MODELING AND PARAMETRIC ANALYSIS OF HEAT AND MASS-TRANSFER PERFORMANCE OF A HYBRID LIQUID DESICCANT ABSORBER

A mathematical model was developed in this work to predict the perform ance of a liquid desiccant absorber integrating indirect evaporative c ooling to achieve an almost isothermal operation. A control volume bas ed numerical method was used to solve the governing equations. A sensi tivity analysis considering a lithium chloride solution, process air a t 32 degrees C and 0.022 kg/kg humidity and return air at 23 degrees C and 0.009 kg/kg humidity was performed. Negligible differences in the rmal performance were found between parallel and counter fluid flow ar rangements. The study predicted a strong dependence of thermal perform ance on the physical size of the absorber, the solution concentration and cooling and process air mass flow rates. A partial load performanc e analysis was used to determine the operation of the proposed absorbe r when it was subjected to a variable cooling and dehumidification loa d. Enthalpy and humidity effectivenesses were defined to report the pa rtial-load performance of the absorber. Both the effectivenesses were found to vary significantly only with the number of mass transfer unit s between the process air and the desiccant solution. Finally, a simpl e model was also developed to predict the performance of the proposed absorber for annual energy consumption estimates. The simple model sho wed a good agreement with the detailed model. (C) 1998 Elsevier Scienc e Ltd. All rights reserved.