Summer is almost here, and many air conditioning systems will be commissioned for start-up in anticipation of the upcoming heat and humidity loads. As part of this commissioning process, service technicians should inspect the evaporator coil and clean it if necessary.
The evaporator, like the condenser, acts as a heat exchanger. Heat and humidity (sensible and latent heat) from the conditioned space travel through the sidewalls of the evaporator coil and vaporize liquid refrigerant flowing through the evaporator. The pressure drop through the metering device causes vaporization of some of the liquid refrigerant in the evaporator, thus causing a lower saturation pressure/temperature in the evaporator. This temperature difference between the lower pressure/temperature refrigerant in the evaporator and the conditioned air traveling through the evaporator is the driving potential for heat transfer to take place.