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954 CHAPTER 36 1958 Guide . *A New Development in Absorption Refrigeration, by A. A. BerestnefT (Re frigerating Engineering, Vol. 57, No. 6, June 1949, p. 553). I Heat Pumps, by Philip Sporn, E. R. Ambrose and T. Baumeister (John Wiley and Sons, 1947). 1 6 Operating Characteristics of Heat Pump Ground Coils, by W. A. Hadley (.Edison Electric Institute Bulletin, Vol. 17, No. 12, 1949, p. 457). Theory of Earth Heat Exchangers for the Heat Pump, by L. R. Ingersoll, F. T. Adler, J. H. Plass and A. C. Ingersoll (ASHAE Tbansactions, Vol. 57,1951, p. 167). 7 Research Results Concerning Earth as a Heat Source or Sink (Edison Electric Institute Bulletin, September 1953) 8 Determination of Coefficient of Performance and Performance Factor of an Electric Heat Pump While Operating on the Heating Cycle (Edison Electric'Institute Bulletin, October 1948). 9 AG&E Experience Proves Commercial Heat Pumps Practical, by E. R. Ambrose (Refrigerating Engineering, May 1955). 10 Practical Heat Pump, by R. G. Werderi (Refrigerating Engineering, May 1956, p. 49). II Evaluating Heat Pump Performance, by F. R. Ellenberger, A. B. Hubbard, W. R. Foote, F. Burggraf and J. J. Martin (ASHAE Tbansactions, Vol. 56,1956, p. 87). 11 Application of the Packaged Heat Pump, by Walter R. Yeary (Air Conditioning Heating and Ventilating, May 1956, p. 89). 18 Dollars in Air Conditioning, by B. R. Askew (Load Magazine, October, 1955). " Electric Motor Drive Versus Competitive Air Conditioning Systems, by G. C. Freyder (Great Lakes Power Club, February 1, 1957). 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.). Refrigeration and Air Conditioning Engineering, by B. F. Raber and F. W. Hutchinson (John Wiley & Sons, 1945). Refrigeration, by J. A. Moyer and R. U. Fittz (McGraw-Hill Book Co.). Refrigerants and Absorbents, by W. R. Hainsworth (Refrigerating Engineering, August and September, 1944). Air Conditioning and Refrigeration, by B. H. Jennings and S. R. Lewis (Inter national Textbook Company, 1944). Refrigeration and Air Conditioning, by Jordan and Priester (Prentice-Hall, Inc., 1948). Heat Pump Applications, by E. N. Kemler and S. Oglesby, Jr. (McGraw Hill Book Co., 1950). Heat Pump Results in Equitable Building, by J. D. Kroeker, R. C. Chewning and C. E. Graham (ASHAE Tbansactions, Vol. 55, 1949, p. 345). A Report on Heat Storage for Heat Pumps (Edison Electric Institute Bulletin, Vol. 18, No. 9, 1950, p. 333). Heat Pump Application to a Newspaper Plant, by J. D. Kroeker, J. H. Bonebrake and J. A. Melvin (ASHAE Tbansactions, Vol. 57, 1951, p. 483). Cost of Operating the Heat Pump in the Equitable Building by J. D. Kroeker and R. C. Chewning (ASHAE Tbansactions, Vol. 60, 1954, p. 157). The Meaning of Boiler Efficiency (Air Conditioning, Heating and Ventilating, March, 1957, p. 61). CHAPTER 37 DEHUMIDIFICATION BY SORBENT MATERIALS Definitions and Principles, Adsorbents, Dehumidification by Solid Adsorbents, Dehumidification Equipment Using Solid Adsorbents, Absorbents, Dehumidification by Liquid Absorbents, Dehumidification Equipment Using Liquid Absorbents, Calculation of Moisture Load, Vapor Transfer to Dehumidified Space ------------------------- --------- ^--------------------------------------------------- DEHUMIDIFICATION as used herein is the reduction of the water vapor content of a given volume of air or other gas. The term thus describes a special case of dehydration which covers the removal of moisture in any form from matter. The degree of dehumidification required varies greatly with different applications, and is one of the prime considerations influencing the choice of a method. Dehumidification may be accom plished by latent heat removal, together with sensible heat removal, as described in Chapters 29, 34, and 35, or by the use of sorbents. Sorbents are substances which have the property of extracting and hold ing other substances (usually gases or vapors, e.g., water vapor), brought into contact with them. All materials are sorbents to a greater or lesser degree. The weight of water held by a substance will increase or decrease, depending upon whether the vapor pressure of the water held by the sub stance is less or greater, respectively, than the partial pressure of water vapor in the surrounding atmosphere. As generally used, however, the term sorbents refers to those materials having a capacity for moisture which is large compared to their volume and weight. Such materials are divided into two general classifications: 1. Adsorbent--A sorbent which does not change physically or chemically during the sorption process. Certain solid materials, such as activated alumina, silica gel, activated bauxites, and activated charcoal have this property. The action of adsorb ents, most of which adsorb some gases and condensible vapors besides water vapor, is selective. Thus, in the case of a mixture containing both water and organic vapors, silica gel would remove the water vapor in preference to the organic vapors, while the averse would be true in the case of activated carbon. The selective property of adsorbents is made use of in some instances for the removal of objectionable and con taminating vapors from an air or gas mixture. (See Chapter 8.) 2. Absorbent--A sorbent which changes either physically, chemically, or both, the sorption process. Calcium chloride is an example of a solid absorbent, while liquid absorbents include solutions of lithium chloride, calcium chloride, lith ium bromide, and the ethylene glycols. ADSORBENTS , The ability of an adsorbent to remove water vapor from a gas is explained oy the fact that the vapor pressure of the water in the adsorbent (when in the reactivated condition) is less than the partial pressure of the water vapor in the surrounding atmosphere. For instance, when an active ad sorbent is brought into contact with a gas of high humidity, there is a tendency for the vapor pressure of the water in the adsorbent to reach equi- onum with the partial pressure of the water in the surrounding gas, with 955