Air-side performance of a parallel-flow parallel-fin (PF²) heat exchanger in sequential frosting

The thermal-hydraulic performance in periodic frosting conditions is experimentally studied for the parallel-flow parallel-fin heat exchanger, henceforth referred to as a PF² heat exchanger, a new style of heat exchanger that uses louvered bent fins on flat tubes to enhance water drainage when the flat tubes are horizontal. Typically, it takes a few frosting/defrosting cycles to come to repeatable conditions. The criterion for the initiation of defrost and a sufficiently long defrost period are determined for the test PF² heat exchanger and test condition. The effects of blower operation on the pressure drop, frost accumulation, water retention, and capacity in time are compared under the conditions of 15 sequential frosting cycles. Pressure drop across the heat exchanger and overall heat transfer coefficient are quantified under frost conditions as functions of the air humidity and air face velocity. The performances of two types of flat-tube heat exchangers, PF² heat exchanger and conventional parallel-flow serpentine-fin (PFSF) heat exchanger, are compared and the results obtained are presented.