Theoretical performance analysis of silica gel and composite polymer desiccant coated heat exchangers based on a CFD approach

Abstract

A solid-desiccant coated heat exchanger (DCHE) technology can be applied to many heat transfer/exchange systems such as air-conditioners, heat pumps, adsorption chillers, and atmospheric water harvesters. Although the existing mathematical models can sufficiently predict the performance of the DCHEs, they are inapplicable for designing a new DCHE as the heat and mass transport coefficients used are derived from pre-determined empirical correlations. Therefore, in this paper, we developed a new mathematical platform to simulate the simultaneous heat and mass transfer phenomena that occur during DCHEs’ dehumidification/regeneration processes. Unlike existing models, the current model considers fluid flow, temperature, and moisture distributions across different domains. The effectiveness of the model was established by validating the performance of silica gel and composite polymer coated heat exchangers under different cooling and hot water temperatures. The maximum discrepancies between the model predictions and experimental data for outlet air humidity ratio and temperature were ±14% and ±12% respectively. A parametric study was then conducted to investigate the effects of key characteristic properties and fin-tube configurations on dynamic performance of DCHE. The respective dehumidification performance of two tube-fin and annular-fin DCHE configurations was observed to record 7% and 40% improvement in moisture removal capacity over the single-fin tube configuration.