Experimental Study on the Frosting and Heat Transfer Performance of Three Rows of Variable Pitch Finned Coils

Abstract

The frost mass in different rows of the outdoor heat exchanger of an air source heat pump is uneven when the ambient temperature is below 0 °C, which leads to a shorter defrosting interval and reduces the heating capacity of the heat pump. In order to improve the problem of uneven frost along the airflow direction in the evaporator, an experimental study is conducted on the frosting and heat transfer performance of three rows of variable pitch (VP) finned coils in different fin pitch combinations under low ambient temperature conditions. The results show that the frosting time of the sample with VP of 5*3*2 is extended by 46.67%, the frost mass per unit of bare tube surface area is reduced by 14.54%, and the average heat transfer power per unit mass and volume is increased by 37.64% and 33.56%, respectively.