There are two cooling methods for refrigeration equipment: direct cooling and indirect cooling. Direct cooling is to install the evaporator of the refrigerator in the box or building of the refrigeration device, and use the evaporation of the refrigerant to directly cool the air in it, and the object that needs to be cooled is cooled by the cold air. The advantage of this cooling method is that the cooling speed is fast, the heat transfer temperature difference is small, and the system is relatively simple, so it is widely used. Indirect cooling relies on the evaporation of the refrigerant in the evaporator of the refrigerator, so that the refrigerant (such as brine) is cooled, and then the refrigerant is input into the cabinet or building of the refrigeration device, and the air in it is cooled by a heat exchanger. This cooling method has a slow cooling speed, a large total heat transfer temperature difference, and a complicated system, so it is only used in fewer occasions, such as salt water ice making and cold storage with constant temperature requirements.
According to different cooling purposes and cooling utilization methods, refrigeration devices can be roughly divided into four categories: refrigeration devices for refrigeration, refrigeration devices for testing, refrigeration devices for production, and refrigeration devices for air conditioning.
Refrigeration devices for refrigeration are mainly used to store or transport food and other goods under low temperature conditions, including various refrigerators, cold storages, refrigerated trucks, refrigerated ships, and refrigerated containers.