f th e p r e s e n t u n i t ; o r, (2 ) t h e s iz e co u ld b e re d u c e d a s w e ll a s r a i s i n g t h e s u r f a c e te m p e r a tu r e . R e f l e c t o r d e s ig n s w ould t h e n b e more p r a c t i c a l f o r a id in g i n t h e p r o p e r d i s t r i b u t i o n o f th e r a d i a n t e n e rg y . S in c e th e t o t a l r a d i a t i o n i s p r o p o r t i o n a l t o th e f o u r t h power o f th e a b s o l u t e te m p e r a tu r e o f th e s o u r c e , i t i s e v id e n t t h a t any i n c r e a s e i n s u r f a c e te m p e r a tu r e w ould b e a c o n s id e r a b le im provem en t. T hrough m ethods u s e d i n th e p e tro le u m i n d u s t r y (2 1 ), t h e s a t u r a t e d v a p o r te m p e r a tu r e a t 80 p s ig was fo u n d t o b e 6 5 5 °F . w hich i s s i g n i f i c a n t i n t h a t - i t i s ab o v e th e i g n i t i o n , te m p e r a tu r e (563°F) o f t h i s f u e l . From t h e s p e c i f i c h e a t o f th e l i q u i d f u e l and i t s h e a t o f v a p o r i s a t i o n a t 80 p s ig (w hich was found t o b e o f n e g l i ­ g i b l e d i f f e r e n c e from t h a t a t 1 4 .7 p s i g ) , i t was fo u n d t h a t th e h e a t r e q u i r e d t o r a i s e t h e f u e l from 5 0 °F . t o a s a t u r a t e d v a p o r te m p e r a tu r e o f 655°F . i s a p p ro x im a te ly 4 52 B T U /lb .. The u s e o f t h i s f u e l i n a p r e s s u r e h e a t- v a p o r iz in g ty p e o f b u r n e r b r o u g h t up th e im p o r ta n t p o in t a s t o th e te m p e r a tu r e o f th e f u e l v a p o r a f t e r i t was t h r o t t l e d th ro u g h th e b u rn e r je t. C o n s id e r a tio n s w ere g iv e n t o m ethods f o r m aking t h i s c a l c u l a t i o n ; h o w ev er, s in c e t h e r e w ere no p u b lis h e d w orks on 44 th e e q u a tio n o f s t a t e o r M o ll ie r C h a rts f o r t h i s ty p e o f f u e l , i t was im p o s s ib le t o make a d i r e c t d e te r m in a tio n o f th e te m p e r a tu r e d ro p a s t h e v a p o r was a d i a b a t i c a l l y expanded from 80 p s ig and 6 5 5 ° F ., t o 1 4 .7 p s i a . From t h e a ssu m p tio n t h a t t h e v a p o r h a d t h e p r o p e r t i e s o f a p e r f e c t g a s and u s in g t h e b e s t o b ta in a b l e v a l u e s f o r t h e s p e c i f i c h e a t s a t c o n s ta n t volum e and p r e s s u r e ( 1 ) , i t was fo u n d t h a t th e te m p e r a tu r e d ro p was l e s s th a n 1 0 °F . T hrough p r o p e r o p e r a t i o n o f t h i s b u r n e r u n d e r n o rm al c o n d i tio n s , i t was fo u n d t h a t a b u rn in g r a t e o f e i g h t g a l lo n s p e r h o u r c o u ld b e a t t a i n e d w ith in a fla m e volum e o f t e n c u b ic fe e t. T h is r a t e o f e f f i c i e n t b u rn in g p ro v e d a d e q u a te f o r m a in ta in in g t h e a v e ra g e te m p e r a tu r e o f th e r a d i a t i n g s u r f a c e a t a p p ro x im a te ly 140 0 °F . The o p e r a t io n o f th e b u r n e r was g e n e r a l l y s t a b l e i n w ind o f l e s s th a n f i v e m ile s p e r h o u r; how ever, i f th e w ind v e l o c i t y ex c e e d e d t h i s f i g u r e , even f o r s h o r t g u s ty p e r io d s , t h e b u r n e r r e q u i r e d c o n s ta n t a t t e n t i o n f o r s a t i s f a c t o r y o p e r a t io n . F a c to r s such a s f u e l te m p e r a tu r e , s u rro u n d in g a i r te m p e r a tu r e , and c l e a n l i n e s s o f v a p o r iz in g c o i l w ere fo u n d t o re d u c e th e b u rn in g e f f i c i e n c y . T h is co u ld b e c o r r e c t e d o n ly by re d u c in g t h e r a t e o f b u r n in g . 45 E x p e rim e n ta l t r i a l s t o Im prove t h e F ro s tg u a r d The o r i g i n a l b u r n e r . The r e l a t i o n s h i p o f t h e b u r n e r t o t h e u n i t p r o p e r i s i l l u s t r a t e d i n F ig . 9 . The a i r i s in tr o d u c e d a t two p l a c e s — t h e p rim a ry a i r a t t h e b a s e o f th e b u r n e r and th e se c o n d a ry a i r i s b ro u g h t i n a t t h e b a s e o f th e u n i t . Through a f l u e g a s a n a l y s i s i t was fo u n d t h a t u n d e r f a v o r a b le c o n d i tio n s e i g h t g a l l o n s o f k e ro s e n e p e r h o u r c o u ld b e b u rn e d c o m p le te ly w i t h i n th e co m b u stio n cham ber. T h is was c a r r i e d o u t w ith 3 ($ e x c e s s a i r and a f l u e g a s te m p e r a tu r e o f 2 0 0 0 ° F .; g iv in g a r a d i a n t s u r f a c e te m p e r a tu r e o f a p p ro x im a te ly 130 0 °F . The te m p e r a tu r e o f t h e f u e l v a p o r was m easured a s 660°F. a t th e p o in t j u s t b e f o r e i t was t h r o t t l e d th ro u g h t h e j e t . T h is m easurem ent was ta k e n b y means o f a th e rm o c o u p le i n a te m p e r a tu r e - w e ll e x te n d in g i n t o th e v a p o r s tre a m . T h erefo re ., th e m easu red te m p e ra tu re c h e c k s w ith t h e c a l c u l a t e d te m p e r a tu r e o f 655°F . f o r t h e s a t u r a t e d v a p o r . B ecause o f u n f a v o r a b le a i r - f u e l v a p o r m ix in g and th e s h o r t p a th o f t r a v e l f o r t h e fla m e , t h e h ig h p e r c e n t o f e x c e ss a i r was r e q u i r e d t o i n s u r e c o m p lete b u r n in g . The a i r was f o r c e d i n a lm o st e n t i r e l y th ro u g h t h e e f f e c t o f a s e v e n -fo o t s ta c k and had v e r y l i t t l e v e l o c i t y o r tu r b u le n c e . 46 F ig u r e 9. The arrangement o f the burner and combustion chamber o f the 3vans Frostguard. 47 The r e q u ire m e n t f o r a h ig h s u r f a c e te m p e r a tu r e demanded. a h ig h f l u e g a s te m p e r a tu r e ; t h u s , g iv in g r i s e t o t h e e x ­ c e p t i o n a l l y h ig h l o s s i n s e n s i b l e h e a t o u t t h e s ta c k . However, t h e n a t u r e o f u t i l i z a t i o n , w hich means a com para­ t i v e l y few h o u r s o f o p e r a tio n p e r y e a r , d o es n o t r e q u i r e a h ig h o v e r a l l o p e r a tin g e f f i c i e n c y ; b u t r a t h e r , a h ig h ra d ia tio n in te n s ity . F o r t h i s r e a s o n t h e r a t e o f b u rn in g was n o rm a lly t e n g a l l o n s p e r h o u r , a llo w in g d e la y e d b u rn in g t o f o llo w t h e f l u e g a s e s o u t t h e s ta c k . H ow ever, b u rn in g h a s t o b e n e a r l y co m p lete t o p r e v e n t a n a p p r e c ia b l e amount o f smoke f o r m a tio n . T hese c o n d itio n s w ere e a s i l y m et u n d e r n o rm al o p e r a tin g c o n d i tio n s w hich a r e c h a r a c t e r i z e d by w e a th e r c o n d itio n s w ith a s u rro u n d in g minimum a i r te m p e r a tu r e o f 5 2 °F . and a w ind v e l o c i t y n o t i n e x c e s s o f 6 kPH. C o ld e r a i r re d u c e d t h e v a p o r iz in g c a p a c ity o f th e b u r n e r c o i l by d i r e c t c o n ta c t and i n d i r e c t l y th ro u g h t h e c o o lin g o f t h e fla m e te m p e r a tu r e . Wind i n e x c e s s o f t h e c r i t i c a l v e l o c i t y o f 6 MPH a p p a r e n tly re d u c e d t h e te m p e r a tu r e o f th e co m b u stio n cham ber by r e d u c in g t h e r a t e o f incom ing a i r t o th e p o in t w here i t was n o t a d e q u a te f o r th e s e l e c t e d r a t e o f b u r n in g . T h is a f f e c t e d t h e v a p o r iz in g c a p a c ity o f t h e c o i l s such t h a t l i q u i d f u e l was e j e c t e d from t h e b u r n e r j e t . The above c o n d i tio n s e i t h e r re d u c e d th e b u rn in g c a p a c ity o r c a u se d a f l u c t u a t i o n i n t h e o p e r a tio n w hich r e q u ir e d 48 c o n s ta n t a t t e n t i o n . F i r s t m o d ific a tio n . The f i r s t a p p ro a c h to w ard im­ p ro v em e n t of t h e F r o s tg u a r d was d e s ig n e d t o i n c r e a s e t h e a i r - v a p o r m ix in g b e f o r e b u r n in g s t a r t e d , f o llo w e d by th e p r o p e r i n t r o d u c t i o n o f se c o n d a ry a i r t o co m p lete co m b u stio n i n a s s h o r t a tim e a s p o s s i b l e . C o n c e n tr ic h o le s w ere d r i l l e d i n t h e b a s e o f th e b u r n e r a s i n l e t s f o r t h e p rim a ry a i r , w h ile l a r g e r h o le s w ere d r i l l e d i n th e b a s e o f t h e u n i t a s i n l e t s f o r t h e se c o n d a ry a i r , F ig . 1 0 . Each g ro u p o f h o l e s was f i t t e d w ith a c o v e r by w hich t h e s i z e o f o p e n in g s c o u ld b e v a r i e d . An i n s p i r a t i n g - m i x i n g v e n t u r i was sh a p ed fro m tw o -in c h c o p p e r tu b in g an d p o s it io n e d r e l a t i v e t o t h e b u r n e r j e t t o i n s p i r a t e a i r an d f a c i l i t a t e a b e t t e r m ix in g o f t h e a i r and f u e l v ap o r. The o u t l e t fro m t h i s i n s p i r a t o r was d i r e c t e d to w ard a c e ra m ic t a r g e t , m ounted a t t h e to p o f t h e v a p o r iz in g c o i l s , t o s e rv e b o th a s a fla m e r e t a i n e r and t o d iv e r g e th e fla m e so t h a t m ore h e a t w ould b e d i r e c t e d a g a i n s t th e v a p o r ­ iz i n g c o i l s . The r e s u l t s o f t h e o p e r a tio n o f t h i s b u r n e r a s m o d ifie d g a v e e v id e n c e t h a t no im provem ent h ad b e e n m ade. A f t e r th e 49 n OOon c8d°S!9o s > O O o °Q -0 ° o o o & ^§ooo°0° O o Ou SCALE: 3/ i 6 - j " F igu re 10. I l l u s t r a t i n g , the f i r s t m o d i f i c a t i o n o f tile Frostguard A 50 b u r n e r became s e l f - g e n e r a t i n g and re a c h e d e q u i l i b r i u m o t h e r ­ w is e , t h e f u e l v a p o r s t a r t e d b u r n i n g w i t h i n t h e i n s p i r a t o r , t h u s e l i m i n a t i n g any ch a n ce f o r im p ro v in g t h e a i r - f u e l v a p o r m ix in g . F o llo w in g t h e a d j u s t m e n t o f t h e a i r i n l e t o p e n in g s , t h e b u r n in g c h a r a c t e r i s t i c s (a s r e l a t e d t o wind e f f e c t and c a ­ p a c i t y ) w ere n o d i f f e r e n t from t h a t o f t h e o r i g i n a l b u r n e r a r r a n g e m e n t. Second m o d i f i c a t i o n . I n p l a c e o f th e c o p p e r i n s p i r a t o r a l a r g e i n d u s t r i a l in s i D i r a to r was p o s i t i o n e d a s i l l u s t r a t e d by F i g . 1 1 . T h is had t h e same d i s a d v a n t a g e a s t h e co p p er i n s p i r a t o r i n t h a t b u r n in g s t a r t e d w i t h i n t h e i n s p i r a t o r ; t h u s , a g a i n e l i m i n a t i n g any p o s s i b i l i t y f o r im p ro v in g t h e a i r - f u e l v a p o r m ix in g . F o llo w in g t h i s t e s t i t was c o n c lu d e d t h a t s i n c e t h e s a t u r a t e d v a p o r te m p e r a t u r e o f t h e f u e l was h i g h e r th a n i t s i g n i t i o n te m p e ra tu re , l i t t l e c o u ld b e done to w a rd m ix in g t h e v a p o r w i t h t h e a i r w it h o u t b u r n in g t a k i n g p l a c e ; p a r t i c u ­ l a r l y w i t h i n t h e c o n f i n e s o f a n i n s p i r a t o r w hich m a in ta in e d t h e v a p o r r e l a t i v e l y c l o s e t o t h e te m p e r a t u r e a t w h ich i t was e j e c t e d from t h e j e t , f o r a s soon a s m ixing r e a c h e d a com­ b u s t i b l e c o n c e n t r a t i o n , b u r n in g w ould i n v a r i b l y s t a r t . A lso , 51 & F igu re 11. I l l u s t r a t i n g tne 3ocond :nodif i c a t i o n of tne F rostguard. i 52 r e g a r d in g t h e v a p o r t e m p e r a t u r e , i t must b e r e a l i z e d t h a t b ecau se o f th e arrangem ent of th e c o i l s f o r v a p o riz in g th e f u e l , th e r e w i l l su re ly be su p e rh e a tin g of th e f u e l vapor d u r in g p a r t o f t h e o p e r a t i o n ; t h i s was fo u n d t o b e t r u e by a c t u a l t e m p e r a t u r e m e asu rem e n ts ( P . 4 5 ) . T h erefo re th e a i r - f u e l v a p o r m i x t u r e w i l l b e above i t s i g n i t i o n t e m p e r a tu r e even a f t e r c o n s i d e r a b l e a i r h a s b e e n added; a t l e a s t , a f t e r enough h a s b e e n added t o p ro d u c e a c o m b u s tib le m i x t u r e . T h ir d m o d i f i c a t i o n . The f a c t t h a t b u r n in g to o k p l a c e w ith in each o f th e e x p e rim e n ta l i n s p i r a t o r s ru le d out t h i s a p p ro a c h a s a l i k e l y im provem ent t o t h e e x i s t i n g b u r n e r . R e a l i z i n g t h e a d v e r s e e f f e c t t h a t t h e wind h a s i n r e ­ d u c in g t h e c a p a c i t y o f t h e u n i t , i t seemed a d v i s a b l e t o p o s i t i o n w ind d e f l e c t o r s o r sco o p s w hich w ould t a k e c a r e o f a r e a s o n a b l e v e l o c i t y r a n g e o f c o n tin u o u s w in d . However, g u s ty c o n d i t i o n s would s t i l l h a v e t h e e f f e c t o f u p s e t t i n g s t a b l e o r e q u i l i b r i u m b u r n in g s i n c e g u s ty w ind c o n d i t i o n s had b e e n found t o re d u c e t h e a i r s u p p ly r e q u i r e d f o r a s u it a b le r a t e of b u rn in g . T h is c o n d i t i o n lo w e r e d t h e fla m e te m p e r a tu r e w h ich r e s u l t e d i n in c o m p le te v a p o r i z a t i o n o f t h e f u e l f o r t h a t p r e s s u r e ; t h u s , c a u s in g t h e b u r n e r t o go o u t u n l e s s n e c e s s a r y p r e s s u r e a d j u s t m e n t s w ere made. I t was. b e l i e v e d t h a t t h i s f a c t o r c o u ld b e c o r r e c t e d by s u r ro u n d in g t h e v a p o r i z i n g c o i l w ith a c e ra m ic w hich would h o ld t h e h e a t 53 ancl g i v e s u f f i c i e n t th e r m a l i n e r t i a t o c o r r e c t f o r t h e f l u c t u a t i o n s i n t h e flam e t e m p e r a t u r e cau sed by t h e g u s ty wind c o n d i t i o n s . T h is i d e a o f p r o v id in g t h e r m a l i n e r t i a was t a k e n i n t o c o n s i d e r a t i o n and t h e u n i t was m o d if ie d a s i l l u s t r a t e d i n F ig . 1 2 . I n a d d i t i o n , w ind d e f l e c t o r s w ere p o s i t i o n e d a t t h e to p and b o tto m o f t h e u n i t t o o f f s e t t h e e f f e c t o f c o n tin u o u s w ind upon t h e a i r su p p ly f o r co m b u stio n . The m o d if ie d u n i t v/as t e s t e d and t h e f o l l o w i n g d a t a a r e t y p i c a l o f th e o p e r a t i n g c h a r a c t e r i s t i c s : A ir t e m p e r a t u r e Wind c o n d i t i o n — 15 MPH 5 8 ° F ., H u m id ity 50/t v a r i e d i n v e l o c i t y b etv/een 5 and F u e l co nsu m p tio n ---- 1 2 .5 g a l l o n s / h o u r F u e l v a p o r t e m p e r a t u r e ---- 6 7 0°F . (th e rm o c o u p le ) E x h au st f l u e g a s t e m p e r a t u r e ---- 2100°F. S u rface te m p e r a tu r e 1450°F . 5 0°F . (th e rm o c o u p le ) (" te m p il-stic k s" ) E x ce ss a i r f o r co m b u stio n ---- 2 5 # ( o r s a t a n a l y s i s ) The r e s u l t s o f t h i s m o d i f i c a t i o n showed a d e c id e d im provem ent i n t h e b u r n e r . The b u r n in g o f 1 2 .5 g a l l o n s o f f u e l p e r h o u r to o k p l a c e c o m p le te ly w i t h i n t h e u n i t p r o p e r y SCALE; - >^"= / Showing the p o s i t i o n of the oeramic m a t e r i a l t o s t a b i liz e the burner f o r the Frostguard. 55 w hich was much b e t t e r t h a n t h e c a p a c i t y o f t h e o r i g i n a l u n i t . T h is r e s u l t e d i n a h i g h e r s u r f a c e t e m p e r a t u r e —g iv in g a con­ s i d e r a b l e i n c r e a s e i n t h e t o t a l e m is s iv e power o f t h e u n i t . D u rin g t h e i n t e r v a l s o f g u s ty w ind t h e b u r n in g became somewhat i n c o m p l e t e . However, i n a l l c a s e s t h e v a p o r i z a t i o n o f t h e f u e l g a v e n o e v id e n c e o f b e in g a f f e c t e d an d t h e b u r n e r would r e g a i n i t s e q u i l i b r i u m a s so o n a s t h e wind d ro p p e d t o i t s n o rm a l v e l o c i t y and a l lo w e d t h e p r o p e r i n t a k e o f a i r f o r co m p lete co m b u stio n .. D isc u ssio n o f r e s u l t s The r e q u ir e m e n t t h a t t h e F r o s t g u a r d o p e r a t e s a t i s f a c t o r i l y u n d e r a wide v a r i a t i o n i n w e a th e r c o n d i t i o n s im posed a d i f f i ­ c u l t p ro b le m i n c o n s i d e r a t i o n o f t h e t y p e o f b u r n e r em ployed. The p r e s s u r e h e a t - v a p o r i z i n g t y p e b u r n e r , o p e r a t i n g on. k e r o s e n e , h a s b een fo u n d t o b e c o m p a r a tiv e ly e r r a t i c even u n d e r c o n s t a n t b u r n in g c o n d i t i o n s , such a s e x p e r i e n c e d i n s i d e a b u ild in g . The u s e o f t h i s t y p e o f b u r n e r o u t i n t h e w e a th e r i s a f a r removed c o n d i t i o n from t h e more o r l e s s i d e a l con­ d i t i o n i n s i d e an e n c l o s u r e . little F or t h i s r e a s o n t h e r e seemed j u s t i f i c a t i o n f o r c o n s i d e r i n g m o d i f i c a t i o n s w hich g a v e o n ly m a rg in a l im provem ents a t optimum c o n d i t i o n s f o r b u r n in g •. 56 The m o d i f i c a t i o n s t r i e d and t e s t e d w ere fo u n d e d on t h e f o l l o w i n g two p r i n c i p l e s : (1 ) f a c i l i t a t i n g b e t t e r a i r - f u e l v a p o r m ix in g b e f o r e b u r n i n g s t a r t s ; and (2 ) a i d i n g t h e v a p o r i z a t i o n o f t h e f u e l by a d d in g th e r m a l i n e r t i a t o o f f s e t t h e l u l l s i n t h e b u r n i n g r a t e a s a r e s u l t o f g u s t y wind con­ d itio n s . The f i r s t tw o m o d i f i c a t i o n s w ere a t t e m p t s a t p r i n c i p l e number one i n t h a t a n i n s p i r a t o r - m i x e r was p l a c e d r e l a t i v e t o t h e f u e l j e t t o draw a i r i n by t h e v e n t u r i a c t i o n o f t h e a r r a n g e m e n t. T h is f a i l e d d ue t o t h e f u e l i g n i t i n g w i t h i n t h e c o n f i n e s o f t h e i n s p i r a t o r w hich g r e a t l y r e d u c e d th e a i r drawn i n . T h is was more o r l e s s s u s p e c te d upon l e a r n i n g t h a t t h e i g n i t i o n t e m p e r a t u r e o f k e r o s e n e was 5 65 °F . The l a s t t e m p e r a t u r e was m e asu red and found t o b e 670°F . w hich w ould i n d i c a t e t h a t t h e v a p o r was s u p e r h e a t e d and t h u s more su b je c t to p r e - ig n itio n . I t i s p o s s i b l e t h a t , th r o u g h p r o p e r d e s i g n and a d j u s tm e n t, t h e i g n i t i o n o f t h e f u e l v a p o r c o u ld b e d e la y e d u n t i l a f t e r p a s s i n g th r o u g h t h e i n s p i r a t o r ; h o w ev er, t o make t h i s p r i n c i p l e work s a t i s f a c t o r i l y f o r an a p p r e c i a b l e v a r i a t i o n i n t h e w e a th e r c o n d i t i o n s seems h i g h l y i m p r a c t i c a l . The t h i r d m o d i f i c a t i o n , w hich e x e m p l i f i e d t h e a d v a n ta g e s I 57 of t h e a d d i t i o n a l t h e r m a l i n e r t i a t h r o u g h t h e u s e o f c e ra m ic , o f f e r s an e c o n o m ic a l and p r a c t i c a l m ethod f o r im p ro v in g t h e s t a b i l i t y o f o p e r a t i o n and t h e t o t a l e m i s s i v e power o f t h e F ro stg u ard . I n c o n j u n c t i o n w i t h t h e a i r scoop and d e f l e c t o r a t t h e b o tto m and t o p r e s p e c t i v e l y , t h i s in n o v a t i o n was fo u n d t o i n c r e a s e t h e s u r f a c e t e m p e r a t u r e by a t l e a s t 100°F . and a llo w e d t h e u n i t t o o p e r a t e s a t i s f a c t o r i l y u n d e r a c o n tin u o u s v/ind o f 5 HPK w ith f l u c t u a t i o n s a s h i g h a s 15 MPH. 58 S t u d i e s t o D evelop a H ig h C a p a c ity Won-pov;ered L iq u id P e tr o le u m F u e l B u r n e r The v a r i o u s f i e l d t e s t s o f t h e F r o s t g u a r d p ro v e d t h a t i n f r a r e d e n e rg y would p r o t e c t v e g e t a t i o n fro m f r o s t damage i f t h e i n t e n s i t y was s u f f i c i e n t l y h i g h . The r e q u i r e d magni­ t u d e o f t h i s i n t e n s i t y d ep end s on t h e minimum a i r t e m p e r a t u r e , t h e accom panying w e a t h e r c o n d i t i o n s , and t h e ty p e o f v e g e ­ ta tio n to be p ro te c te d . F or t h e f r e e z i n g c o n d i t i o n s most l i k e l y t o b e e n c o u n t e r e d d u r in g t h e tim e when c r o p s a r e v u l n e r a b l e , an d f o r t h o s e p l a n t s w hich h a v e t h e i r f o l i a g e v /e ll ex p o sed , such a s s t r a w b e r r i e s , to m a to e s , e t c . ; t h e r e q u i r e d r a d i a t i o n was d e te r m in e d t o b e b e tw e e n n i n e and t e n BTU's p e r h o u r p e r s q u a re f o o t —m easured p e r p e n d i c u l a r t o th e d ii'e c ti o n of th e r a d i a t i o n . The F r o s t g u a r d g e n e r a l l y m a i n t a i n s t h i s i n t e n s i t y a t s e v e n ty f e e t from t h e u n i t . S in c e r e f l e c t o r s o f p r a c t i c a l l e n g t h and sh a p e s do n o t o f f s e t a p p r e c i a b l y t h e d e c r e a s e i n i n t e n s i t y w ith d is ta n c e ( t h i s r e l a t i o n s h i p i s a c c u r a te ly e x p r e s s e d by t h e I n v e r s e S q u are Law o f R a d i a t i o n from a p o i n t s o u r c e ) , t h e r e i s a n e x c e s s o f en e rg y im p in g in g upon th e v e g e ta tio n w ith in th e c i r c l e o f a se v e n ty -fo o t ra d iu s , w ith t h e v e g e t a t i o n i n c l o s e t o t h e u n i t r e c e i v i n g en e rg y g r e a tly in excess of th a t re q u ire d f o r safe p r o te c tio n . 59 Of c o u r s e , t h e e f f e c t i v e d i s t a n c e o f s e v e n ty f e e t c o u ld be in c re a se d by b u ild in g th e u n i t s l a r g e r or in c re a s in g th e s u r f a c e t e m p e r a t u r e ; h o w ev e r, t h i s w ould n e c e s s a r i l y i n c r e a s e t h e a l r e a d y e x c e s s e n e rg y f o r c l o s e r v e g e t a t i o n . T h is would s u r e l y make t h e a p p l i c a t i o n o f t h i s u n i t q u e s t i o n a b l e from an ec o n o m ic a l s t a n d p o i n t , ev en f o r t h e h i g h e r - v a l u e d c r o p s . The a l t e r n a t i v e was t o c o n s i d e r s m a l l e r u n i t s (re d u c e d e m is s iv e po w er) sp aced c l o s e r t o g e t h e r . T h is i s t h e s o l u t i o n u se d by i l l u m i n a t i o n e n g i n e e r s i n o r d e r t o a c c o m p lis h s a t i s ­ f a c t o r y l i g h t d i s t r i b u t i o n w here r e f l e c t o r s a r e n o t p r a c t i c a l . However, t o make u s e o f s m a l l e r u n i t s r e q u i r e s t h a t t h e i n i t i a l m a in te n a n c e and o p e r a t i n g c o s t b e p r o p o r t i o n a l l y red u ce d . O b je c tiv e The smudge p o t s a n d s o - c a l l e d o r c h a r d h e a t e r s w h ic h a r e p r e s e n t l y u s e d i n t h e c i t r u s f r u i t a r e a s a r e one answ er t o t h e u s e o f s m a ll b u r n e r u n i t s f o r f r o s t c o n t r o l . (As a f a c t o f h i s t o r i c a l i n t e r e s t t h e s e same u n i t s w ere u s e d i n M ich ig an d u r i n g t h e t w e n t i e s ) . These h e a t e r s u n q u e s t i o n a b l y a r e a s o u rc e o f c o n s i d e r a b l e i n f r a r e d en e rg y i n a d d i t i o n t o th e s e n s ib le h e a t tr a n s f e r r e d to th e a i r . They h a v e b e e n p ro v e n t o b e a n e f f e c t i v e f r o s t c o n t r o l m e a s u r e . Trie 60 g r e a t e s t o b je c tio n to th e u se of th e se h e a te r s , p a r tic u la r ly i n t h e c i t r u s a r e a s o f C a l i f o r n i a , i s t h a t t h e g e n e ro u s amount o f smoke g i v e n o f f c o n ta m in a te s h o u s e h o ld s i n t h e s u r r o u n d i n g u r b a n a r e a s , w hich a r e g e n e r a l l y l o c a t e d i n t h e v a lle y s. T h is f a c t o r d o e s n o t a p p e a r t o b e o f p rim a ry im p o r ta n c e i n M ic h ig a n due t o t h e a d v a n ta g e o f more l e v e l to p o g r a p h y and t h e w ide s e p a r a t i o n o f t h e farm an d u r b a n areas. H ow ever, t h e smoke c o n t a m i n a t i o n would a f f e c t t h e co m m ercial v a l u e o f some c r o p s . O th er c i t r u s a r e a s h a v e fo u n d t h e smudge p o t and o r c h a r d h e a te r i n s u f f i c i e n t a s p r o te c tio n a g a in s t th e o cc asio n al c o ld w ind-blovjn f r e e z e s an d f o r t h i s r e a s o n f a r m e r s a r e n o t t o o a n x i o u s t o s t o c k them a s a f r o s t c o i i t r o l m e a su re . From t h i s d i s c u s s i o n i t i s o b v io u s t h a t any d ev e lo p m e n ts w i l l h a v e t o b e a t l e a s t an im provem ent o v er t h e e x i s t i n g sm a ll-ty p e h e a te r s . Im provem ents v/hich r e d u c e t h e e x c e s s i v e amount o f smoke l i b e r a t e d w i l l s u r e l y b e welcomed. A ls o , any means o f i n c r e a s i n g t h e i n f r a r e d e m is s iv e power o f sm a ll u n its w ill in c re a se t h e i r e ffe c tiv e n e s s fo r f r o s t co n tro l under a l l c o n d itio n s . Hie o b j e c t o f t h i s i n v e s t i g a t i o n was t o d e v e lo p a nonuow ered b u r n e r o f s m a ll s i z e w hich g a v e a r a d i a t i o n i n t e n s i t y 61 o f 10 B T U /f t^ /H r . a t 25 f e e t , b u r n in g no more t h a n 1 .5 g a l l o n s o f k e r o s e n e p e r h o u r w ith l e s s t h a n one gram o f smoke p e r m in u te . P ro c e d u re The p r im a r y r e q u i r e m e n t was t o d e s i g n a k e r o s e n e b u r n e r w hich w ould a c c o m p lis h t h e above s p e c i f i c a t i o n s . I t may a p p e a r fro m a c a s u a l o b s e r v a t i o n t o b e a r a t h e r sim p le p ro b lem ; h ow ever, a f t e r a few a t t e m p t s , i t became c e r t a i n t h a t f a i l u r e s w e re t h e r u l e i n s t e a d o f t h e e x c e p t i o n . It i s t r u e t h a t t o i n c r e a s e t h e o u tp u t o r r a t e o f b u r n in g o f a l i q u i d f u e l b u r n e r r e q u i r e s o n ly t h a t more f u e l b e t u r n e d on, f o r t h e l i g h t e r f r a c t i o n s w i l l b u rn r e a d i l y and p e r ­ p e tu a te an e v e r in c re a s in g r a t e o f b u rn in g . However, a t t h e same tim e t h e r e w i l l b e a g r e a t e r i n c r e a s e i n t h e smoke o u tp u t. A ls o , i t h a s b e e n p ro v en th r o u g h t h e v a r i o u s t y p e s o f c o m m e rc ia lly a v a i l a b l e b u r n e r s , t h a t v a p o r i z i n g , e i t h e r t h e r m a l l y or m e c h a n i c a l l y , i n c o m b in a tio n wTi t h a b l a s t o f a i r fro m a n e x t e r n a l l y pow ered f a n w i l l f a c i l i t a t e c l e a n e f f i c i e n t b u r n i n g a t p r a c t i c a l l y any ch osen r a t e . T h is , h o w ev er, i s f a r removed fro m t h e r e q u i r e m e n t s t h a t n o pov/er s o u r c e b e u s e d and t h a t t h e c o n d i t i o n s u n d e r w hich t h e b u r n e r wri l l o p e r a t e a r e s u b j e c t t o wide v a r i a t i o n s . 62 The problem i s a l s o c o m p lic a te d b y h a v in g t o i n c o r p o r a t e th e req u ire m e n t f o r p ro p e r d i s t r i b u t i o n of th e g e n e ra te d r a d ia n t en erg y . T h is means t h a t t h e s u r f a c e w hich i s t o p ro d u c e t h e r a d i a t i o n m ust b e s i z e d , sh a p e d , a n d h e a t e d so t h a t t h e b e s t p r a c t i c a l d i s t r i b u t i o n o f t h e r a d i a n t e n e rg y can b e a c c o m p lis h e d w i t h t h e l e a s t r e f l e c t o r c o s t . B ased on t h e s e c o n s i d e r a t i o n s , i t was a d v i s a b l e t o con­ s t r u c t b u r n e r d e s i g n s w h ich seemed t o o f f e r tii e g r e a t e s t p o s s i b l e ch a n ce t h a t t h e l i q u i d f u e l would b e v a p o r i z e d , m ixed w i t h s u f f i c i e n t a i r , an d t h e n b u r n e d w ith t h e g r e a t e s t ^ p o s s i b l e e f f i c i e n c y w i t h a minimum o f smoke f o r m a t i o n . O ther th a n s t u d y i n g t h e b a s i c r e q u i r e m e n t s f o r b u r n in g a f u e l o f known p h y s i c a l and c h e m ic a l p r o p e r t i e s , t h i s was a t r i a l and e r r o r method o f d e v e lo p m e n t. S e v e r a l d i f f e r e n t b u r n e r s w ere b u i l t a n d i n o r d e r t o f a c i l i t a t e a c o m p a r a tiv e t e s t o f t h e s e b u r n e r s and t o stu d y t h e r e l a t i v e a d v a n ta g e s o f s u b s e q u e n t m o d i f i c a t i o n s on e a c h b u r n e r , a t e s t i n g a rra n g e m e n t v;as a s se m b le d w hereby con­ t r o l l e d c o n d i t i o n s c o u ld b e m a i n t a i n e d . In a d d itio n to a f f o r d i n g a c o m p a r a tiv e t e s t t o en hance d e v e lo p m e n t, t h e s t a n d a r d t e s t p r o v i d e d a b s o l u t e d a t a w hich e n a b le d an e v a lu ­ a tio n o f th e b u rn er f o r f i e l d a p p lic a tio n s . 63 F ig . 1 3 . A rrangem ent f o r T e s t i n g N on-pow ered L iq u id P e tr o le u m B u r n e r s . The co m p lete t e s t i n g a rra n g e m e n t i s i l l u s t r a t e d i n F i g . 15. m i s i s e s s e n t i a l l y an ex h au st s ta c k w ith th e n e c e ss a ry a t t a c h m e n t s a n d o u t l e t s t o a f f o r d a co m p lete a n a l y s i s o f t h e e x h a u s t g a s e s from e a c h o f t h e s e v e r a l b u r n e r s t e s t e d . T h is i n c l u d e d a m easure o f t h e c o m p o s itio n o f t h e g a s e s v/ith a 64 c o n v e n t i o n a l o r s a t ; e x h a u s t g a s t e m p e r a t u r e w i t h a ch ro m e la lu m e l th e r m o c o u p le ; and f i b e r g l a s s f i l t e r s f o r c a t c h i n g t h e smoke w hich g a v e a m e a s u re o f t h e t i m e r a t e o f smoke l i b e r ­ a tio n . To a c c o m p lis h t h e l a t t e r , t h e e x h a u s t s t a c k was b r a n c h e d i n t o two s e p a r a t e p i p e s w i t h p r o v i s i o n s f o r i n s e r t i n g f i b e r g l a s s f i l t e r p a c k s a c r o s s e a c h o f t h e b r a n c h p i p e s , and w ith t h e u s e o f a f l u e d i v e r t e r , t h e e x h a u s t g a s e s w ere a llo w e d t o p a s s t h r o u g h e i t h e r o f t h e f i l t e r s f o r a m easured i n t e r v a l of tim e . T h is a r r a n g e m e n t p r o v e d i n a d e q u a t e f o r an a c c u r a t e a b s o l u t e m easurem ent o f t h e smoke g i v e n o f f ; h o w ev er, an a p p r o x i m a t i o n was p o s s i b l e w h ich a l lo w e d a r e l a t i v e com­ p a riso n fo r t h i s fe a tu re of th e b u rn e rs. The d r a f t was in d u c e d by b o th t h e chimney e f f e c t and a su c tio n fa n . T h is f a n a i d e d i n sm o oth ing o u t v a r i a t i o n s , and i n c o n j u n c t i o n w ith t h e d r a f t r e g u l a t o r o r b a l a n c e r , i t was p o s s i b l e t o m a i n t a i n a v e r y n e a r l y c o n s t a n t d r a f t o f 0.?." H2 0 . The r a d i a n t e n e rg y d i s t r i b u t i o n was d e te r m in e d w ith a c a l i b r a t e d t h e r m o p i l e a t t h e end o f a s e v e n - f o o t arm w hich was p i v o t e d a t t h e c e n t e r - l i n e o f t h e r a d i a t i n g s u r f a c e , F ig . 1 4 . A t t h e p i v o t e d end a p o i n t e r moved on a c a l i b r a t e d a r c t o g i v e t h e a n g u l a r p o s i t i o n o f t h e t h e r m o p i l e above and belo w t h e h o r i z o n t a l . 65 F ig . 14. A p p a r a tu s f o r M easu rin g t h e R a d ia n t E nergy D i s t r i b u t i o n fro m H e a t e r U n i t s . The f u e l c o n su m p tio n r a t e was m e asu red d i r e c t l y by h a v in g t h e f u e l c o n t a i n e r r e s t i n g on s e n s i t i v e p l a t f o r m s c a l e s (2 o z. p e r d i v i s i o n ) . The r e s u l t s fro m t h i s t e s t a rra n g e m e n t c o u ld b e d u p l i ­ c a t e d v jith s u f f i c i e n t a c c u r a c y ; su c h t h a t , w i t h t h e e x c e p ti o n o f t h e smoke m e asu rem e n t, t h e d a t a a f f o r d a m e asu re o f t h e a b s o l u t e v a l u e s a s w e l l a s g i v i n g a r e l a t i v e co m p ariso n f o r 66 th e d if f e r e n t b u rn e rs . The b u r n e r s w e re n o t e d t o h a v e a h i g h e r r a t e o f f u e l co n su m p tio n ( a p p r o x im a t e ly a tw e lv e p e r c e n t i n c r e a s e ) when b u r n in g i n d o o r s u n d e r t h e t e s t i n g a p p a r a t u s a s compared t o f r e e b u rn in g o u ts id e th e b u ild i n g . The 0 .2 " HgO d r a f t t h e b u r n e r s e x p e r i e n c e d u n d e r t e s t i s somewhat h i g h e r t h a n t h e d r a f t p ro d u c e d by t h e same b u r n e r when o p e r a t i n g f r e e l y , and t h i s , c o u p le d w i t h a s t i l l a m b ie n t a i r t e m p e r a t u r e o f 7 0 ° F . , e x p l a i n s t h e d i f f e r e n c e i n f u e l c o n s u m p tio n . As a r e s u l t , t h e t o t a l e m i s s i v e power o f a b u r n e r u n i t was somewhat h i g h e r f o r t h e i n d o o r c o n d i t i o n s a s com pared t o o u td o o r c o n d i t i o n s . H ot a l l t h e d i f f e r e n t b u r n e r s c o n s t r u c t e d w ere t e s t e d , n o r a l l th e t e s t s reco rd ed in t h i s p ap e r. A co n sid e ra b 3 .e p a r t o f t h e work was c u t - a n d - t r y r e s u l t i n g i n m o d i f i c a t i o n s w hich p r o v e d t o b e o f n o a p p a r e n t v a l u e f o r t h e i n v e s t i g a t i o n o r t o b e o f no c o n seq u en c e i n f u t u r e work a l o n g t h i s l i n e . Only t h o s e u n i t s c o n s t r u c t e d a l o n g d i f f e r e n t b a s i c a r r a n g e m e n ts f o r c a r r y i n g o u t t h e p r o c e s s o f c o m b u stio n a r e r e c o r d e d h e r e i n an d t h e s e a r e b e l i e v e d t o b e d e v e lo p e d a s f a r a s p r a c t i c a l . E x i s t i n g n o n -p o w e re d l i q u i d p e tro le u m f u e l b u r n e r s The s i m p l e s t o f a l l t y p e s o f b u r n e r s u s e d f o r f r o s t 67 F ig . 1 5 . Open P o t B u r n e r s . c o n t r o l i s t h e " s m u d g e - p o t" , w hich may b e an y o p e n -to p con­ t a i n e r su c h a s a l a r d p a i l , b u c k e t , o r o t h e r i n e x p e n s i v e c o n ta in e r of s im ila r ty p e . T h is h e a t e r h a s h ad e x t e n s i v e u s e i n t h e c i t r u s a r e a s ; h o w e v e r, t h e n u i s a n c e o f t h e smoke and t h e l a b o r r e q u i r e d t o m a i n t a i n an d s e r v i c e them h a s p r a c t i ­ c a lly e lim in a te d t h e i r a p p lic a tio n . U n ite d S to v e Company o f Y p s i l a n t i , U ic h ig a n a t t e m p t e d a n im provem ent by f i t t i n g t h e to p o f t h e c o n t a i n e r w ith a s p e c i a l l i d w h ich would p r e ­ sum ably i n c r e a s e t h e b u r n i n g e f f i c i e n c y , t h u s r e d u c in g t h e smoke p ro b le m , F ig . 1 5 . F o r p u r p o s e s o f c o m p a riso n , 68 p a r t i c u l a r l y w i t h o p e n - to p c o n t a i n e r s , t h i s h e a t e r was t e s t e d a n d .th e r e s u l t s a r e g iv e n i n F ig . 1 6 . A s i m i l a r t e s t was made o f t h e b u r n i n g c h a r a c t e r i s t i c s o f a n o p e n - to p f i v e - g a l l o n p a i n t b u c k e t . The r e s u l t s o f t h i s t e s t a re g iv e n i n F ig . 17. For f u r t h e r p u r p o s e s o f c o m p a riso n , t h e " R e t u r n - S t a c k 11 o ic h a r d h e a t e r , d e v e lo p e d a t t h e U n i v e r s i t y o f C a l i f o r n i a , F i g . 1 8, was t e s t e d and t h e r e s u l t s a r e g i v e n i n F i g . 1 9 . T h is h e a t e r u s e s t h e th e r m a l s i p h o n i n g e f f e c t o f t h e s t a c k gas r e t u r n tu b e t o d i l u t e th e c o n c e n tr a tio n of f u e l v apor w i t h i n t h e bov/1 o f t h e h e a t e r . T h is d i l u t i o n r e d u c e s tli e r a t e o f f o r m a t i o n o f f r e e c a rb o n d u r i n g t h a t p a r t o f t h e b u r n in g p r o c e s s when t h e r e i s i n s u f f i c i e n t oxygen f o r com­ p l e t e b u r n in g ( 1 7 ) . Then, a s t h e d i l u t e d v a p o r p a s s e s up t h e s t a c k , t h e a d d i t i o n a l a i r r e q u i r e d i s i n t r o d u c e d th r o u g h lo u v re s in th e s ta c k ; a s a r e s u l t , th e b u rn in g i s p r a c t i c a l l y c o m p le te . F ir s t t r i a l burner E f f o r t s w e re made t o a p p r o a c h t h e e f f i c i e n c y o f t h e r e t u r n - s t a c k o r c h a r d h e a t e r a n d a t t h e same tim e t o i n c r e a s e t h e b u r n in g c a p a c i t y i n o r d e r t o p r o v i d e a h i g h t e m p e r a t u r e / ■•'■/. B u r n in g r a te /' / / 7: q .v s 'G a L s / p * ^ / / S tv to tc e O u t p u t , t>£ < 5K A'N s/A * iR U T ; E / / / / / / / / _ .o 0 _• ' ’’’ \ . . ... *;____ .1\ . ' \ / i . .v . I I F ig u re 16. Burning c h a r a o t e r i s t i c s and r a d ia n t energy d i s t r i b u t i o n f o r t h e United s t o ^ e Company Orchard Heater. c W -' R A n d r/o tf J N ’ TZN SiTjg / t r / ' JO H-o y x /o \ xr\ SO &VRNIU6 /fjQTp, a<5/ G /jts/tiO; S tfo K B Outpu t , 3 - o g x -a m s / w * ■ / s v. y >* Figure 17. Burning o h a r a o t e r i s t i o s and r a d ia n t energy d i s t r i b u t i o n f o r an open-topped c o n t a i n e r . n D R A F T REGULATOR F ig u r e 18. The R e t u r n - s t a c k Orchard :Ieater developed at the U n i v e r s i t y o f C a l i f o r n i a . 72 ' —I /SO' 1 ^ 'i. f. . P / zdz/ jt / o p iN T E H S iry /o *7o /BUPN/P6 R ate , x / o ~?A t i ' . \ JO / ; -SO -°0 S-54- Gals/ w ** S m o P E O u t p u t , o-SS c p a m s / m / H’ E X H / 9 U S T G P S TEM P. / 4 - 7 0 ° P £ K C £ 5 5 / 4 /£ P o p C om a . J O V o 0° \ F igu re 19. Burning c n u r u c t e r i s t i c s and rad ian t energy d i s t r i b u t i o n f o r the R e t u r n - s t a c k Orchard Heater. 73 i i^jjk aj F ig . 20. J , trim i.l w ,. .c . F i r s t T ria l B urner, s u r f a c e a s a s o u r c e o f i n f r a r e d e n e rg y . R e a liz in g th e need f o r v a p o riz in g th e f u e l in th e p resen ce o f s u f f i c i e n t a i r t o a l l o w a d e q u a te i n t e r m i x i n g or a e r a t i o n , i n a l a r g e p a r t b e f o r e b u r n in g h a s p r o g r e s s e d a p p r e c i a b l y , t h e f i r s t a t t e m p t was a d e s i g n w h ich would p re su m a b ly s a t i s f y t h i s c o n d itio n . F i g . 20 g i v e s a n o v e r a l l v iew o f t h e b u r n e r and t h e 74 f o l l o w i n g d i s c u s s i o n s h o u ld make c l e a r t h e i d e a s w h ich w ere ta k e n u n d e r c o n s i d e r a t i o n a t t h a t tim e . The b o tto m p o t ­ shaped s e c t i o n w i l l be r e c o g n i z e d a s t h e v a p o r i z i n g bowl o f a s t a n d a r d b u r n e r u s e d e x t e n s i v e l y f o r d o m e s tic h e a t i n g , e i t h e r w i t h o r w ith o u t a f a n . F o r t h e a p p l i c a t i o n a t hand t h i s p a r t of th e u n i t fu rn is h e d th e h e a t to v a p o riz e th e b u lk o f t h e f u e l from a s p e c i a l pan l o c a t e d up i n t h e main p a r t o f t h e co m b u stio n cham ber. A i r i s i n t r o d u c e d th r o u g h t h e s i d e s o f b o t h t h e b o tto m s e c t i o n and t h e co m b u stio n cham ber. fig u re . T hese o p e n in g s a r e i l l u s t r a t e d i n t h e accom panying As n o t e d , t h i s u n i t r e q u i r e s t h e f u e l t o b e i n a s e p a r a t e c o n t a i n e r e l e v a t e d a t l e a s t t h r e e f e e t and f e d i n th r o u g h a f l o a t v a l v e i n o r d e r t o m a i n t a i n a c o n s t a n t r a t e o f f u e l f lo w . The e x t r a p a r t shown i n t h e f i g u r e i s a n e n c lo s e d con­ t a i n e r , e x c e p t f o r a s m a ll opening a t t h e t o p , w h ich was t r i e d i n s i d e t h e chamber a s t h e c o n t a i n e r f o r v a p o r i z i n g t h e b u lk of t h e f u e l . T h is was an a t t e m p t t o p r e v e n t b u rn in g on t o p o f t h e l i q u i d f u e l ; how ever, i t was p ro v e n t h a t t h e open d i s h - t y p e c o n t a i n e r was b e t t e r f o r t h i s p u r p o s e . The t e s t r e s u l t s a r e g i v e n i n F ig . 21. These d a t a show a c o m p a r a tiv e ly h i g h r a t e o f b u r n in g ( 1 .8 g a l l o n s / h r . ) w hich s u p p o r t s a h ig h e m i s s i v e power f o r t h e r a d i a t i n g s u r f a c e . 75 /SO0 -z $ 0* & UR///a/ 6 t f / i r e / / . S Z 6 >?is,//v/?. sM O K C Ou t p u t , / . * /T X f/J U S T < 5 js TEM P.f / J Z O a/ r E x c e s s ^ / e r o e Co m g „ S z % o* Figure 2 1 . Burning c h a r a c t e r i s t i c s and r a d ia n t energy d i s t r i b u t i o n f o r the F i r s t T r i a l Burner. f 76 F ig . 22. Second T r i a l B u r n e r . The smoke o u tp u t o f 1 . 4 g ra m s/m in . i s n o t n e c e s s a r i l y h i g h f o r t h e r a t e o f b u r n i n g , b u t c o n s i d e r a b l y h i g h e r th a n t h a t f o r th e R e tu rn -s ta c k h e a te r . N e v e r t h e l e s s , f o r m ost a p p l i ­ c a t i o n s t h e o b j e c t i o n t o t h e smoke p l u s t h e c o m p a r a tiv e ly h ig h m a n u f a c tu r in g c o s t w ould p r e v e n t i t s u s e . Second t r i a l b u r n e r The seco nd t r i a l b u r n e r u n i t i s i l l u s t r a t e d i n F ig . 22, an d t h e b a s i c p r i n c i p l e i s t o droD t h e f u e l fro m t h e to p down 1 77 th r o u g h t h e i n s i d e o i t h e s t a c k an d co m b u stio n chamber t o s t r i k e a t a r g e t t h r e e i n c h e s abo ve t h e b a s e o f t h e u n i t . T here a r e a i r h o l e s a lo n g t h e s l o p i n g p a r t o f t h e chamber a s w e l l a s i n t h e b o tto m a n d s i d e s o f t h e lo w e s t s e c t i o n ; t h e id e a b e in g t o h a v e t h e f u e l v a p o r i z e a s i t f e l l th ro u g h t h e i n t e n s e h e a t o f t h e e n c l o s u r e , a n d a t t h e same tim e p r o v id e s u f f i c i e n t l y d i s t r i b u t e d a i r to b rin g about e f f i c i e n t b u rn in g . S in c e t e m p e r a t u r e i n c r e a s e s t h e r a t e o f a co m b u stio n r e a c t i o n , t h i s a r r a n g e m e n t a p p a r e n t l y h a s m e r i t a s a means o f i n c r e a s i n g th e r a te o f b u rn in g . F i g . 23 i n c l u d e s t h e t e s t d a t a f o r t h i s u n i t and a g a i n t h e b u r n in g r a t e (1 .5 g a l l o n s / h r . ) i s c o m p a r a tiv e ly h ig h w hich i s r e f l e c t e d i n t h e r a d i a t i o n i n t e n s i t y . However, t h e smoke o u t p u t i s i n c r e a s e d o v e r t h e f i r s t t r i a l b u r n e r even th o u g h t h e b u r n i n g r a t e i s l e s s . I t was o b s e rv e d t h a t heavy o r l a r g e p a r t i c l e s o f c a rb o n form ed a lo n g t h e d e s c e n d in g s tre a m o f l i q u i d th r o u g h o u t t h e e n t i r e d r o p . T h is i n d i c a t e s , a h ig h c o n c e n t r a t i o n o f f u e l v a p o r i n t h e a b s e n c e o f a d e q u a te a i r w hich e v i d e n t l y a c c o u n t s f o r t h e i n c r e a s e i n smoke o u tp u t. I t i s of i n t e r e s t t h a t th e r a d ia tio n i n t e n s i t y of t h i s u n i t is co n sid e ra b ly h ig h e r th a n f o r th e R e tu rn -s ta c k h e a te r even th o u g h t h e i r b u r n i n g r a t e s a r e i d e n t i c a l . I n c o n n e c ti o n .-A x ^. /x’A otATto*/rtrertstry J r/% -l r~ Ks L. B U ftN tN 6 K A T E f A S S M o ke O u tp u tt /. 6 6 /jL S .A V 6 P /W S /* itn - E A H ytU S T G /7S T E H # , AZ S O 0/ ? . / ? XCESZ A l/P /T o p C o p fS , Z O f o A- / VV /\ • \ // / ■ / .1 Figure 2 6 . Darning c h a r a c t e r i s t i c s . and r a d ia n t energy d i s t r i b u t i o n f o r the second T r i u l Burner. 79 w ith t h i s , i t was fo u n d t h a t t h e e x h a u s t g a s t e m p e r a t u r e was h ig h e r f o r th e R e tu rn -sta c k h e a te r 1 2 8 0 ° F .) . (1470°F. compared t o The e v id e n c e i n d i c a t e s t h a t d e l a y e d b u r n in g was ta k in g p la c e in th e case of th e R e tu rn -s ta c k ty p e , a t l e a s t more so t h a n t r i a l b u r n e r No. 2; t h i s r e d u c e s t h e maximum flam e t e m p e r a t u r e w i t h i n t h e com b ustion cham ber s i n c e a s i g n i f i c a n t p a r t of t h e h e a t i s l i b e r a t e d o u ts id e th e c o n fin e s of t h e u n i t . As a r e s u l t , l e s s h e a t i s t r a n s f e r r e d t o the. s u rfa c e to be d isc h a rg e d a s r a d i a n t en erg y . The R e t u r n - s t a c k h e a t e r was e v i d e n t l y o p e r a t e d c o n s i d e r a b l y abo ve i t s r a t e d c a p a c i t y w h ile b u r n e r No. 2 d i d a f a i r l y c o m p le te job o f b u r n in g w i t h i n t h e b u r n e r p r o p e r . T h ir d t r i a l b u r n e r As an e f f o r t t o s o lv e t h e smoke p ro b le m a s s o c i a t e d w ith n on-pow ered b u r n e r d e s i g n s , t h e p r i n c i p l e o f t h e o ld f a s h i o n e d k e r o s e n e co o k in g s to v e was b o rro w e d . T h is w i l l b e r e c o g n i z e d from F i g . 24 by t h e c o n c e n t r i c r i n g s o f p e r f o r a t e d s h e e t s t e e l w hich make up t h e c h a n n e ls f o r e f f e c t i n g b u r n in g c o n d itio n s. P i e c e s o f f i r e b r i c k w ere c u t t o t h e p r o p e r shape and p l a c e d a t t h e b o tto m o f t h e s e c h a n n e ls t o s e r v e a s a w ic k f o r t h e k e r o s e n e w h ich was m a in ta in e d a t a c o n s t a n t l e v e l by t h e f l o a t v a l v e . Hi i s a r r a n g e m e n t nrov ed t o g i v e co m p lete co m b u stio n and I 80 F i g . 24. T h ir d T r i a l B u rn e r.- t h e f la m e was n o n -lu m in o u s o r b l u e i n c o l o r w i t h v e r y l i t t l e v o lu m e - - c o n s i d e r i n g t h e r a t e o f b u r n i n g . However, s a t i s ­ f a c t o r y o p e r a t i o n was s e n s i t i v e t o wind c o n d i t i o n s an d p o s i t i o n w ith r e g a r d t o b e in g l e v e l . To a p p ro a c h a p r a c t i c a l c a p a c i t y o f h e a t l i b e r a t i o n a n u n u s u a l l y l a r g e amount o f c h a n n e l would b e n e c e s s a r y , r e q u i r i n g a h i g h m a t e r i a l and l a b o r c o s t f o r m a n u f a c tu r e ; t h u s , e l i m i n a t i n g t h i s a p p r o a c h from p r e s e n t c o n s i d e r a t i o n s i n c o n n e c ti o n w i t h t h e f r o s t c o n t r o l p ro blem . 1 81 D isc u ssio n of r e s u l t s The two m ethods o f a d d in g h e a t t o v e g e t a t i o n , d i r e c t r a d i a t i o n and c o n v e c ti o n o f s e n s i b l e h e a t , f o r i t s p r o t e c t i o n from f r o s t damage h a v e b e e n p r o v e n e f f e c t i v e . B o th a r e em ployed t o a more o r l e s s d e g r e e d e p e n d in g upon t h e h e a t s o u r c e , w e a th e r c o n d i t i o n s , and t y p e o f v e g e t a t i o n . Each h a s m e r i t o r a d v a n ta g e s o v e r t h e o t h e r ; e . g . r a d i a n t e n e rg y shows more e f f e c t d u r in g windy c o n d i t i o n s an d on lo w g ro w in g v e g e ­ t a t i o n , w h i l e b u r n e r d e s i g n s w hich r e l e a s e t h e g r e a t e r p a r t o f t h e e n e rg y th r o u g h s e n s i b l e h e a t a r e n o t on ly c h e a p e r b u t more p r a c t i c a l f o r s t i l l c o n d i t i o n s on t r e e - t y p e v e g e t a t i o n when t h e r e i s a c o m p a r a t i v e l y h ig h t e m p e r a t u r e g r a d i e n t w ith e le v a tio n . T h is i n v e s t i g a t i o n was aimed t o i n c r e a s e t h e p e r c e n t o f h e a t l i b e r a t e d th r o u g h r a d i a n t e n e rg y from s m a ll n o n -p o w e re d liq u id fu e l b u rn ers. The r e q u i r e m e n t s w ere t h a t t h i s be a c c o m p lis h e d w i t h o u t a p p r e c i a b l e smoke r e l e a s e ( l e s s t h a n 1-gram p e r m i n u t e ) , and t h a t t h e i n i t i a l c o s t b e k e p t s u f ­ f i c i e n t l y low t o a l l o w c o m p a r a tiv e ly c l o s e s p a c in g d u r in g o p e r a t i o n (10 t o 15 p e r a c r e ) . The r e s u l t s o r f i n d i n g s may b e a d e q u a t e l y summarized as fo llo w s: 1. The 11sm ud ge-po t" t y p e h e a t e r d e v e lo p e d by U n ite d 1 82 S to v e Company g a v e n o e v id e n c e o f a d v a n ta g e s o v e r any o r d in a r y o p e n -to p p e d c o n t a i n e r . The l i d d o e s slow down t h e r a t e o f b u r n i n g , b u t t h i s can b e a c c o m p lis h e d w ith a c o v e r o f any k in d . 2. The f i r s t arid seco n d t r i a l b u r n e r s had s u f f i c i e n t l y h ig h b u r n in g r a t e s t o s u p p o r t a n i n c r e a s e d r a d i a t i o n i n t e n s i t y . However, t h e y g a v e o f f c o m p a r a tiv e ly l a r g e am ounts o f smoke and would b e somewhat h i g h e r i n i n i t i a l c o s t . 3. The t h i r d t r i a l b u r n e r h a d i d e a l b u r n in g c h a r a c ­ t e r i s t i c s i n r e g a r d t o c o m p le te n e s s w i t h i n a s m a ll fla m e v olum e; h ow ever, t o a t t a i n s u f f i c i e n t h e a t r e l e a s e c a p a c i t y , an e l a b o r a t e u n i t b o t h i n s i z e and c o s t would be r e q u i r e d . A ls o , t h e b u r n i n g was fo u n d t o b e t o o s e n s i t i v e f o r t h i s a p p lic a tio n . 4. The R e t u r n - s t a c k o rc h a i'd h e a t e r was fo u n d t o m eet t h e a d v e r t i s e d s p e c i f i c a t i o n s ; t h u s , making t h i s b u r n e r v e ry u s e f u l f o r t h i s a p p l i c a t i o n i n v iew o f t h e low i n i t i a l and o p e r a t in g c o s t . The r a d i a t i o n i n t e n s i t y i s lo w e r t h a n t h a t d e s i r e d , h o w ev er, t h i s can b e o f f s e t by sp a c in g them c l o s e r t o g e t h e r w h ich i s p o s s i b l e b e c a u s e o f i t s lo w c o s t . 83 D evelopm ent o f a L i q u i f i e d P e tr o le u m Gas B u rn e r f o r t h e G e n e r a t i o n o f R a d ia n t E n erg y f o r F r o s t C o n t r o l The i n c r e a s i n g a v a i l a b i l i t y a n d com m ercial d i s t r i b u t i o n o f l i q u i f i e d p e t r o le u m g a s e s (LPG) d e f i n i t e l y p l a c e s t h i s f u e l on t h e l i s t o f p o s s i b l e s o u r c e s o f e n e r g y . I t s in h e re n t h i g h fla m e t e m p e r a t u r e , and t h e e a s e o r s i m p l i c i t y w i t h which c l e a n e f f i c i e n t b u r n in g i s a c c o m p l is h e d , malces i t e v i d e n t t h a t t h i s f u e l o f f e r s a d v a n ta g e s n o t r e a l i z e d i n o t h e r f u e l s . A ls o , s i n c e t h i s f u e l h a s a h i g h v a p o r p r e s s u r e a t n o rm a l t e m p e r a t u r e s a n d b e c a u s e o f t h e l i g h t m o le c u le s o f h y d r o ­ c a r b o n s , i t i s e a s i l y m ixed w i t h a i r t o form a n i d e a l c o m b u s tib le m i x t u r e . Hi i s r e s u l t s i n s im p le r b u r n e r s , malting t h e u s e o f s m a l l e r u n i t s p l a c e d c l o s e r t o g e t h e r e c o n o m ic a lly f e a s i b l e ; t h u s , p r o v i d i n g p r o t e c t i o n a g a i n s t more a d v e r s e c o n d itio n s of f r o s t fo rm a tio n . A ls o , t h e s m a l l e r u n i t s s h o u ld f a v o r t h e s m a ll o p e r a t o r who w i l l b e more a b l e t o s a t i s f y h i s r e q u i r e m e n t s — t h a t f o r w hich t h e l a r g e r more e x p e n s iv e u n i t s would b e i m p r a c t i c a l . The tu rn -d o w n o r v a r i a t i o n i n b u r n i n g r a t e o f an LPG b u r n e r g e n e r a l l y h a s a w ide r a n g e — fro m p r a c t i c a l l y o f f t o f u l l c a p a c i t y —w hich c a n b e c o n t r o l l e d a c c u r a t e l y an d a u t o ­ m a tic a lly . T h is a l l o w s f o r t h e a d j u s t m e n t o f t h e b u r n in g r a te to s a tis f y th e p re v a ilin g f r o s tin g c o n d itio n s; th u s, 84 a f f e c t i n g a s a v in g i n t h e f u e l con su m p tio n 'which i s e i t h e r i m p o s s i b l e o r i m p r a c t i c a l w i t h t h e l i q u i d p e tr o le u m f u e l b u rn ers. A n o th e r a d v a n ta g e i s r e a l i z e d i n t h a t t h e f u e l i s u n d e r c o n s i d e r a b l e p r e s s u r e o f i t s ov.n a c c o r d , making p o s s i b l e t h e u s e o f c e n t r a l s t o r a g e t a n k s v ;ith s m a ll p i p e s a s d i s t r i ­ b u tio n l i n e s . T h is would b e a n i d e a l a rr a n g e m e n t f o r l a r g e r a r e a s and c ro p s o f a p erm a n en t n a t u r e o r f o r t h o s e p l o t s on w hich t h e same t y p e o f c ro p i s grov.n y e a r a f t e r y e a r . The d i s a d v a n t a g e comes i n t h e c o s t o f t h e f u e l w h ich a t p re se n t p r ic e s i s c o n sid e ra b ly h ig h e r th a n th e liq u id f u e l s . T h is i s due i n g r e a t p a r t t o t h e s m a ll t o t a l amount d i s ­ t r i b u t e d and t h e s m a ll l o t s i n w hich r e t a i l e d . T h is f u e l i s b e in g lo a d e d a t t h e p r e s e n t tim e i n t h e o i l f i e l d s a t from t h r e e t o t h r e e and one h a l f c e n t s p e r g a l l o n i n t a n k c a r l o t s , w hich com pares f a v o r a b l y w i t h l i q u i d f u e l s . T h erefo re, i t i s assum ed t h a t c r e a t i n g a demand i n any p a r t i c u l a r a r e a i s t h e r e q u i r e m e n t f o r r e d u c i n g t h e c o s t ; a n d , i f an i n d i ­ v i d u a l c o n s u m e r 's demand w a r r a n t s , h e would a f f e c t a c o n s i d e r a b l e s a v in g by b u y in g i n t a n k c a r l o t s . The above comments p o i n t up t h e a d v a n ta g e s w hich LPG o f f e r s a s a p o s s i b l e f u e l v /ith w hich t o g e n e r a t e i n f r a r e d e n e rg y f o r f r o s t c o n t r o l ; and f o r c e r t a i n a p p l i c a t i o n s t h e s e a d v a n t a g e s w i l l d e f i n i t e l y o u tw eig h t h e d i s a d v a n t a g e - - c o s t . 85 F or t h i s r e a s o n work was s t a r t e d on t h e dev elop m ent o f a p r a c t i c a l p ro p a n e b u r n in g u n i t w hich would s e r v e a s a s o u r c e o f i n f r a r e d e n e rg y f o r f r o s t c o n t r o l . O b je c tiv e B e ca u se o f t h e p r e s e n t c o s t o f p ro p a n e a s d i s t r i b u t e d i n 100# c o n t a i n e r s ( a p p r o x im a te ly 5 0 ^ / g a l l o n ) , i t was a d ­ v i s a b l e t o work f i r s t on d e s i g n s w hich would a d e q u a te ly s e r v e t h e g ro w e rs o f f l o w e r s , s t r a w b e r r i e s , and o t h e r h i g h e r v a lu e d t r u c k c r o p s . Then, a s i t s u s e expanded o r a s t h e f a r m e r became c o n v in c e d o f i t s v a l u e , t h e a p p l i c a t i o n m ig h t w e l l s p r e a d t o o t h e r t y p e s o f c r o p s a s t h e f u e l c o s t was reduced. S i n c e c e n t r a l s t o r a g e t a n k s w i t h p e r m a n e n tly i n s t a l l e d f e e d l i n e s a r e e x p e n s iv e , i t was c e r t a i n t h a t t h e i n i t i a l or e x p e r i m e n ta l h e a t e r s would h a v e t o o p e r a t e i n d i v i d u a l l y a s a u n it. T h is i n d i c a t e d t h a t e a c h b u r n e r would h av e t o b e sup­ p l i e d from a t a n k a t i t s p o s i t i o n . I n d i s c u s s i n g t h i s p ro b lem w ith t h e lla n a g e r o f S h e l l O i l ’ s LPG b o t t l i n g p l a n t a t L a n s in g , L ic h i g a n , i t was l e a r n e d t h a t t h e r e t a i l e r s w ould make t h e i n s t a l l a t i o n s f o r a p p r o x im a te l y $ 6 / u n i t . T h is i n c l u d e s a p r e s s u r e r e g u l a t i n g v a l v e , two 100# c o n t a i n e r s , an d t h e n e c e ssa ry co n n e c tio n s. The m a in te n a n c e o f t h i s s e tu p would 86 b e a r e s p o n s i b i l i t y o f t h e r e t a i l e r , who would d e l i v e r t h e p r o p a n e a t oOp a g a l l o n t h e r e a f t e r . F o llo w in g t h i s e n c o u ra g in g i n f o r m a t i o n t h e o b j e c t was t o d e s i g n a h e a t e r - u n i t o f minimum c o s t w hich p r o t e c t e d s u f ­ f i c i e n t a r e a t o make t h e s e t u p a s e c o n o m ic a l a s p o s s i b l e . W ith t h e s e c o n s i d e r a t i o n s i n m ind, p l u s a know ledge o f t h e en e rg y r e q u i r e d t o p r o t e c t a g a i n s t t h e m ost l i k e l y f r o s t , t h e f o l l o w i n g s p e c i f i c a t i o n s w ere drawn up w h ic h , i f m et, would make t h i s a p p l i c a t i o n p r a c t i c a l on t h e h i g h e r v a l u e d c r o p s — even u n d e r t h e p r e s e n t r e t a i l c o s t o f p ro p a n e : 1. A h e a t e r u n i t t h a t c o u ld b e p r a c t i c a l l y s u p p o r te d e i g h t f e e t ab o v e t h e g ro u n d w hich would p ro d u c e a r a d i a t i o n i n t e n s i t y o f 9 B T U / s q . f t . / H r . a t 25 f e e t from t h e b a s e o f t h e u n i t (m easu red p e r p e n d i c u l a r t o t h e d i r e c t i o n o f p r o p a g a t i o n ) . 2. Burn l e s s t h a n 1 . 5 g a l l o n s o f p ro p an e p e r h o u r a t a p r e s s u r e l e s s th a n 26 p s i g . o. C ost n o more t h a n 85 p e r h e a t e r u n i t . 4. E a s i l y l i g h t e d an d d e p e n d a b le i n o p e r a t i o n . P ro c e d u r e Due t o t h e r e l a t i v e l y few h o u r s o f o p e r a t i o n r e q u i r e d p e r y e a r i n l l i c h i g a n and s u r r o u n d i n g a r e a s , t h e in v e s tm e n t c o s t f o r any h e a t e r u n i t i s t h e p r im a r y c o n s i d e r a t i o n . T h ere­ f o r e , t h e d e s i g n m ust be cheap i n m a t e r i e l c o s t a s w e l l a s i n I 37 01' f a b r i c a t i o n o r c o n s t r u c t i o n . s im p lic ity For t h i s r e a s o n th e m ost e f f i c i e n t d e s i g n , i n r e s p e c t t o optimum d i s t r i b u t i o n o f maximum r a d i a n t en e rg y p e r u n i t h e a t i n g v a l u e o f f u e l b u r n e d , would n o t n e c e s s a r i l y b e t h e m ost p r a c t i c a l . The abo v e r e a s o n i n g l e d t o t h e c o n c l u s i o n t h a t r e f l e c t o r s would be e m i t t e d and t h a t a r i g h t c i r c u l a r cone o f t h e p r o p e r i n c lu d e d a n g l e ( d e te rm in e d from t h e g eo m etry o f t h e r e l a t i o n ­ sh ip b e t u e e n t h e p o s i t i o n o f t h e u n i t above t h e ground an d t h e d i s t a n c e fro m i t s b a s e ) would g i v e t h e b e s t p r a c t i c a l d is trib u tio n . assumed t h a t , c4S7°F. ta in e d . To d e t e r m in e t h e s i z e o f t h i s cone i t was s i n c e t h e fla m e t e m p e r a t u r e o f p ro p a n e i s ( 1 6 ) , a s u r f a c e t e m p e r a t u r e o f 1 6 0 0 °F . c o u ld b e m ain­ T h is was c o n s id e r e d t h e maximum t e m p e r a t u r e f o r w hich ca rb o n s t e e l would have a u s e f u l l i f e . I t can b e shov.n t h a t t h e no rm al i n t e n s i t y from a u n i t a r e a o f a b la c k b o a y i s g iv e n a s a f u n c t i o n o f t h e te m p e r a t u r e o f t h e body by t h e f o llo w in g re la tio n sh ip I (2 ): = cr_T*J_ - 3 T U /f t ? / H r . 77 4 = 1 7 .5 x lG / 0 B fU /F t5 T4 ( S t e f a n - S o l t s m a n n 1s co n sta n t) g - to ta l e n issiv ity T - a b s o l u t e t e m p e r a tu r e o f b o d y , (.3 f o r o x id iz e d s t e e l s u rfa c e ) From t h i s , assum ing .3 a s t h e t o t a l e n i s s i v i t y o f a s t e e l 38 s u r i'a c e and i o r I„ = (2 5 ) 2 x 9 ( i n t e n s i t y r e q u i r e d a t one f o o t iro n : t h e s o u r c e t o g i v e a n i n t e n s i t y o i 9 B T u / F t .^ / H r . a t 25 i e e t ) , t h e r e q u i r e d c r o s s - s e c t i o n a l o r p r o j e c t e d a r e a i c r t h e cone i s g i v e n a s , __ Ac -fit _ 9 k g _______________ _ ^ y r r 2- ~ S T * € ~ / z 3 x/o~'°x Z o Z o \ . S 77 Vi'ith. t h e s e d a t a a s a b a s i s a 60° r i g h t c i r c u l a r cone n ic h a s l a n t h e i g h t o i one i o o t mas iorm ed i r o n 13 gauge h o t r o l l e d c a rb o n s t e e l . S i x t y - t h r e e 1 /4 " h o l e s v;ere sp a c e d i n che s u r i'a c e o i t h i s cone t o s e r v e a s e x h a u s t p o r t s a n a open­ i n g s i c r d i r e c t r a d i a t i o n i r o n t h e ila m e an d th e c e ra m ic p l a c e m hich c o v e rs c u e t o p o i t h e co ne. T h is d e s i g n g i v e s a p r o j e c t e d a r e a o i a p p r o x im a te l y .4 5 s q u a r e i e e t mhich i s .27 s q u a r e i e e t l e s s t h a n t h e t h e o r e t i c a l r e q u i r e m e n t . cmever, s i n c e t h e r e mas n o may o i e v a l u a t i n g t h e added e i i e c t o i t h e h o l e s i n t h e s u r i a c e , i t mas a d v i s a b l e t o con­ s t r u c t t h i s sim p le u n i t u n m il i u r t h e r e x p e r i m e n t a l e v id e n c e mould j u s t i i y l a r g e r d e s i g n s . The norm al t o t h e s u r i a c e o i t h i s cone m i l l i r e e r s e c t t h e g ro u n d a t 14 i e e t ir o n i t s base mhen t h e cone i s p o s i t i o n e d 8 i e e t h i g h . A 32 ° r i a n t c i r c u l a r cone mas i c r n e d i r o n t h e same ty p e ( 89 and w e ig h t m a t e r i a l and w ith t h e same s u r f a c e a r e a ( s l i g h t l y l e s s p r o j e c t e d a r e a ) a s t h e 60° c o n e . However, 141— 7 /3 2 " h o l e s w ere s p a c e d i n t h e s u r f a c e o f t h i s cone w hich r e p r e s e n t s 1 .7 tim e s more p o r t a r e a th a n t h a t f o r t h e 60° co n e . Each o f t h e s e co n es w ere a t t a c h e d t o i n s p i r a t o r s (# 7 0 -2 -5 5 ) made by W orth A m erican B u rn e r M a n u fa c tu r in g Company. The g a s spud o r j e t was d r i l l e d w i t h a # 56 d r i l l . A ll th e a i r f o r co m b u stio n e n t e r s th r o u g h t h e i n s p i r a t o r . As an economy m easu re a p e r f o r a t e d d i s k was p l a c e d o v e r t h e d i s ­ c h a rg e end o f t h e i n s p i r a t o r i n t h e p l a c e o f a more ex­ p e n s iv e b u r n e r t i p . F i g . 25 i l l u s t r a t e s t h e s e u n i t s and t h e m ethod f o r c o n n e c tin g t h e f u e l l i n e from t h e p r e s s u r e r e g u l a t o r t o t h e 5 /8 " s t a n d a r d g a l v a n i z e d p i p e w hich s e r v e s b o t h a s a s u p p o r t and c o n d u it f o r t h e g a s s u p p ly . D isc u ssio n o f r e s u l t s The two u n i t s w ere t r i e d and fo u n d t o o p e r a t e s a t i s ­ fa c to rily . S in c e t h e y w ere n o t t e s t e d u n d e r f r o s t c o n d i t i o n s , t h e n e x t b e s t e v a l u a t i o n w as-a—h e a t —b a l a n c e a n a l y s i s i n con­ j u n c t i o n w ith a m e a su re o f t h e r a d i a n t en e rg y d i s t r i b u t i o n v;hich i s r e c o r d e d i n F i g . 26 and F i g . 2 7 . B ased on p r e v io u s f i n d i n g s t h i s a n a l y s i s can b e i n t e r p r e t e d i n te r m s o f t h e 90 F ig . 25. E x p e r im e n ta l P ro p a n e B u r n e r U n i t s . p o s s i b l e p r o t e c t i o n t h a t may b e e x p e c te d u n d e r a c t u a l f r o s t ­ in g c o n d i t i o n s . The a i r t e m p e r a t u r e a t t h e tim e o f t h i s t e s t v;as 6 0 ° F . , c l e a r an d n o w in d . The h e a t e r u n i t s w ere t e s t e d i n s u c c e s s i o n w'ith i d e n t i c a l c o n d i t i o n s p r e v a i l i n g . The t o t a l e m is s iv e pow er and t h e r a d i a t i o n t h a t f a l l s belov/ t h e h o r i z o n t a l v/ere c a l c u l a t e d by W o h l a u r e 's method (25 ). T hese r e s u l t s a r e r e c o r d e d on t h e d a t a s h e e t s . I t is 91 - J 3 u / r n i m c * s ^ /r Y e ■ • / ■ ■ ■ • ^ .V; / ' r ^ r t s P /e r s s o # £ -'‘-gs?s/< ' ' ------- ' / > x ' ' - • N\ • / / /: / ■/ / • h roI £ /Z 0 r4 T A L fffiO W / ' X - x .'./ Y ? X ■"/ ./•• I / "■ i \ \ / - X v \ / / V , e . / 5 ° ' f . ^ T 0/4 //? /^AO/AT/on :-\A \> \ . \ / s / 3 0 •.3 v \ ✓. A \ ' \ X v ' V\ A ■ V V\ V-V-. w . \ / A ■ ,A ' \ " \ ; > , / V ■■V'X V \ . v• ■X \ \ - • Yv\ •' . • ’ VX X \ \ ! X -\ V X - X \ ' ‘ • -V X \ / \ V \ .. ; A . ; ' i • : T l t i b / A N T J M T £ r t5 /r / A T / - 0 1 v / 6 c’A I# k )X A ...* AO ,. ; : » A !a■** .. . '■ •■ -A ■• f ■ • ': \ * \ ^ A A a a V A U - X - '- 'S r--/ \ \ B T. \u' /h #v \ ' ■ ■• XT ■ A v\ /. \ > / . / ;': 'Y X X . ’■ . '£&*>/A r/ON S' ' .\ ITjFM tR' !-1/s o o *K^^ "■■/: \ 'x X . Lyj/s foe Co*..- -Co. / a s : £ 5 [h'5-& 7o ex cess Tora l ■ / - ■ j^ S ^ C A r k r / t S £ S x: '''"[ ■\ y '■ / ■\ i -/ \ . i \ N• n: Figure 26. 3urning c n a r a c t e r i a t i o a and rad ian t energy d i s t r i b u t i o n f o r the 60° type propane burner. i 92 \ - . .... .. .............................. ... £ 3 u R N ll'tG . S urface T o .T A fL / / in : ...* '. /& ? T £ Temp. : S' ^oA S P '/•£&$ °F ‘ - / ^ A P Z / f 'f / o A 3 f L o w W o x /Z O M T A L E 5 5 U/?E-■£PPS/<-, v • /5, 7 S d BTU/H&, » - , , f't ■r yti ' Vi V '^ V \ ' Vi • • ./.'I >' ..' V" • w i> M N T . /* r e t* s /w \ ■\<\<'.'i , l. ■. A r / \ - B 7 y f r 4 ( H * > ) x (Q ~ l \ s.r, 'K V/v • , I / i / \ \ V F igu re 27-. Burning c h a r a c t e r i s t i c s and r a d ia n t energy d i s t r i b u t i o n For t h e 32° type propane burner. 93 o f i n t e r e s t t o n o t e t h a t t h e 32° cone i n d i c a t e s a t o t a l r a d i a t i o n 1 .2 3 t im e s g r e a t e r t h a n t h a t f o r t h e 60° co n e, even th o u g h t h e s u r f a c e t e m p e r a t u r e s w ere a lm o s t e q u a l a s m e a su re d w ith a n o p t i c a l p y r o m e te r . The o r s a t a n a l y s i s i n d i c a t e d in c o m p le te co m b u stio n i n r e g i s t e r i n g 2.5% CO. T h is r e p r e s e n t s a -5.8% e x c e s s a i r o v e r t h a t r e q u i r e d f o r p e r f e c t c o m b u stio n . The g r o s s o r h ig h h e a t i n g v a l u e f o r p r o p a n e i s g iv e n a s 2 1 ,6 9 0 B T U /lb . o f v a p o r ( 2 2 ) . A t t h e b u r n in g r a t e o f 5 . 9 l b s . / h r . t h e p o t e n t i a l h e a t r e l e a s e i s 1 2 8 ,0 0 0 B T U /h r .' However, b e c a u s e o f t h e l o s s r e s u l t i n g from in c o m p le te c o m b u stio n , w h ich was c a l c u l a t e d a s 14% o f t h e t o t a l p o s s i b l e e n e r g y , t h e a c t u a l h e a t r e l e a s e d am ounted t o 1 1 0,00 0 BTU /hr. From t h i s d a t a i t i s fo u n d t h a t , from t h e r a d i a t i o n m e te r r e a d i n g s , t h e 6 0 ° cone r a d i a t e d 19.5% o f t h e h e a t a c t u a l l y l i b e r a t e d , w h ile t h e 3 2 ° cone r a d i a t e d 24%. T h is a p p e a r s t o b e somewhat l e s s t h a n t h e amount o f en e rg y t h a t sh o u ld h a v e b e e n r a d i a t e d , p a r t i c u l a r l y f o r a s u r f a c e t e m p e r a t u r e o f 1 50 0°F . T h e re was r e a s o n t o d o u b t t h e a c c u r a c y o f t h e r a d i a t i o n m e te r a t t h e tim e t h e s e . m easu rem e n ts w ere t a k e n due t o t h e f a c t t h a t some o f t h e th e r m o c o u p le s h ad b e e n r e - a r r a n g e d s i n c e t h e l a s t 94 c a lib ra tio n . A ls o , s i n c e t h e t h e r m o p i l e i s c o v e re d w i t h l i t h i u m f l u o r i t e , t h e c a l i b r a t i o n c o n s t a n t i s o n ly an a v e r a g e v a l u e w hich c o u ld b e much d i f f e r e n t th a n t h e a c t u a l c a l i b r a t i o n f o r t h e i n t e n s i t y and t e m p e r a t u r e u n d e r con­ s id e ra tio n . F u r t h e r e v id e n c e t h a t t h e r e c o r d e d r a d i a t i o n i n t e n s i t i e s w ere t o o low comes from a c o n s i d e r a t i o n o f t h e o v e r a l l h e a t b alan ce . From t h e l a t e s t v a l u e s f o r t h e s p e c i f i c h e a t s of th e e x h a u s t g a s e s (14) t h e s e n s i b l e h e a t d i s c h a r g e d by way o f t h e e x h a u s t g a s e s ( te m p e r a t u r e o f 1 5 0 0 ° F .) was a p p r o x i ­ m a te ly 5 4 ,0 0 0 BTU /hr. The r a t e o f c o n v e c ti o n from t h e s u r f a c e o f t h e cone was c a l c u l a t e d t o b e a p p r o x im a te l y 2 0,00 0 BTU /hr. (3 ). T h is w ould l e a v e a p p r o x im a te ly 3 6 ,0 0 0 BTU/hr. t o b e d i s c h a r g e d th r o u g h r a d i a t i o n , w h ich am ounts t o 33^ o f t h e t o t a l e n e rg y . A ls o , from t h e i n t e n s i t y r e l a t i o n s h i p g i v e n on p age 87 a s u r f a c e t e m p e r a t u r e o f 1515°F. and .8 e m i s s i v i t y , t h e i n t e n s i t y i s c a l c u l a t e d t o b e 2900 BTU/Ft2 . / H r . T h is do es n o t a c c o u n t f o r t h e a d d i t i o n a l e f f e c t due t o t h e h o l e s i n th e s u rfa c e . The c o l o r t e m p e r a t u r e o f t h e s e h o l e s was 1750°F. (as m e asu red w i t h t h e o p t i c a l p y r o m e te r ) . A n o th e r f a c t o r w hich f a v o r s t h e r e a s o n in g t h a t t h e m e te r c a l i b r a t i o n was i n e r r o r r e s u l t s from t h e g e n e r a l c a s e t h a t t h e t e m p e r a t u r e 95 as m easured v /ith an o p t ic a l pyrom eter i s somewhat l e s s th an th e r e a l su r fa c e tem p era tu re (a t l e a s t 1 0 °F .)« I n view o f t h e a b o v e c o n s i d e r a t i o n s i t seems l o g i c a l t h a t t h e i n t e n s i t i e s a s r e c o r d e d sh o u ld b e i n c r e a s e d by 1 . 3 t im e s t h e i r g i v e n v a l u e s . To u s e t h e s e e n e rg y d i s t r i b u t i o n p l o t s f o r f i n d i n g t h e i n t e n s i t y a t an y p o i n t on t h e g ro u n d i t i s only n e c e s s a r y t o assum e t h e h e a t e r u n i t t o be l o c a t e d a t some s e l e c t e d h e ig h t ( 8 - f e e t ) and by tr i g o n o m e t r y f i n d t h e a n g l e t h a t t h e d i r e c t i o n t o t h e p o i n t i n q u e s t i o n makes v /ith t h e 0 o r n a d i r (downward v e r t i c a l ) . Read t h e i n t e n s i t y a t 1 - f o o t i n t h i s d i r e c t i o n from t h e g r a p h , c a l c u l a t e t h e d i s t a n c e t o t h e p o i n t by tr i g o n o m e t r y and d i v i d e t h e i n t e n s i t y by t h e s q u a re of t h i s d is t a n c e ; th u s , g iv in g t h e i n t e n s i t y a t t h a t p o in t. As an example t h e f o l l o w i n g p ro b lem i s assum ed: F in d t h e i n t e n s i t y a t 20 f e e t from e i t h e r u n i t when th e y a r e 8 - f e e t h ig h ? A ng le from n a d i r , 0 » tan"-** 2 0 /8 = 6 8 .2 ° From e n e rg y d i s t r i b u t i o n c u r v e s , F o r 60° cone — I ^ ( i n t e n s i t y a t 1 - f o o t ) = 2320 BTU/Ft2 . / H r . F o r 32° cone — I j = ° r7° r' •Q'nTT/w2 / u " L ( d i s t a n c e t o p o i n t on g ro u n d 96 « I n t e n s i t y a t 20 f e e t from 60° cone = 2320/L 2 = 2320/4-64 = 5 BTU/Ft . / H r . o r , by a p p ly in g t h e s u g g e s te d c o r r e c t i o n , i n t e n s i t y = 5 x 1 . 5 s 6 .5 BTU/Ft2 . / H r . I n t e n s i t y a t 20 f e e t from 32° cone = 2720/464 = 5 . 8 BTU/Ft2 . / H r . o r = 5 . 8 x 1 . 3 = 7 .5 4 BTU/Ft2 . / H r . These c a l c u l a t i o n s show t h e a p p a r e n t a d v a n ta g e o f t h e 52° cone o v e r t h e 6 0° cone i n g i v i n g a more f a v o r a b l e d i s ­ t r i b u t i o n of th e r a d ia n t en erg y . Making a l lo w a n c e f o r t h e p r o b a b l e e r r o r s i n t h e r a d i a t i o n i n t e n s i t y , th e ev id en ce fa v o rs an e x p e rim e n ta l a p p l i c a t i o n o f t h e 3 2 ° c o n e - ty p e w ith a s many h o l e s a s p o s s i b l e th r o u g h its su rface. A ls o , a c e ra m ic m a t e r i a l sh o u ld b e a t t a c h e d t o t h e b o tto m s i d e o f t h e ce ra m ic t o p , a llo w in g t h i s a d d i t i o n t o p r o j e c t down i n t o t h e volum e o f t h e co n e . T h is w ould in c r e a s e th e r a d i a t i o n th ro u g h th e h o le s in t h e s u rfa c e . W ith t h e above im p rov em en ts t h i s t y p e o f h e a t e r u n i t s h o u ld p ro v e t o p r o v id e s u f f i c i e n t p r o t e c t i o n when sp aced f i f t y f e e t a p a r t a t an e le v a tio n of e ig h t f e e t . I t w ill re ­ q u i r e an o p e r a t i o n u n d e r n a t u r a l f r o s t i n g c o n d i t i o n s t o d e te r m in e t h e r e a l v a l u e o f t h i s u n i t and t h e l a t e bloom ing f l o w e r s s h o u ld p r o v id e a n i d e a l p ro v in g g r o u n d s . 97 Summary The p r i n c i p a l c a u s e o f damage t o a g r i c u l t u r a l c r o p s by f r e e z i n g r e s u l t s from r a d i a t i o n - t y p e f r o s t . I t was found t h a t t o u s e r a d i a n t e n e rg y a l o n e r e q u i r e s a r a d i a t i o n i n ­ t e n s i t y o f 10 E T U / s q . f t . / h r . t o p r o t e c t low grow ing v e g e t a t i o n a g a i n s t t h e f r o s t i n g c o n d i t i o n s m ost l i k e l y t o o c c u r d u r in g t h e grow ing s e a s o n . However, f o r t h e few c o ld w in d -b o rn e f r e e z e s w h ich h av e o c c u r r e d , t h e r a d i a t i o n i n t e n s i t y h a s t o b e i n c r e a s e d t o a p p r o x im a te ly 65 B T U / s q . f t . / h r . The u s e o f c o n v e c te d o r s e n s i b l e h e a t h a s p ro v e d t o affo rd p ro te c tio n a g a in st ra d ia tio n -ty p e f r e e z e s . T his m ethod i s p r a c t i c a l p a r t i c u l a r l y f o r v e g e t a t i o n two f e e t or more ab o v e t h e g ro u n d , and when t h e t e m p e r a t u r e g r a d i e n t i s s u f f i c i e n t l y h ig h (te m p e ra tu re in v e r s i o n ) . In c o n tra s t, u n d e r c o n d i t i o n s o f a p p r e c i a b l e wind l i t t l e can b e done to w ard h e a t i n g t h e s u r r o u n d in g a i r t o p r o v id e p r o t e c t i o n f o r v e g e ta tio n a g a in st fre e z in g . However, i n t h e m a j o r i t y o f c a s e s dam aging f r e e z e s do n o t accompany a p p r e c i a b l e w ind. The F r o s t g u a r d , w h ich was d e s ig n e d t o p r o v i d e p r o t e c t i o n e x c l u s i v e l y th r o u g h r a d i a n t e n e r g y , was fo u n d t o b e e x p e n s iv e i n te rm s o f t h e amount o f p r o t e c t i o n a f f o r d e d . b u r n e r was somewhat e r r a t i c i n i t s o p e ra tio n . A ls o , t h e T h is s tu d y A 98 on t h e F r o s t g u a r d was made w i t h two o b j e c t i v e s i n m ind: (1 ) t o r e d u c e t h e fla m e volum e so t h a t t h e s i z e o f t h e u n i t s c o u ld b e made s m a l l e r i n o r d e r t h a t p r a c t i c a l r e f l e c t o r s would f a c i l i t a t e b e t t e r d i s t r i b u t i o n o f t h e g e n e r a t e d r a d i a n t e n e rg y , and (2 ) t o i n c r e a s e t h e d e p e n d a b i l i t y o r s t a b i l i z e th e b u rn in g . F o llo w in g an a n a l y s i s o f t h e p h y s i c a l an d c h e m ic a l p r o p e r t i e s o f k e r o s e n e , e x p e r i m e n t a l a t t e m p t s w ere made t o im prove t h e F r o s t g u a r d a lo n g t h e above two l i n e s . To re d u c e tii e f la m e volume r e q u i r e d a b e t t e r m ix in g o f t h e a i r and f u e l - v a p o r b e f o r e b u r n in g s t a r t e d . However, s i n c e t h e i g ­ n i t i o n t e m p e r a t u r e o f k e r o s e n e i s b elo w i t s s a t u r a t e d v a p o r t e m p e r a t u r e a t 80 p s i g , b u r n in g would s t a r t a s soon a s s u f ­ f i c i e n t a i r was e n t r a i n e d t o g i v e a c o m b u s tib le m ix t u r e . T h erefo re , sin c e th e b u rn e r i s of th e p re s s u re h e a t-v a p o riz in g ty p e , l i t t l e c o u ld b e done t h a t w ould in d u c e a b e t t e r a e r a t i o n o f t h e f u e l v a p o r i n o r d e r t o r e d u c e t h e fla m e volum e. The r e a s o n t h a t t h e F r o s t g u a r d f a i l e d t o o p e r a t e s a t i s ­ f a c t o r i l y i n wind i n e x c e s s o f 5 KPH r e s u l t e d from a l a c k o f s u f f i c i e n t a i r f o r c o m b u stio n , w hich re d u c e d i t s v a p o r i z i n g c a p o .c i t y . T h is p ro b lem was s o lv e d t o a s a t i s f a c t o r y d e g r e e by p l a c i n g a wind d e f l e c t o r and scoop a t t h e to p an d b o tto m , r e s p e c t i v e l y , o f t h e u n i t , and by t h e a d d i t i o n o f a c e ra m ic m a te r ia l around th e v a p o riz in g c o i l . The w ind d e f l e c t o r and scoop to o k c a r e of t h e s t e a d y w ind 'w hile t h e c e ra m ic h e l d s u f f i c i e n t h e a t t o c a r r y t h e v a p o r i z a t i o n th r o u g h t h e g u s t y wind c o n d i t i o n s . A ls o , t h e ce ra m ic p ro d u c e d a s u f ­ f i c i e n t l y h i g h t e m p e r a t u r e s u r r o u n d in g a t t h e i n i t i a l p o i n t of c o m b u stio n t o r e d u c e t h e f la m e volum e somewhat. As a r e s u l t t h e s u r f a c e t e m p e r a t u r e was i n c r e a s e d by a p p r o x im a te ly 1 0 0 ° F . w i t h t h e same f la m e volum e. F o llo w in g t h e c o n c l u s i o n t h a t b e t t e r r a d i a n t e n e rg y d i s t r i b u t i o n c o u ld be more p r a c t i c a l l y c a r r i e d o u t by t h e u s e o f s m a l l e r u n i t s s p a c e d c l o s e r t o g e t h e r , work was c a r r i e d on t o d e v e lo p a s m a ll n o n -p o w e re d l i q u i d p e tro le u m f u e l bu rn er. The o b j e c t i v e was t o a c c o m p lis h a h i g h r a t e o f b u r n in g i n o r d e r t h a t a c o n s i d e r a b l e p a r t o f t h e t o t a l h e a t l i b e r a t e d w ould b e d i s c h a r g e d a s r a d i a n t e n e rg y ; t h i s had t o b e c a r r i e d o u t w i t h a minimum o f smoke. S e v e r a l d i f f e r e n t p r i n c i p l e s w ere t r i e d w i t h v a r y in g degrees of su c cess. However, i n v iew o f t h e c o s t , o p e r a t i o n , and smoke o u t p u t , i t was fo u n d t h a t t h e p r i n c i p l e employed by t h e R e t u r n - s t a c k O rchard H e a te r ( a s d e v e lo p e d by t h e U n i v e r s i t y o f C a l i f o r n i a ) was t h e b e s t . The i n c r e a s i n g d i s t r i b u t i o n o f l i q u i f i e d p e tro le u m g a s e s p l a c e s t h i s f u e l a s a p o s s i b l e s o u r c e o f h e a t energy f o r f r o s t damage c o n t r o l . The s i m p l i c i t y v.ri t h w hich t h i s f u e l can b e b u r n e d e f f i c i e n t l y t o g iv e r a d i a n t en e rg y a s w e l l a s s e n s ib le h e a t g iv e s r i s e to d e f i n i t e ad v a n ta g e s. P re se n tly , t h e c o s t i s a p p a r e n t l y a d i s a d v a n t a g e ; how ever, t h e low f i r s t c o s t o f b u r n e r u n i t s , low m a in te n a n c e c o s t , c h e a p n e s s w ith w hich t h e r a t e o f b u r n i n g f o r such a b u r n e r can be m o d u la te d and a u t o m a t i c a l l y c o n t r o l l e d , and t h e p o s s i b i l i t y o f com bining su c h a s e tu p i n t o a p erm an en t i n s t a l l a t i o n ; may w e l l o utw eig h t h e c o m p a r a tiv e ly h i g h f u e l c o s t . One o f t h e o b j e c t i v e s o f t h i s s tu d y was t o d e v e lo p a LPG b u r n e r - u n i t w hich would b e p r a c t i c a l f o r t h e g r o w e rs o f f l o w e r s and h i g h e r v a lu e d t r u c k c r o p s . Such a u n i t was d e s ig n e d and te s te d to e v a lu a te i t s o p e ra tin g c h a r a c t e r i s t i c s . The r e s u l t s o f t h i s t e s t i n d i c a t e d t h a t t h e u n i t was re a d y t o b e t r i e d under n a tu r a l f r o s t in g c o n d itio n s. The ty p e o f v e g e t a t i o n and f r e e z i n g c o n d i t i o n s w i l l , o f c o u r s e , d e te r m in e t h e e x t e n t o f p r o t e c t i o n a f f o r d e d ; ho w ev er, i t i s s u g g e s te d t h a t t h e s e u n i t s b e sp aced f i f t y f e e t a p a r t an d e i g h t f e e t h i g h . The above s p a c in g i s s u g g e s t e d f o r f a i r l y w e l l exposed v e g e t a t i o n , such a s to m a to e s , s t r a w b e r r i e s , e t c . , an d f o r t h e f r o s t i n g c o n d i t i o n s most l i k e l y t o o c c u r d u r i n g t h e n o rm a l grow ing season. acre. The c o s t i s e s t i m a t e d a t $10 p e r u n i t o r $160 p e r T h is c o s t i n c l u d e s , (1 ) r e n t on t a n k s (two p e r u n i t ) , (2) r e g u l a t o r s , an d (o) b u r n e r - u n i t s . 101 C o n c lu s io n s B oth r a d i a n t en erg y and c o n v e c te d o r s e n s i b l e h e a t a r e u se d i n v a r y in g amounts f o r t h e p r o t e c t i o n o f v e g e t a t i o n from f r o s t damage. R a d ia n t en e rg y i s more e f f e c t i v e on low growing v e g e t a t i o n , and i f a p p l i e d v /ith s u f f i c i e n t i n t e n s i t y w i l l p r o t e c t u n d e r f r e e z i n g c o n d i t i o n s which a r e accom panied by a p p r e c i a b l e w in d . C onvected h e a t i s more p r a c t i c a l f o r v e g e t a t i o n above two f e e t when t h e r e i s l i t t l e and on c o m p a r a tiv e ly l e v e l g ro u n d s u r f a c e . or n o wind Any b u r n e r d i s c h a r g e s b o th t y p e s o f h e a t e n e rg y ; h ow ever, t h e p a r t i c u l a r d e s ig n d e t e r m i n e s th e r e l a t i v e a m o u n ts. B o th m ethods a r e more e f f e c t i v e when r e l e a s e d a t s e v e r a l p l a c e s o v e r a c e r t a i n a r e a th a n from o n ly a few p l a c e s — f a v o r i n g s m a ll h e a t e r - u n i t s . L arg e r a d i a t i o n equ ip m en t i s i n e f f i c i e n t i n i t s d i s t r i ­ b u t i o n o f r a d i a n t en e rg y and s e n s i b l e h e a t , a n d i s n e c e s s a r i l y e x p e n s iv e — a f a c t o r w hich r e s t r i c t s i t s a p p l i c a t i o n t o t h e h ig h e r v alu ed cro p s. The p r e s s u r e h e a t - v a p o r i z i n g ty p e o f b u rn e r used in th e p re s e n t u n i t i s in h e re n tly e r r a t i c in i t s o p e r a t i o n and r e q u i r e s c o n s i d e r a b l e m a in te n a n c e f o r s a t i s ­ fa c to ry o p e ra tio n . The p r i n c i p l e employed by t h e R e t u r n - s t a c k Orchard H e a te r s e r v e s v e r y w e ll t o b r i n g a b o u t th e e f f i c i e n t c l e a n 102 b u r n i n g o f a c o m p a r a tiv e ly h ig h f u e l r a t e . I t i s ev id en t t h a t t h i s h e a t e r v;as d e s ig n e d p r i m a r i l y t o h e a t o rc h a rd t y p e c r o p s ; h o w ev e r, by r e - d e s i g n i n g so t h a t more o f t h e r a d i a t i o n would b e d i r e c t e d downward, t h i s p r i n c i p l e c o u ld be' u s e d f o r t h e p r o t e c t i o n o f low grow ing v e g e t a t i o n . B ecau se o f t h e low i n i t i a l c o s t , l a c k o f n e e d f o r m a in te n a n c e , and low o p e r a t i n g c o s t , a h e a t e r c o n s t r u c t e d on t h i s p r i n c i p l e c o u ld b e p o s i t i o n e d c l o s e enough t o g e t h e r t o a f f o r d p r o t e c t i o n a g a i n s t t h e m ost p r o b a b le f r e e z e s . The l i q u i f i e d p e tro le u m g a s b u r n e r - u n i t o f f e r s p r a c t i c a l f r o s t damage c o n t r o l on c r o p s such a s f l o w e r s o r o t h e r h i g h e r v a l u e d c r o p s , and p a r t i c u l a r l y th o s e c r o p s w hich may become c o n ta m in a te d by o t h e r b u r n e r s . A ls o , t h i s t y p e o f b u r n e r c o u ld b e i n c o r p o r a t e d i n t o a n a u t o m a t i c a l l y c o n t r o l l e d s e t u p , w hich c o u ld b e m o d u la te d t o a r a t e o f b u r n in g t h a t would p r o te c t a g a in s t th e p r e v a ilin g fre e z in g c o n d itio n ; th u s, e f f e c t i n g a s a v in g i n t h e f u e l c o n su m p tio n . 103 LITERATURE CITED 1. C r o f t , H uber 0. T r a n s m is s io n , New Y ork. Thermodynamics F l u i d Flow and H eat p . 300. M cGraw -Hill Book C o ., I n c . 1938. 2. C ro ft, op. c i t . p . 180.- 3. C ro ft, op. c i t . p . 210. 4. D o u g h erty , G. T. P r i v a t e Com munication d a t e d Jan. 1 9 , 1950. 5. D uggar, B en jam in Li. V o l. I . 6. B io lo g ic a l E f f e c ts of R a d ia tio n . p . 78 4 . M cG raw -H ill Book C o ., Inc. New Y ork.. F a r r a l l , A. Vi., S h eld o n , W. H . , and H ansen, C. P r o t e c t i o n o f Crops from F r o s t Damage Through t h e Use o f R a d ia n t E nerg y. S ta tio n L lich ig an A g r i c u l t u r a l E x p erim e n t Q u a rte rly B u lle tin . 2 9 :5 3 -6 4 . November, 1946. 7. F a rra ll. op. c i t . p p . 5 7 -6 0 . 8. G a rd n e r, V i c t o r R . , B r a d f o r d , F . C ., and H ooker, H. The F u n d am e n tals o f F r u i t P r o d u c tio n , M cG raw -H ill Book C o ., I n c . 9. G ib so n , George T a y l o r . A pp. 4 1 6 -4 1 7 . Hew Y ork. 1939. S tudy o f t h e Use E nergy f o r F r o s t P r e v e n t i o n , M ic h ig an S t a t e C o lle g e .. D. p p. 5 - 8 . of E le c tr ic a l T h e s is M.S. 1948. 10. G ib so n , op. c i t . p p . 8 -2 5 . 11. G ib so n , op. c i t . p p . 2 5 -3 7 . A 104 12. H a s s le r, F ra n c is J e f f e r s o n . U t i l i z a t i o n o f R a d ia n t E nergy f o r t h e P r o t e c t i o n o f V e g e t a t i o n from F r o s t Damage, pp. 56-85. C o lleg e . T h e s is LI.S. M ichigan S t a t e 1948. 15. H a ss le r. op. c i t . p p . 5 1 -5 1 14. H o t t e l , H. C ., W i llia m s , G. C ., and S a t t e r f i e l d , C. N. Thermodynamic C h a r t s f o r Com bustion P r o c e s s e s . One. p . 4-1. Jo h n W iley and Sons, I n c . P art New Y ork. 194 9. 15. Hougen, O la f A. and W atson, K enneth M. P rin c ip le s. S o n s, I n c . P a r t One. New Y ork. C hem ical P r o c e s s p p . 52 9-5 42 . Jo h n W iley and 1947. 16. Hougen. op. c i t . p . 540. 17. L e o n a rd , A. S. and K ep n e r, R o b e rt A. O rchard H e a t e r . R e tu rn -S ta c k C a lifo rn ia A g ric u ltu re . 4 :8 -1 0 . J u n e 1950. 18. McAdams, W illia m H. H e a t T r a n s m is s io n , IvIcGraw-Hill Book C o ., I n c . 19. P e r r y , Jo h n H.. E d itio n , Y ork. New York. p p. 5 9 5 -5 9 4 . 1942.. C hem ical E n g in eers* Handbook. p . 146 1. Second M cGraw -Hill Book C o ., I n c . 19 4 1 . 20. P erry , op. c i t . p . 2598. 21. P erry , op. c i t . pp. 1 5 9 9 -1 4 0 1 . New 105 2 2. Rohman, A ., Denny, L. C ., and K rappe, .J. M. B u ta n e -P ro p a n e G a se s, Inc. 25. Los A n g e le s . \ i e l d , L ero y D. 25. Weld. op. c i t . 26. Young, F lo y d 0. S c r a n to n , 1940. A T ex tb o o k o f H e a t. The l i a c m i l l a n Co. Damage. I llu m in a tio n E n g in e e rin g . I n t e r n a t i o n a l Textbook Co. P e n n s y lv a n ia . 24. W estern B u s i n e s s P a p e r s , 1945. S c h i l l i n g , Eugene W. p p. 5 1 - 5 2 . p. 52. Handbook Hew Y ork. p p . 3 44 -36 4. 1948. p . 351.. F r o s t and t h e P r e v e n t i o n o f F r o s t F a r m e r s ' B u l l e t i n Ho. 1538. USDA. 1947. 106 ACKNOVYLEDGEMENTS The n a t u r e o f t h i s s tu d y makes i t i m p r a c t i c a l t o e x p r e s s e x p l i c i t l y t h e names o f t h o s e i n d i v i d u a l s and f i r m s who con­ t r i b u t e d i n some way t o f u r t h e r t h i s i n v e s t i g a t i o n . As a r e s u l t t h e a u t h o r w is h e s t o m e n tio n o n ly t h e f o l l o w i n g i n a p p r e c ia tio n o f t h e i r o u tsta n d in g a s s i s t a n c e : P r o f e s s o r A. W. F a r r a l l o f t h e A g r i c u l t u r a l E n g in e e rin g D e p a rtm e n t f o r h i s g u id a n c e i n t h i s m a t t e r and h i s e f f o r t s i n s e c u r i n g an d malting a v a i l a b l e t h e n e c e s s a r y fu n d s f o r th is in v e stig a tio n . D r. W. il. C a r l e t o n o f t h e A g r i c u l t u r a l E n g in e e r in g D epartm en t f o r h i s h e l p f u l s u g g e s t i o n s on t h a t p a r t o f t h e s tu d y r e l a t e d t o t h e u s e o f l i q u i f i e d p e tro le u m g a s e s , h i s c o r r e c t i v e s u g g e s t i o n s i n re v ie w in g t h e m a n u s c r ip t, and h i s g e n e r a l i n s p i r a t i o n a l comments from tim e t o t i m e . Mr. K. I . C r i t t e n d e n o f S h e l l O il Company f o r making a v a i l a b l e , a t no c o s t t o t h e c o l l e g e , c o n s i d e r a b l e LPG f u e l and eq u ip m e n t. Mr. Ted D a v ie s o f N o rth A m erican B u r n e r M a n u fa c tu rin g Company f o r making a v a i l a b l e e x p e r i m e n t a l g a s i n s p i r a t o r - 107 b u r n e r s and f o r h i s h e l p f u l s u g g e s t i o n s a s t o t h e i r u s e .