Document 5L2Db8wyppE8vkppJKo549mw0

\722 CHAPTER 39 1948 Guide hm enthalpy of mixture. Av > enthalpy of saturated vapor. Avd ; enthalpy of saturated vapor at discharge of valve.or compressor, Avs ! enthalpy of saturated vapor at state s entering compressor. hp ' horsepower. Pi - pressure of saturated liquid and vapor at discharge of compressor. Pa = pressure of saturated liquid. psig = pressure pounds per square inch, gage. psia - pressure pounds per square inch, absolute. Q quantity of heat, Btu. Qc ` heat loss from condenser, Btu per pound refrigerant. 'Qj heat dissipated in cooling water, Btu per hour. s entropy. As entropy change between suction and discharge. T'- absolute temperature, Fahrenheit degrees. ' average temperature, Fahrenheit degrees, absolute, of gas passing through compressor. ' Tc condenser temperature, Fahrenheit degrees, absolute, Ts evaporator temperature, Fahrenheit degrees, absolute. fad ; degrees superheat at discharge condition of vapor leaving compressor, ti discharge temperature, Fahrenheit degrees. Vc : clearance, percentage of volume, swept by piston, which is contained in spaces at end of cylinder when piston is at end of stroke (clearance includes valve spaces, etc.) Vs specific volume of gas at suction, cubic feet per pound, Vi. specific volume of gas at discharge, cubic feet per pound. Wr ' refrigerant rate, pounds per minute, x proportion of liquid in mixture of vapor and liquid. REFERENCES -1--Application and Economy of Steam Jet Refrigeration to Air Conditioning, by A. R. Mumford and A. A. Markson (A.S.H.V.E. Transactions, Vol. 44, 1938, p. 33). *--The Application of Storage Refrigeration to Air Conditioning, by C. F. Boester (A.S.H.V.E. Trans actions, Vol. 45, 1939, p. 675). 3--Use of Cold Accumulators in the Air Conditioning Field, by R. W. Evans and C. J. Otterholm (A.S.H.V;E. Transactions, Vol. 48/ 1942,`p. 123). . 4--Cooling Homes, A Field for Refrigeration, by A. R. Stevenson, presented at the symposium of the Refrigeration with Gas Committee of the American Gas Association, April 20; 1926. The Heat Pump,.An Economical Method of Producing Low-grade Heat from Electricity, by T. G. N. Haldane {Electric Review. Vol. 105, p. 1161-1162, December 27, 1929, and I. E. E. Journal, Vol. 68, p. 666-675, June, 1930). ' Edison Building.Heated and Cooled by.Electricity, by H. L. Doolittle {Power, Vol. 74. p. 384, September 8; 1931). House Heating by Pump with 5 to 1 Pick-up Ratio, by Gilbert Wilkes and R. E. Marbury {Electrical World, Vol. 100, p. 828, December 17, 1932). An All Electric Heating. Cooling and Air Conditioning System, by Philip Sporn and D. W. McLenegan (A.S.H.V.E. Transactions, Vol. 41, 1935, p. 307). Heat Pump Choice and Cost of Various Systems, by S. P. Goethe {Refrigerating Engineering, July. 1947, p. 24). ' BIBLIOGRAPHY Refrigerating Data Book, Vol. 1 (American Society of Refrigerating Engineers). Refrigeration Engineering, by H. J. Macintire (John Wiley & Sons)/': Theory of Mechanical Refrigeration, by N. R. Sparks (McGraw-Hill Book Co., Inc.). Refrigeration and Air Conditioning Engineering, by B. F. Raber and F. W. Hutchin son (John Wiley & Sons). Refrigeration, by J. A. Moyer and R. U. Fittz (McGraw-Hill Book Co., Inc.). Refrigerants and Absorbents, by W. R. Hainsworth (Refrigerating Engineering, August and September, 1944). Refrigeration and Air Conditioning, by B. H. Jennings and S. R. Lewis (International Textbook Company). Chapter 40 AIR DISTRIBUTION Standard* for Satisfactory Conditions, Definitions, Mechanics of .Air Distribu tion, Outlet Performance, Types of Air Outlets, Outlet Location and Selec. tion. Directional and Volume Control, Return and Exhaust Intakes, ,Specific Applications CORRECT air distribution contributes as much or more to the success of a forced air heating, ventilating, cooling or air conditioning system as does any other single factor. An air conditioning system may deliver the required quantity of conditioned air and still fail to give satisfactory ~ room conditions because of poor air distribution. The scope of the chapter is limited to the air distribution within the conditioned space. Reference is made to the distributing duct system only insofar as it affects the performance of the air distribution outlet. See Chapter 41 for informa tion on. air duct design. STANDARDS FOR SATISFACTORY CONDITIONS The object of air distribution is to create within the space the proper combination of room temperature, air motion and humidity, whether by cooling, heating or ventilating. The purpose to be accomplished deter mines the factors to be controlled. For instance, in many industrial applications it is necessary to maintain proper standards throughout a large portion of the space; sometimes almost throughout the entire enclosure. In these cases design room temperature, room air motion and humidity will depend entirely upon the requirements of the product and its manufacturing processes. If, however, comfort of the occupants is the principal objective, con sideration of the occupied zone (floor to 6 ft above floor level) is primarily required. In order to obtain comfort conditions within this zone, stand ard limits have been set up as acceptable effective temperatures. This term comprises air temperature, motion, humidity and their physiological effect on the surface of the human body. Any variation from accepted standards of one of these elements may result in discomfort to the occu pants. The same effect may be caused by lack of uniformity of condition's within the space or by excessive fluctuation of conditions in the same part of the space. Such discomfort may arise due to excessive room air temperature variations (horizontally, vertically, or both), excessive air motion (draft), failure to deliver or distribute the air according to the load requirements at the different locations, or too rapid fluctuation of room temperature or air motion (gusts). In addition the noise level created by the introduction of supply air should be kept within acceptable limits, and streaking or smudging of walls or ceilings should be prevented. With reference to permissible room air motion it is not possible to. establish a specific standard covering the entire complex problem of air distribution. Velocities less than 15 fpm generally cause a feeling of air stagnation, whereas velocities higher than 65 fpm will disturb loose paper sheets on desks and may result in a sensation of draft. Air velocities of 25 to 35 fpm in the occupied zone are most satisfactory, but air motion of 20 to 50 fpm will usually be acceptable, particularly when the lower part of this range of velocity is used in cooling applications and the higher 723