THE EFFECT OF. OCTADECYLAMINE ACETATE ON OVERALL HEAT TRANSFER COEFFICIENTS Thesis for the Degree of M. S. MECHIGAN STATE COLLEGE Dana Duana Squire 1955 This is to certify that the thesis entitled The Effect of Octadecylamine Acetate on Overall Heat Transfer Coefficients presented by Dana Duane Squire has been accepted towards fu.lfillment of the requirements for _Mfi,_ degree in LhemianEngineering 4% Major professor Date ;?W/fi 4%“ ES / / 0-169 THE EFFECT OF OCTADECYLAMINE ACETATE ON OVERALL HEAT TRANSFER CGESFICIENTS BY DANA DUANE SQUIRE AN ABSTRACT Submitted to the School of Graduate Studies of Michigan State College of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Chemical Engineering 1955 APPROVED: x//1::::jfifi:2523::EE25:1:A44252fE7’ ABSTRACT Octadecylamine acetate is used for corrosion inhibition in many present day operations. Increase in heat transfer not due to the reduction of corrosion has been observed in plant equip- ment. It has been theorized that this amine, by forming a non- wettable surface, produces this increase in heat transfer by promoting dropwise condensation and/or by better run off of the condensate. The prOblem involved in this research is to study these effects of better heat transfer in the laboratory and in pilot plant operation. A miniature laboratory model of a heat exchanger was made- and increases of 10.8 percent in overall heat transfer coefficients was determined. This was a result of both.better run off of condensate and promotion of dropwise condensation. Filmwise condensation could not be obtained in the pilot plant heat exchanger because of contamination between the main line steam and the heat exchanger. Oil used in the threading and cutting of pipes was of sufficient quantity to promote dropwise condensation. Consequently, when octadecylamine was added a decrease in heat transfer resulted. This decrease is believed to be the result of a reaction between the octadecylamine acetate and the oil. This is also true in the case of corrosion inhibition. If there is oil in a system, the corrosion inhibition of octadecyl- amine acetate is greatly reduced. Dana Duane Squire THE EFFECT OF OCTADECYLAMINE ACETATE 0N OVERALL HEAT TRATSFER COEFFICIENTS By DANA DUANE SQUIRE A THESIS Submitted to the School of Graduate Studies of Michigan State College of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Chemical Engineering 1955 ‘1‘ .‘u «.0 \‘all ACKNOWLEDGEMENT Sincere thanks are due to Dr. C. C. Dewitt for his guidance and interpretation of the results in the writing of this thesis. Dr. M. F. Obrecht has given continued active interest and encouragement since he initiated the research. The author also expresses grateful acknowledgement to W} B. Clippinger, whose mechanical ability and suggestions made laboratory operation possible. Q"! 3 "£303 TABLE OF ABSTRACT A CKI‘JGFILEDGETLENT INTRODUCTION . . . . . . . . . HISTORY........... HEAT TRANSFER RELATIOE‘QSHIPS . PROCEDURE .......... DATA AND RESULTS . . . . . . . GRAPHS AND DIAGRAIIS . . . . . DISCUSSION . . . . . . . . . . CONCLUSIONS 0 o o o o e o o o BIBIIIUERAPTIY O O O O O O O O O 0 CONTENTS PA GE 0 o o o o o o o o o o o 0 l2 0 o o o o o o o o o o o o 25 a o o o o o o o o o o o o 32 BTIiHTHOO HOA‘I ' SI ............. BS ............. SE ............. TE ............ BE ............. "IO MEAT TOAHTBCA Y4339x’fl?liflhfl$il . . . . . . . . . HOITOUOCHTEZI ........... ISIOTCIH . REEIBMCITAITH flEEEIiAIIT TAI‘IH . . . . . . . . . . SRUOHOOH‘I . . . . . . . BTJURHFI (TEA ATM] . . . . . EWOAIC (MA amass . . . . . . . . . . HOIZBUOBICI . . . . . . . . . al-‘IOIBUJOVIOO . . . . . . . . . YYHAHOCIJHIE INTRODUCTION INTRODUCTION Octadecylamine acetate has, for the past eight years, been used for prevention of corrosion in steam and condensate return lines (26). Denman (3) first reported the use of this amine for treating boiler'water. Octadecylamine acetate functions by the principle of forming a film of long chain polar amine molecules '(ll, 26) on the metal surface. This mono-moleculear film is believed to maintain nonewettable characteristics (2, 2h, 25, 26). When a saturated vapor such as steam.contacts a surface whose temperature is below the dew point of the saturated vapor, con- densation results. Normal filmwise condensation does not occur on a nonawettable metallic surface(l, 9,21, 26). There are two extreme types of condensation; these are dependent on the condition of the condensing surface (I). The normal type of condensation encountered on a wettable metallic surface is called "filmwise condensation." "Filmwise condensation" involves the formation of a continuous layer of liquid condensate on the metallic surface. This continuous layer introduces a resistance to heat transmission through the metallic wall as shown in Figure A of Diagram I. The other extreme type of condensation,commonly known as "dropwise condensation", most generally occurs when the metallic surface is rendered nondwettable. The mechanism of dropwise condensation is exemplified by the following cycle. Vapor condenses on a nondwettable metallic surface in tiny, minute drops which gradually grow in size, until a critical size is reached. This critical size is said to depend on the angle of inclination of the surface, the contact angle of drop, the surface tension of the liquid, and the density of the liquid (6). 'When the critical size is reached, the drop "sweeps" the surface collecting other droplets of condensed vapor and, moving downward, leaves behind it a bare strip of metallic surface exposed. This cycle thus eliminates resistance to heat transmission due to the liquid layer shown in Figure B of Diagram I. The effectiveness of octadecylamine acetate and salts for corrosion inhibition in return condensate lines has been exten- sively investigated (11, 23, 26). Case histories (17, 18, 26) of operations using octadecylamine acetate for corrosion inhibition, show an increase in capacity or efficiency not due to elimination of the corrosion layer or fouling resistance. It has been theorized by investigators (2, 17, 2h, 26) that dropwise condensation occurs and higher overall heat transfer coefficients results. The purpose of this study was to investigate (l) the effectiveness of octadecylamine acetate as a promoter of drop- wise condensation, (2) the conditions under which octadecylamine acetate acts as a promoter of dropwise condensation, (3) the effect of octadecylamine acetate on overall heat transfer co- efficient. HISTORY Schmidt, Schurig, and Sellschopp (2), in 1930, initiated the study of the effect in induced dropwise cendensation heat transfer coefficients. These investigators, using a steam chamber and metal disc cooled by a high velocity of jet water, found that values of steam side coefficients could be increased five to seven times the values predicted by the theoretical formula of Nusselt (16). This condensation was due to small amounts of oil in the steam. Spoelstra, (22) in 1931, observed that fouled tubes from evaporators in Javanese sugar mills, even after cleaning, snowed a marked decrease in heat transmission. Spoelstra discovered that the pores of the scale on these tubes contained thirty percent oil- like, organic substances. subsequent investigations proved that tubes with a thin scale, if oily, had higher overall heat transfer coefficients than tubes which had no scale. Spoelstra's later apparatus was similar to that shown in Diagram.II; he observed the type of condensation which resulted on different types of surfaces. No heat transfer coefficients were reported. In 1932, Jakob (10) reported that direction and velocity of steam is a very important factor in determining the type of con- densation. Jakob observed that at high steam.velocities film condensation occurred.while at low steam velocities mixed conden- sation resulted. The type of condensation appeared to be a function of cleanliness and other physical characteristics of the surface. .14.. Nagle (15) in 1935, was issued a patent covering the use of certain reagents for inducing dropwise condensation, which usage was alleged to increase steam condensation efficiency. This patent was a result of studies Nagle and Drew (1h) had previously completed; studies in which an attempt was made to explain the effects of surface conditions and types of various promoters, generally polar organic compounds, modes of condensation. Nagle and coaworkers, later in the same year, presented papers (h, 13) in which these conclusions were made: (1) clean steam, condenses in a filmwise manner on clean surfaces, rough or smooth. (2) steam condenses in a dropwise manner only if the cooling surface is contaminated. (3) dropwise condensation is more easily promoted on smooth surfaces. In the late thirties, Emmons (5) found that the number of molecular layers of dropwise condensation promoter (stearic acid) had very little effect on the percent of dropwise condensation. Fitzpatrick, Baum,and.McAdams (7) concluded that larger increases in capacity of a given apparatus would result if dropwise conden- sation occurred. The apparatus used was a condenser made of 5/8 inch No. 18 guage metal tubing arranged vertically inside a copper plated steam jacket ten feet long. A fattybacid promoter in the power plant steam caused immediate dropwise condensation and, consequently, filmwise condensation could not be obtained. The subject under consideration was apparently dropped until l9h9 when Fatica and Katz (6) published an article of a highly theoretical nature in which dropwise condensation was found to depend on the angle of inclination of the condensing surface, surface tension of the liquid condensing, density of the liquid condensing, and the contact angle of the condensed droplets with the metal surface. Two years later, Hampson (8) determined that the persistancy of dropwise condensation depended not only on these factors, but, also on the rate of condensation, method of application of promoter, and shape of condensing surface. It should be noted that no references could be found where dropwise promoting additives were used in any type of heat transfer equipment other than laboratory size. HEAT TRANSFER RELATIONSHIPS The fundamental heat transfer relationship (19) used to evaluate heat transfer data in heat exchangers is: Q - UA (mm Where: Q - heat transfer rate, Btu./Hr. U I overall heat transfer coefficient, Btu./Hr./Ft.2/°F. A = heat transfer area, ft.2. (At)m - logarithmic temperature difference or driving force, °F. The overall heat transfer coefficient, U, is the reciprocal of the sum of the resistances to heat transmission expressed as: U ' 1 .or 1 R8 + Rf + Rw + Rm l. + _i + h s +~.§L hf k ables where: h8 - steam side film coefficient, Etu./Hr./Ft.2/°F. hf - fouling factor due to dirt, scale, corrosion, etc., Btu./Hr./Ft.2/°F. X = thickness of metal wall through which heat is transferred, ft. k - thermal conductivity of metal, Btu./Hr./ Ft.2/°F. In a heat exchanger using steam as the heating media the mean temperature difference is calculated by: (At)m - (T - t1) - (T - t2) 1n (T — t1) (T - t2; where: T 8 temperature of condensing steam. tl - temperature of water inlet. t2 = temperature of water outlet. PROCEDURE a7- PROCEDURE A. Finger Type Condenser The finger type condenser (see Diagram II) similar to that used by Spoelstra (22), Emmons (5), and Nagle and Drew (lb) was made from two pieces of copper tubing. The smaller copper tube (do - 0.250 in., di - 0.190 in.) was inserted in the larger copper tube (Do I 0.500 in., Di - 0.h35 in.) and soldered into place in an annular mechanism assimiliating the water side of a minature condenser. ‘water was introduced into the inside tube from the top and traveled down the tube within 0.125 in. 1;.0625 in. of the end. At this point, the water entered the larger tube, reversed its direction, and traveled the entire length (6.5 in.) of the outside tube into a half gallon jar where it was weighed in one minute increments. This condenser was held by a cork which also supported a thermometer for steam temperature measurement and a laboratory type reflux condenser. The cork was covered with tinfoil to prevent any impurities from the cork to enter the system and placed in a two liter Erlemeyer flask containing one liter of distilled water. The distilled water generated a constant source of atmospheric steam.upon heating with a Bunsen burner. The advantages of this system are: (l) a "closed" systamtias provided by the use of the reflux condenser by which clean atmospheric pressure could be generated for long periods of time. (2) clear, accurate visual observation could be maintained at all times a -8- (3) apparatus could be dismantled, cleaned thoroughly, and put together with a minimum amount of time and effort. Extreme cleanliness of apparatus being a necessity, the follow- ing system of cleaning was adopted. The finger type condenser was ground with four successively finer grades of emery cloth and, finally, rubbed and polished thoroughly with crocus cloth. Condenser, Erlemeyer flask, tinfoil, reflux condenser, and contact parts were scrubbed with "Ajax", a commercial scouring agent, and rinsed thoroughly with tap water and.then with distilled water. The scrubbing and rinsing procedure was repeated until distilled water formed a liquid layer on all parts of the system. Hereafter, when any reference to cleaning of apparatus is made, the procedure out- lined in this paragraph was followed. The system was allowed to reflux for one hour at an estimated ninety percent filmwise condensation surface. Data was obtained in the following manner: (1) water rate was adjusted by use of valve from.main water line. (2) system was allowed to reach equilibrium (outlet temperature constant). (3) inlet temperature was measured.with a calorimetric thermometer (I 0.05°F.). (h) outlet temperature was measured at the beginning of a one-minute time interval and at the end of the time interval. If any deviation in temperatures occurred, an arithmetic average was taken. (5) outlet water was collected in a half gaLlon jar over such time interval and weighed. The finger type condenser was again cleaned thoroughly and stearic acid powdered, sprinkled on a clean cheesecloth, was rubbed on the outer surface of the larger copper tube. Stearic acid powder was used because references (1, S, 8) indicated that stearic acid gave the non-wettable surface necessary for the promotion of excellent dropwise condensation. Thus, run thirty-nine through sixty—nine were made; good dropwise condensation was observed. The apparatus was again cleaned and the system allowed to reflux for approximately five to six hours at which time one-hundred per- cent filmwise condensation was observed. The system was cleaned with "Filmeen", a commercial grade of octadecylamine acetate, rubbed on the surface of the condenser. After ten minutes of operation, approximately forty-five percent dropwise condensation was observed a and "better run-off" occurred. Runs seventy through one-hundred and two were made. B. Laboratory Heat Exchanger The heat exchanger used in the laboratory was a two-pass, sixteen tube per pass, shell and tube heat exchanger. The tubes were 18 BEG, 5/8 inch outside diameter, which gave a surface area of 10.h square feet. The tube bundles were removed from the shell and soaked for five days in a six percent solution of Dearborn '* Steam condensate dropped at a much faster rate from the bottom of finger type condenser -10- Company's Formula 13h, inhibited hydrochloric acid. subsequent examination of these tubes showed that most of the scale accumulated in more than four years of operation had been removed. A four point recorder was used to take continuous temperature readings at the (l) inlet cooling water, (2) outlet cooling water, (3) steam temperature in shell, and (h) temperature of condensate. It was observed that the condensate temperature was lower than the steam temperature, so a larger steam trap was substituted. However, the water flow rates varied so widely that continuous data from the four point recorder could not be used. Finally, calibration thermometers (:;0.09°C.) were used to obtain desired temperatures readings. The steam pressure was regulated by'a "dead weight" pressure valve. The steam was from the University Power Plant line. A MiltonpRoy'"Mini-pump" was first used to pump small.amounts of concentrated octadecylamine acetate solution into the steam line between the "dead.weight" pressure valve and the heat exchanger, but due to the character of the octadecylamine acetate solution the "balls and checks" were soon plugged. Finally, a 1/6 horsepower, single phase, MiltonsRoy'pump was obtained which successfully pumped desired concentrations in properly regulated amountes. Tne feed solution of octadecylamine acetate was dissolved in a 150 pound calibrated feed tank in 170°F. condensate water. The rate of feed, based on steam condensation rate, was controlled by adjusting the strokes of the pump. -11- Runs one through ten were made after two days of continuous operation without introducing any promoter. Data was taken in the same manner described for the finger type apparatus. Runs eleven through nineteen were made on the fourth day and runs twenty through twenty-eight were made on the seventh day of continuous operation. Octadecylamine acetate was then introduced into the steam system at two to four parts per million. The finger type condenser was placed in position B (see Diagram III); steam slowly injected into this apparatus allowed observations of the type of condensation. The condensate formed in droplets previously described and runs twenty-nine through thirty-four were made after ten hours of operation. Feeding octadecylamine acetate at one hundred parts per million runs thirty-five through forty-three were made; partial dropwise condensation and a white scum-like material was observed in miniature condenser apparatus. The finger type condenser was then placed in position A (see Diagram III), where almost one hundred percent dropwise condensation was observed. The finger type condenser was cleaned and main line steam from the power plant injected into apparatus; only filmwise condensation was observed over a three day period. DATA AND RESULTS -12.. DATA AND RESULTS A. Finger Type Condenser Surface highly polished, no promoter, 90% filmwise condensation observed. 'water Inlet Outlet Steam. ‘Water Heat Transfer Run Rate Temp. Temp. Temp. Velocity Coefficient No. #/Min. 'F. °F. °F. th/Sec. BtuLZHrg/Ft.2/°F 1 1.88h 5h.h 6h.8 208.5 0.57h 162.9 2 1.888 58.0 6h.5 208.0 0.57h 16h.6 3 1.88h 53.9 6b.h 207.5 0.57h 165.1 h 1.88h 5h.0 6h.h 208.0 0.578 163.0 5 2.063 58.2 61.7 208.0 0.798 162.2 6 2.078 5h.1 61.5 207.5 0.80h 161.5 7 2.156 53.7 61.0 208.0 0.83h 16h.3 8 2.157 Sh.8 62.3 208.5 0.838 169.7 9 2.172 53.8 60.9 207.5 0.8h0 161.2 10 2.359 53.7 60.5 208.0 0.913 167.1 11 2.359 58.3 60.8 208.0 0.913 160.3 12 2.375 5h.1 60.7 208.0 0.919 163.6 13 2.391 5b.2 60.5 208.0 - 0.925 157.2 lb 2.h53 5L.2 60.h 207.5 0.9h9 159.2 15 3.869 53.h 58.0 206.5 1.3h2 165.9 16 3.t88 53.5 58.0 207.5 1.3h8 162.8 17 3.531 53.9 58.5 207.5 1.366 168.8 18 3.88h 52.7 56.9 207.0 1.h87 166.8 19 3.906 52.8 57.0 207.5 1.511 168.9 water Inlet Outlet Steam 'Water Heat Transfer Run Rate Temp. Temp. Temp. Velocity Coefficie t No. #/Min. °F. °F. °F. Egg/Sec. Btu./Hr./Ft. /°F 20 3.922 53.1 57.1 208.0 1.517 161.3 21 3.953 53.3 57.3 207.0 1.529 163.9 22 b.156 5h.h 58.3 208.3 1.608 167.8 23 b.203 52.8 56.6 207.6 1.626 168.2 2t n.219 52.8 56.6 207.8 1.632 16u.6 25 b.250 52.8 56.5 207.9 1.6hh 161.h 26 b.266 52.8 56.h 207.5 1.650 157.9 27 8.656 52.9 56.3 207.8 1.801 162.h 28 8.672 52.9 56.3 207.h 1.807 163.h 29 b.906 52.8 56.1 207.6 1.898 166.1 30 6.8hh 53.7 56.0 208.2 2.6h7 161.3 31 7.126 5h.1 56.h 208.2 2.756 167.9 32 7.219 52.8 55.0 207.8 2.792 162.2 33 7.h06 53.0 55.1 207.6 2.868 159.3 3h 7.h06 52.9 55.0 208.0 2.86h 158.8 35 7.500 52.9 55.0 207.6 2.901 161.2 36 9.806 53.0 5b.? 207.3 3.638 163.8 37 10.875 58.1 55.5 208.5 b.206 156.7 38 11.000 5h.3 55.7 208.2 8.255 158.5 Average Mean Heat Transfer Coefficient 163.1 Btu./Hr./Ft.2/'F. Surface highly polished. Stearic acid powder rubbed on surface. Good dropwise condensation observed. ‘Water Inlet Outlet Steam 'Water Heat Transfer Run Rate Temp. Temp. Temp. Velocity Coefficiept No. #/M1n. ‘8. °F. °F. Ft,[sec. Btu./Hr./Tt. ‘F 39 1.869 58.0 65.8 209.0 0.568 182.8 80 1.500 53.9 66.0 209.0 0.580 191.8 81 1.516 58.0 65.8 208.8 0.586 182.2 82 1.531 53.9 65.5 207.8 0.592 188.5 83 2.656 53.8 60.0 208.8 1.027 170.8 88 2.738 53.9 60.2 208.5 1.058 178.8 85 2.750 53.7 60.0 208.8 1.068 179.2 86 2.750 53.6 60.3 208.6 1.068 191.0 87 3.625 53.6 58.6 208.0 1.802 187.6 88 3.656 53.5 58.6 208.0 1.818 192.9 89 3.656 53.9 58.8 208.2 1.818 185.5 50 3.738 53.9 58.8 208.0 1.888 173.9 51 8.806 53.6 57.8 208.2 1.708 171.8 52 8.806 53.0 57.2 207.8 1.708 190.5 53 8.806 53.3 57.6 208 .0 1.708 195.0 58 8.500 53.8 57.5 208.6 1.781 188.9 55 5.133 52.8 56.2 208.8 1.985 178.2 56 5.156 52.7 56.2 .208.8 1.998 183.8 57 5.156 52.9 56.3 208.8 1.998 178.7 58 5.188 52.8 56.1 208.6 2.007 187.7 59 5.900 53.8 56.3 208.5 2.288 175.3 -15- ‘Water Inlet Outlet Steam ‘Water Heat Transfer Run Rate Tgmp. Tgmp. Tsmp. Velocity Coefficiegt° No. #[Mln. F. F. F. Ft./Sec. Btu:[Hr.[Sq. F 60 5.968 53.5 56.3 207.0 2.308 172.7 61 5.968 53.8 56.2 208.5 2.308 170.9 62 6.032 53.5 56.3 208.5 2.333 172.9 63 6.626 53.5 56.1 208.5 2.563 176.2 68 6.656 53.2 55.8 208.5 2.575 176.6 65 6.656 53.2 55.8 208.5 2.575 176.6 66 8.616 53.1 55.2 208.5 3.333 188.3 67 8.688 53.0 55.0 208.5 3.361 176.9 68 8.718 53.2 55.2 208.5 3.372 177.6 69 8.782 53.0 55.0 209.5 3.397 177.5 AVERAGE MEAN HEAT TRANSFER COEFFICIENT 180.8 Btu./Hr./Ft.2/°F. Surface highly polished. Octadecylamine acetate rubbed on surface. 85% dropwise condensation and "better run-off" observed after 10 minutes of operation. ‘Water Inlet Outlet Steam 'Nater Heat Transfer Run Rate Temp. Temp. Temp.. Velocity Coefficient No. g_f/M1n. °F. °F. ‘8. Ft.[Sec. Btu./Hr./Ft.€/”F 70 2.202 58.2 62.2 208.5 0.852 188.3 71 2.203 58.0 61.9 208.0 0.852 182.8 72 2.219 58.1 61.9 208.0 0.858 181.8 73 2.219 59.0 61.8 206.5 0.858 180.7 -16- Water Inlet Outlet Steam Hater Heat Transfer Run Tgmp. Temp. Tgmp. TcEmp. Velocity Coefficiept No. F. 'F. F. F. Ftp/Sec. Btu./Hr:/Ft.g[°F 78 2.891 58.2 60.3 208.0 1.118 188.0 75 2.906 58.1 60.1 208.0 1.128 181.6 76 2.922 58.0 60.1 208.5 1.130 185.1 77 2.938 58.2 60.3 208.0 1.136 186.9 78 3.656 58.0 58.7 208.0 1.818 178.2 79 3.672 58.0 58.8 208.5 1.820 182.2 80 3.688 58.0 58.7 208.0 1.827 179.7 81 3.688 58.0 58.7 208.5 1.827 179.1 82 3.689 58.0 58.6 208.0 1.827 175.8 83 3.689 53.8 58.7 208.5 1.827 186.7 88 3.703 53.9 58.6 208.0 1.832 180.3 85 3.703 53.9 58.7 208.5 1.832 183.6 86 8.078 58.3 58.5 208.5 1.577 177.0 87 8.098 58.3 58.8 208.0 1.588 178.1 88 8.375 58.0 .57.9 208.0 1.692 176.5 89 8.375 58.0 58.0 208.5 1.692 180.8 90 8.806 53 .9 57.8 208.0 1.708 177.6 91 8.812 58.3 57.9 208.0 1.861 179.2 92 8.886 58.3 57.9 208.5 1.875 179.9 93 8.886 58.3 57.9 208.0 1.878 180.5 98 8.938 58.3 58.0 208.5 1.910 188.6 95 5.938 58.8 57.3 208.0 2.297 178.0 96 5.986 58.8 57.8 208.0 2.308 185.0 97 6.000 58.8 57.3 208.5 2.321 179.3 98 6.032 58.3 57.3 208.5 2.333 186.3 -17- 'Water Inlet Outlet Steam ‘Hater Heat Transfer Run Rate Temp. Temp. Temp. Velocity Coeffici nt No. #/Min. °F. 'F. °F. Ft./Sec. Btu./Hr.[F.[°F 99 7.790 58.5 56.7 208.0 2.998 175.9 100 7.812 58.8 56.6 208.0 3.022 177.2 101 7.812 58.8 56.6 207.5 3.022 177.7 102 7.886 58.5 56.7 208.5 3.035 177.5 AVERAGE MEAN HEAT TRANSFER COEFFICIENT 180.68 Btu./Hr./Ft.2/°F. -18.. DATA B. Laboratory Heat Exchanger No promoter, third day of continuous operation. Atmospheric pressure 28.9 inches of mercury. 'water Inlet Outlet Steam. Steam £32? 2733.. T331?‘ T???“ 5352. £82.. 1 37.93 58.0 197.2 38.0 88.2 2 39.52 58.0 197.2 38.5 88.7 3 81.21 58.0 193.1 33.5 87.7 8 86.88 58.0 183.9 33.5 87.7 5 55.88 53.9 168.8 33.0 87.2 6 59.35 53.8 161.9 32.0 86.2 7 78.78 53.6 151.2 32.0 86.2 8 89.35 53.5 180.0 31.0 85.2 9 101.38 53.8 130.8 31.0 85.2 10 139.09 53.1 111.2 31.0 85.2 No promoter, fourth day of continuous operation. Atmospheric pressure 29.15 inches of mercury. Water Inlet Outlet Steam Steam Run Rate Temp . T emp . Pres s . Press . No. #/Min. °F. °F. P.S.I.G. P.S.I.A. 11 33.38 56.2 207.1 38.5 88.8 13 83.02 56.1 186.9 33.5 87.8 -19- ‘Water Inlet Outlet Steam Steam TS? 2851:. T??? T523" £52. £33. 18 88.58 55.9 179.8 33.0 87.3 15 61.58 55.8 159.1 32.5 86.8 16 69.77 55.8 151.2 32.0 86.3 17 88.80 55.1 180.8 32.0 86.3 18 98.68 58.9 133.2 31.0 85.3 19 118.32 58.8 128.2 31.0 85.3 No promoter, seventh day of continuous operation. Atmospheric pressure 28.91 inches of mercury. 'Water Inlet Outlet Steam. Steam 32? 2233.1. T??? TT‘? PETE. SETH. 20 30.77 55.3 207.7 36.0 50.2 21 38.81 55.1 190.8 38.0 88.2 22 82.62 58.9 188.8 38.5 88.7 23 89.23 58.8 175.3 38.0 88.2 28 60.33 58.6 158.0 33.0 87.2 25 77.88 58.8 186.8 32.5 86.7 26 98.19 58.3 133.9 31.5 85.7 27 96.65 58.2 130.6 32.0 86.2 28 118.98 58.1 122.8 31.5 85.7 -20- Octadecylamine acetate as promoter. Atmospheric pressure 28.59 inches of mercury. Two to four parts per million. 'water Inlet Outlet Steam Steam $2? 27132.. T??? TEE" £882. £883. 29 50.73 55.8 171.3 36.5 50.5 30 57.79 55.2 162.3 36.0 50.0 31 70.52 55.0 189.8 36.0 50.0 32 86.03 58.7 137.5 354) 89.0 33 107.80 58.6 128.9 38.0 88.0 119.5 32.5 86.5 38 119.79 58.5 Octadecylamine acetate as promoter. One hundred parts per million. Atmospheric pressure 28.8 inches of mercury. 'Water Inlet Outlet Steam Steam Run Tsmp. Temp. Tgmp. Press. Press. No. F. F. F. P.S.I.G. P.S.I.A. 35 27.27 55.7 179.5 38.5 52.6 36 31.20 55.8 176.0 36.5 50.6 37 37.29 55.0 167.9 35.0 89.1 38 86.82 58.9 162.0 35.0 89.1 39 58.33 58.5 189.8 38.0 88.1 80 81.38 58.3 131.8 33.5 87.6 81 91.10 58.3 128.5 33.0 87.1 82 100.10 58.3 122.0 33.0 87.1 83 108.30 58.1 116.2 32.5 86.6 -2l- RESULTS B. Laboratory Heat Exchanger (Con'd) No promoter, third day of continuous operation. Atmospheric pressure 28.9 inches of mercury. Heat Transfer ,-3 'Water Run Coefficient x 1‘) Velocity _ 1 No. Btu./Hr./Ft.2/°F Ft./Sec. V'8 V73 1 222.0 8.505 0.821 0.501 1.996 2 230.2 8.388 0.839 0.518 1.930 3 230.5 8.338 0.857 0.535 1.869 8 238.5 8.268 0.520 0.598 1.688 5 230.1 8.386 0.616 0.678 1.875 6 228.3 8.380 0.659 0.717 1.395 7 289.0 8.016 0.830 0.8615 1.161 8 255.6 3.912 0.992 0.9936 1.006 9 251.6 3.975 1.125 1.0987 0.910 10 283.8 8.102 1.580 1.813 0.708 No promoter, fourth day of continuous operation. Atmospheric pressure 29.15 inches of mercury. Heat Transfer _ _3 “Water Run Coeffi cierzlto Uo 3‘ 1° Velodty . 8 _1_8 No. Btu:/Hr./Ft. / F Ft./Sec. v V 11 216.9 8.610 0.371 0.853 2.208 12 211.2 8.735 0.821 0.501 1.996 13 220.9 8.527 0.878 0.558 1.805 Heat Transfer 1 -3 Water Run Coefficie fig Xilo Velocity .8 .—lg No. Btu./Hr./Ft. Ft.[Sec. v V’ 18 227.8 8.389 0.539 0.609 1.682 15 228.1 8.862 0.683 0.737 1.357 16 228.9 8.369 0.778 0.815 1.227 17 288.5 8.028 0.981 0.9851 1.015 18 250.2 3.997 1.095 1.0753 0.930 19 289.6 8.006 1.269 1.210 0.826 No promoter, seventh day of continuous operation. Atmospheric pressure 28.91 inches of mercury. Heat Transfer _ _3 Water Run Coefficient UO 3 10 Velocity .8 .13 No. Btu./Hr./Ft.2/°F Ft./Sec. V V’ 20 199.6 5.010 0.338 0.821 2.375 21 208.2 8.803 0.827 0.507 1.972 22 213.1 8.693 0.869 0.585 1.835 23 219.6 8.558 0.582 0.612 1.638 28 217.2 8.608 0.668 0.721 11387 25 280.9 8.151 0.856 0.883 1.133 26 283.1 8.118 1.036 1.0287 0.972 27 235.3 8.250 1.063 1.0502 0.952 28 285.5 8.073 1.268 1.206 0.829 -23- Octadecylamine acetate as promoter. Two to four parts per million. Atmospheric pressure 28.59 inches of mercury. Heat Transfer 1 water Hun Coefficient . ‘80 x 10‘3 Velocity 8 'ES 80. Btu./Hr./Ft. / F. Ft./Sec. V' V' 29 210.1 . 8.760 0.563 0.632 1.582 30 218.7 8.658 0.681 0.701 11827 31 221.3 8.519 0.783 0.822 1.217 32 227.7 8.392 0.955 0.9638 1.038 33 233.6 8.281 1.192 1.1502 0.8698 38 280.0 8.167 1.330 1.256 0.796 Octadecylamine abetate at promoter. One hundred parts per million. Atmospheric pressure 28.8 inches of mercury. Heat Transfer .1 _3 ‘water Run Coefflclegto U o x 10 Velocity .8 '_:.L8 No. Btu./Hr./Ft. / F. Ft./Sec. v V 35 122.9 8.137 0.300 0.382 2.618 36 136.9 7.305 0.383 0.825 2.353 37 150.3 6.653 0.810 0.880 2.083 38 178.6 5.727 0.515 0.588 1.701 39 172.7 5.790 0.598 0.663 1.508 80 198.6 5.035 0.895 0.9188 1.093 81 212.9 8.697 1.002 1.000 1.000 82 209.0 8.785 1.101 1.073 0.932 83 197.8 5.066 1.187 1.122 0.891 ~28- TABLE OF RESULTS Finger Type Condenser Average Mean Heat Condition Transfer Coeffficient Increase Btu./Hr./Ft. / F (Percent) No Promoter 163.1 -- Stearic Acid 180.8 10.85 Octadecylamine Acetate 180.68 10.80 ORAPHS AND DIAGRAl-IS 250 {5' 8 OVERALL m7 TRANSFER COEFFICIENT-B.T.U./HH.FT.20F. H o O *2;- GRAPH I X - NO PROMOTER 0.2 0.8 0.6 WATER VELOCITY-FT. 0.8 FER SEC. 1.0 1.? 26: D- - D 1 GRA 2-1] popomo 100 popomo 1.2 0. 1 80 mm 8 m m. e m mm on m 2$ m m, , m 2 1 .mowhmcmz\.D.H.mIBZMHOHmhmoo mmmmz ohsmwmnm . onuwozwooon.iu_ .\\\\iopHa> Emopm QGHA can: DISCUSSION -32- DISCUSSION A. Finger Type Condenser The amount of heat transferred was determined from.weight flow rate of cooling water and temperature rise in the cooling water. The megnitude of the calculated overall heat transfer coefficients could not be compared with previous studies (5, lb, 22) on this type of apparatus; no data of this nature was reported. The magnitude of the overall coefficients seem to be a little conservative. This was also true for values reported by Wilson (27) on small straight pipes. 'Wilson concluded that "quantities of air collecting on the water side greatly increased the resistance to heat flow" (27). This is believed to be the case perhaps, to a greater extent in the finger type apparatus because as the water reversed its direction at the end of the miniature condenser pockets of air could possibly be built up and gradually creep along the inside of the larger copper tube, thus increasing the resistance to heat transfer. Very large resistances are reported by Perry (19) for air or gas films. Another reason for the comparatively low heat transfer co- efficients be the thickness of the condensate film. Although no accurate measurements of this thickness could be made an abnormally thick condensate layer was observed. A plot of overall heat transfer coefficients against velocity gave a straight line relationship with a slope of zero. Due to this fact, the overall heat transfer coefficients could be averaged -33... directly for the magnitudes of velocities used. Nagle and Drew (1h) who used a small visual condenser, reported that, less than fifteen percent variation in overall heat transfer coefficients was observed when the water rate was varied between h.l7 and 12.17 lbs./min. In the case of the finger type condenser, the largest deviation was 6.36 percent variation from the mean when the water rate was varied between l.h8h and 11.000 lbs./min. This, along with the abnormally thick condensate layer observed, might lead to the conclusion that the condensate layer or air film was a controlling resistance. A relative comparison between the mean average heat transfer coefficients of the film condensate and the type of condensation promoted by octadecylamine acetate show an increase of 10.8 percent. Although only approximately'hS percent of the condensate seemed to be forming in drops in the case of the octadecylamine acetate a much greater run off was observed. Because of the fact that only LS percent of the surface area was covered with drops and that the mean overall heat transfer coefficients almost equaled those determined using stearic acid where 100 percent dropwise condensation was observed, the increased heat transmission was concluded to be also due to the greater condensate run off rate. B. Laboratory Heat Exchanger The heat transfer coefficients, calculated from the data for the octadecylamine acetate promoter are plotted on Graph II, while those obtained in the absence of the promoted are plotted on Graph I. The promotemlinduced coefficients were lower than those determined -31;- without the promoter. A'Hilson (27) plot was made (Graph III) by plotting the reciprocal of overall heat transfer coefficients against water velocity. The quality of the power plant steam was then questioned. Tests were made employing the finger type apparatus at positions A and B as shown in.Diagram III. Results of the type of condensation observed are plotted in Graph IV. Inspection of this graph shows that while the main line steam gave pure filmwise condensation, the test apparatus system gave varying degrees of dropwise condensation. It appears that oil used in the threading and cutting of pipes and/or contaminants in new pressure regulating valve and/or pipe compound were of sufficient quantity to promote dropwise condensation even after a six month period of irregular operation. Thus, dropwise condensation was present before the promoter was introduced and, therefore, hindered the correct application of the amine. In the case of the one hundred.parts per million application of amine, the slope of the curve is much steeper at the low water velocity ranges than the slope of the curves at two to four parts per million and no promoter. This would indicate a "washing" action which removed a possible emulsion of amine and water from the surface of the tubes (13). One would suspect from observation made on the finger type apparatus that there is a hindering or an undesirable reaction between the contaminants and the promoter. The net result is -35- probably a decrease in non-wettability of the amine; since it has been reported (26) that the corrosion inhibition of the filming amines are reduced in plants having excessive quantities of oil in steam. CONCLUSIONS -36 - CCNCLUSIONS The following conclusions were made from the data and results reported: A. Finger Type Condenser (l) (2) (3) (b) octadecylamine acetate rubbed on the surface of a highly clean and polished copper surface promotes forty-five percent dropwise condensation. the direct effect of octadecylamine acetate on overall heat transfer coefficients show an increase of 10.8 percent. the increase of these overall heat transfer coefficients is due to better condensate run off and promotion of drop- wise condensation. -higher overall heat transfer coefficients obtained by stearic acid were almost equaled by the use of octadecyl- amine acetate. B. Laboratory Heat Exchanger (1) (2) oil used in cutting and threading of pipes is of sufficient quantity to promote dropwise condensation over the period of time considered in this research. if further'wark is to be done with steam condensation, a continuous, contaminant free source of steam is required, and a new, clean heat exchanger with.a pyrex plate glass window to observe type of condensation. l. 2. 7. 8. 9. 10. -37- BIBLIOGRAPHY Brown, G. G. and Associates, "Unit Operations," John'Eiley & Sons, Inc., New York, pp. 1.1.8463, 1950. Denman,'w. L., “Improvement of Heat Transfer by the Use of Filmeen," Dearborn Chemical Co., Chicago, 111., Bulletin No. 9hl, ( August 3, 19Sh). Denman, W. L., "Method of Treating'Water Including Boiler 'Waters and Composition Therefore," U. S. Patent No. 2,h00,5h3. Drew, T. B., W. M. Nagle, and‘w. Q. Smith, "The Conditions for Drapwise Condensation of Steam," A.I.Ch.E. Trans., Vol. . 31, pp. 605-21, 1935. Emmons, H., "The Mechanism of Drop Condensation," A.I.Ch.E. Trans. Vol. 35, pp. 109-122, 1939. Fatica, N., and D. L. Katz, "Dropwise Condensation," Chemical Engineering Progress, Vol. hS, November, 19h9, pp. 661-675. Fithatrick, J. P., S.Baum, and W. H. McAdams, "Dropwise Condensation of Steam on Vertical Tubed," A.I.Ch.E. Trans. Vol. 35. pp. 97-197, 1939. Hampson, H., "Proceedings of the General Discussion on Heat Transfer,“ Inst. of Mech. Engrs. London, & American Soc. of Mech. Engrs., New York, pp. 58-61, 1951. Jakob, N., "Heat Transfer," John Wiley'& Sons, Inc., New York, pp. 693-696, 19h9. Jacob, H., "Zeit. Ver deut. Ing." Vol. 76, pp. 1161, 1932. Kahler, H. L., and J. K. Brown, "Experiences with Filming Amines in Control of Condensate Line Corrosion," Combustion, January, 19Sh, (Reprint). McAdams,‘W. H., “Heat Transmission," 3rd Ed., McGraw-Hill Book Co., New York, pp. 3h7-351, 195b- Nagle, W. M., G. S. Bays, L. M. Blenderman, and T. B. Drew, "Heat Transfer Coefficients During Dropwise Condensation of Steam," A.I.Ch.E. Trans. Vol. 31, pp. 593-60h, 1935. Nagle,'W. N., and T. B. Drew, "The Dropwise Condensation of Stem," AoIeCheEe Tran-Se V01. 30, pp. 217-255, 19330 15. 16. 1?. 18. 19. 21. 22. 23. 2b. 25. 26. 27. -33- Nagle, W. M., U. 5. Patent 1,995,361 March 26, 1935. Nusselt,'w., "Zeit. Ver. deut. Ing." Vol. 60, pp. 5h1-509, 1916. Obrecht, H. F., "Filming Inhibitors for Corrosion Control and Increased Heat Transfer in Steam Condensing Systems," Not Published. To be presented at h6th Annual National District 'Heating Association, Chicago, Hay 2h, 1955. Obrecht, M. F., et a1., "How Filming Amines Control Corrosion in Piping," Heating, Piping and Air Conditioning, May 1955, pp. 129-132. Perry, J. H., "Chemical Engineer's Handbook," 3rd Ed., HcGraw- Hill Book Co., 1950, pp. h56-h98. Schmidt, E., L! Schuring, and'W. Sellschopp, "Techniéhe I-iechanik und Thermodynamik", Edition 1, pp. 53, 1930. Shea, F. L., and N.‘w. Krase, "Dropwise on Film Condensation of Steam," A.I.Ch.E. Trans. Vol. 36, pp. h63-h90, l9h0. Spoelstra, H. J., "Arch. Suikerind, " Vol. 39, pp. 905-56, 1931. Staff Reporter, "Hare Heat, Less Corrosion," Chemical Eng., pp. lbO, April, 1955. Tanzola,'W} A., and J. G. Weidman, "film Forming Corrosion Inhibitors also Aid Heat Transfer," The Paper Industry, April, l95h: pp. h8e 'weidman, J. 0., "Experiences with Filming Amines for Improving Heat Transfer," Presented at American Power Conference, April 1, 19550 In press. Wilkes, J.'W.,'W. L. Denman, and M. F. Obrecht, "Filming Amines - Use and Misuse in Power Plant‘Water - Steam Cycles," Proc. 17 Ann. Amer. Power Conf., April 1, 1955. Wilson, E. E., "A Basis for Rational Design of Heat Transfer Apparatus," Amer. Soc. Mech. Engrs. Trans., Vol. 3?, pp. h7‘82: 19150 sip 13 '5? _ ‘ arse 9341 - 3 an award! LIBRARY » 3 A «03 $774 Squire ‘l‘i‘i‘i‘i‘il‘ii 1293 024 44