HI-85-10-2 -- The Laboratory Evaluation of the Heating Mode Part-Load Operation of an Air-to-Air Heat Pump PDF

The laboratory evaluation of the part-load Coefficient of Performance (COP) and capacity of an air-to-air heat pump were conducted in a parametric study of heat pump on-time, off-time, and outdoor ambient temperature. A split-system heat pump was instrumented and tested in the heating mode to gain better understanding of the physical processes of the cycling phenomena that degrade heat pump COP and capacity.

Improvement in cycling COP and capacity was observed by controlling off-cycle refrigerant migration. Best cycling COP and capacity performance occurred for cycling tests conducted with refrigerant isolated in the indoor heat exchanger during the off-cycle, coupled with 2 min of extended indoor blower operating during the off-cycle.

The analysis of loss per on and off cycle revealed refrigerant dynamics to cause appreciable time delays in establishing steadystate heat pump COP.

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