Causes of frosting of cold storage compressors and solutions

Causes of frosting of cold storage compressors and solutions

Frosting at the return port of a cold storage compressor is a very common phenomenon in refrigeration systems. Under normal circumstances, system problems will not occur immediately, and subtle frosting is usually not handled, and will be improved or aggravated with changes in some cold storage conditions. Phenomenon, if the frosting phenomenon is more serious, then you need to find out the cause of the frosting first. The root cause of this situation is that the refrigerant flowing through the evaporator cannot fully absorb the heat needed to expand to the predetermined pressure and temperature.

　　 The temperature, pressure and volume of the return air are relatively low. There are two reasons for this problem.

　　 1. The evaporator cannot absorb heat normally, or the cold energy generated by the evaporator cannot be taken away. The appearance is that the return liquid temperature and pressure are normal or slightly lower, and the frosting starts from the compressor air return port to the evaporator. After a long period of time, it freezes from the compressor air return port to the evaporator and throttle valve to the evaporator section. , And finally there is low pressure.

　　2. Due to the small amount of refrigerant, the low evaporation pressure of the evaporator leads to a low evaporation temperature, which will gradually cause condensation in the evaporator to form an insulating layer and transfer the expansion point to the return air of the compressor to cause frosting of the return air of the compressor. If the amount of fluorine is normal or excessive, and if the high pressure pressure is low due to conditions such as excessive condensation heat exchange, the refrigerant at the front end of the throttle valve under the same volume will reflect the low pressure and high quality.

At the initial throttle valve opening, the quality of the refrigerant liquid flowing through the throttle valve will be more than normal, and the heat that needs to be absorbed from the evaporator will also be higher. If the corresponding heat cannot be fully absorbed from the evaporator, it will cause the compressor to return. The temperature of the trachea is low. At the same time, due to the low pressure at the front end of the throttle valve, the pressure at the back end of the throttle valve will also be low. If this Dalian cold storage installation system is an expansion valve, (detect the temperature and pressure of the return air pipe, the pipe temperature decreases, the opening decreases, and the pressure decreases Opening degree increased) Compared with the normal state, the opening degree will not be adjusted too much, then the low pressure condition will be maintained until the compressor return air is frosted. This appears to be a fluorine-deficient phenomenon (high pressure, low pressure and low pressure). Frost.

Finally, I need to remind everyone that if the evaporator outlet freezes and the return gas superheat is reduced, there may be too much refrigerant, because one of the inevitable conditions for the evaporator to freeze is that the evaporation temperature must be below 0 degrees! And more refrigerant will cause the evaporation temperature to rise.