Simulation of adsorption process in a rotary solid desiccant wheel

Solid desiccant air dehumidifier systems are widely used to supply dry air for many industrial processes. As humid atmospheric air flows through the system, the water vapor in the air is adsorbed by the desiccant material, resulting in dry air leaving the system. A numerical solution has become the preferred choice for determining the performance criteria of desiccant materials. The aim of this study is to determine the moisture removal capacity (MRC), dehumidification effectiveness (ε_DW), and thermal effectiveness (ε_th) of a solid desiccant wheel material using a numerical method. A representative three-dimensional model of an air channel enclosed with desiccant material was developed and meshed using triangular elements. Flow simulations were carried out under a transient condition. The model was validated by comparing the simulation results for moisture content and air temperature at the outlet of the air channel with similar results using experimental data obtained from the literature. The relative errors for the desorption process were found to be 0.14% for air temperature and 3.7% for air humidity. For the adsorption process, they were around 3.2 and 0.01%, respectively. These figures indicate that the numerical model has an excellent ability to estimate the desiccant material performance. It was also found that at any given regeneration temperature, silica gel-CaCl₂ has the highest MRC, dehumidification effectiveness, and thermal effectiveness compared to silica gel B and Zeolite 13X.