낮은 주변 온도에서 공기 소스 히트 펌프의 열용량 감쇠 이유
We all know that it is inevitable that the heat generated by the air source heat pump will attenuate with the decrease of the outdoor ambient temperature. We can summarize several reasons for the attenuation as follows:
01. The drop in evaporating temperature will cause the suction pressure of the compressor to drop and the suction specific volume to increase, which will lead to a drop in the heating capacity per unit volume of the refrigerant. This is the main reason for the heat attenuation of the air source heat pump.
02. The drop in suction pressure will cause the compressor pressure ratio to increase and the lubrication effect to deteriorate; the volumetric efficiency of the compressor will drop, resulting in a decrease in the actual air delivery volume and a decrease in the heating capacity.
03. The increase in suction specific volume and the decrease in the volumetric efficiency of the compressor will lead to a decrease in the mass flow of the refrigerant, resulting in a decrease in the heat transfer coefficient of the refrigerant side of the evaporator and the condenser, and the heat absorbed by the evaporator and the heat released by the condenser ( equivalent to the heating capacity) is reduced.
04. The drop in suction pressure will lead to an increase in the dryness at the inlet of the evaporator, an increase in the dynamic viscosity of the liquid refrigerant and a decrease in the density of the gaseous refrigerant on the low pressure side, and an increase in the flow pressure drop in the evaporator and the suction line. If the suction pressure of the compressor is maintained unchanged, the evaporation pressure and its corresponding saturation temperature will increase, the effective heat exchange temperature difference of the evaporator will decrease, and the heat absorption of the evaporator will decrease, which will also lead to a decrease in the heating capacity.
05. When the surface temperature of the evaporator fins is lower than the dew point temperature of the humid air and lower than 0 degree , the surface of the evaporator is frost; 서리층의 성장 속도는 습한 공기의 수분 함량이 증가하고 증발 온도가 감소함에 따라 증가합니다. 서리층의 두께가 증가하면 증발기의 열 저항과 바람 저항이 모두 증가하고 가열 용량이 급격히 감소합니다.
The air source heat pump must be defrosted periodically to operate normally, and the heating capacity during defrosting is zero or even negative, resulting in a decrease in the average heating capacity.
