jaue2023+026: Performance Enhancement of Heat Pump Air-conditioner with Superhydrophobic Evaporator

Abstract

Residential buildings frequently employ heat pump air-conditioners for winter heating. Its advantages over electric and coal-fired heating include great energy effectiveness and low emissions. However, the outside evaporator's frosting has a significant negative impact on the performance of heat pump air conditioning systems in low-temperature and high-humidity environments. In this paper, a finned-tube heat exchanger with superhydrophobic characteristics was prepared by the wet chemical etching method and applied to a heat pump air- conditioner. Compared with a conventional hydrophilic evaporator heat pump air-conditioning unit, it is found that surface hydrophobicity greatly increased the performance of heat pump systems under severe frosting conditions. During a single frosting cycle at stable heating operation, the maximum heat transfer rate of the superhydrophobic evaporator unit was 1.52 times that of the hydrophilic evaporator unit. Throughout the same operating condition for 35 minutes, the coefficient of performance (COP) of the superhydrophobic evaporator unit increased by 34.35%. The frost formation was roughly 52.06% decreased than that of hydrophilic surfaces due to the higher nucleation barrier for droplet condensation on superhydrophobic surface. Additionally, the time required for the superhydrophobic evaporator to reach the defrosting criteria was about 1.76 times that of the hydrophilic evaporator, resulting in fewer defrosting cycles within a given period of time and less overall energy usage. This study provides theoretical support for using superhydrophobic evaporators in heat pump air-conditioning systems.