Modeling comparison and theoretical study of mass transfer characteristics for desiccant coated air channel under isothermal dehumidification

Abstract

Coupled heat and mass transfer phenomena are encountered in desiccant coated dehumidifier, and their numerical modeling is becoming indispensable. In this study, three conjugate heat and mass transfer models were compared to clarify the effects of interparticle mass transfer and local kinetic non-equilibrium on modeling accuracy, and the models were validated by experiment results of silica gel and FAM Z01 coated dehumidifiers with single one air channel. Furthermore, a parametric study on the separate mass transfer characteristics of the dehumidifier under isothermal dehumidification was conducted based on one of the improved models. Results demonstrated that the effect of interparticle mass transfer should be involved, while the local kinetic non-equilibrium tends to be considered for desiccants with steep isotherm shape. Parametric study revealed that as air velocity increases, both air- and solid-side mass transfer change significantly, while desiccant layer thickness, interparticle porosity and isotherm shape mainly affect solid-side mass transfer. The average mass transfer Biot numbers Bim of desiccant layer with relative low thickness of 0.1 mm under various parameters are in the same order of magnitude as 1, indicating that the mass transfer resistance on solid side cannot be ignored generally.