INDUSTRIAL AND ENGINEERING CHEMISTRY
May, 1941
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TIME,
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FIGURE 11. WATER CONTENTOF ELBOWMACARONI IN PRELIMINARY DRYER
10
15 FREE WATER (DRY
20
25 BASIS),
30
FIGURE 13. COMMERCIAL RATESOF IN SECONDARY DRYERB DRYING
70
FIGURE 12. RATE OF DRYINGELBOW MACARONI IN PRELIMINARY DRYER
period was obtained. Near equilibrium the rates of drying are, in general, lower for spaghetti than for the flat sheets which had not been subjected to the higher pressures. The conditions of run 15 duplicated run 14 except that the air velocity was raised from 95 to 220 feet per minute. The rates of drying for the two are plotted in Figure 10. Both runs are entirely in the falling-rate period. The values of K are shown in Table IV.
Tests on Commercial Equipment Tests 17, 18, 19 were made on a four-pass conveyor dryer heated a t an average temperature of 106’ F., a humidity of 0.0265 pound water per pound of dry air, and an average air velocity of 250 feet per minute. The moisture distribution of elbow macaroni is shown in Figure 11, and the rates of drying based on the outer area are given in Figure 12. Run 6 was made on the equipment described previously when operating under the usual plant conditions. The drying rates are shown in Figure 13.
Nomenclature area of drying surface, s ft. F = free water, lb. free HaO/%. dry material H = humidity, lb. HaO/lb. dry air H w = saturated humidity at wet-bulb temperature IC: = film coefficient of diffusion, lb. HoO/(hr.)(sq. ft. area) (unit humidity difference) K =e constant R = rate of drying = dw/A&, lb./(hr.)(sq. ft.) e = time, hr. w = weight, lb.
A
=
Subscripts a = main stream of air f = fallin rate period 0 = mitiafvalue w = surface of evaporation
Literature Cited (1) Am. Assoc. Official Agr. Chem., Standard Methods of Analysis 8th ed., 1936.
Atkinson, IND. ENQ.CHEM.,14, 913 (1922). Badger and McCabe, “Elements of Chemical Engineering”, pp. 308-9, 2nd ed., New York, McGraw-Hill Book Go., 1936. Binnington and Geddes, Cereal Chem., 13,497 (1936). Ceaglske and Hougen, Trans. Am. Inst. Chem Engrs., 33,
218-314 (1937). Heisig and Cameron, IND. ENQ. CHEM., Anal. Ed., 5, 420
(1933). Heisig and Gernes, Ibid., 6 , 166 (1934). Hoskins, Glen, Food Industries, 4, 49 (1932). Hougen, 0.A., Chem. & Met. Eng., 47,757 (1940). International Critical Tables, Vol. I, p. 281 (1926). Lindsay, D. C., “Drying and Processing of Materials by Conditioned Air”, pp. 128-31, Newark, N. J., Carrier Eng. Gorp., 1929. Rasseau, Francis, Food Industries, 11, 689,691 (1939). Shepherd, Hadlock, and Brewer, IND.ENQ.CHEM., 30, 388-97
(1938). Sherwood, T. K.,Perry’s Chemical Engineer’s Handbook, p. 1223, New York, McGraw-Hill Book Go., 1934. Sherwood, T. K., Trans. Am. Inst. Chem. Engrs., 32, 160
(1936). Valdes, Francisco, Food Industries, 8, 620 (1936). Walker, Lewis, McAdams, and Gilliland, “Principles of Chemical Engineering”, 3rd ed., pp. 613,644,New York, McGrawHill Book Go., 1937. PEEWQNTIUD by P. L. Earle &a partial fulfillment for the M.S. degree in ohemioal engiheering at the University of Minneaota, 1939.
Economic Pipe Size-Correction A few typographical errors unfortunately occurred in our paper “Economic Pipe Size in the Transportation of Viscous and Nonviscous Fluids” [IND.ENQ. CHEM.,32, 1251 (194O)l. The corrections are as follows: Left-hand column: lines 6 and 8, change 0.000135 to 0.00135; Equation 10,change 0.088 to 0.88. Right-hand column: line 28 from bottom, change “multiplied” to “divided”; line 25 from bottom, change “multiplying” to “dividing”. B. R. SARCHET AND A. P. COLBURN
