CONJUGATE COMPUTATION OF TRANSIENT FLOW AND HEAT AND MASS TRANSFER BETWEEN HUMID AIR AND DESICCANT PLATES AND CHANNELS

Abstract

This is a numerical study of dehumidification of humid air in laminar and turbulent flows (333 ≤ Re ≤ 6,000) over desiccant (silica gel)-lined finite flat plates and in channels. The problem is treated as conjugate flow, heat, and mass transfer, and solved by using a finite control-volume method. The effects of the plate thickness (3 ≤ b ≤ 7 mm), the Reynolds number (333 ≤ Re ≤ 3,333), and the turbulence intensity (1 ≤ TI ≤ 10%) on the dehumidification process are investigated. The results show that increasing the desiccant plate thickness decreases the heat and mass transfer coefficients by 25% and 22% at t = 10 s and x = 0.11 m, respectively, in comparison to a thin plate. Mass transport rates increase with Re, e.g., at t = 20 s, W_ave increases by 50% as Re is increased 10-fold from 333 to 3,333. Turbulent flow in channel desiccants increases the rate of dehumidification, e.g., an increase in Re from 600 (laminar) to 6,000 (turbulent) results in an increase in W_ave by 22% at t = 20 s. Also, increasing the turbulence intensity from 1% to 10% increase W_ave by 7%.

The first author is grateful for the financial support of his graduate studies by his employer, The General Organization of Technical Education and Vocational Training of Saudi Arabia, the Saudi Arabian Cultural Mission in Washington, DC.