1. The refrigerator car has poor heat insulation or sealing performance;

The poor thermal insulation performance is due to the lack of mutual adhesion between the inner and outer skin of the car body, or the insufficient thickness of the thermal insulation layer, resulting in poor thermal insulation effect. The main reason is the improper selection of insulation layer thickness in design or the poor quality of insulation materials in construction. In addition, the insulation and moisture-proof performance of insulation materials may be damaged in the process of construction and use, so that the insulation layer will be affected by moisture, deformation and even erosion. The results show that the thermal insulation capacity of the thermal insulation material decreases, the heat loss of the car body increases, and the temperature of the car body decreases obviously. Another important reason for the large cold loss is the poor sealing performance of the car body, and more hot air enters the car from the air leakage. In general, if there is condensation at the door sealing strip or the heat insulation wall of the car body, the sealing is not tight. In addition, frequent opening and closing of doors or multiple people entering the car will also increase the heat loss of the refrigerated car. Try to avoid opening the door of the car body to prevent a lot of hot air from entering the car body. Of course, when the refrigerated car body enters the warehouse frequently or the quantity is too large, the heat load increases sharply, and it usually takes a long time to cool to the specified temperature.

2. Too thick frost or too much dust on the surface of evaporator;

Another important reason is the low heat transfer efficiency of the evaporator, which is mainly caused by too much frost or too much ash on the surface of the evaporator. Because the surface temperature of the evaporator is mostly lower than 0 ℃ and the humidity of the evaporator is high, the moisture in the air is 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 evaporator surface from being too thick, it is necessary to defrost regularly. There are two defrosting methods:

a) Stop and defrost. That is, stop the compressor, open the door, let the temperature rise, and restart the compressor after the frost layer melts automatically.

b) After the goods in frost warehouse are moved out, hot tap water is directly used to wash the surface of the evaporator drain pipe, so that the frost layer dissolves or falls off. Too thick defrosting layer will lead to poor heat transfer effect of the evaporator. In addition, due to long-term uncleanness and too thick dust on the surface of the evaporator, the heat transfer efficiency will be significantly reduced.

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