Influence of input variables on the irreversibilities of a CO2 heat pump.

The effects of several input parameters (refrigerant amount, inlet water temperatures, throttle valve opening and water flow rates) on heat pump losses were investigated in this study. For regression analysis, design-expert® software was used in experimental designs. Heat pump losses in terms of Lorentz efficiencies, second law efficiency and component irreversibilities were used as response to the experimental design. Lorentz efficiency responses were related to the input variables using polynomial equations model. Lorentz efficiency had an average of 18.9% while the second law efficiency had an average of 13.6%. With individual components, it was observed that the throttle valve had the highest irreversibility with a mean of 75.3% of all losses. The other three components had approximately similar irreversibilities with the compressor average being 10.3%, the evaporator average being 6.3% and the gas cooler average being 8.1%.