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-1178 CHAPTER 47 1958 Guide M . = weight of stock dried in a continuous dryer, pounds per hour. Mi = weight of stock charged in a discontinuous dryer, pounds per batch. Ap = pa ~ p& -- vapor pressure difference, atmospheres. pa = partial pressure of water vapor in air, atmospheres, p, = vapor pressure of water at tB, atmospheres. U = air or gas temperature, Fahrenheit. =' temperature of particle, solid or surface of evaporation, Fahrenheit. tw ~ wet-bulb temperature of drying air, Fahrenheit. h = make-up air temperature, Fahrenheit. tt = temperature of air entering stock, Fahrenheit, is = exhaust air temperature, Fahrenheit. . imi = entering stock temperature, Fahrenheit. tmt ~ leaving stock temperature, Fahrenheit. At = (ift -- t0) = temperature difference between air and surface of evaporation, Fahrenheit. Atm = logarithmic mean between temperature entering and leaving the bed, and the wet-bulb temperature, Fahrenheit. W\ = humidity ratio of entering air, pounds of water vapor per .pound of dry air. Wt = humidity ratio of leaving air, pounds of water vapor per pound of dry air. w = moisture content on dry basis at any time 0, pounds of water per pound. wc = critical moisture content, pounds water per pound dry material. tPd = water content, dry basis, of the drop as it enters the drying chamber, pounds per pound of dry solid. w -- moisture content at equilibrium with external conditions, pounds per pound dry material. u>o -- initial moisture or moisture content at start of diffusional period, pounds per pound dry material. = drying rate, pounds of water per (hour) (pound dry material). dw\ = constant drying rate, pounds per (hour) (pound dry material). o to)duA = falling rate, pounds water per (hour) (pound of dry stock). t 9 = time, hours. p. = bulk density of dry granular bed, density of dry particle, pounds per cubic foot. REFERENCES 1 Drying, by W. R. Marshall, Jr. and S. J. Friedman, Perry's Chemical Engineers Handbook, McGraw-Hill Book Co., Inc., New York, 3rd Edition, 1950. Indicated material supplied by W. R. Marshall, Jr. and S. J. Friedman, authors of the Section on Drying in the Third Edition of the Chemical Engineers* Handbook. Pernnssion to use this material has been kindly granted to The Guide by the Editor, John H. Perry, and by McGraw-Hill Book Company, publishers of the Chemical Engineers* Handbook. * The Drying of Foods, by W. R. Marshall, Jr. (Heating, Piping and Air Condition ing, September to December, 1942, and November and December, 1943). * Drying Materials in Trays, by C. B. Shepherd, C. Hadlock and R. C. Brewer (.Industrial and Engineering Chemistry, April, 1938). 4 Heat, Mass and Momentum Transfer in the Flow of Gases through Granular Solids, by B. W. Gamson, G. Thodos and O. A. Hougen (Transactions, American Institute of Chemical Engineers, 1943). , * What the Air Conditioning Engineer Should Know About Drying (Heating and Ventilating, December, 1942). 6 Calculations for Dryer Design, by W. M. Grosvenor, (Transactions, American Institute of Chemical Engineers, Vol. 1, 1908, p. 184). ^Industrial Drying Systems 1179 7 Steps in the Selection of^Drying Equipment, by S. J. Friedman (Heating and Ventilating. Vol. 48, February, 1951, Page 95).. , . 8 Spray Drying, by Ben B.-Fogler and Robert V. Kleinschmidt(Industrial and Engineering Chemistry, December, 1938). 9 Tobacco Curing (Virginia Agricultural Experiment Station Technical Bulletin 116, January, 1951). 10 Agricultural Index. (H. B. Wilson Co., New York, N. Y.) . BIBLIOGRAPHY The Temperature of Evaporation, by W. H. Carrier (A.S.H.V.E. Transactions, Vol. 24, 1918, p. 25). , . Thermodynamic Properties of Moist Air, by John A. Goff and S. Gratch (A.S.H.V.E. Transactions, Vol. 51,1945, p. 125). Factors Influencing the Performance,of Rotary Dryers, by C. F. Prutton and C. 0. Miller (Transactions. American Institute of Chemical Engineers,.Part 1, February, 1942; Part 2, August, 1942). Drying of Solids by Through Circulation, by W. R. Marshall and O. A/Hougen (Transactions, American Institute of Chemical Engineers, 1942). Factors That Influence Dryer Performance, by A. Weisselberg (Chemical .and Metallurgical Engineering, August, 1932). S'"' Typical Dryer Calculations, by 0. A. Hougen (Chemical and Metallurgical En gineering, January and March, 1940). Symposium on Drying, Articles by W. K. Lewis, W. H. Carrier, A. E. Stacey, Jr., R. S. Fleming, R. G. Metz, G. B. Ridley, C. O. Lavett, D. J. Van Marie (Industrial and Engineering Chemistry, May, 1921, pp. 427-460). Studies in Rotary Drying, I and II, by S. J. Friedman and W. R. Marshall, Jr. (Chemical Engineering Progress, 1949). Symposium on Drying (Industrial and Engineering Chemistry, 1938). Principles of Drying Lumber and Humidity Diagram, by H. D. Tiemann (Forest Service Bulletin, 104,1912). The Drying of Solids, by T. K. Sherwood (Bulletin, Massachusetts Insiituie of Technology, Nos. 237, 247, and 258). Radiant Energy Drying with Heat Lamps, by T. P. Brown (Metal Industry, Vol. 37, Dec. 1939, p. 607). Shying by Sublimation, by E. W. Flosdorf (Food Industry, Vol. 17, Jan. 1945, p. Evaporative Drying System, by F. H. Slade (Food Manufacturing, Vol. 18, March, 1943, p. 70). High Frequency Methods'in Gluing and Drying Wood, by I. R. Berkness (Wood Products, Vol. 45, 1940, p. 12). Development of the Unit Operations of Chemical Engineering: Drying, by T. K. oherwood (Chemical & Metallurgical Engineering, Vol. 42, p. 214). The Spray Dryer--Its Possibilities in Industry, by D. W. Biocheno (Food Manu facturing, Vol. 19, June, 1944, p. 195). Mechanism and Rate of Drying by Near-infra-red Radiation, by L. E. Stout, K. J. Oaplan and W. G. Baird (Transactions American Institute of Chemical Engineers. Vol. 41, 1945, p. 283). w Engineering Problems of the New Vegetable Dehydration Industry, by W. B. Van Arsdel (A.S.H.V.E. Transactions, Vol. 49, 1943, p. 49). Electronic Dehydration of Foods, by V. W. Sherman (Electronics, Vol. 17, 1944, Air Conditioning and Engineering, American Blower Co., 1935. Drying in Industrial Plants, J. O. Ross Company. Elements of Chemical Engineering, by Badger and McCabe (McGraw-Hill Co., Fan Engineering, Buffalo Forge Co. ie Trockentecknik, by M. Hirsch (Julius Springer, Berlin, 1932). rying (Kent*s Mechanical Engineers Handbook). rying, by W. H. Carrier (Mark's Mechanical Engineers Handbook). iln Drying of Lumber, by A. Koehler and R. Thelen, New York, 1026.