Experimental investigation on performance of desiccant coated microchannel heat exchangers under condensation conditions

Desiccant coated heat exchanger (DCHE), which can be adopted to construct a solar cooling system or desiccant heat pump system, can realize both sensible and latent load removal to provide comfortable supply air. Although it is difficult to avoid condensation in a practical application, the condensation condition of DCHEs is rarely studied. In this paper, a series of condensation experiments are carried out on the desiccant coated microchannel heat exchanger (DCMHE) under conditions with high temperature and high humidity ratio. First, by changing the temperature of cooling water, the unique dynamic characteristics of condensation different from non-condensing conditions are discussed, and the influence of desiccant coating is analyzed. Then, the parametric effects of inlet air velocity and fluid temperature on the mass transfer, heat transfer, and pressure drop performance of DCMHE are analyzed. The results show that the changing trend of the dynamic curve can be used as a sign to judge whether condensation exists or not. And the performance of DCMHE is still stable under continuous condensation conditions, which is not affected by the condensation water. In the dehumidification stage, the condensation dehumidification is dominant. In the aspect of parametric analysis, with the velocity of inlet air increasing from 0.5 m/s to 2.4 m/s, the average moisture removal in a cycle period Delta d(DE,ave) of DCMHE reduces by 40%, while the dehumidification results per unit time air Delta(MDE) of DCMHE increases by 192%. The optimal inlet air velocity range is 1.5 m/s-2.4 m/s, considering the dehumidification and heat recovery efficiency synthetically. Due to the thermal resistance of desiccant coating, total cooling load, the effectiveness of heat exchanger, and NTU of DCMHE is about 31%, 27%, and 26% lower than that of MHE. And the effect of desiccant coating on heat transfer performance is comparatively small at high wind speed. The experimental results are expected to provide a reference for the system design of desiccant coated heat exchangers. (C) 2020 Elsevier B.V. All rights reserved.