Evaporators

Refrigeration evaporator

Refrigeration evaporator plays an important role in refrigeration and air conditioning system. It is where the heat transfer and cooling effect takes place. The evaporator is basically a heat exchanger that removes heat from a source, typically the supply air stream, and uses this heat to evaporator the liquid refrigerants. It is in the evaporators where the actual cooling effect takes place in the refrigeration and the air conditioning systems. The evaporators are heat exchanger surfaces that transfer the heat from the substance to be cooled to the refrigerant, thus removing the heat from the substance. The cooling portion of the vapour compression cycle occurs at the evaporator. In the evaporator, the refrigerant is encased in tubing, and does not come in direct contact with the source stream.

Evaporators can be classified as direct expansion types and chilled water system types utilizing shell and tube heat exchangers. They are also classified in different manner depending on the method of feeding the refrigerant, construction of the evaporator, direction of air circulation around the evaporator, application and also the refrigerant control.

In the evaporator the refrigerant enters at very low pressure and temperature after passing through the expansion valve. This refrigerant absorbs the heat from the substance that is to be cooled so the refrigerant gets heated while the substance gets cooled. Even after cooling the substance the temperature of the refrigerant leaving the evaporator is less the than the substance. The refrigerant leaves the evaporator in vapor state, mostly superheated and is absorbed by the compressor.