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Why It Need Defrost On Evaporator?
Mar 01, 2018


1. The impact 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 air dew point temperature. Food and air moisture will precipitate and condense on the pipe wall. When the wall temperature is below 0 °the water condensation is condensed into a frost. Frosting is also the result of normal operation of the refrigeration system, so a small amount of frosting is allowed on the evaporator surface.


Since the thermal conductivity of the frost is too small, it is one percent or even a few hundredths of the metal, so the frost forms a larger thermal resistance. Especially when the frost is thick, it is like insulation. This makes the evaporator in the cold not easily distribute, affecting the evaporator cooling effect. Eventually cold storage can not reach the required temperature. At the same time, the evaporation of refrigerant in the evaporator should be weakened. Ammonia that is not completely evaporated may be drawn into the compressor and cause a liquid-strike accident.



2. The impact of defrosting on the local environment


There are lots of ways of defrost, such as artificial sweep frost, refrigerant heat cream, water defrost, electric defrosting and so on. For smaller refrigeration systems, manual defrosting and electric defrost can be used. However, it should be done while the system is down. For larger refrigeration systems, refrigerant frost and water defrost should be used. Due to the compressor exhaust heat defrosting heat source, so the refrigerant heat defrosting should be carried out under the conditions of the refrigeration system. It seems that no matter what kind of defrost method will affect the cold storage temperature especially the refrigerant heat defrost. Because of the branch warehouse, that is, part of the warehouse only refrigeration, and the other part of the warehouse defrosting. Defrost requires longer time, the impact on the library temperature is even greater. If the warehouse temperature fluctuation is too large, it will affect the quality of food in the store, especially the quality of fresh food. The melted cream needs timely cleaning, otherwise it will cause the warehouse ground frozen


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