Performance comparisons of desiccant wheels for air dehumidification and enthalpy recovery

Desiccant wheels have two major applications: air dehumidification and enthalpy recovery. Since the operating conditions are different, heat and mass transfer behaviors in the wheels are quite different. In this paper, the performances of desiccant wheels used in air dehumidification and enthalpy recovery are compared with each other. To accomplish this task, a two-dimensional, dual-diffusion transient heat and mass transfer model which takes into account the heat conduction, the surface and gaseous diffusion in both the axial and the thickness directions is presented. Effects of the rotary speed, the number of transfer units, and the specific area on the performance of the wheel are investigated and compared in the two situations. The cycles that the desiccant and air undergo in the wheel are plotted in psychrometric charts to demonstrate the different heat and moisture transfer mechanisms during the dehumidification and enthalpy recovery processes.