Document zvV2GV3MyjxQLR9ZNMg71qba

HEATING VENTILATINC AIR. CONDITIONING CUIDE 1943 ' 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 -5- 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 (Sen -- Sn) = 41.3 (127 -- 8.6) = 4,880 Btu perpound fuel. Heat available for heating material = 16,005 -- 4,880 = 11,125 Btu. Fuel used in second hour = 1,072,008 -H 11,125 = 96.5 lb oil = 14.3 gal. Total oil used per load = 25.6 + 14.3 = 39.9 gal..' Heating Load First Hour Sand...... Binder. Water.____________________ Evaporation Superheat Heated to 212 F 212 F 212 F 66.7% . 66.7% X 120,120 142 gjjjj X 7,920 0.667 X 116,520 0.667 X 9,800 Btu = 51,688 = 3,408 17,040 = 77,680 = 6,530 Total Per Ton--------------------- ------------------------------------ ;......................................... 156,346 For 6 ton Steel plates Radiation >> 390 F 422 F Avg 6 X 156,346 320 X 30,000 X 0.12 352 X 856 X 0.30 = 938,076 = 1,152,000 = 90,394 Heating Load Second Hour Binder. Water. Evaporation______________ Superheat..._______ _____ ,__ 400 F 400 F 33.3% 33.3% 3^ X 120,120 188 33^ X 7,920 , \ 0.333 X 116,520 0.333 X 9,800 = 68,432 = 4,512 ' = 38,840 = . 3,270 Total Per Ton--:----------------------------------------------............ ..............______,_______ 115,054 For 6 ton Steel plates Radiationb 6 X 115,054 ' 690,324 460 70 X 30,000 X 0.12 = 252,000 575 505 X 856 X 0.30 = ; 129,684 Total.--------,--------- ------_----------:------------------------------ _______________________ = 1,072,008 Binder oxidizes and liberates heat, which is neglected in this calculation. ^Average value of coefficient is less than 0.3 because oven is not up to 575 F. This is neglected. 422 F is arrived at by taking area under curve as compared to area under 575 F ordinate. ' 762: CHAPTER 4). DRYING 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.HiV.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 {Transactionsf 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). 763 i