Methods to shorten the defrost time on a heat pump air conditioner were studied. The experiment was carried out using a one horsepower heat pump, and the energy balance during defrosting was analyzed. We found that the following methods are effective to shorten the defrosting time: (1) increase in power input to the compressor during defrosting, (2) utilization of the compressor for energy storage, and (3) reduction of the water left on the outdoor heat exchanger.

A heat pump with the new defrosting system was constructed on an experimental basis. Its defrost time was 1 minute and 55 seconds under the defrost condition of Japanese Industrial Standard. The defrost time of a conventional heat pump is about 4 or 5 minutes.

Units: SI