The capability of predicting the effects of refrigerant charge on the steady-state performance of a heat pump is addressed. Rather extensive test data for one particular residential air-to-air heat pump are compared with the predictions of HPSIM, a computer model with the capability of tracking refrigerant mass distribution within the various components. The need to properly account for parasitic volumes and all internal volumes of the heat pump is underscored.

KEYWORDS: refrigerants, heat pumps, heat flow, calculating, coefficient of performance, steady state, domestic, air air heat pumps, comparing, computer programs, fluid flow