This study deals with heat transfer performance of plate condenser used for heat pump water heater in the condition where the refrigerant as superheated vapor is cooled to a subcooling liquid with large subcooling. Since condensate liquid might affect the refrigerant flow distribution, the both effects of the wave height of plates and gravity were examined. The gravity effect was evaluated by the experiments for horizontal and vertical orientation. HFC-134a was used as the working fluid. In the results, a deterioration in heat transfer rate due to the maldistribution of refrigerant flow was observed. The amount of decrease became larger with the larger wave height of the corrugation. The tendency was larger for the horizontal orientation. In the results for plate heat exchanger with single refrigerant path, it was found that the condensing flow behavior for the horizontal orientation was strongly affected by the wave pattern of the corrugation, because the condensed liquid tended to flow along the wave pattern of the lower plate due to gravity. The flow behaviors might cause maldistribution of the refrigerant flow.
