What is the reason that the temperature of the freezer cannot drop

What is the reason that the temperature of the freezer cannot drop

It is a common phenomenon that the temperature of the supermarket freezer does not drop and the temperature drops slowly. Now I will briefly analyze the reasons for the slow temperature drop, hoping to bring some help to friends in the industry.

　　 One. The cold storage loss is large due to poor heat insulation or sealing performance of the freezer

The reason why the thermal insulation performance is poor is that the insulation layer thickness of pipes, insulation boards, etc. is not enough, and the effect of heat insulation and heat preservation is not good. It is mainly caused by improper selection of the insulation layer thickness during design or poor quality of insulation materials during construction. . In addition, during the construction process, the thermal insulation and moisture-proof performance of the thermal insulation material may be destroyed, causing the thermal insulation layer to be damp, deformed, or even eroded. The thermal insulation capacity of the thermal insulation material decreases, the loss of cooling capacity increases, and the temperature drop significantly slows down. Another important reason for large cold loss is poor sealing performance, and more hot air invades from the leak. Generally, if condensation occurs on the sealing strip of the door or the insulation seal of the freezer, it means that the seal is not tight. In addition, frequent opening and closing of doors or more people entering the warehouse together will increase cooling capacity loss. Try to avoid opening the door to prevent a large amount of hot air from entering. Of course, when stocks are frequent or too large, the heat load increases sharply, and it generally takes a long time to cool down to the specified temperature.

　　 2. The evaporator surface has too thick frost or too much dust, and the heat transfer effect is reduced

　　 Another important reason for the slow temperature drop is the low heat transfer efficiency of the evaporator, which is mainly caused by the thick layer of frost or excessive dust on the surface of the evaporator. Since the surface temperature of the freezer evaporator is mostly below 0°C and the humidity is relatively high, the moisture in the air is very easy to frost or even freeze on the surface of the evaporator, which affects the heat transfer effect of the evaporator. In order to prevent the frost layer on the evaporator from being too thick, it needs to be defrosted regularly.

　　 Two simpler defrost methods are introduced below:

　　①Shut down and defrost. That is, stop the compressor, open the door, let the temperature rise, and restart the compressor after the frost layer automatically melts.

　　②Frost. After the goods in the freezer are moved out, directly wash the surface of the evaporator pipe with hot tap water to dissolve or fall off the frost layer. In addition to thick frosting in Guigang display cabinet factory, the heat transfer effect of the evaporator will be poor, and the surface of the evaporator will be too thick due to long-term uncleaned, and its heat transfer efficiency will also be significantly reduced.

　　3. There is more air or refrigerated oil in the evaporator of the supermarket freezer, and the heat transfer effect is reduced

Once more refrigerant oil is attached to the inner surface of the heat transfer tube of the evaporator, its heat transfer coefficient will be reduced. Similarly, if there is more air in the heat transfer tube, the heat transfer area of ​​the evaporator will decrease and the heat transfer will be reduced. The efficiency will also drop significantly, and the temperature drop will slow down. Therefore, in daily operation and maintenance, attention should be paid to timely removing the oil on the inner surface of the evaporator heat transfer tube and exhausting the air in the evaporator to improve the heat transfer efficiency of the evaporator.

　　 Fourth, the throttle valve is improperly adjusted or blocked, and the refrigerant flow is too large or too small

　　 Improper adjustment or blockage of the throttle valve will directly affect the refrigerant flow into the evaporator. When the throttle valve is opened too large, the refrigerant flow is too large, the evaporating pressure and evaporating temperature will also increase, and the temperature drop rate will slow down; at the same time, when the throttle valve is opened too small or blocked, the refrigerant flow Also decrease, the cooling capacity of the system will also decrease, and the temperature drop rate of the warehouse will also slow down.

　　 Generally, it can be judged whether the refrigerant flow rate of the throttle valve is appropriate by observing the evaporating pressure, evaporating temperature and frosting of the suction pipe. Throttle valve blockage is an important factor affecting refrigerant flow. The main cause of throttle valve blockage is ice blockage and dirty blockage. The ice blockage is due to the poor drying effect of the dryer. The refrigerant in Guigang Showcase Factory contains moisture. When it flows through the throttle valve, the temperature drops below 0℃. The moisture in the refrigerant freezes and blocks the throttle valve hole. ; Dirty blockage is caused by the accumulation of more dirt on the inlet filter of the throttle valve, and the flow of refrigerant is not smooth, resulting in blockage.