Second Law Analysis of Solid Desiccant Rotary Dehumidifiers

[+] Author and Article Information
E. Van den Bulck, S. A. Klein, J. W. Mitchell

University of Wisconsin, Solar Energy Laboratory, Madison, Wisconsin 53706

J. Sol. Energy Eng 110(1), 2-9 (Feb 01, 1988) (8 pages) doi:10.1115/1.3268233 History: Received April 01, 1986; Online November 11, 2009


This paper presents a second law analysis of solid desiccant rotary dehumidifiers. The equations for entropy generation for adiabatic flow of humid air over a solid desiccant are developed. The generation of entropy during operation of a rotary dehumidifier with infinite transfer coefficients is investigated and the various sources of irreversibility are identified and quantified. As they pass through the dehumidifier, both the process and regeneration air streams acquire nonuniform outlet states, and mixing both of these air streams to deliver homogeneous outlet streams is irreversible. Transfer of mass and energy between the regeneration air stream and the desiccant matrix occurs across finite differences in vapor pressure and temperature and these transfer processes generate entropy. The second law efficiency of the dehumidifier is given as a function of operating conditions and the effect of finite transfer coefficients for an actual dehumidifier is discussed. It is shown that operating the rotary dehumidifier at conditions that minimize regeneration energy also yields a local maximum for the second law efficiency.

Copyright © 1988 by ASME
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