RESPIRATION RATE OF HARVESTED FORAGE By Robert Herrick Wilkinson AN ABSTRACT OF A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Agricultural Engineering 1964 ABSTRACT RESPIRATION RATE OF HARVESTED FORAGE by Robert Herrick Wilkinson Cold storage provides one method of maintaining high quality fresh hay and reducing dry matter losses. Knowledge of the effects of moisture content, crop maturity, storage temperature and time on the dry matter losses, and rate of respiration of the hay and its associated microorganisms, is valuable for de- signing cold storage systems for hay. A respiration chamber was constructed to hold samples of 100 lbs. of fresh hay. The temperature, relative humidity and rate of air flow were con- trolled. Heat production, moisture and weight losses on the product were deter— mined. Experiments were conducted on alfalfa using: temperatures at 250, 450, 650 and 800F.; moisture contents of fresh, 70% w. b. , and wilted, 50% w.b. , and crop stages of mature and immature. Maximum rates of respiration were deter- mined over a 3 to 5 day period. The respiration rate of fresh alfalfa was studied by storing the material for as long as 30 days. The respiration rate increased with an increase in either moisture con- tent or temperature or both, ranging from zero to 25, 200 Btu/hr. -ton D. M. at SOOF. for fresh immature alfalfa over a 3-5 day period. Wilting the material reduced the respiration rate to 7550 Btu/hr. -ton D. M. at 800F. and 48.9% moisture, w.b. Respiration of alfalfa at 250F. was zero, regardless of the moisture content or stage of maturity. Robert Herrick Wilkinson Respiration rate and dry matter losses continue to decrease with time in storage as a result of cell aging and a slight drying effect. The dry matter loss of fresh material stored at 600F. exceeded the loss of high quality field cured hay after 13 days in storage, being approximately 565 lb. /ton D. M. The dry matter loss of fresh material stored at 450E. exceeded the loss of field cured hay after three weeks in storage. Fresh hay can be stored at 3001?. for several months be- fore the total loss will exceed the loss during field curing. Hay can be stored in— definitely at 25°F. Very immature fresh wheatgrass demonstrated a respiration rate ap- proximately 10, 600 Btu/hr. -ton D. M. higher than alfalfa for corresponding con- ditions. Wheatgrass respired at a rate of 35, 800 Btu/hr. -ton D. M. and alfalfa respired at 25,200 Btu/hr. -ton D. M. at 800F. At 250E, wheatgrass has a res- piration rate of 10, 600 Btu/hr. —ton D. M. An equation was developed to calculate the rate of respiration of fresh alfalfa between 300F. and 8OOF. This equation has the form: R: (6.56t _ 100)e (.000208t - .018) 9 where: R = respiration rate Btu/hr. -100 lb. fresh. t = temperature OF. G = time, hours. This equation is valid up to 150 hours after harvest. The Q10 found for alfalfa ranged from 2.2 at 48°F. to 1. 4 at 80°F. Approved COM d' W {77y RESPIRATION RATE OF HARVESTED FORAGE By Robert Herrick Wilkinson A THESIS Submitted to Michigan State University in partial fulfillment. of. the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Agricultural Engineering 1964 VITA CANDIDATE FOR THE DEGREE OF DOCTOR OF PHILOSOPHY Robert Herrick Wilkinson Final Examination: April 30, 1964, Agricultural Engineering Building, Room 218. Dissertation: Respiration Rate of Harvested Forage. Outline of Studies: Major subject: Agricultural Engineering Minor subjects: Mechanical Engineering (Refrigeration) Biographical Items: Cr0p Science Born: September 23, 1931, Detroit, Michigan. Schooling: High School: Cass Technical, Detroit, Michigan 1946-1949 Aeronautical Program Undergraduate Studies: Wayne University 1949-1951 Mechanical Engineering Michigan State University 1951-1953 B. S. Agricultural Engineering Graduate Studies: Experience: 1954-1955 Michigan State University 1955-1956 M. S. Major subject: Agricultural Engineering (Soil and Water) Minor Subject: Soils Statistics Michigan State University 1960-1964 Ph. D. Agricultural Engineering (Processing) Project Engineer, Tractor and Implement Division Ford Motor Company Robert Herrick Wilkinson Experience: (continued) 1956—1959 Agricultural Engineer, Research, Michigan State University . 1959-1960 Instructor, Michigan State University 1960-1964 Graduate Assistant, Michigan State University Member: American Society of Agricultural Engineers Alpha Gamma Rho ACKNOWLEDGMENTS Recognition, appreciation, gratitude and my most sincere thanks are expressed: To Dr. Carl W. Hall, Agricultural Engineering Department, for his guidance, interest and unfailing support throughout this study. The examples of pro— fessional discipline set by Dr. Hall as well as his personal friendship and counsel have been inspirational and I consider myself privileged to have had this experience. To Dr. Carter M. Harrison, Crop Science Department, Professor Donald J. Renwick, Mechanical Engineering Department, and Dr. Frederick H. Buelow, » Agricultural Engineering Department, for their counsel and advice and their assistance on the guidance committee. To Dr. Alexander H- Mark, Chief Engineer Advance Research Design, Massey- Ferguson Company, and Dr. Arthur W. Farrall, chairman of Agricultural Engineering Department, for providing financial support and facilities to carry out this study. To Fred W. Bakker-Arkema and Verl E. Headley, fellow graduate students in Agricultural Engineering, for their assistance in the laboratory, their sug- gestions and companionship. To James B. Cawood, Glen Shiffer and Harold W. Brockbank of the Agricultural Engineering Department for helpfulness and interest during construction and ii use of the equipment. To Ellen, my wife, for her patience and understanding. These studies could not have been completed without her very real personal sacrifices, assistance and support. iii TABLE OF CONTENTS ACKNOWLEGMENTS . LIST OF TABLES . . . LIST OF FIGURES . . . . ................... LIST OF SYMBOLS . CHAPTER I. INTRODUCTION Objectives CHAPTER 11. REVIEW OF LITERATURE . Factors Affecting Respiration . Losses in Storage . . . 'Heat Development of Hay . Heat Measurement. Respiration Rates and Drifts Losses of Dry Matter in Field Curing and Conventional Handling CHAPTER III. EQUIPMENT AND PROCEDURE Calculations . Chamber Construction Controls Temperature Cooling Humidity . Air Flow . Calibration Heat Infiltration to the Chamber Air Flow . iv Page 22 22 24 26 26 26 27 28 28 28 30 TABLE OF CONTENTS - Continued CHAPTER III. - Continued Heat Output Measurement . Experiments . Procedure CHAPTER IV. DISCUSSION AND RESULTS The Equipment The Chamber . . Air Flow Measurement . . Temperature Measurement . Respiration Curves . Dry Matter Losses Respiration Equation . CHAPTER V. SUMMARY AND CONCLUSIONS Summary Conclusion REFERENCES . APPENDIX . Sample Calculations . List of Constants Used . Page 30 31 32 34 34 34 35 36 36 41 59 67 67 68 70 74 74 77 TABLE LIST OF TABLES Summary of respiration rates and losses Accumulative heat of respiration and dry matter loss Slopes and intercepts of respiration curves Respiration values, calculated vs. experimental . vi Page 47 55 63 66 FIGURE 10. 11. 12. 13. 14. LIST OF FIGURES Cross section of respiration chamber . Thermocouple locations . Chamber and instruments (M.S.U. Photo No. 621576-6) Chamber evaporators and heaters (M.S.U. Photo No. 621636-2) Resistance heaters for chamber (M.S.U. Photo No. 621636-4) Refrigeration compressor (G) and graduated cylinder for condensate (I) (M.S.U. Photo No. 621636-3) Precision hot wire anemometer (M.S.C. Photo No. 64624-1) Placing hay into chamber (M.S.U. Photo No. 621646-6) Spraying condensate back on material (M.S.U. Photo No. 631635-2) Pump to spray condensate (M.S.U. Photo No. 631635-3) Heat of respiration, fresh immature alfalfa . Heat of respiration, fresh mature alfalfa Heat of respiration, wilted immature alfalfa . Heat of respiration, wilted mature alfalfa . vii Page 16 18 18 19 19 20 20 21 21 43 44 45 46 LIST OF FIGURES - Continued FIGURE 15. 16. 17. 18. ’ 190 20. 21. 22. 23. 24. 25. Correlation of the heat of the experiment and the heat of the calculated dry matter loss of alfalfa . Correlation of the heat of the experiment and heat of the dry matter loss of alfalfa as determined by chemical anaIYSis O O O O O O O O D O O 0 O 0 O O O Respiration of alfalfa as affected by moisture and tem- perature up to 100 hours. . . . . . . . . Heat of respiration of reed canarygrass, fresh mature Heat of respiration of wheatgrass, fresh immature . Heat of respiration, fresh alfalfa, extended test Dry matter loss vs. time for alfalfa Respiration rate: of fresh alfalfa, constant moisture Slopes of respiration curves vs. time . Slopes of respiration curves, k vs. temperatures Original respiration rate vs. temperature . viii Page 49 50 51 52 53 54 57 58 62 64 65 B B 5 merge CF? LIST OF SYMBOLS are a specific heat dry basis Dry Matter inside surface conduction outside surface conduction original rate of respiration conductivity factor line slope conductivity factor mass flow line 810pe line slope pressure density heat immediate rate of respiration temperature over all heat conduction time wet basis sq. ft. Btu/1b. -°F. Btu/OE-sq. ft. 0 Btu/ F.-sq. ft Btu/hr. - 1001b. Fresh Btu/hr.-in.-OF.-sq. ft. Btu/hr. °F.-sq. ft.—tota1 thickness lb. /min. 1n. of H20 lb. /cu. ft. Btu/hr. Btu/hr. - 100 lb. Fresh °F. Btu/0F. - hr. hours - sq. ft. CHAPTER I INTRODUCTION Hay has long been the most important harvested crop for livestock feed. In terms of acreage harvested and tonnage fed it far exceeds any other crop, be- ing approximately 100 million tons annually in the U. S. Despite this distinction, haymaking has been and continues to be one of the most laborious jobs on the farm. The practice of harvesting hay in the long loose form has been decreas- ing rapidly since the end of World War II, when balers and choppers became available, but much handling and labor continued in the haying operation. The search for easier and more satisfactory techniques has continued with such in- novations as elevators, blowers, smaller bales and automatic bale throwers. Other mechanical devices for more effective mowing, conditioning, picking up, moving and feeding the hay have been employed with varying degrees of success, but the total haymaking procedure remains very laborious and dependent on good drying weather for quality hay. Since the discovery in 1952 that hay would stick together if compressed sufficiently, there has been considerable speculation about the advantages of har- vesting and handling hay in 2 - 10 oz. units called wafers. This naturally led to investigations of the means of producing such wafers and alleged advantages; i. e. easier handling, automatic mechanical feeding, minimum dust, reduced weather 1 hazard in harvesting and increased animal gains. The research done on hay wafering indicates that this method of har- vesting will not be the complete answer to a new and revolutionary haymaking process. Thus, further study of the processes of making hay was stimulated. One of these concepts was that of refrigerating the fresh cut hay, thus keeping a fairly high moisture content, and reducing spoilage and heating to a point that quality hay resulted. In order to accurately calculate cooling loads for the harvested hay, it is necessary to know the amount of heat to be expected from respiration and bac- terial action at various conditions of temperature, humidity, moisture and ma— turity. A comparison between the dry matter loss of hay caused by convention- al harvesting, as opposed to the losses incurred by storing under various con- ditions is a point of economic importance. Either a definite increase in the qual- ity of the hay or a reduction in the loss of dry matter or both, could possibly justify any increased expense of this method. It is with these specific problems of respiration heat of harvested hay and dry matter loss that this study is concerned. Objective 8 1. To develop equipment suitable for measuring respiration heat of forage ma- terial and associated microorganisms. 2. To find the maximum heat of respiration under various conditions of tem- perature, moisture and maturity of forages. To find the dry matter loss of the forage material over various storage periods. To find the rates of respiration as related to time and moisture content. To correlate variables involved in the respiration rate of forages. CHAPTER II REVIEW OF LITERATURE Although haymaking has been an established practice for many centur- ies, "making hay" has for the most part been an "art” with very little scientific experimentation to establish what makes good hay better, in less time, with less labor and cost. Practical experience has shown that bay of approximately 13-18% mois- ture content will generally "keep" in fair condition, but a higher moisture con- tent may result in heating and spoiling of the hay and even spontaneous combus- tion. Exactly why high moisture hay "heats" and how much heat is generated under various conditions, have long been matters of interest and conjecture. Although there has been very little research done on hay specifically, the studies conducted in measuring amounts and rate of heating in respiration of other products indicate the expected result of an increase when temperature and moisture increase. Factors Affecting Respiration Numerous investigators have pointed out that respiration increases with increase in the moisture content. Snow and Wright (1945) have shown that in bran, this increase was due to two causes. 1.) As the moisture content rose, 4 the respiration of the plant cell increased and 2.) the respiration of develOping microorganisms increased. They found that less than 13% moisture gave low respiration, 15-19% moisture was not safe for long storage, and 20% or more resulted in rapid deterioration. In a closed container there was a correspond- ing increase in N and a decrease in dry matter. 2 Bailey and Gurjar (1918) also reported factors affecting the respiration of wheat grain. They found respiration increased with moisture, temperature, (up to 55°C. after which respiration deer-eased) period of dampness, and un- soundness. Respiration decreased with density, plumpness, increased CO and 2 lack of O . 2 Coleman and others (192 8) reported that as the moisture increased the respiration of sorghum grain increased. They found no sharp increase in res- piration at 14% as with wheat and that broken grain and increased temperatures also increased respiration. Over 14% moisture and IOOOF. the stored grain tended to "go out of condition. " The metabolic heat and moisture produced by insect activity in the stored grain may be of considerable importance. Lindgren (1935) found 350C. to be the optimum temperature for insect activity and their heat of respiration could initiate the "heating" of the grain, causing it to go out of condition. Milner and Geddes (1945) found high moisture grain caused heating that resulted in air movement and CO2 concentrations in the upper portions of the grain in storage. Bailey (1921) made an interesting observation in the storing of corn. He found that the rate of respiration was higher later in the storage life than it was immediately after harvest. Possibly a form of dormancy was involved due to a reduced rate of diffusion of 02 into the cells, or of CO2 from the cells. The fact that cracked, broken and sprouted kernels respired more than sound grain, and that the germ of the grain was more active in respiration than the endosperm was reported by Bailey and Gurjar (1920). Von Schreven (1956) has reported that although the moisture content of any hay was the most important factor promoting heating, the nitrogen top-dress- ing on the growing crop, high clover content, young grass and large stacks (low aeration) also promoted heating. A study by Burik and Orth (1954) states that respiration will take place at moistures above 20% and that the heat output is directly proportional to the density volume, protein content and fineness of chopping. They suggested that the hay be kept below 40°C. (104OF.) in order to decrease nutrient loss and pre- vent the build up of heat "loving" organisms. Above 450C. there is a marked decrease in digestible protein and a loss of 10-15% of dry matter. The temper- ature fluctuation showed an initial peak at 2-1/2 days followed by an 11 day rest period. This was followed by temperature peaks caused by microorganisms. Cooling was applied to keep temperature below 40°C. Losses in Storage Schole (1962) has presented work on the respiration losses of wheat. He found that the limits of decay rarely exceeded 1%. (This was for a recently dried upper layer.) If the limit of decay was exceeded (visible mold) the res- piration losses increased up to 6. 5% of the initial dry matter. . Dawson and Musgrave (1950) reported that the relative humidity low enough to prevent mold in a given time was approximately the same for all hays. They found that hay could be stored at 25°C. and 70% relative humidity for 200 days. Their conclusion was that the differences in time of molding were not so much properties of the hay as they were of the organism population differences. Kane (1937) has shown that the loss of carotene under field drying can be as'much as three times as high as the loss of green color. Eighty percent of the carotene can be lost in 24 hours of fielddrying. This could be reduced by quick drying. Losses were increased by temperature increases and expo- sure to light. The storage work by Wright (1941) on grasses showed that the rate of mold was directly pr0portional to the relative humidity. Safe storage occurred at about 67% relative humidity (13% moisture). Long storages might result in increased mold activity. Seventy-five percent relative humidity was not safe. A chart relating the time required for mold to develop vs. temperature in wet hay was presented by Terry (1947a). This chart shows the minimum time to moldis approximately 40 hours in a range between 800 to IOOOF. Above or below these temperatures the time to mold increased rather sharply. Heat Development of Hay Several studies have been made in an attempt to determine what pro- portion of the heat required to dry hay can be acquired from the hay itself. Hall (1957) presented a summary of this work and pointed out that a large portion of ‘ the wide variation in results was due to variations in environment and product. Terry (1947b) suggested four factors which affected the heat of respir- ation. He predicted respiration to 1.) increase with relative humidity increase; 2.) decrease with air flow increase; 3.) decrease as the surface area % volume ratio increased; and 4.) to increase with temperature to a maximum and then decrease. He estimated the heat output from hay could be 5000 Btu/ lb. of D. M. (75% of maximum heat available) and at a cost of $12. OO/ton of hay at 15% mois- ture, this was expensive heat. Experimenting with barn curing of hay with heated air, Strait (1944) brought out the fact that heated air shortened the curing time, eliminated mold and resulted in better quality hay. He reported that approximately 40% of the heat required to dry the hay was produced by the respiration of the hay. His data showed that with an air flow of 13, 000 c.. f.. m. approximately 1. 9 Btu/lb. of dry air was deve10ped. This was equivalent to 9800 Btu/hr. -ton dry material. Frudden (1946) pointed out that rate of moisture removal was depen- dent on 1.) rate of air flow; 2.) condition of air, temperature and humidity; 3.) heat of fan; and 4.) heat from bacterial action. He estimated factors 3 and 4to be approximately 10-15% of the total effect. The work done by Dawson and Musgrave (1946) indicated that the heat of the air stream temperature decrease was approximately 40% of the total heat removed and that the humidity increase was approximately 20%. The balance of the heat was from the dry matter loss (combustion of glucose) and was as much as 60% of the heat required to dry the hay. The heat required to evaporate mois- ture from partly cured hay was greater than that required to evaporate moisture from a free surface, but the difference was negligible. This fact was also con- firmed by Dale and Johnson. (1955) 9 In an experiment involving a large quantity of hay, Hendrix (1947) re— ported that 63% of the heat required for drying came from respiration. For the period of time involved and the quantity of hay used, this amounted to an aver- age of 6600 Btu/hr. -ton dry matter. Feldman (1956) has a rather complete analysis of the oxidation equa— tion C 6H1 2O 6 + 602 and under the condition of his experiment (20% moisture hay, 10% ash), claimed that of the 3750 K. -Ca1. released, 1900 K. -Cal.were available for drying the hay after evaporation of its own water and any water formed by the reaction. This amounts to 51% of the heat released by one kilogram of dry matter or 3420 Btu/lb. of dry matter consumed. The heat generated by partially cured hay was appreciable. Davis and Barlow (1948) suggested that this might account for the drying observed in the upper layers of hay even though the air reaching these layers had reached ahigh humidity. Heat Measurement In general, the rate of respiration may be found experimentally by one of two ways. The most common technique is that of utilizing the endothermic relationship of O . 06H12 6 + 602+6H20+ 6C02 + 673 cal where the material respiring is considered to be the simple sugar glucose, and oxidation is complete. The amount of CD2 liberated is carefully measured and the amount of heat liberated is derived by the relation of 2. 6 cal. per 1 gm. C02. This is the most common method of making this calculation, as the equipment 10 required and techniques lend themselves to laboratory procedures. The other method, not so commonly used, is to construct a calorimeter device, in which the heat values can actually be measured. Many studies have been made on the respiration rate of fruits and veg- etables using the method of measuring the C02 evolved. A rather complete tab- ulation of the results of these studies is presented by U. S.D.A. Handbook No. 66 and by Hall (1963). Numerous techniques and variations in equipment, all utilizing the CO2 measuring principle have been reported. Haller and others (1932) reported re- sults on various fruits using a laboratory method in which both 02 consumption and C02 evolved were measured. This allowed respiratory ratio 9%2 to be cal- 2 culated. Musgrave and Moss (1961) and Thomas and Hill (1937) carried out ex- periments under field conditions using plastic canopies under which C02 emis— sion was measured. An apparatus to automatically measure CO2 by an absorbing solution and the replacement of 02 by an electrolytic generator has been reported by Wagner and Porter (1961). As the technique of basing heat output on the amount of CO2 evolved is the method most applicable to laboratory situations and since it is by far the most widely used method of making respiration measurements, its dependability is important. To check the correlation between heat output based on CO2 evolved and actual measured heat output, Green, Hukill and Rose (1941) set up experi- ments to make both measurements simultaneously. Their rather elaborate 11 equipment and meticulous methods showed the heat indicated by the CO2 method to be within 10% of actual measurements. In the construction of chambers for measurement of heat output of bio- logical products, temperature, humidity and air flow must be controlled. In this respect, calorimetric chambers have similar problems to those of growth chambers. Morris (195 7) has presented two possible arrangements for the control of temperature and humidity in a plant growth room. Both arrangements use a cooler to dehumidify the air and a heater to adjust the temperature. The first method is a full flow arrangement and the second utilized a bypass of the cooler, thus reducing cooling and heating loads. He points out that the air circulation rate should be kept as low as possible in order to reduce the heating and cool- ing load. Changes in sensible heat affected only the heat load, but changes in dew point affected both heating and cooling loads. Housely and others (1961) have published recommendations for a growth room. They found 160 air changes per hour desirable. Humidity was added as needed by steam injection and CO controlled by bleeding 10% air change per 2 hour. In this case as well as Morris's work, lights and special cooling were required. A complete analysis of the errors involved in making heat measure- ment in calorimetric chambers has been made by Schaper (1959). He compared accuracy of the non recirculating air type as opposed to the recirculating type and reports far greater accuracy w1th less rigid controls for the recirculating type. 12 Respiration Rates and Drifts Materials that are respiring are generally characterized by a term called the Respiratory Quotient. The Respiratory Quotient (RC2) is the ratio of CO2 evolved to O2 consumed during the respiration process. Briefly a R.Q, of 1 indicates carbohydrates respiring; R.Q . of .7 indicates fats and 1. 33 indicates acids as the respiring material. This subject is discussed in most text books that deal with the subject of plant respiration or plant physiology. Excellent discussions are presented by Stiles and Leach (1960) and by James (1953). The Q10 term is one that is useful in respiration work. The Q 10 value of a material is the ratio of reaction rate at one temperature to the reaction rate at a temperature 10°C. lower. For most biological products at room temperature Q10 is approximately 2. The Q10 may not be constant as the temperature varies from low to high but may drop 5%. It usually will vary with age of the plant. As biological materials continue to respire over a period of time, cer- tain physiological changes may take place which affect the rate of respiration and the R.Q. and Q10 values. These changes are referred to as respirator drifts. James (1953) presents a discussion of respirator drifts and compares the drifts of detached leaves of cherry laurel and barley which respire at very different rates. Although cherry laurel and barley have different time scales in the initial rate of respiration and the time to complete respiration, the shape of the respiration curves is very similar. Cherry laurel has an initial respiration 13 rate approximately one—fifth that of barley, but continues to respire five times as long, 60 days as opposed to 12 days. But despite this difference in time scales, both products exhibit 3 peaks: the first shortly after being detached, the second about one-half life and the third shortly before death. Respiration rate W CO2 mg/ gm time The cause of respiratory drifts, although not completely understood as yet, seems to be keyed to stability of protein. In any event, drifts occurred in all tissues and the drifts observed in detached leaves may be considered to be an acceleration of the drifts that would occur in the fall if the leaves were left on the plant. The yellowing of leaves or loss of chlorophyll is accompanied by an in- crease in respiration. This is also reported by Fisher (1960). He found the R.Q. fell to about 0. 8 at this time. Beinhart (1962) studied the effect of light intensity and temperature on respiration of white clover. He found the maximum rate occurred at 300C. for all light intensities, and that at 100C. the light intensity did not effect the rate. In studying the respiration drift of white clover and ryegrass during drying, Greenhill (1959) added more evidence to the fact that respiration de- creased directly with moisture content. He reported that respiration continued throughout most of the drying period, but at a decreasing rate and appeared to Stop about 35% moisture (d. b. ). 14 Losses of Dry Matter in Field Curing and Conventional Handling A multitude of investigations have been made on the losses from var- ious aspects of hay harvesting and handling. Shepherd (1954) has presented a very complete summary of these losses in field curing of hay and has cited numerous references for the losses described. Losses in Field-Cured Hay Plant respiration 4-15% (Depending on the weather) Leaf shatter 2-5 % grass hay 3-35% legume hay 15-20% legume under most favorable conditions Leaching by rain 5-14% During mow storage (18-25% moist) Usually 2 - 6% (may go to 8-10%) (ZS-50% moist) 6 - 39% + heating, sweating and poor quality Total dry matter losses - field cured - (Various references) Ordinary handling 5-26% 13-24% 17% Unfavorable conditions 36. 1% loss 40 . 6% loss Nutrient losses (usually higher than D..M, losses) 20-40% of D. M. removed by water leaching 30% of phosphorous 65% of potash 20% of crude protein 35% of nitrogen free extract In presenting a summary of the losses in harvest, storage and feeding value of alfalfa and corn silage, Hoglund (196 3) suggested the figure on the following page. 15 Field Cured Barn Dried Hay 3O Wilted Silage g A Haylage , / b Conditioned 10 __ / Baled Ha I// y %/ l l l I J l U] o— 70 60 40 30 2O 10 PERCENT MOISTURE AT TIME OF HARVEST This bears out the fact that losses are reduced by handling the hay at a higher moisture content. By so doing losses due to leaf shatter in crushing, raking, tedding during harvesting are reduced as well as losses due to prolonged weather exposure . Hllllll W _ m r e m 0.. m m. a a M WW. dam L>//\< new. 4 D Amp. .7 /////////// / //_ \r\ 3| H T / /////// / /////////// %. / / / / 2 V //// //// / / //Aw/// S r e t l 17 T- Thermocouple locations. Figure 2 . 18 .2823: can H8dpoad>o $58.20 .v enema mucofisbmfi use pongno .m 93mg 19 Figure 5. Resistance heaters for chamber. Figure 6. Refrigeration compressor (G) and graduated cylinder for condensate (I). 20 Figure 7. Precision hot wire anemometer to calibrate air flow. Figure 8. Placing hay into chamber. 21 Figure 9. Spraying condensate back on material. ’-‘ - Figure 10. Pump to spray condensate. CHAPTER III EQUIPMENT AND PROCEDURE Preliminary tests on the amount of heat produced by hay were conduc~ ted in 1960 using an insulated chamber in which no effort was made to control temperature. The results of these tests indicated that quantities of heat of ap- proximately 3000 Btu/ton-hr. for the first 5 hours, increasing to 10,500 Btu/- ton-hr. and then decreasing, were produced. These results are in agreement with the results reported in the literature. From these preliminary results it was decided that a calorimeter ap- proach to the problem would be feasible and interesting as opposed to the more common technique of basing the Btu output on the respiration equation of C6H1206 + 602 = 6CO2 + 6H20 + heat. It was proposed to construct a chamber wherein the temperature, humidity and air flow could be controlled, measured and recorded. Calculations The chamber was of sufficient capacity to handle 100 lb. samples. Based on a loose hay density of 450 cu. ft. /ton, this is equivalent to approxi- mately 23 cu. ft. The chamber was constructed of 8" thick styrofoam walls covered inside and out with thin aluminum sheet. The outside dimensions were 96" high, 52" wide and 68" deep. (See Fig. 1) The outside area of the chamber 22 23 was 209 sq. ft. ; the inside area 124 sq. ft. giving an average area of 166. 5 sq. ft. The k value of styrofoam is .24 Btu/hr. 1n.-OF.-sq.ft. K. for 8 in. o = . 03 Btu/hr.- E-sq. ft. Calculated Heat Transfer Q = AM k = .24 Btu/in. °F. sq. ft. 1,5,1. x = 8" 0 hi k ho hi =2 Btu/ F.-sq. ft. no: 2 Btu/ °F. -sq. ft. Design for 0 A A t = Q Outside temp. = 75 F. 1 _8__ 1 Inside temp. = 25°F. 2 + .24 + 2 At = 50°F. U: . 0303 Q box = 166.5 sq.ft. x 500 x .0303 Q box = 252 Btu/hr. Heat from hay @ 6000 Btu/ton/hr. = 300 Btu/hr from 100 lbs. Total heat load = Q box + Q hay = 252 + 300 = 552 Btu/hr. This is equivalent to about 1/ 20 ton of refrigeration. Although this amount would theoretically be sufficient to handle the heat load at equilibrium, experience has shown that 1/2 ton provides the additional capacity necessary for faster pull down, and additional heat infiltration around doors and from fans. In order to measure the heat given off by the hay and to remove this heat, a liquid heat exchanger was first considered. Temperature would have been controlled by blowing the air over the coils at the desired temperature. 24 Heat from hay would be measured by Q=MCp At where M = mass flow Cp = Specific heat At = change in liquid temperature This method was discarded because of the high specific heat of the li- quid and corresponding lowAt for a given quantity of heat. As air has a specific heat of .24 as Opposed to approximately one for liquid, the rise in air temperature would be about four times as much as liquid for a given mass flow and quantity of heat. It was felt that this greater temper- ature rise with air temperature measurement would reduce error and design proceeded on this basis. Chamber Construction The chamber was constructed with walls and doors made of 8 inch thick styrofoam covered with aluminum. A lap type door on both front and back was provided to facilitate servicing equipment and placing samples in the chamber. A steel frame was built around the outside of the aluminum chamber to support the doors. Door hinges and fasteners of the walk-in cooler type were used. Doors were hung using epoxy resin and sheet metal screws to hold hinges to the door. Double gasketing was placed around each door. Several types of gas- keting were experimented with before finding one that was satisfactory. Due to the very large doors, a gasket that was difficult to deflect, provided too much resistance to door closing and did not seal well. A rather serious heat leak was found to exist due to the aluminum sheet on the inside surfaces of the doors and the door jams. The metal on these 25 surfaces ran uninterrupted from the outside to the inside and conducted much heat into the chamber. This fault was corrected by making a 1/8 inch saw cut, through the aluminum, completely around the door jams, and on the matching surfaces of the doors. Gasketing was then placed over the sawcut. This saw cut effectively reduced the heat conducted to the chamber on these surfaces. (Fig. 5). Air flow was provided with four 12 inch propeller type fans in the bot- tom of the chamber. The fans were shrouded and ganged together with a v-belt and pulleys. Variable air flow was desired and achieved by using a series wound motor (Black and Decker 3/4 H. P. @ 7000 r.p. m. ) and controlling its speed by use of a variac. In order to keep the heat input to the chamber at a minimum, the motor was mounted outside and fan driven through a 1/2 inch shaft. All fan bearings and driveshaft bearings were sealed ball bearings to keep friction heat at a min- imum. Fan speed could be varied from 0 to 1750 r.p.m. At low speed the drive motor tended to overheat and the installation of a small cooling fan motor was required. (Fig. 3, H). Experience showed that it was not necessary to vary the air flow. Re- sults were good simply by moving the air at a rate sufficient to keep the air con- tent of the chamber well mixed. This was at a variac setting of 45 volts and re- sulted in flows of approximately 75 cu. ft. /min. An air straightener (Fig. 2) was provided to reduce turbulence of air due to fans. For some experiments it was desirable to maintain the material in the chamber at as nearly a constant moisture as possible. To achieve this objective 26 a small hose pump was constructed to pump the condensate to the top of the cham— ber and allow it to spray from holes in several copper tubes. Any moisture that ran through the material was caught in a tray, returned to the one gallon sump tank, which was equipped with a float controlled on—off switch for the pump. (Fig. 10). Controls Temperatures The use of air temperature-rise to calculate sensible heat produced in the chamber requires that the air temperature be known at the inlet and outlet of the chamber. This information was obtained by installing a Taylor two-pen con- troller-recorder which utilized a 24 hour circular chart 0 to 80°F. The instru— ment was equipped with capillary sensing bulbs, one of which was installed be- low the hay chamber (inlet) and controlled a resistance heater, in order to main- tain and record a set temperature. The other bulb was placed above the hay chamber (outlet). This provided a record of the change in air temperature At as the air moved through the hay. In addition to this control and sensing device, a 16 point recording po- tentiometer was used to check and record temperature at various places through- out the chamber. (Fig. 2). Cooling The cooling unit selected was a direct expansion refrigeration unit us- ing R 12 refrigerant. It was Kelvinator unit of 1/2 ton rated capacity and proved to be quite satisfactory. Precise evaporator temperature was required so that 27 a desired dew point might be obtained and cooling load not be excessive. This precise control was achieved by using a thermostatic expansion valve and an evaporator pressure regulator (back pressure regulator). The evaporator tem- perature was directly proportional to the evaporator pressure. The pressure could be varied from suction pressure up to maximum of 75 p. s. 1. thus provid- ing controlled evaporator temperatures frcm 00 to 800E. Three variations of evaporator design were tried before finding one with sufficient cooling area, and air flow characteristics. The evaporator was designed with a pan to collect condensation. Condensation was measured and recorded as an indication of latent heat. When Operating at temperature below 32oF. it was necessary to have a means of defrosting the evaporator. Defrost- ing was done by using a solenoid valve in the compressor discharge line to give hot gas defrosting along with a thermotape positioned to melt any ice in the con- densation tray. During tests run below freezing, defrosting was done every 12 hours during the first week, then every 24 hours. Data were recorded before defrosting. The air flow was interrupted temporarily and the thermotape and solenoid valve were activated. Defrosting was usually completed in 15—20 min— utes then the chamber put back in normal Operation. This procedure was simple and worked very well. Humidity A record of the operating humidity in the chamber was made with a Fox» boro dewcel unit. This provided a good check on the conditions but. due to the difficulty of reading temperatures and the psychrcmetric chart to a fraction of a degree, a more reliable measure of latent heat was made by measuring the 28 average rate of condensation. The condensation in milliliters per hour was re- corded and multiplied by the equivalent latent heat of water to give the quantity of heat contained in the moisture. Air Flow Air flow measurement proved to be one of the most difficult variables to measure. This was due to the very low flow rates and eddy currents in the chamber. Various methods were tried. An orifice which is simple and accur- ate did not allow sufficient flow with the head available. A pitot tube was not satisfactory due to low velocity. A low velocity air flow measuring technique using a timed drop of a balloon in a tube was not satisfactory due to turbulence. A vane anemometer was used to give an indication of air flow but was not considered accurate enough for calculation. Air flow measurement was fi- nally achieved by installing a micromanometer to give pressure drop across the hay chamber. Pressure drop was recorded throughout the experiments. Pres- sure drop was then correlated to air flow by use of a hot wire anemometer. Thus, any pressure drop could be directly converted to air flow. Calibration Heat Infiltration to the Chamber Measurements of heat flow, sensible and latent, include heat from the chamber walls as well as heat from the hay. In order to accurately know the heat of hay respiration, the infiltration of heat must be known. Several tech- niques were used to acquire these values. A typical example follows: The fans were operated as during a test and the temperature in the chamber allowed to reach an equilibrium (1). This chamber temperature and 29 the outside temperature were recorded. A heater of known wattage was then turned on, and temperature allowed to come to a new equilibrium (2). The temperature rise from equilibrium (1) to equilibrium (2) was due to the heat equivalent of the wattage input. The heat leakage of the chamber (UA value) could then be calculated from the relation: Q wattage = uAAt Btu/min. watt UA = .1768 Btu/min. -°F. 56 watts x .05688 UA x 18°F. 10.6 Btu/hr. -°F. The UA(Btu.,/hr. -OF.) of the chamber was then known and could be used for all needed calculations. The UA value of the total chamber as found from this procedure was 10. 6 Btu/hr. -OF. As only 29% of the total wall area was in contact with the hay chamber, only this proportion of the UA value contributed to the measurable heat in the chamber. This proportion of the UA values was: .29 x 10. 6 Btu/ hr. -0F. = 3.08 Btu/ hr. 0F. The heat infiltration of consequence was then found by Q= At x 3. 08 Btu/hr. —OF where At is the difference in temperature between the inside and outside of the chamber. Using this value of UA and knowing the equilibrium temperature (1) of the fans and outside temperature (sink) the heat input of the fans could be calcu- lated from: Q fans UA At Q fans 10.6 x 19 = 200 Btu/hr. The heat from the fans does not affect the heat measurement in the chamber, as the fans are below the air temperature sensing devices and not be- tween them . 30 Air Flow As all airflow passed through the evaporator, and the cross section here was smaller, a higher, more reliable velocity resulted. For calibration of the air flow the outlet of the evaporator was extended with cardboard so that a uniform carefully measured cross section resulted. This cross section was divided into 12 equal areas. The hot wire anemometer (. 005" tungsten wire,mo- del HWD, Flow Corporation) was positioned in the center of each area, and the local velocity measured for each of several different air flows. The average velocity for each flow was found, and a position selected that represented this average velocity. (Fig. 7). The hot wire was placed in this position and the average air flow measured as the air flow (and Ap of chamber) was varied by placing various quantities of hay in the chamber. The air flow velocity and thus mass air flow was then plotted against theAp of the chamber. Using this curve, any 4p in the chamber could be directly converted to mass of air flow. Heat Output Measurement To check the reliability of the heat output measurements a known heat input was used in the chamber and a comparison made with the measured values. A 1500 watt immersion type water heater was used for the heat input. The watt- age to the heater was controlled with a variac and ranged between 150 - 300 watts for various tests. The wattage was maintained constant throughout any one test and was checked with a Weston watt meter (model 310). The heater was placed in a five gallon container of warm water. The container of water was supported by a scale in order that the weight of water evaporated might be measured and recorded. After the wattage input had been selected, the chamber was allowed 31 to operate 12-24 hours to establish equilibrium conditions. Then the original weight of water in the container and its temperature were recorded. Periodi- cally, throughout the test and at the end of the test, (3—4 days) the condensate, air flow, temperature rise of air, water temperature and amount of water evap- orated from the container were measured and recorded. Using these data, a comparison was made between the total water evaporated and the total conden- sate collected and between the total heat input known from the wattage to the to- tal heat measured as determined from the latent heat + sensible heat - heat in- filtration. The results from these tests showed the condensate to average 96% of the amount of water evaporated in the chamber. This figure was affected slight- 1y by the ratio of vapor pressure within the chamber to the vapor pressure of the surrounding room. Sealing both doors with masking tape reduced the effect but did not completely eliminate it. The total heat measurement averaged 86% of the heat input. These figures were considered in the calculation of the heat of res- piration of material as explained in the discussion. Experiments After careful consideration, it was decided to run experiments on pure alfalfa with variables of temperature, moisture and maturity. Temperatures of 25, 45, 65 and 80°F. were selected as those representing the usual range of temperatures that hay in storage might encounter. Two variables of moisture were selected. These were broadly classed as fresh and wilted. Fresh was taken immediately from the field with no drying 32 (70%), and wilted material was cut and allowed to dry to (50%) moisture. Maturity was arbitrarily divided into two classifications as immature and mature. Immature material was considered to be any crop condition up to 1/2 bloom. Mature material was considered to be 1/2 bloom to past bloom. These variables provided a maximum of 16 different experimental con- ditions. Each of these experiments was run for a period of from 3—5 days, dur- ing the summer and fall of 1962. During the summer and fall of 1963, six experiments of extended time were run. The duration of experiments was 30 days for tests at 30 and 45°F. , and 10 to 14 days for tests at 600F. All experiments were made on fresh alfal- fa. The first three tests at 30, 45 and 600F. allowed the material in the cham- ber to slowly dry out as moisture was condensed on the cooling coils. During the last three tests at these temperatures, the condensation moisture was sprayed back on the hay surface in an attempt to keep the material at a more constant moisture. Procedure The procedure used in making an experimental test was to first select an appropriate experiment to correspond to the maturity of the hay. 1. The hay was cut and taken directly to the chamber or allowed to wilt, which- ever the experiment required. 2. The hay was raked by hand and gathered into two large plastic bags, approx- imately 50 lbs. in each. 3. The hay was weighed and a sample of the material taken for moisture and chemical analysis. 10. 11. 12. 33 The hay was then placed in the chamber, care being taken to spread it even- ly across the chamber and thermocouples were placed in the hay. The evaporator was wetted to reduce any error due to having the evaporator wet at the finish of the test. The chamber was then closed and the original hay temperature recorded. The chamber was then put into Operation, air circulation fans were started, the motor cooling fan started, and the evaporator temperature selected and compressor turned on. Data were recorded at 1, 3, 6, 8 and 12 hour intervals throughout the dura- tion of the experiment. Data included the time, the temperature at 16 loca- tions in the chamber, the pressure drop across the hay chamber, the watt- age drawn by the compressor, the total watt-hours required for the experi- ment, the dewpoint (for relative humidity) in the top of the chamber and the amount of condensation during this interval of the experiment. The conden- sate was discarded after measuring except for experiments 4, 5 and 6 in 1963 as described above. At the end of the experiment (3 days minimum) the hay was again sampled. Samples were taken from the top, middle and bottom portions of the cham- ber. These samples were analyzed for chemical changes and moisture content. The final total weight was recorded and the hay then discarded. This basic procedure was used in some 28 different tests run during the summer and fall of 1962, and on the six extended time experiments run in 1963. CHAPTER IV DISCUSSION AND RESULTS The Equipment Much thought and care went into the planning and construction of the equipment. However, numerous slight changes were made during the construc- tion, initial test and calibration period to improve the design. Occasionally al- terations were made throughout the two years of work with the chamber, always with the aim of improving sensitivity and performance. The Chamber Several changes made during construction which have been mentioned are: 1. Use of a larger compressor. 2. Change in gasketing to improve door sealing. 3. Place cut in the aluminum doors and jams to reduce heat flow. 4. Change in evaporators. 5. Change in the air flow measuring devices. 6. Relocation of thermocouples. Calibration of the chamber using a known heat input as described pre- viously, revealed the heat measurement made by the chamber to have an error 34 35 of about 10%. Approximately two-thirds of this error was due to measurement of latent heat which was apparent from the discrepancy between the amount of condensate collected and the amount of water evaporated in the chamber. To reduce this loss, caused by differences between vapor pressure of the chamber and the room, the doors were completely sealed with two-inch wide masking tape in addition to double gasketing. This precaution reduced the losses significantly, but was a tedious Operation as tapes had to be removed and re- placed each time the chamber was Opened. A more convenient method might be the use of clamps on the doors to give the same degree of sealing with less labor. The panels used in constructing the chamber were made by cementing an aluminum sheet to eight-inch thick styrofoam. The cement used was one hav- ing a brittle characteristic when hardened. This characteristic, in time,caused some loosening of the aluminum sheet from the styrofoam due to difference in the coefficient of expansion and contraction of aluminum and styrofoam as the cham— ber went through extremes in temperature. This could be very easily corrected by use of a cement having some flexibility in its hardened state. Air Flow Measurement Although the method used to determine the air flow (1. e. , calibrating pressure drop across the hay against air flow) was satisfactory, investigations of more direct reading devices might be desirable before further use is made of the chamber. While another device may not be any more accurate than the pre— sent technique, conceivably it could provide a more straightforward method, re— ducing time, effort and possibly human error. The fan arrangement for achievement of forced air circulation performed well, and except for the replacement of an occasional v-belt and worn ball bearing. 36 it provided trouble-free performance. Throughout these experiments, a constant fan speed was found to be satisfactory and the provision to give variable fan out- put was not used. The air flow and pressure available from the present design were quite sufficient for these experiments. For other air flow requirements, possibly a push-pull arrangement using squirrel cage fans on both sides of the hay chamber, would provide an air flow with a greater head and less turbulence. The motors for these fans could be mounted either inside or outside the chamber depending on their size and position. Temperature Measurement Although thermocouples can usually be relied upon to give accuracy of 1/2 - 10F. , an examination of the calculations will bear out that an error of this magnitude could produce an error of 40-80 Btu/ hr. In experiments with products having low respiration rates an error of this magnitude could be very significant. With this in mind, the possibility of including thermopiles at the inlet and outlet of the chamber might be considered. This would increase the sensitivity to air temperature change and enhance the accuracy of work with products of low res- piration rates. Respiration Curves The results of the experiments were carefully studied so that the most accurate interpretation of the data might be achieved. Several methods of an- alyzing the data were used. The techniques used to determine the heat of res- piration were as follows: 37 1. The temperature sensing devices and dewcel were used to measure the sensible heat and latent heat in the known air flow. This method was extreme- ly critical and prone to error if used as such. As little as 1/2 - 10F. error in reading the dewcel made sufficient difference in the latent heat readings that con- siderable error resulted for the total overall experiment. 2. The condensation was collected as a measure of the latent heat of the experiment. This technique. although less prone to human error, could not be used as the absolute correct value of latent heat on all experiments. Experi- ments with extremes in temperature have sufficient differences in vapor pres- sures between the inside and outside of the box that some loss or gain in conden- sate occurred. Although, the total amount of condensate on these extreme ex- periments could not be considered correct, the "rate" of the collection was a reliable indication of the rate of respiration. 3. The total dry matter loss during the experiment was calculated, knowing the total weight loss, and initial and final moisture contents. The heat equivalent of the dry matter loss was used as a measure of respiration heat. Although this method gave good correlation with other methods, the results de- pended on the small samples to represent the total material in the chamber. A slight variation in moisture content could affect the results. 4. Chemical analysis of the material were made from the samplings using the standard bio chemical procedure. Total carbohydrate was determined and the heat equivalent of carbohydrate loss was calculated as the heat of respir- ation. (Carbohydrates were considered to be glucose C 6H 0 1. Again this 12 6’ technique gave good correlation for most. experiments, but on one or two where 38 agreement was not good, the importance of good sample representation and ac— curate moisture values was recognized and believed to be responsible for the error. Although correlation for most of these methods was acceptable for most experiments, a technique that treated all experiments the same, avoided as much as possible questionable values, and still gave good results and correlations was desirable. As the heat produced by the dry matter loss was the major source of heat in the early stages of storage (microorganisms not being well established, Burcik and Orth (1954), it was thought that a balance between the dry matter por- tion of the total weight loss and the heat removed from the material (including the water, as latent heat) would provide a better technique. This relation took the form: 6740 Btu/lb. D. M. [Total Wt. loss (15.) - H20 loss 4113.)] = 1060 Btu/lb. [H20 loss (lbfl + sensible heat (Btu) - Chamber wall heat (Btu) From this relationship the dry matter portion of the total weight loss of a parti- cular experiment and the total water loss could be found. The total water loss was then used to adjust the "rate" of condensate collected to establish a "rate" of latent heat removed for the experiment. Using this technique, the latent heat, sensible heat and chamber wall heat were calculated for each increment of time for each experiment. The heat of respiration for each increment of time was totaled to give the rate of respira- tion and the total heat produced for the duration of the experiment and compared 39 with other methods of calculating the heat output. These values are plotted in Figures 11 to 17 and the results of these calculation summarized in Table 1. Figure 15 expresses results of Table 1, showing the correlation of the total experimental heat measurements to the calculated heat equivalent of the dry matter loss. The correlation is very good. A similar correlation of experimen- tal heat to the heat equivalent based upon the chemical analysis dry matter loss is shown in Figure 16. Errors in sampling for the chemical analysis are large- ly responsible for the somewhat poorer correlation shown here. However, the values are still of the same magnitude. It should be pointed out that valid comparisons between respiration rates and dry matter losses can be made between various treatments of the data within any one experiment. However, in comparing rates and losses between different experiments, care must be used that the losses or rates are based up- on the same duration of time and refer to the same initial amount of dry matter. Figures 11 and 14 show the rate of respiration per 100 lbs. of material as it went into the chamber. In these curves, a parameter of temperature is used in plotting the heat of respiration for material of various conditions against the time. It should be pointed out that the very high initial values of several curves, for example curve (8) and curve (7) Figure 12, are due to the sensible heat during the pull down from the field temperature (approximately 80—900F. ) to the experimental temperatures of 300F. and 45oF. respectively. The experiments at 800F. in Figures 11 and 14 show a hump at approxi- mately the one day point. This was caused by the instability of temperature 40 control at the higher temperature, which caused a brief loss of control and cor- responding higher rate of respiration. Figures 11 to 14 show that hay stored at 25oF. regardless of its mois- ture or maturity will have "0 " respiration rate following the initial pull down and freezing period. On the other hand hay stored at 3001’. (above the freezing point of hay) experiences a measurable quantity of respiration. Using the "flatter" portions of these curves to eliminate "pulldown" ef- fect and temperature fluctuation effects, the average respiration of alfalfa for the initial 3-4 day (7 0-100 hours) intervals was established. These values are plotted on Figure 17 to illustrate the effect of temperature and moisture on res- piration. In subsequent discussion, it will be pointed out that the rates of respir- ation are not constant, but continue to decrease. However, in order to make comparisons the rate curves were assumed to be straight lines for the short du- ration of three days, thus enabling an average rate of respiration to be calculated. These average rates of respiration are shown in Table 1 as Average Respiration, Btu/hr. -ton D. M. Plotting respiration rate vs. moisture and temperature in three dimen- sions, a surface is developed that shows the inter—relationship of these variables. The figure illustrates that regardless of the temperature, when the moisture con- tent is approximately 10%, the respiration rate approaches zero. On the temperature axis, the respiration rate is zero at 250F. (below freezing of alfalfa) regardless of the moisture content. The "hump" shown at the 28-3OOF. area for higher moistures is the result of a freezing-thawing affect 41 on respiration. The rate of respiration increases with an increase in either moisture or temperature or both. Thus, values experiencing this interaction develop the concave surface illustrated in Figure 17 . No data were taken above 800F. , thus the general "expected" trend of the surface is indicated by broken lines. As the temperature continues to increase, the respiration rate will reach a maximum and then begin to decrease. This is due to the coagulation of protein, death of cells and destruction of contributing microorganisms. The influence of protein content (degree of maturity) on respiration was not sufficient to demonstrate any noticeable pattern, and hence did not seem to have any predictable effect on respiration within the limits of these tests. The respiration curves for reed canarygrass and wheatgrass (Figures 18 and 19) are included for comparative purposes. Wheatgrass appears to have a higher respiration rate and a lower freezing point than alfalfa, demonstrating a measurable amount of respiration at 250F. , while alfalfa respiration at this temperature drops to zero. Dry Matter losses The rate of dry matter loss for varying storage temperatures is illus— trated in Figure 21. To provide a comparison of the fresh storage losses to those of field curing, the summary of losses as given by Shepard (1954) are plotted. These dry matter losses for field cured hay are for ”most favorable" conditions, with no leaching losses by rain. As the short run experiments (35 days) of 1962 did not indicate how the respiration behaved after a matter of weeks, 42 data were taken during 1963 for periods up to 30 days. Plotting these results, Figure 20, and integrating the areas under the curves gave an indication of the total respiration losses incurred. These losses are shown in Table 2 with cor- responding dry matter loss equivalents. The accumulative dry matter losses for an increment of time is plotted in Figure 21. From this figure, fresh material stored at 600F. would have the same dry matter loss as good quality field cured hay at approximately 13 days. For longer storage periods the losses in fresh material at 600F. would exceed the losses of field curing. The losses from fresh material stored at 450E. would exceed the losses of field cured hay after approximately three weeks of storage. Losses from material stored at 3OOF. would not exceed field curing losses until it had been in storage several months. From the zero slope of the 250F. curve, it can be assumed that after the material is frozen it may be kept indefinitely without losses. In order to determine what influence the slight drying effect had on the decreasing rate of respiration throughout storage, experiments 4, 5 and 6 were run in 1963. In these experiments, condensate moisture was put back on the ma- terial in attempt to maintain a more constant moisture. The results of these ex- periments are shown in Figure 22. In this rather artificial situation, the res- piration is seen to decrease but at a slower rate than that of experiments 1, 2 and 3, Figure 26. This indicates that the drying effect (reduced moisture con- tent) does affect the respiration rate, as would be expected. It is interesting to note that the 30 and 450F. curves of Figure 22 have the same type of slow cycling drift shown by James (1953). As experiments .3133 ensuefififltnmoh .coSepEmop mo “mom .2 enemas mass; .325 mm mm mm on “Es > D G G I let let 1 l e l_ I 1? _ _ a 1 mm. am! 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O .OOH O .HO thH .mcmwtwm H. .3 OH. .OH OOH .OH mm .N mom .OH OOO .N. OH .H mm ON 3 .OH. O .qu O .OO ON1OH .homwtmm ON. .5 OOO .OH OOH. .OH on .H OOO .OH OOO .m mm . mm .3 OOO .s E. .OO ms .mmH wnHH Hemmém mmaamueoaze 23mg swam mm. mm... am a... mm M... m / .q. ... . a 8... m as. a. as a a pm 13 and I'm 1. SIS m. I.“ m. mu fin nu. WI am a we. mm mm as m... We a .18 a e mm m m. w. n. “1.1 m. m 1 .0... m. m. .p % 6. z e m. u s B 0 ms m: u. s M a. m m. m a S n W m. d S 9 mu: 8 .l. . . m8 .0 . m _. m... m m s .q . N . . . . 626280 1 momeH was owned noflafiamom Ho madam .H 383. HEAT OF RESPIRATION, TOTAL Btu. / EXPERIMENT DURATION 49 35, 000 30, 000 25, 000 20, 000 15, 000 10, 000 5, 000 I I 5000 10, 000 15, 000 20, 000 25, 000 30, 000 Figure 15. HEAT EQUIVALENT OF DRY MATTER LOSS, Btu. Correlation of the heat of the experiment and the heat of the calculated dry matter loss of alfalfa. 35, 000 HEAT OF RESPIRATION, TOTAL Btu. / EXPERIMENT DURATION 50 35,000 6913 856 35,000 ()8 695 25,000 65?? (319 C317 ////// 20,000 ////// ()7 15,000 / @18 10,000 (436 6914 5,0003éig9/ 1:12 .1 ‘1’ "V5,000 10,000 15,000 20,0001 25,000 30,000 HEAT EQUIVALENT OF CHEMICAL ANALYSIS DRY MATTER LOSS, Btu. Figure 16. Correlation of the heat of the experiment and heat of the dry matter loss of alfalfa as determined by chemical analysis. HEAT or REBPIRATION Btu. /hrs. - TON D. M. (thousands) 51 , / \\\ / \/ 32 / \ /,\ \ //\ \ 28 x’ \ \ \)\ 24 \ // \g 5 + x,“ ~ / - Q 53’ / / / ,9“ 20 i / / / Q / ‘b 16 9’ q,Q «Q ,0? 12 Q98) .7, 1 (9&5 8 5“ $30; ,5» ”Q 4 «1* 0 <9 7 “9° / / / L/ / Q 74 60 50 40 30 20 11M» MOISTURE, %w.b. Figure 17. Heat of respiration of alfalfa as affected by moisture and temper- ature up to 100 hours. 52 om .onfidfiunmob .mmmhwiwfiwo coon £0323on mo 3mm .3??th muse: . ESE. 0H db 8 3. 8 on _ M1 _ r, _ G d a 69 .mofi, - «N am mu O .momo - S xm «w . fl- com cow. com com "11 0014931 N18 ‘NOIlVHIdSHH JO .LVHH 53 .opfldgwsnmofi .mmmmwumonts .cofimuamog mo “mom .3 onswa muse: . WEE. om om LJw om .momm- 5 am m0» Aw .momwummxm Till Illa .mome- 3. Km mT- - -lm. .moom - em xm fil: Iii ,oom , oo¢ com com 'SQI OOI ' 'Slq/ ’MH ‘NOILVHICISEIH JO .LVEIH 54 .38 “509838 | «:33 :mod .cofiaamop mo anon .om opswwm was: .35. can com ooH \. $2 .832: in .3 magma muse: .HEH 93 com com 2: dfl__*_.___dmfi_ ________fl___fi_4___fi Au 1 ... mm \B\\@\ u" l lewxlel l . l x I \9\\®l\@\ I .9151 .e. - \‘Q‘él \\ I _ .r \s .._. l. ommponvm .homm 1 :\ :ofldw. mos” $3 I swsssm .moom @ul||® X. _ “.1 5...... ills 511 - 3H8 .m m \ \ II] o m com a I 9\®\ I 8.26 25E 1. xx L \®\Q L \ 4X K \: x .L é\a. _ _ \ — — L an 5 3 mod.) \ 61 s _ E OOH com com cod. com ocw HHLIVW LHCI .EIO NOL/ 'SQI ‘SSO’I 11511.le KHCI 58 .8339: “53950 6&me smog“ mo San :oflanamom .NN onswwm musondmza. cos com 8m 2:. com com 2: _____ ____.L____ ____ ____i____ m a l 5 1.5.1.! 1 B \‘l‘lIIIIII/E/l \\m tal/[BI l B E B // m a . I} l _H m @ ® _ 0 O a _1 1mm! D 0 @ll 9 G . ll «.4» l 4, 4... s. o _.... £ ® 1 ,V 0000 _ e e m e 9 wé @ one .. - In 0] a Q Q #o/I G l z_| _ fig 4 Q m. 1 938$ .moom mTI|lullB __1 . _1 398$ .mofi. OT JO... 7 owaufim .hoom T l l l IQ .1 OOH com com cow '9CII OOI "S-III/ 'MEI ‘NOLLVHICISEIH .110 LLVEIH 59 4, 5 and 6 did not extend until complete death of the tissues. the curve corre- sponds to only the first half of those illustrated by James. The Respiration Equation One of the objectives. as stated previously, was to develop a respira- tion equation, relating the variables involved. From such an equation the value of respiration under given conditions could be immediately determined. As the maximum rates of respiration are of most interest and importance for calcula~ tion and design of storage and cooling equipment, the discussion here is limited to the case of maximum respiration. The results discussed previously indicate that for any given tempera-- ture the maximum rate of respiration is found immediately following harvest when the material is freshest. Using this as an operating premise, a method is presented to calculate the respiration rate of fresh alfalfa for temperatures be-— tween 300 and 800F. , and up to 150 hours after harvest. The results of experiments 1, 2 and 3 shown in Figure 20 are used to illustrate the method used. Other experiments on fresh material are used to provide additional points helpful in establishing slopes. The respiration data for these experiments were plotted on semilogarithm paper, Figure 23, with the respiration rate on the log scale and time on the linear scale. A "best" straight line was put through these points from time 0 to 150~200 hours. This line has the form as follows: 60 R = Ie (4.1) where: R = respiration, Btu/hr. s time, hr. k slope I = intercept An examination of Figure 23 shows that the lower the temperature the steeper the slope, due to the lower respiration rates at low temperatures. Cal- culating the slopes (k) of these semi log plots and plotting them on rectangular coordinates as k vs. temperature 0F. gives Figure 24 where k = -nt + A t = temperature 0E . (4, 2) Extending the straight line of any particular temperature curve back to time ”0 " on the semi-log plots eliminates the sensible pull down heat of the pro- duct. The intercept I, at the time 0 is an indication of the initial respiration rate for that particular temperature. The intercepts for each temperature are tabulated in Table 3 and plotted against temperature in Figure 25. This figure takes the form of a straight line, having an equation I=B+mt (4% Combining the equations: R =19. 3‘" (4.1) k = -nt+A (4.2) I = B + mt (4. 3) An equation can be written in which respiration is a function of temper- ature, time and the initial rate of respiration. 61 This takes the form: -(-nt + A) e- R = (B + mt)e (4. 4) Calculating the intercepts and slopes of k and I in Figures 24 and 25 and substi- tuting these values into the equation gives the equation: (. 000208t-. 018) e R = (6.56t - 100)e (4.5) Using this equation, the respiration rate (Btu/hr. —100 lb.)- for any given temper— ature between 300 and 800F. and for any time between 0 and 150 hours can be calculated. Table 4 provides a comparison between calculated values of respir— ation and experimental values as plotted on two different coordinate systems. A study of Figure 25 reveals an interesting relationship. The usual con- rate at tOC rate @(t—lOUC) cept of the Q10 value ( ) for reactions, particularly those of a chem- ical nature, is that Q10 will be more or less constant in the range of ordinary temperatures. If the Q10 ratio were constant over the range of temperatures of Figure 25 this curve would take an exponential shape using the variables shown. Allowing that experimental error may exist in the values plotted, it could be pos- sible to actually have this gentle curve over this temperature range, and still fall within the limits of error of the straight line shown. However, respiration data for biological products, fruits and vegetables (U.S. DA. 1954) over a similar range of temperatures, exhibit Q10 values that vary as much as from 8. 0 to 1.2. It is conceivable that the Q10 variation of res- piration and microorganism of hay from 2.2 @ 480F. to 1.4@ 800F. is a more valid indication of the respiration than first impression might indicate. HEAT OF RESPIRATION, Btu. /hrs.- 100 lbs. 62 e 4:) 60°F. Storage 300 (B 53—— - —.-{;_1 45°F. Storage @— - - - - '9 30°F. Storage 200 1 Line Form: -ke % B R=Ie (4. 1) 100 \— '\ 70 ~—-@ 50 k \ a E ‘Q 40 A—QEEK - 3" {9‘ \ \ I «K \ \\ 9 a 69 \ ‘ \ E] E‘ L“ 20 \ \ x \ (r) \ 10 ® \ 6 Q 9 ..__ 8 7 l , l o 100 200 300 400 500 TIME, hours Figure 23. Slopes of respiration curves vs. time. 63 Table 3. Slopes and Intercepts of Respiration Curves. Orig. Resp. Temp. SIOpe Exp. No. Rate (1) 0F. k 3-63 105 30 . 0122 1-63 200 45 . 00902 2-63 275 60 . 0046 8 340 30 . 0106 7 290 45 . 069 11 210 45 . 0878 6 300 65 . 00571 10 300 65 . 00444 13 380 80 . 00215 .ombpoQEB .m> x a mezzo :oSmnEmon Ho momofim .wm opswfim . ho . mflDBémQE m9 om 2. oo on 3. on on 2 mm 1 moo. : woo . ® 1 woo. 64 woo . I. 038. «8. @ II C‘. womooo .I wHo . n < l «Lo. Am .i a: n < n x ”Each on: I. mac. wHo . omo . 65 mo ow mm 0.333988 .m> 8m.“ "85¢prng 35sz .mm 93th . mo mflDEémmEMH on ma. ow mm omen a i mm 6H: coalum 958 u H ”Show was OOH com com 03N HSEIHJ 'SH'I 001-°sm/'ms ‘(I) NOIlVHIdSH‘cI 'IVNIDI‘HO 66 Table 4. Respiration Values, Btu. /hr. -100 lb. Fresh. Calculated Vs. Experimental. 45°F. 60°F. Obtained by Obtained by Time, Calcu- Experiment Calcu- Experiment Hours lated Semilog Rectang. lated Semilog Rectang. 25 157.0 160 160 256.0 248 254 50 126.5 127 115 223.0 200 220 75 102.0 102 88 194. 5 180 195 100 82.0 82 65 169. 5 161 174 125 66. 1 65 55 148 148 155 Using the relationship R z (6.56,; _ 100) e(. ooozost - .018) e to calculate respiration v alues CHAPTER V SUMMARY AND CONC LUSIONS Summary The study required the construction of a respiration chamber large enough to hold samples of 100 lb. of fresh hay. The chamber was equipped to control temperature, humidity and air flow, and to make measurements of heat, moisture and weight losses of the product. Experiments of 3-5 days in length were conducted on alfalfa using: storage temperatures of 250, 450, 650 and 8OOF. ; material at moisture contents of 50% w.b. and fresh (approximately 70% w. b. ); and cr0p stages of immature and mature. Respiration rates for these 16 experiments were plotted using tem- peratures as parameters and the dry matter losses over the 3-5 day period were determined. The rate of respiration of the hay and its associated microorganisms and dry matter loss increased with an increase in temperature of storage and moisture content. The age of crop (maturity) did not show any trend in these ex- periments. Average values of the heat of respiration over a 3-5 day period for fresh alfalfa ranged from zero at 250 up to 24, 800 Btu. /hr. -ton D. M. at 800F. Wilting the material decreased these respiration values. Respiration values and dry matter losses for wheatgrass and reed can- arygrass are shown for comparison with alfalfa. 67 68 Experiments of longer duration were conducted on fresh alfalfa. Tests at 300F. and 450F. were run for 30 days and tests at 6OOF. were run for 10-14 days. Results of these tests revealed the changes in respiration rate and dry matter loss with extended storage. The rate of respiration continued to decrease as the material continued to age and as moisture was removed in cooling. The lower the storage temper- ature the lower the respiration rate and correspondingly longer storage life. From the results of the longer tests an equation was developed from which the maximum respiration rate can be calculated for fresh alfalfa within the temperature limits of 300 and 80°F. Conclusions 1. The rate of respiration of alfalfa increased with an increase in moisture content and/or temperature of the storage, reaching a maximum in these experiments of 25, 200 Btu. /hr. -ton-D. M. at 80°F. and 70% moisture w.b. over a 3—day period. 2. Protein content (maturity) did not follow any predictable trend and had the least affect of the variables studied on rate of respiration. 3. Heat of respiration for fresh, immature alfalfa ranged from zero at 25°F. to 25,200 Btu. /hr. -ton D. M. at 80°F. for 3-«5 day tests. This corre- sponds to a dry matter loss of zero at 250F. to 89. 7 1b. /day~-ton D. M. at 800F. 4. Respiration rates of wilted alfalfa hay ranged from 2460 Btu. /hr. ~ton D. M. at 45°F. to 12,800 Btu/hr. ~ton D. M. at 80°F. for 3~5 day tests. 9. 69 At 25°F. the heat of respiration of hay is nil regardless of crop condition. After the initial temperature pulldown was accomplished the respiration rate decreased at a fairly uniform rate, as aging and the slight drying affect of cooling took place. The dry matter losses due to respiration of fresh hay stored at 60°F. would exceed the dry matter losses of high quality field cured hay after 13 days in storage. The losses of fresh hay stored at 45°F. would ex- ceed field curing losses after 3-4 weeks in storage. Fresh hay can be stored at 30°F. for several months before losses will exceed field cur- ing losses, and fresh hay can be stored at 250F. indefinitely. The rate of respiration of fresh alfalfa hay (approximately 70% w.b.) can be calculated for temperatures between 300 and 80°F. by the equa- tion R = (6.5“ _ 100)e (.000208t - .018) 9 Where t = temperature, 0F. e = time, hours R = respiration, Btu. /hr. -100 lb. Fresh Very immature wheatgrass demonstrated a respiration rate approximately 10, 600 Btu/hr. -ton D. M. higher than alfalfa for corresponding condi- tions . REFERENCES Bailey, C. H., "1921. Respiration of shelled corn. Technical Bulletin 3. Minn. Agr. Expt. Sta. Bailey, C. H., and Gurjar, A. M. 1920. Respiration of paddy rice and milled rice. Jour. of Biological Chemistry 44(10):9. Bailey, C. H., and Gurjar, A. M. 1918. Respiration of stored wheat. Jour. of Agr. Research. 12:685. Beinhart, George , 1962. Temperature and light effect on respiration of white clover. Plant Phy. 37(11):709. Burcik, E. , and Orth, A. . 1954. Ein neues Verfahren der Heuslockentlfiftung durch Saugluft. Landtechnische Forschung. 1321. Coleman, Rothger, Fellows. 1928. Respiration of soybean grain. U.S.D.A. Tech. Bul. 100. Novem- ber. Dale, A. C., and Johnson, H. K. 1955. Heat required to vaporize moisture in wheat and shelled corn. Purdue Engr. Exp. Sta. Research Bulletin 131. Davis, R. B. Jr., and Barlow, Gordon Jr. 1948. Supplemental heat in mow drying of hay II. Agr. Engr. 29(6):251. Dawson, J. E. , and Musgrave, R. B. 1946. Respiration in hay as a source of heat for barn drying partially cured hay. Agr. Engr. 27(12):565. Dawson, J. E., and Musgrave, R. B. 1950. Effect of moisture potential on occurrence of mold in hays. Agron. Jour. 42:276. 70 71 Feldman, F. 1956. Ausnutzung der Selbsterwarmung des Heues. Landtechnik 2(1):44. Fischer, Hermann 1960. Uber den Atmungsanstieg bei vergilbenden Blattern. Det. deutsch. bot. Gesell. 73(11):60. Frudden, C. E. 1946. Factors controlling the rate of moisture removal in a barn hay curing system. Agr. Engr. 27(3):109. Green, W. P., Hukill, W. V., and Rose D. H. 1941. Calorimetric measurement of the heat of respiration of fruits and vegetables. U.S.D.A. Tech. Bul. 771. .March. Greenhill, W. L., (Victoria, Australia) 1959. Respiration drift of harvested pasture plants during drying. Jour. Sci. Food Agr. 10:495. Hall, C. W. 1957. Drying Farm Crops. Edwards Brothers, Ann Arbor, Michigan. Hall, C. W. 1963. Processing Equipment for Agricultural Products. Edward Bro- thers, Ann Arbor, Michigan. Haller, M. H., Harding, P. L., Lutz, J. M., and Rose, D. H. 1932. The respiration of some fruits in relation to temperature. Am. Soc. Hort. Sci. Proc. 28:583. Hendrix, A. T. 1947. Heat generated in chOpped hay and its relation to drying effect. Agr. Engr. 28(7):286. Hoglund, R. C. 1963. Comparative storage losses and feeding value of alfalfa and corn silage. Unpublished manuscript. M. S.U. Ag. Econ. Dept. Housley 8., Curry, B., and Rowlands, D. G. 1961. A growth room for plant research. Jour. of Agr. Engr. Research. 6(3):203. James, W. O. 1953. Plant Respiration. Oxford. Kane, E. A., et al. 1937. The loss of carotene in hays and alfalfa meal during storage. Jour. of Agr. Res. 55:837. 72 Lindgren, D. L. 1935. Respiration of insects in relation to the heating of grain. Tech. Bul. 109. Minn. Agr. Exp. Sta. Milner, Max, and Geddes, W. F. 1945. Grain storage studies, Part I. Cereal Chemistry, 22:477. Morris, L. G. 1957. The control of temperature and humidity in artificially illuminated rooms. Part II. Jour. of Agr. Eng. Res., 2:11:30. Musgrave, R. B., and Moss, D. N. 1961. Photosynthesis under field conditions. Crop. Sci. 1:37-41. Schaper, Lewis 1959. . Methods for evaluating heat available in hay drying. Unpublished M.S. Thesis. Purdue U. Lafayette, Ind. Schole, Bernhard 1962. Atmuhgsverluste bei Weizen in a Abhangigkeit von Temperatur, Lagerzeit und Wassergehalt. Landtechnische Forschung, 2(4):48. Sheperd, J. B. et a1 1954. Experiments in harvesting and preserving alfalfa for cattle. U.S.D.A. Tech. Bul. 1079. Snow, D., and Wright, N. C. 1945. The respiration rate and loss of dry matter from stored bran. Jour. Agr. Sci. 35:126. Strait, J. 1944. Barn curing of hay with heated air. Agr. Eng. 25(11):421. Terry, C. W. 1947a. Relation of time and operating schedule to hay quality, mold de— velopment, and economy of operation. Agr. Engr. 28(4):141. Terry, C. W. 1947b. Some 1947 results of barn hay drying respiration. Agr. Engr. 29(5):208. Thomas, M. D. , and Hill, G. R. 1937. The continuous measurements of photosynthesis respiration, and transpiration of alfalfa and wheat growing under field conditions. Plant Physiol. 12:285. U.S.D.A. Commercial stor age of fruits,vegetables, florist and nursery 1954 stocks. Handbook No. 66. 73 Von Schreven, D. A. 1956. Some factors in connection with the heating of hay. Neth. Jour. of Agr. Sci. (4)2265. Wagner, H. G., and Porter, F. A. 1961. Apparatus for auto. measurement of 02 uptake by electrolytic re- placement OfQZ consumed. (Low'llemp. Res. Sta. Cambridge, Eng.) Biochem. Jour. 81:614. Wright, 1941. Storage of artificially dried grass. Jour. Agr. Sci. 31:194. APPENDIX Sample Calculations To Convert m1. of Condensate to Btu.of Latent Heat Ex. 7 Data: July 24 9:00 a.m. 1m1.= 10.0. = lgram 453.6 grams: 1 lb. 1, 060 Btu./1b. 453.6 grams/1b. 96. 8 m1/11 hr. X = 206 Btu. /hr. Heat Equivalent of Dry Matter For 1 molecular weight and aerobic respiration —c— + . . C6HIZOG+602 6H20 6C02 + 673 Kg Cal 673 Kg' cal' = 3.74 M = 14.85 Btu. /gram = 6, 740 Btu/1b. 180 grams grams To Calculate Dry matter Loss from Known Weight Loss Ex. 7 Data: Weight loss = 17. 25 lb. 6, 740 (Wt. loss - H20) = 1, 060 H20 - Total Wall Heat + Total Sensible Heat 6, 740 Btu./1b. (17.25 lbs. - H20) = 1, 060 H20 - 6, 721 Btu. + 10, 029 Btu. 6, 740 x 17.25 - 3, 308 = 7, 800 H20 H20 = 14.5 lb. Dry Matter = 2. 75 1b. Correction Factor for Condensation Rate Ex. 7 Data: Total Condensate = 6, 943 ml = 15. 3 lbs. Calculated Moisture Loss = 14. 5 lbs. Latent Heat (Based on Condensation) adjusted by factor = fi—g = . 95 74 75 Heat Liberated Based Upon Chemical Analysis Data Ex. 6 F. eimm. -65°F. Percent crude fiber + percent nitrogen free extract = percent total carbo— hydrate Original weight (106. 75 lb.) x original total carbohydrate (21. 69% w. b.) = original lb. of carbohydrate (2 3. 2 lb.) Final weight = 70. 50 lb. Final carbohydrate = 28. 71% w. b. Final lb. of carbohydrate = 20.2 lb. Loss of carbohydrate = 23.2 - 20.2 = 3.0 lb. Heat equivalent of the dry matter = 3. 0 1b. x 6740 Btu. /lb. = 20, 200 Btu. Average Rate of Respiration Btu. /hr. -ton D. M. for 3-5 Day Period Ex. 7 45°F. Subtract pulldown heat on experiment of 30, 45 and 650F. Total heat - pulldown heat .= 17, 901 Btu. - 3544 Btu.= 14357 Btu. Heat (Btu) = 14,357 (Btu.) Time (Hr.) 66.0 Hr. = 217.5 Btu. /hr. per 34. 73 1b. D. M. Ave. heat of respiration = 12, 500 Btu. /hr. -ton D. M. Rate of Respiration at Temperature "t" and Time "9" Att=45°F, e = 25 hr. R z (6.56 t _ 100)e (. 000208t - .018) e R = (6_56 x 45 _ 100)e (.00208 x 45 - .018) 25 R = (295 _ 100)e (.00936 - .018) 25 R_ 195 z 195 6.216 1.2415 R = 157 Btu./hr. - 100 lb. Fresh 76 Maximum Absolute Error of Respiration Equation R - 1e—ke " . 2 -. 1 R = (6.56t—100)e( 00° 081; ° 8)° Error of Variables + A k=;.001 AI = - 15 Btu./hr;-1001b. + A 9 = - 0 3R 3R Max. abs..{3.R-—aI AI+ 3k Ak AR = e-kQAI + Ole _k9Ak AR At 9 = 0 hours, AR =AI At 9 = 10 hours and t = 45°F. AB = e ('OOOZOSX45“°1°)1° 1 + 10(6.56x45-100)e 15 1950 .001 AR‘1.09 + 1.09 = e(.000208t -.018)6A1 + 9 (6.561: _ 100)e (. 000208t-. 018)0A k (. 000208x45-.018)10Ak AR = 13. 75 + 1. 74 = 15.49 Btu./hr. -100 lb. Calculate R at 6210 hours and t = 45°F. = 179 Btu. /hr. -100 lb. Maximum Absolute Percent Error — Probable Error = lf(13.75)2 + (1.74)2 x 100 = 8.55 = 13.85 Btu./hr.-100 lb. or 7.75% 77 List of Constants Used Latent Heat of Water = 1060 Btu. /1b. Density of Air: Temp'ooF° ,o lb./cu.ft. 25 .083 320 .081 450 .079 650 .076 800 .074 Specific Heat of Air (cp) = .24 Btu./1b.-°F. Heat Infiltration to Hay Chamber (UA) value = 3. 08 Btu. /hr. -OF. Watts x . 05688 = Btu. /min. ’l.llnlllll’t ' ‘