Getting Superheat and Subcooling


Reliable and efficient refrigeration effects


Superheat is the temperature difference between the actual temperature of a vapour and its saturation temperature (ie the temperature at which it can change state). For reliable and efficient refrigeration the correct degree of superheat must be achieved at the evaporator exit.  Too much and you will have insufficient capacity, too little and you could carry liquid out of the evaporator into the compressor leading to mechanical failures.

Subcooling the liquid refrigerant before it enters the expansion valve increases the system capacity and prevents flash gas from forming. In a refrigeration system, there should be subcooled liquid refrigerant in the liquid line between the receiver and the expansion valve.

Explore these guides and videos to find out more about these important principles. (Contains external links)

Maths of efficiency

Quiz on Pressure Enthalpy

Refrigerant Matters