1, Poor heat insulation and sealing of cold room causes losing large cooling;
Poor insulation performance is due to insufficient thickness and lower quality of insulation on refrigeration pipes, cold room insulation walls, etc., It is mainly caused by improper selection of insulation panels thickness during design or poor quality of insulation material during construction. In addition, during the construction, the moisture resistance of heat insulation materials may be damaged, causing the insulation panels to be damped, deformed, or even eroded. Its heat insulation capacity is reduced, and the loss cooling of cold storage room is increased accordingly, then cause the cold room temperature slows down.
Another important reason for the large cooling loss is the poor sealing performance of the cold room, and more hot air penetrates into the cold room from the leak. Generally, if condensation occurs on the sealing strip of the cold room doors or the seal of the cold storage room insulation wall, it indicates that the seal is not tight. In addition, frequent opening and closing of the cold room doors or a large number of people entering the cold room together will also increase the cooling loss. Try to avoid opening the cold room doors to prevent a lot of hot air entering the cold room. Of course, when the cold room frequently receives goods or the quantity is too large, the thermal load increases sharply, and it usually takes a long time to cool down to the required temperature.
2, The thick frost and more dust on the surface of the refrigeration evaporator will cause the heat ex-changer reducing;
Another important reason for the cold room temperature dropping slowly is the low heat ex-changer of the evaporator, which is mainly caused by the thick frost or much dust on the evaporator surface. Since the surface temperature of the evaporator in the cold room is mostly lower than 0 ° C, and the humidity of the warehouse is relatively high, the moisture in the air is likely to frost and even freeze on the surface of the evaporator, which affects the evaporator heat ex-changer. In order to prevent the thick frost on the surface of the evaporator, it needs to be defrosted regularly.
3, More air or refrigeration oil in the evaporator will cause the heat ex-changer reducing.
Once more refrigerant oil is attached to the inner surface of the evaporator heat ex-changer tubes, its heat ex-changer coefficient will decrease. Similarly, if there is more air in the heat ex-changer tubes, the heat ex-changer area of the evaporator will decrease and its heat ex-changer will be reduced. So the temperature in cold room will dropping slowly. Therefore, in the daily operation and maintenance, should pay more attention to timely removing the oil on the inner surface of the heat ex-changer tubes and exhausting the air in the evaporator to improve the heat transfer efficiency of the evaporator.
4, Improperly adjusted or blocked of the throttle valve will cause the refrigerant flow too large or too small.
Improper adjustment or blockage of the throttle valve will directly affect the refrigerant flow into the evaporator. When the opening degree of the throttle valve is too large, the flow rate of the refrigerant is too large, and the evaporation pressure and the evaporation temperature are also increased, and the temperature of the cold room will drop slowly. At the same time, when the opening degree of the throttle valve is too small or blocked, the refrigerant flow rate is also reduced, the cooling capacity of the system is also reduced, and cold room temperature will also drop slowly. Generally, you can judge whether the refrigerant flow rate of the throttle valve is appropriate by observing the evaporation pressure, evaporation temperature, and frosting of the suction pipe. Throttle valve clogging is an important factor that affects the flow of refrigerant.
5, Low efficiency of the refrigeration compressor will cause lower cooling capacity;
Due to the long-term operation of the refrigeration compressor, severe wear of the cylinder liner and piston ring and other components, the clearance will increase, the sealing performance will decrease accordingly, the air transmission coefficient of the refrigeration compressor will also decrease, and the cooling capacity will decrease. When the cooling capacity is less than the heat load of the cold room, the temperature of the cold room will drop slowly. The refrigeration capacity of the compressor can be roughly judged by observing the suction and discharge pressure of the compressor.
6, Lack of refrigerant in the refrigeration system;
There are two main reasons for the lack of refrigerant. First, the refrigerant charge less. Another reason is that there is a lot of refrigerant leakage in the system. In this case, you should first find the leak point, focus on the inspection of the pipeline and valve connections, repair the leaked part, and then fill the refrigerant with sufficient amount.