Theoretical Study on the Dehumidification Behaviors of Dual-Desiccants Coated Cross-Flow Heat Exchanger with Staged Adsorption-Desorption Process

Abstract

The conventional desiccant coated heat exchangers (DCHEs) suffer from the inefficient utilization of regenerative energy and the inadequate dehumidification capacity of a single desiccant. In this study, a concept of dual-desiccants cross-flow DCHE with staged adsorption-desorption process was proposed to strengthen dehumidification capacity and energy efficiency simultaneously. In order to guide the construction of proposed DCHE, the steady-state dehumidification capacity of single-desiccant (specifically, silica gel, FAM Z01, FAM Z05 and EMM-8) cross-flow DCHE was investigated by thermodynamic analysis. The dual-desiccants cross-flow DCHE was thus constructed, and its numerical model was established to investigate the dehumidification characteristics. Theoretical analysis revealed that single-desiccant cross-flow DCHEs exhibit different optimal relative humidity ranges for dehumidification. The minimum regeneration temperature driving dehumidification cycle increases as the lower supply air humidity is required. Numerical results demonstrated that the staged adsorption process ensures a large dehumidification capacity across a wide humidity range, including low humidity conditions., Meanwhile, the staged desorption process facilitates the cascade utilization of energy and the direct recovery of regenerative waste heat. For dual-desiccants cross-flow DCHE utilizing silica gel and EMM-8, the moisture removal capacity  MRCⅠ,Ⅱ and dehumidification coefficient of performance  DCOPⅠ,Ⅱ can reach 0.012 kg/kg and 0.41, respectively.

Keywords: dehumidification, Desiccant coated heat exchanger, Heat and mass transfer, Staged adsorption-desorption, Air-conditioning.