Experimental investigation of silica gel and zeolite coated fin-tube heat exchangers under arid climatic conditions

Abstract

In this paper, a novel concept of an atmospheric water generator (AWG) based on desiccant coated heat exchangers (DCHEs) is presented. Two silica gel coated heat exchangers (SGCHEs) and two zeolite coated heat exchangers (ZCHEs) were prepared by coating a desiccant material on the surface of a conventional air-to-water fin-tube heat exchanger. An experimental set-up was built to investigate the performance characteristics of the prepared DCHEs in terms of the moisture removal capacity MRC, the effective duration of the process te, and the total moisture mass transferred during the dehumidification/regeneration cycle MT. The influence of the regeneration hot-water temperature Tw,in on the performance characteristics was also analysed. The experimental results showed that ZCHEs have better performance characteristics under arid climatic conditions than SGCHEs. It was found that the ZCHEs have approximately four times higher value of the moisture transferred during the dehumidification/generation cycle MT compared to the SGCHEs, 10.15 g for the ZCHEs and 2.60 g for the SGCHEs. Moreover, it can be concluded that the influence of the regeneration water temperature Tw,in for ZCHEs is not as critical as for SGCHEs. The experimental results indicated that when the regeneration hot-water temperature Tw,in decreases from 85 °C to 65 °C, the moisture transferred during the dehumidification/regeneration cycle MT for the ZCHEs decreases from 10.15 g to 7.11 g representing a 30% decrease in the system performance, while for the SGCHEs the same decrease in the regeneration hot-water temperature Tw,in causes a significant decrease in the moisture mass transferred during the cycle MT from 2.60 g to 0.85 g, representing a 67% decrease in the system performance.