The role and characteristics of the evaporator in the refrigeration system
The role of the evaporator in the refrigeration system
The equipment used for heat exchange between the refrigerant and the low-temperature heat source in the refrigeration system is located between the throttle valve and the return steam header of the compressor, or between the liquid supply pipeline and the return steam pipeline of the vapor-liquid separation equipment, and Installed in cold rooms or places that require cooling and freezing. The function is to make the throttled low-pressure refrigerant absorb the heat of the object to be cooled and vaporize, thereby reducing the temperature of the object to be cooled.
Classification and characteristics of evaporators
The heat transfer process of the evaporator: the refrigerant boils on one side, and the cooled medium flows continuously on the other side. Factors affecting the heat transfer of the evaporator: Similar to the heat transfer of the condenser, F is constant, and △tm is appropriately increased, mainly because Try to improve the heat transfer coefficient, k depends on many factors such as the thermal properties of the cold and hot fluids, the flow conditions, the characteristics of the heat transfer surface, and the structural performance of the evaporator. The function is to make the throttled low-pressure refrigerant absorb the heat of the object to be cooled and vaporize, thereby reducing the temperature of the object to be cooled.
1. According to the classification of cooling medium
Evaporator for cooling liquid
There are various structural forms such as shell and tube type, riser tube type, spiral tube type and coil type.
Evaporator for cooling air
It is customary to be divided into cooling tube evaporator and air cooler (or air cooler)
Contact evaporator (cooling solids)
For example, the plate evaporator in the flat plate freezing device absorbs the heat of the cooled object through the throttled low-pressure refrigerant and evaporates, thereby reducing the temperature of the cooled object.
2. According to the refrigerant supply method
Flooded evaporator:
-When the evaporator is working normally, the cylinder should be filled with refrigerant liquid with a height of about 70%~80% along the vertical cylinder diameter.
Non-flooded evaporator:
-Currently mainly used in Freon refrigeration system
Circulating evaporator:
At present, this type of evaporator is widely used in large-scale cold storage. At this stage, the air cooler is widely used as the evaporator, and the throttling low-pressure refrigerant absorbs the heat of the object to be cooled and vaporizes, thereby reducing the temperature of the object to be cooled. It is mostly a complete set of equipment consisting of an axial flow fan and a cooling exhaust pipe. It relies on the fan to force the air in the refrigeration warehouse to flow through the cooling exhaust pipe in the box to conduct heat exchange to cool the air, so as to achieve the purpose of reducing the temperature of the warehouse. , Different from the cooling method of the exhaust pipe, the air cooler adopts the form of forced convection.
