The influence of evaporating temperature on refrigeration system

The influence of evaporating temperature on refrigeration system

Household air conditioners generally cannot adjust the evaporation temperature! The cold storage and other devices can be adjusted in small amounts, and the increase in the evaporation temperature is mainly in the design and manufacturing stage!

The temperature when the refrigerant evaporates in the evaporator is also the saturation temperature of the refrigerant corresponding to the evaporating pressure. It has a greater impact on the refrigeration efficiency. Every time it decreases by 1 degree, the same cooling capacity needs to increase the power by 4%. If conditions permit, it is beneficial to increase the evaporating temperature appropriately to improve the cooling efficiency of the air conditioner. The evaporating temperature of household air conditioners is generally 5-10℃ lower than the air outlet temperature of the air conditioner. During normal operation, the evaporating temperature is 5-12℃, and the outlet temperature is 10-20℃.

　　How to adjust the evaporation temperature

　　 Evaporation temperature adjustment, in actual operation, is to control the evaporation pressure, that is, to adjust the pressure value of the low pressure gauge. During operation, the low pressure pressure is adjusted by adjusting the opening of the thermal expansion valve (or throttle valve). The expansion valve opening degree is large, the evaporation temperature rises, the low pressure pressure also rises, and the cooling capacity will increase; if the expansion valve opening degree is small, the evaporation temperature decreases, and the low pressure pressure also decreases, the cooling capacity will decrease.

Factors affecting the change of evaporating temperature During the actual operation of the refrigeration device, the change of the evaporating temperature is very complicated. It is not only directly controlled by the expansion valve (throttle valve), but also with the heat load of the cooled object and the heat transfer of the evaporator. The area is related to the capacity of the compressor. When one of these three conditions changes, the evaporating pressure and temperature of the refrigeration system will inevitably change accordingly. Therefore, to ensure that the evaporating temperature operates stably within the specified range, the operator needs to understand the evaporating temperature change in time, according to the evaporating temperature The changing law of evaporating temperature should be adjusted timely and correctly.

　　 The effect of changes in thermal load on the evaporation temperature. The so-called thermal load refers to the amount of heat released by the object to be cooled. The change in heat load is the change in the amount of heat released by the cooled object. During the operation of the refrigeration device, changes in the thermal load often occur. When the heat load increases and other conditions remain the same, the evaporation temperature will increase, the low pressure pressure will also increase, and the superheat of the suction will increase. In this case, the expansion valve can only be opened to increase the circulation of refrigerant, and the expansion valve cannot be closed to reduce the low pressure due to the increase in low pressure. Doing so will make the suction superheat greater, the exhaust temperature will rise, and the operating conditions will deteriorate. When adjusting the expansion valve, the adjustment amount should not be too large each time. After adjustment, a certain period of operation must pass to reflect whether the heat load and the cooling capacity are balanced.

The influence of the change of refrigeration compressor energy on the evaporation temperature. When the energy of the refrigeration compressor is increased, the suction volume of the compressor will increase accordingly. Under other conditions unchanged, the high pressure will increase, the low pressure will decrease, and the evaporation will occur. The temperature will drop accordingly. In order to continue to maintain the evaporation temperature required by the production process, the expansion valve must be opened to increase the low pressure pressure to the specified range. After the refrigeration compressor runs for a period of time with increased energy, as the temperature of the refrigerated material drops, the evaporation temperature and low pressure pressure will gradually decrease (the expansion valve does not make any adjustments). This is because the temperature of the refrigerated material drops and the heat load decreases. . In this case, it should not be mistaken that the pressure drop is due to insufficient liquid supply to open the large expansion valve to increase the liquid supply. Instead, the expansion valve should be closed to reduce the energy operation of the refrigeration compressor, otherwise, excessive energy will occur. If the liquid supply is too high, the refrigeration unit may run with liquid or run into oil accidents.