1. Poor heat insulation or sealing performance of refrigerated trucks;
The reason for the poor thermal insulation performance is the lack of mutual adhesion between the inside and outside skin of the car body, or the insufficient thickness of the insulation layer, and the thermal insulation effect is poor. The main reason is the improper selection of insulation layer thickness in design or the poor quality of insulation materials in construction. In addition, in the process of construction and use, the insulation and moisture resistance of the insulation material may be damaged, so that the insulation layer is affected by moisture, deformation and even erosion. The thermal insulation capacity of the thermal insulation material decreases, the heat dissipation loss of the car body increases, and the temperature of the car body decreases significantly. Another important reason for the large cold loss is the poor sealing performance of the body, and more hot air enters the car from the leak. Under normal circumstances, if there is condensation in the door seal or the body insulation wall seal, it means that the seal is not tight. In addition, frequent opening and closing doors or multiple people entering the car together will also increase the heat loss of the refrigerated car. Try to avoid opening the doors of the body to prevent a large amount of hot air from entering the body. Of course, when the refrigerated car body is frequently entered into the warehouse or the amount of storage is too large, the heat load increases sharply, and it usually takes a long time to cool to the specified temperature.
2. The surface of the evaporator is too thick or dusty;
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, affecting the heat transfer effect of the evaporator. In order to prevent the evaporator surface from being too thick, it must be defrosted regularly. There are two defrosting methods:
① Parking defrost. That is, stop the compressor operation, open the door of the warehouse, let the warehouse temperature rise, and restart the compressor after the frost layer automatically melts.
② After the goods are moved out of the warehouse, wash the surface of the evaporator drain pipe directly with hot tap water to dissolve or fall off the frost layer. In addition to the thick defrosting layer, the heat transfer effect of the evaporator will be poor, and the heat transfer efficiency of the evaporator surface will be significantly reduced due to the long-term unclean dust.
