Evaporator is an important component along with other key components of the refrigeration system such as compressors, condensers, and expansion equipment. The reason for refrigeration is to remove heat from air, water or other substances.
It is here that the liquid refrigerant expands and evaporates. It acts as a heat exchanger that transfers heat from the cooling material to the boiling temperature.
There are two types of Evaporator
(1)The forced convection type uses a fan or pump so that the liquid can be cooled upon evaporation.
(2)The natural convection type consists of a liquid that is naturally cooled to evaporate. Due to the density difference of cold and hot liquid.
Evaporator Construction Type There are three types of evaporation. Construction that is commonly used today:
Bare-tube and plate surface construction consistsof the entire surface exposed to evaporative refrigerant. Finned constructions are bare-tube coils with fins (metal plates usually aluminum). More detailed discussion on such design will be provided here.
The wings are added to the bare-tube to increase heat transfer capacity. They act as heat collectors that pick up heat from the surrounding air and transport it to refrigerant inside the tube therefore improving efficiency in cooling the surrounding air. They are best used in air-cooling space, where the temperature is around 34 ° F.
Having wings means that the surface area for heat transfer is increased. This means that the feather coils may be more compact in design than the same capacity of the bare-tube type.
Thermal Contact and Fin Spacing
Good thermal contact between the fins and tubes is a must to ensure efficient heat transfer. They can be soldered together. Another more practical method is to expand the wings by pressure as they cut across the surface of the tube so a good thermal contact is established. The difference of the fin depends on the operating temperature of the coil. The low temperature application uses only 1 fin.
In air conditioning applications, 14–16 fins per inch may be used, unless it is designed in such a way that frost does not accumulate in the coils. Excessive fining may reduce evaporator capacity. Design engineers must therefore perform a proper system calculation and simulation in the design phase by restricting the flow of air over the coil.