Comparison of the heating performance of an inverter-driven heat pump system using R410A vapor-injection into accumulator and compressor

In cold regions, a refrigerant injection technique has been used for enhancing heating capacity and avoiding the excessively high discharge temperature which is detrimental to reliability of a heat pump system. The heat pump system in this study having an additional refrigerant injection line into the accumulator was tested to compare with the heating performances of classic vapor-injection cycle. The heat pump system was designed to inject vapor refrigerant into the compressor and accumulator, selectively. Although the refrigerant injection into the compressor (classic vapor-injection cycle) was more effective to enhance heating capacity, the refrigerant injection into the accumulator could decrease discharge temperature and increase both heating capacity and COP slightly at the condition of high compressor frequency. In terms of mass balance, the injection stream into the accumulator substituted the evaporatorʹs suction stream flowing to the compressor, so the mass flow rate of condenser was not increased as much as the amount of injected refrigerant.