Start-up characteristics of a R290 rotary compressor for an air source heat pump under low ambient temperature condition

Abstract

Due to its excellent thermodynamic properties, low GWP refrigerant R290 is found to be promising alternative refrigerant. However, due to its special physical properties, high oil discharge rate and throttle valve blockage may occur for the R290 heat pump system under low temperature start-up conditions. In this paper, the transient characteristics, including the temperature, heat exchange rate, phase change rate, oil discharge rate and the liquid level of the oil sump, of a R290 rotary compressor used in the heat pump system under low temperature conditions are theoretically and experimentally studied. A transient heat and mass transfer model in the compressor is proposed, which considers the phase change of refrigerant in the shell. The experiment was carried out on the start-up characteristics of the compressor and the mathematical model was verified. The results show that high rotation speed and low temperature are the main reasons for the condensation of R290 in the shell. The excessive liquid refrigerant in the shell leads to a high oil discharge rate of up to 22 %. This paper will provide guidance for the use of R290 refrigerant under low temperature conditions.