Quote Originally Posted by frank View Post
Superheat is the term for the amount of heat added to a fluid above its phase change point.

Water boils at 100C at sea level atmospheric pressure and changes phase to a vapour. If you continue to add heat energy to the vapour, the vapour becomes superheated. So, for water vapour (steam) at 105C you could say that 5K of superheat has been added.

It is easier to understand the term when refering to water if you are not conversant with refrigerants and their boiling points.

Subcooling can be understood as the opposite of superheating. If you have steam at 100C and you cool it so it becomes condensate, then any temperature below 100C (at sea level pressure) can be refered to as subcooling. Water at 95C has been subcooled by 5K.

Superheat - the amount of heat energy added above saturation point (phase change)
Subcool - the amount of heat energy removed below saturation point (phase change)
It is absolutely right the way you explained the question about superheat.