Performance investigation and exergy analysis of two-stage desiccant wheel systems

Two-stage desiccant wheel systems are an effective way to improve the dehumidification performance. In the present study, the performances of a one-stage system and a two-stage system with identical heat transfer areas are compared, with particular emphasis on the required heating source temperature. The exergy and unmatched coefficient (ξ) are applied to analyze the destruction of the heat and mass transfer processes. Compared to the one-stage system, the regeneration temperature (Tr) of the two-stage system is lower. The required hot water temperature (Th) depends on the supplied water flow rate and Ap/Ar of the desiccant wheel. When Ap/Ar = 1, Th of the two-stage system is lower only when the supplied water flow rate is relatively high. And due to different heat transfer area distribution demand, the exergy destruction of two-stage system is higher than one-stage system. When Ap/Ar = 3, the two-stage system has greater advantages. ξ of the desiccant wheel decreases from 2.9 to 2.2 when the number of stages increases from 1 to 2, leading to lower exergy destruction of the desiccant wheels and higher exergy efficiency.