evaporators fall into two categories; refrigerant to air and refrigerant to secondary refrigerant types.
the most simple of the refrigerant to air type is in the form of a bank of tubes with an extended surface of gills or fins.
in these the refrigerant is expanded in the tube while the air is passed over the fins by circulating fans.
this type of unit will be found in the domestic cold stores in which the fan and coil unit are one, and larger version in direct expansion cargo or air conditioning system where the fan or fans may be remote