Effect of defrost on evaporator condenser

1.The effect of frost on the refrigeration system

When the cold storage refrigeration system is in normal operation, the surface temperature of the evaporator is much lower than the dew point temperature of the air, and the moisture in the food and air will precipitate and condense on the tube wall. If the temperature of the pipe wall is lower than 0°, the dew will condense into frost. Frosting is also a result of the normal operation of the refrigeration system, so a small amount of frosting is allowed on the surface of the evaporator.

Because the thermal conductivity of frost is too small, it is one percent, or even several hundredths, of metal, so the frost layer forms a large thermal resistance. Especially when the frost layer is thick, it is like heat preservation, so that the cold in the evaporator is not easy to dissipate, which affects the cooling effect of the evaporator. In the end, the cold storage cannot reach the required temperature. At the same time, the evaporation of the refrigerant in the evaporator should also be weakened. Incompletely evaporated ammonia liquid may be sucked into the compressor and cause liquid hammer accidents.

2. The impact of defrosting on the local environment

There are many ways to defrost, such as artificial defrosting, refrigerant heat melting, water defrosting, electric defrosting, etc. For smaller refrigeration systems, manual defrosting and electric heating defrosting can be used. But it should be done while the system is down. For larger refrigeration systems, refrigerant hot-melt frosting and water-melting frosting should be used. Due to the heat source of the compressor's exhaust-type hot-melt frost, the hot-melt frost of the refrigerant should be carried out under the operating conditions of the refrigeration system. It seems that no matter which defrosting method is used, it will affect the temperature of the cold storage, especially the refrigerant hot melting frost. Because it has to be divided into warehouses, that is, some warehouses are not cooled, while the other part of the warehouses are defrosted. The defrosting time is longer, and the influence on the storage temperature is also greater. If the storage temperature fluctuates too much, it will affect the quality of the food in the storage, especially the quality of fresh food. The melted frost should be cleaned in time, otherwise it will cause freezing of the warehouse floor.