NATURAL DRAFT COOLING TOWER SIR: Two interesting articles by Furzer (1968a,b) deal with natural draft cooling towers. The author is apparently unaware of the work of Chilton (1952), who presented an analysis which is essentially the same as Furzer’s. The Chilton coefficient and duty coefficient referred to by Rish and Steel (1959) are related to Furzer’s tower number and specification number. Crawshaw (1963-64) carried out extremely careful tests on a large natural draft cooling tower and concluded that large variations in the resistance factor, N , occurred, and that in consequence the Chilton coefficient (or tower number) could not be assumed to be a constant for each liquid flow rate. However, this assumption is a useful one when a rapid approximate answer is required. literature Cited
Chilton, H., Trans. Inst. Elec. Engrs. 99, Part 2 (1952). Crawshaw, C. J., Proc. Inst. Mech. Engr. 178, No. 35 (1963-64). Furzer, I. A., IND.ENG.CHEM.PROCESS DESIGNDEVELOP. 7, 555 (1968a). Furzer, I. A . , IND.ENG.CHEM.PROCESS DESIGNDEVELOP. 7, 561 (196813). Rish, R.. F., Steel, T. F., Proc. A m . SOC.Ciuil Engrs., Power Dioision 85, Po5 (October 1959).
Alan H . Stenning Lehigh Uniuersity Bethlehem, Pa. I8015
SIR: Chilton’s method (1952) for the design of natural draft cooling towers is well known and is widely used a t the present time. The method is based on a simple empirical correlation of test data on these towers. The first paper (Furzer, 1968a) presents a new method for the design of the towers which is based on a solution of the conservation and rate equations for the system. The accuracy of the method is shown by a statistical test of published data on these towers. Chilton was unsuccessful in solving these equations and introduced a number of arbitrary curves which is the basis of his method. The new design method avoids this empiricism, and all its associated difficulties, as shown by Crawshaw (1963-64). The second paper (Furzer, 1968b) introduces a new constraint on the liquid loading which has not been previously reported. So these two papers (Furzer, 1968a,b) are an extension of the analysis given by Wood and Betts (1950) and do not follow the empirical approach of Chilton. literature Cited
Chilton, H., Trans. Inst. Elec. Engrs. 99, Part 2 (1952). Crawshaw, C. J., Proc. Inst. Mech. Eng. 178, Part 1, NO. 35 (1963-64). Furzer, I., IND.ENG. CHEM.PROCESS DESIGNDEVELOP. 7, 555 (1968a). DESIGNDEVELOP. Furzer, I., IND.ENG. CHEM.PROCESS 7, 561 (1968b). Wood, B., Betts, J. L., Proc. Inst. Mech. Engrs 163, 54 (1950).
I . Furzer Imperial College London, England
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