RESEARCH PAPERS: Heat and Mass Transfer

An Analytical Approach to the Heat and Mass Transfer Processes in Counterflow Cooling Towers

[+] Author and Article Information
Chengqin Ren

College of Mechanical and Automotive Engineering, Hunan University, Changsha, 410082, Chinarenchengqin@163.com

J. Heat Transfer 128(11), 1142-1148 (May 09, 2006) (7 pages) doi:10.1115/1.2352780 History: Received May 06, 2005; Revised May 09, 2006

Quick and accurate analysis of cooling tower performance, outlet conditions of moist air, and parameter profiles along the tower height is very important in rating and design calculations. This paper developed an analytical model for the coupled heat and mass transfer processes in counterflow cooling towers based on operating conditions more realistic than most conventionally adopted Merkel approximations. In modeling, values of the Lewis factor were not necessarily specified as unity. Effects of water loss by evaporation and water film heat transfer resistance were also considered in the model equations. Within a relatively narrow range of operating conditions, the humidity ratio of air in equilibrium with the water surface was assumed to be a linear function of the surface temperature. The differential equations were rearranged and an analytical solution was developed for newly defined parameters. The analytical model predicts the tower performances, outlet conditions, and parameter profiles quickly and accurately when comparing with the numerical integration of the original differential equations.

Copyright © 2006 by American Society of Mechanical Engineers
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Grahic Jump Location
Figure 1

A schematic diagram of a counterflow cooling tower

Grahic Jump Location
Figure 2

Parameter profiles along the vertical length of the tower for the conditions with tw,i=40°C, ta,i=35°C, twb,i=20°C, Wa,i=0.00852kgw∕kga, NTU=3, and Ẽ=11




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