A novel desiccant wheel for desiccant-evaporative cooling

Desiccant/evaporative cooling systems offer an environmentally friendly alternative to conventional vapor compression chillers. The desiccant wheel is the heart of this heat-driven cooling system. A conventional desiccant wheel uses a solid desiccant such as silica gel for dehumidification in an adiabatic process. The main drawback of the system is the excessive heating of the supply air and desiccant material during dehumidification. This increases the partial pressure of water on the desiccant material and reduces the amount of moisture that can be removed from the air. To overcome this problem, a novel non-adiabatic desiccant wheel design has been investigated. This new wheel has an internal heat transfer structure with alternative channels for dehumidification and for indirect cooling of the dehumidification process. The supply air and regeneration air streams flow axially in opposite directions whereas the cooling air enters axially at the centre of the wheel and exits radially, achieving simultaneous cooling and dehumidification of the supply air. A numerical model for this design is developed and a representative channel of the wheel was constructed to validate the model. Predicted modeling results show good agreement with experimental results.