Simulation of Hybrid Packed Desiccant Beds for Dehumidification and Drying

The conventional vapor compression refrigeration cycle based air dryers are used widely for the applications of required pressure dew point temperature up to +2~3°C. However, for the industrial and pneumatic applications, the required pressure dew points are as low as -10°C, -30°C or -50°C and also up to -75°C, which is achieved by the adsorption based packed bed desiccant dryers. This paper presents the results of numerical simulation of hybrid packed desiccant beds under coupled heat and mass transfer during the adsorption and desorption phases under wide operating conditions. The bed containing a homogenous mixture of multiple desiccant types along the vertical axial direction has been investigated. A CFD code has been developed using the finite volume method which models the heat conduction and mass diffusion for these hybrid beds. The numerical results of the present model are validated with experimental data from literature and show good agreement for exit air temperature and moisture content. The improvement in moisture removal capacity, relative moisture removal efficiency, and dew point temperature or pressure dew point for these hybrid desiccant beds are investigated.