Mathematical investigation of different parameters of the passive desiccant wheel

Abstract

A passive desiccant wheel is a rotating dehumidifier that can be regenerated using the room’s return (exhaust) air and does not require hot air for regeneration as in the active desiccant wheel. In this study, a one-dimensional mathematical model has been developed to analyze the parameters of the passive wheel and to compare this with the existing active desiccant wheel. To transform the active desiccant wheel into the passive desiccant wheel, silica gel B has been utilized as the desiccant material since it operates better in a saturated air environment. Additionally, a cooling coil has been placed in front of the wheel to provide saturated and cold air. Therefore, regeneration has been accomplished without the usage of external heat due to the relative humidity difference between the return air and the saturated air. From the mathematical results of this study, it has been found that the optimal ratio of process area to regeneration area and rotational speed of the passive desiccant wheel are 0.44 (i.e., regeneration area is equal to the 69% of total wheel cross section) and 7–15 rph, respectively. Similarly, the optimum regeneration and process velocity of the passive desiccant wheel was found to be 2 m/s. Further, the exit temperature of the process air of the passive wheel is less than the active wheel in all cases because the return air of the room has been used for reactivation, which is the fundamental advantage of a passive wheel over an active wheel and is suitable to supply in the room.