The present study investigated the performance of the evaporator for the residential heat pump under frosting condition. The size of all evaporators was 400 × 250 × 12.7 mm (W × H × D). Key experimental parameters were fin type (plate and slit fin), fin pitch (1.3, 1.4 and 1.5 mm), the face velocity of air (0.5, 1.0, 1.5 and 2.0m/s), and the number of row (1 and 2) of the heat exchanger. The ethylene glycol-water mixture was used as a refrigerant. The test was done in a phychrometric calorimeter chamber.The air side pressure drop and heat transfer rate were measured as frost grew. The pressure drop of the evaporator under frosting with the slit fin was higher than that with the plate fin. It increased as the number of rows increased, the fin pitch decreased, and the air velocity decreased for the slit fin. The heat transfer rate of the evaporator under frosting with the slit fin was higher than that with the plate fin. It increased as the air velocity increased even though it was not much affected by the other parameters for the slit fin. The EF decreased as frost grew to be lower than one. The HGR decreased to be lower than one as frost grew. It decreased as the number of row increased.
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