Experimental study on an inverter heat pump air conditioner with a vapor-bypassed evaporator

This paper presents an experimental study on the performance of an inverter heat pump air conditioner with a vapor-bypassed evaporator. The vapor-bypassed evaporator, in which a phase separator is set in the middle of the refrigerant circuit to bypass vapor refrigerant, can reduce the refrigerant pressure drop and enhance the system overall performance. The tested heat pump system can be operated at two modes, i.e., vapor-bypassed (VB) mode and conventional heat pump (CH) mode. The testing results indicate that as the heating capacity ranges 1900–4900 W, the COP of VB mode is improved by 4.1%–11.6% over CH mode under the H1 condition (indoor: 20.0/15.0 °C; outdoor: 7.0/6.0 °C). When operated under the H2 condition (indoor: 20.0/15.0 °C; outdoor: 2.0/1.0 °C; frosting condition), the system at VB mode yields 11.2% higher average heating capacity and 4.4% higher COP over CH mode at a fixed compressor speed of 95 Hz. Generally, using the vapor-bypassed evaporator has a great potential for improving the performance of a heat pump air conditioner especially under high heating capacity conditions.