Experimental Research On R32 Air Source Heat Pump Unit With Vapor Injection & Liquid Injection Cooling

It’s very urgent to find out the alternative refrigerant with the gradual elimination of R22. In recent years, R32 has been widely concerned, because of its good thermodynamic properties, friendly to the environment and low price. But it has a big problem that the compressor discharge temperature is too high for the application. Therefore, this paper improved the conventional R32 air source heat pump, using vapor or liquid injection to reduce the discharge temperature, then designed a R32 air source heat pump unit with vapor injection and liquid injection, and successfully developed a prototype, carried out a detailed and comprehensive experimental study in lots of conditions for the unit. The experimental results showed that:When the unit is running in cooling, with the increase in the room temperature, the cooling capacity and EER rise, but the power changes little. At the same time, the compressor suction pressure and suction temperature rise, and the discharge pressure and discharge temperature almost unchanged; with the increase of the outdoor temperature, cooling capacity and EER decrease gradually, but the power rises. At the same time, the discharge pressure and discharge temperature rise, and the suction pressure and suction temperature remain unchanged. When the outdoor temperature is higher, the compressor discharge pressure and discharge temperature will be high, and at the time the liquid injection can effectively control and reduces the discharge temperature of the compressor. Liquid injection can reduce the discharge temperature about 20 ℃ within 2 min, and controls it below the setpoint, then ensure the safe, stable and reliable operation of the unit.When the unit is running in heating, with the increase in the room temperature, the heating capacity changes little, but the power rises, the EER decreases. At the same time, the compressor suction pressure changes little, but the suction temperature rises gradually, and the discharge pressure and discharge temperature rise too. With the increase of the outdoor temperature, the heating capacity and EER rise, the power rises little. At the same time, the suction pressure, suction temperature and discharge pressure rise, but the discharge temperature rises first and then decreases. When the outdoor temperature is low, the evaporator is easy to frost, and resulting in poor performance. And at the time the vapor injection can improve the performance of the system. And vapor injection can reduce the discharge temperature about 13℃ within 1.5 min, ensure the safe and reliable operation of the unit.Results of this research can provide reliable experimental data and reference for the research of R32 replace R22 and the development work of R32 air conditioners in the air conditioning industry, and it also provides technical guidance practicable for the performance improvement of R32 air conditioner.