The evaporator is where heat is absorbed into the refrigeration system. An evaporator is basically a heat exchanger with refrigerant tubes and extended surfaces. The extended surfaces are often referred to as fins. The evaporator’s function is to efficiently transfer heat from the surrounding area to the phase-changing refrigerant flowing through the evaporator. The refrigerant will be phase changing from a liquid to a vapor as it travels through the evaporator, absorbing heat. As the evaporator’s heat load changes, an expansion-type metering device, at the entrance of the evaporator, will control the flow of refrigerant through the evaporator. The metering device will also ensure that all of the liquid in the evaporator has fully vaporized before exiting the evaporator.
The evaporator is a major component in the refrigeration system, and an efficient evaporator plays a key role in saving energy. Many commercial and industrial evaporator assemblies consist of an evaporator coil, an expansion device, fans, defrost heaters, and a liquid line solenoid valve. By carefully timing, managing, and controlling each of these components with an evaporator-efficiency controller (Figure 1), the evaporator is able to provide the maximum output, with the minimum amount of energy input.