Theoretical analysis of transient heat and mass transfer during regeneration in multilayer fixed-bed binder-free desiccant dehumidifier: Model validation and parametric study

Abstract

A numerical model is presented for the prediction of transient heat and mass transfer characteristics during the regeneration process in a multilayer fixed-bed, binder-free desiccant dehumidifier. Experiments were carried out in a previous study that provided the benchmark data for validation of the current model under different temperatures and velocities of the regeneration air. A spherical microsphere silica gel having a pore diameter of 2.7 nm was used as the adsorbent during the experiments. In the first part of this study, model validation was performed for different temperatures (314.4–325.0 K) and velocities (0.6–0.9 m s−1) of regeneration air. The results showed that at a fixed regeneration temperature (325.0 K), the model predicted mass of the desorbed water as well as the desiccant bed and air temperatures were in a good agreement with the previously reported experimental results. With a decrease in the temperature and velocity of the regeneration air, the model slightly underpredicted the experimentally obtained mass of the desorbed water; however, the deviation remained within a reasonable limit. Upon validation, a parametric study was carried out to show how the heat and mass transfer characteristics of the microsphere silica gel during desorption depended on the intrinsic material properties (e.g., desorption rate constant, diffusivity, and desorption isotherm) and mechanical design parameters of the device (e.g., convective heat transfer coefficient, porosity, and thickness of the desiccant bed).