22 May 2008
For heat pumps used in the cold region, it is very important to obtain appropriate heating capacity. Several studies using a variable speed compressor and an additional heater have been performed to enhance heating capacity at low ambient temperatures.
However, for outdoor temperature conditions below -15oC, it is still difficult to obtain enough
heating capacity above the rated heating capacity. In recent studies, a two-stage cycle using gas injection showed noticeable heating performance improvement at low temperature conditions. In this study, a two-stage heat pump system with a rated capacity of 3.5 kW was tested. The heating performance of the gas injection cycle was measured and analyzed by varying refrigerant charge amount and EEV opening at the standard heating condition. The heating performance of the gas injection cycle was compared with that of the non-injection cycle with a variation of refrigerant charge amount. The heating capacity and COP of the injection cycle were improved by 2-10% at the optimal charging condition.