Document pBQ99yrzMg7vjvenKeGpk65Jk

136 CHAPTER;?. S. M. Henderson and R. L. Perry:Agriculiural Process Engi neering (John Wiley and Sons, New York, 1955). H. K. Johnson and A C. Dale: Heat required to vaporise moisture (Agricultural Engineering, Vol. 35, October 1954, p. 705). " C. M. Milne: Functional Requirement* fort Drying Hay (M. 8. Thesis, Purdue University, 1954). : M C. K. Shedd: Resistance of grains and seeds to air flow (Agri cultural Engineering, VoL 34, September 1953). u C. W. Hall: Analysis of air flow in grain drying (Agricultural Engineering, VoL 36, April 1955, p. 247). " D. B. Brooker: Pressure patterns in grain drying systems established by numerical methods (American Society of Agricul tural Engineer* Transactions, Vol. 4, No. 1, 1961, p. 72). *.r J. M. Bunn and W. V. Hukill: Pressure Pattern Predictionsfor Nan-Linear Air Floto^Through Porous Media (American Society of Agricultural Engineers Paper 62-408, Washington, D. C., June 1962L j M N. C. Ives,.-W. V. Hukill, and R. A. Saul: Grain ventilation and drying patterns (American Society of Agricultural Engineers, VoL 2, No. 1, 1959, p. 95). " . l( Jr'B: Shepherd: Experiments in Harvesting and Preserving Alfalfa for Dairy Cattle reed (Technical Bulletin No. 1079, United States Department of Agriculture, 1954). * -- ** E. J. Hoffman, G. F. Lum, and A. L. Pitman: Retention of carotene in alfalfa stored in atmospheres of.low oxygen content (Journal of Agricultural Research, VoL 71, 1945, p. 361). ' C. R. Thompson, et aL: Carotene Stability in Alfalfa (Techni- . ,1965; Guide Arid Data Book cal Bulletin No. 1232, Agricultural Research Service, United States Department of Agriculture). ** C. A. Cabell, R. E. Davis, and R. A. Saul: Relation of Drying Air Temperature, Time, and Air Flou Rate to the Nutritive Value of of Fidd-SheUed Com (Technical Progress Report, 1957-58, ARS 44-41/Agricultural Research Service, USDA, November 1958): R. A. Saul: Cost of Drying Shelled Com Related to Mechanical Damage (Bound Ofice Report, Harvesting and Farm Processing Research Branch, ARS, Agricultural Engineering Department, Iowa State University, Ames, Iowa, 1964). ** J. L. Steele and K. A. Saul: Laboratory Measurements of the Rate af Deterioration'of Grain During Drying (Paper presented at Annual Meeting of Mid-Central Section of ASAE, Lincoln, Nebraska, March 1962). _ ** G. Nf Pranks and C. 8. Shaw: Multipath Dryingfor Control ling Moisture wi Cotton (U. S. Department of Agriculture,' ARS 42-69, August 1962)'. : ** C. S. Shaw and G. N. Franks: Cottonseed Drying and Storage at Cotton Gins (USDA, ARS, Technical Bulletin 1262, May 1962). 'n W. C.'Bailey, T. E. Pickett, and J. G. Futral: Rapid curing adversely affects quality of peanuts (Peanut Journal and Nut World June 1954)/ ./ ... ** HJ A_"Kramei: Engineering aspects of rice drying (Agricul tural Engineering Vol. 32/JanUaiy<l951, p. 44). n J. L. Schmidt and W. V. Hukill: Effect of artificial drying on yield of head rice and the germination of rice (Rice Journal, 59: 13,.1956, p. 31). < ... . CHAPTER 10 AIR CONDITIONING IN THE PREVENTION AND TREATMENT OF DISEASE fa-nee on Patients; Control of Airborne Infection; Operating Room*. Exp/orion Hazard, Room Conditions/ Nurseries for Pre mature Infants: Requirements, Equipment, Control of Airborne Infection; Patient Rooms; Allergic Disorders/ Hyperthermia; Hypothermia; Fog Therapy; Oxygen Therapy; Pollutants; Odors,- Maintenance of Air Conditioning Systems AIR CONDITIONING complements biologic processes ^\. for the exchange of heat and water and removes most of the hazardous particles or offensive products of human ac tivity from the environment. Its purposes can best be achieved, once the bade physiologic functions are understood. Temperature regulation in the human is'summarized diagrammatically in Fig. 1. Heat loss in a resting individual occurs by three processes: vaporisation from the skin and Inngw, 25 percent; radiation from the skin, 60 percent; and convection, 15 percent. Loss by conduction from a clothed individual is negligible. Shade, cool surroundings, air currents, and immersion in cold water are conventional means of in creasing heat loss. As the ambient temperature reaches that of the body, these methods are ineffective, and therefore con trol of relative humidity becomes of paramount importance.1-* The body temperature of an insulated man rises about 3.6 F deg per hour by the retention of heat from his metabolism* Sweating, panting, and more rapid circulation of the blood through the skin are the physiologic methods of augmenting loss of heat.4 On a hot desert day, a man may produce more than a liter of sweat in an hour. When loss of his body weight approaches 5 percent, physical deterioration results; per ception is distorted, and judgment falters. When the loss approximates 10 percent, delirium, convulsions, deafness, and insensibility to pain ensue. Death from explosive heat or heat stroke results from a 12 percent loss. Death is caused by stagnation of blood flow due to increasing viscosity of the blood. Metabolic heat can no longer be dissipated to the skin and respiratory tract, and body temperature rises to a fatal level. The role of the skin in temperature regulation of the body is widely recognized. The more remarkable part played by the respiratory tract is little appreciated. Air conditioning is important because it can compensate for critically aberrant body functions in this vitally important area. The temperature and relative humidity of inspired air are brought to body temperature and to a saturated level, prior to reaching the lungs, by turbulent convection and evaporation of water from the mucosa (mucous membranes) lining the Pper respiratory tract (Fig. 2).4 When the inspired air is woter and drier Hum alveolar air (the air in the lungs), there , ceaenj rapooeibiUtj lor this chapter b --to TC 1.4. Phybotocr ad Homan Ecmroeinent. processes cool the mucosa. During expiration, heat and water are recovered from the alveolar air (98.6 F, 100 percent RH) as it impinges on the colder mucosa of the nasopharynx (Fig. 3). The Ammint of this exchange depends upon the degree to which the alveolar air is cooled by the mucosa. Since the cool ing of the mucosa is dependent upon the ambient temperature And humidity, it is these factors that determine the heat and water balance that results from respiration. In hot climates,. the ambient humidity is critical in deter mining heat loss. When hot, saturated air is inspired, insig- FACTOta INCREASING nificant evaporative cooling occurs; indeed, the nasopharyn geal mucosa may gain heat from inspired air and water vapor that condenses' on the cooler mucosa.' During expiration,1 alveolar`air is discharged-fully saturated at 98.6 F/Underthese conditions,- the body nets a gain'in both heat'and-water.Lowering the relative humidity permits evaporative cooling to 137