Document zbzmajMGxvNw1mJp3B27BM7Y3

HEATING VENTILATING AIR CONDITIONING CUIDE 1944 Heat in air exhausted from oven at 422 F per pound fuel burned = 0.333 X 123.9 X (Sm - Sn) = 41.3 (91 - 8.6) = 3,400 Btu. Btu available for heating material = 16,005 -- 3,400 = 12,605 Btu per pound fuel. Fuel used in first hour = 2,180,470 -s- 12,605 = 173 lb = 25.6 gal. During the second hour the heater capacity will be much greater than required. If an automatic oven temperature control operates on the oil supply, the delivery tem perature of the air entering the oven and the quantity of oil burned will decrease, the air supply being constant. Heat in air exhausted = 41.3 (Sai -- Sn) = 41.3 (127 -- 8.6) = 4,880 Btu per pound fuel. '' Heat available for heating material = 16,005 -- 4,880 = 11,125 Btu. Fuel used in second hour = 1,072,008 -5- 11,125 = 96.5 lb oil = 14.3 gal. Total oil used per load = 25.6 + 14.3 = 39.9 gal. Sand.. ... . Binder Water. _ Evaporation... Superheat............ Total Per Ton For 6 ton Steel plates.. Radiationb Total.. ... Heating Load First Hour Heated to 212 F 212 F 9.1 ? p 66.7% 66.7% 330 X 120,120 142 330 X 7,920 0.667 X 116,520 . 0.667 X 9,800 ^ Btu = 51,688 3,408 = 17,040 77,680 -- 6,530 390 F 422 F Avg 6 X 156,346 320 X 30,000 X 0.12 352 X 856 X 0.30 . 156,346 -- `=5 938,076 = 1,152,000 = 90,394 Heating Load Second Hour Sand_____ Binder3... Water.. _ _ Evaporation... Superheat. Total Per Ton. 400 F 400 F 33.3% 33.3% For 6 ton Steel plates Radiation1*.. ------------------------ --------:------------------ TotaL. 460 575 188 330 X 120'120 330 X 7,920 0.333 X 116,520 0.333 X 9,800 - . 68,432 = . 4,512 ~ 38,840 = 3,270 115,054 6 X 115,054 70 X 30,000 X 0.12 505 X 856 X 0.30 ss . 690,324 = 252,000 129,684 finder oxidizes and liberates heat, which is neglected in this calculation. 1 ^Average value of coefficient is le&'tban 0,3 because oven is not up to 675 F. This is neglected. " 422 F is arrived at by taking area under curve as compared to area under 575 F ordinate.. i 748," . CHAPTER 41. DRYINC SYSTEMS ESTIMATING METHODS Values based on practical experience are available for rough estimating of drying problems. The temperature will drop approximately 8.5 F per grain of water evaporated per cubic foot of air (measured at 70 F) or approximately 0.62 F per pound of air at any temperature. Air will drop 55 F per cubic foot for each Btu extracted. Generally air will absorb from 2 grains to 5 grains per cubic foot of air in one passage through an air dryer, depending on the temperature and the degree of contact with the material. The amount of steam required to evaporate a pound of water will vary from 1.5 lb to a more usual figure of from 2.5 to 3 lb of steam per pound of water evaporated. REFERENCES Drying Apparatus, by H. C. Russell (A.S.H.V.E. Transactions, Vol. 18, 1912, p. 76). Commercial Drying Apparatus, by L. P. Dwyer (A.S.H.V.E. Transactions, Vol. 22, 1916, p. 479). Artificial Drying with Special Reference to the Use of Gas, by G. C. Shadwell (A.S.H. V.E. Transactions, Vol. 23, 1917, p. 231). Drying by Evaporation, by F. R. Still (A.S.H.V.E. Transactions, Vol. 23, 1917, p. 255). High Temperature Drying, by Burt S. Harrison (A.S.H.V.E. Transactions, Vol. 24, 1918, p. 7). The Temperature of Evaporation, by W. H. Carrier (A.S.H.V.E. Transactions, Vol. 24, 1918, p. 25). Address on Dehydration, by H. C. Gore (A.S.H.V.E. Transactions, Vol. 24, 1918, p. 323). Food Dryers and the Use of School Houses for Drying, by W, L. Fleisher (A.S.H.V.E. Transactions, Vol. 24, 1918, p. 339). Memorandum Concerning Fruit and Vegetable Dryers, by Alfred S. Kellogg (A.S.H. V. E. Transactions, Vol, 24, 1918, p. 359). Progress in the Dehydration Industry, by C. E. Mangels (A.S.H.V.E. Transactions, Vol. 26, 1920, p. 99). Dehydration, by Ralph H. McKee (A.S.H.V.E. Transactions, Vol. 26, 1920, p. 105). Commercial Dehydration, by J. E. Whitley (A.S.H.V.E. Transactions, Vol. 26; 1920, p. 551). Drying of Fruits and Vegetables, by Ray Powers (A.S.H.V.E. Transactions, Vol. 27, 1921, p. 241). Drying as an Air Conditioning Problem, by A. W. Lissauer (A.S.H.V.E. Trans actions, Vol. 27, 1921, p. 251). A Chronological Survey of Drying and Driers, by J. E. Bolling (A.S.H.V.E. Journal, Vol. 27, October, 1921, p. 715). Dehydration and Freshening of Codfish, by Henry W. Banks, 3D (A.S.H.V.E. Transactions, Vol." 28, 1922, p. 143). Construction of Farm Dehydrators in California, by A. W. Christie and G. B. Ridley (A.S.H.V.E. Journal, Vol. 29, 1923, p. 687). Study of Air Velocity and Temperature in Vegetable Dehydration, by A. W. Christie and K. Matsumoto (A.S.H.V.E. Journal, Vol. 33, June, 1927, p. 381). Air Conditioning and Food Dehydration (Heating and Ventilating, December, 1942, p. 35). Adiabatic Drying of Hygroscopic Solids, by A. M. McCready and W. L. McCale (Transactions, American Institute Chemical Engineers, 1933). Limitations of Diffusion Equations in Drying, by O. A. Hougen, H. J. McCauley and W. R. Marshall (Transactions, American Institute of Chemical Engineers, 1940). 749