Performance of a Single-Family Heat Pump at Different Working Conditions Using Small Quantity of Propane as Refrigerant

The performance of a domestic heat pump that uses a low quantity of propane as refrigerant has been experimentally investigated. The heat pump consists of two minichannel aluminium heat exchangers, a scroll compressor, and an electronic expansion valve. It was charged with the minimum amount of refrigerant propane required for the stable operation of the heat pump without permitting refrigerant vapor into the expansion valve at incoming heat source fluid temperature to the evaporator of +10°C. The inlet temperature of the heat source fluid passing through the evaporator was varied from +10°C to ?10°C while holding the condensing temperature constant at 35°C, 40°C, 50°C, and 60°C, respectively. The minimum refrigerant charges required at above-tested condensing temperatures were found to decrease when the condensing temperature increased and were recorded as 230 g, 224 g, 215 g, and 205 g, respectively. The results confirm that a heat pump with 5 kW capacity can be designed with less than 200 g charge of refrigerant propane in the system. Due to the high solubility of propane in compressor lubrication oil, the amount of refrigerant which may escape rapidly in case of accident or leakage is less than 150 g.