Heat Exchanger, Heat Pump, Outdoor Unit, Heat Transfer, Pressure Drop, Refrigerant distribution
We developed a new type of a heat pump outdoor unit using an aluminum flat tube heat exchanger in order to improve the energy saving capability of an air conditioner. There are several difficulties in keeping a desired drainage performance, frost formation performance, as well as even distribution of refrigerant, when applying the flat tube heat exchanger to heat pump outdoor units. In order to achieve the same drainage performance and the frost formation performance as those of conventional heat exchangers, we have adopted new plate fins with ellipse cutouts. Flat tubes were inserted in the ellipse cutouts, and the slit position on a plate fin was properly adjusted. In order to achieve the even distribution of refrigerant, an aluminum distributor and 3-way pipes were installed to the evaporator. In this report, first we describe features of the flat tube heat exchanger. Next, we present and explain experimental results of the air-side heat transfer coefficient and the air-side pressure drop on the condition of dry, wet, and frost state respectively. Moreover, we present experimental results of the total heat transfer performance, including the refrigerant performance, under the conditions of the condensation and the evaporation. Finally, we explain the heat transfer performance and the effect of the flat tube heat exchanger to a conventional one in the case that the developed heat exchanger was mounted in heat pump outdoor unit.