Refrigerant release, seasonal energy efficiency, room air conditioner, over compression
The room air conditioner is widely used in residential and office buildings for both cooling and heating. However, the operation condition of the room air conditioner changes largely due to the variations of the cooling/heating load of the room, the indoor temperature and the outdoor one, which always decreases the efficiency of the compressor and eventually the seasonal energy efficiency of the air conditioner. The refrigerant release technology relieves even eliminates the over-compression loss of scroll compressor by bypassing the refrigerant in the compression chamber to the suction pipe under small system pressure ratio conditions, By using it, the efficiency of the air conditioner can be increased. The effect of refrigerant-releasing on the annual energy performance of the room air conditioner is analyzed and the applicability is evaluated in this paper. The typical residential and office building models are built in a building load simulation software, DeST. The annual cooling and heating loads of these buildings located in different climate zones are calculated. The numerical models of the fixed speed and inverter room air conditioners with and without refrigerant-releasing function are built and verified. For the air conditioner with refrigerant-releasing, a control strategy to activate the refrigerant release is determined to keep the efficiency as well as satisfy the indoor load. Based on the calculated cooling/heating load and the models of the air conditioners, the energy consumptions of all four kinds of air conditioner during each hour can be calculated. Finally, the performance of variable and fixed speed air conditioner with and without refrigerant release in the cooling period and heating period is obtained and the contribution of refrigerant-releasing is evaluated. The results show that the variable speed air conditioner with refrigerant-releasing saves 24.2~25.5% and 18.9~25.3% energy compared to the one without refrigerant release for the office and residential buildings, respectively. For the fixed speed air conditioner, the refrigerant-releasing technology decreases 20.2~23.0% and 17.1~23.6% energy consumption for residential and office building, respectively. Variable speed air conditioner with refrigerant release saves more energy than fixed speed one. The refrigerant-releasing technology has good applicability for the room air conditioner and should be considered as an effective method to enhance the seasonal performance for it.