WHAT IS SUPERHEATED STEAM ?

                Superheated steam is steam with temperature and enthalpy higher than the values specified for this pressure in the saturated steam table.

For example :

Steam at 10 bar pressure with a temperature of  200 Deg C is called superheated steam, but when compared with the saturated steam tables the temperature will be just 180 Deg C.

Superheated steam has a much lower heat transfer coefficient than the saturated steam. If superheated steam is used to transfer heat in a heat-exchanger, part of the heated surface is used to cool the superheated steam down to saturated steam temperature.  The amount of heat that is exchanged during this saturation process is small, but still it occupies a relatively large portion of the heated surface. The most important step in the heat transfer process takes place during the condensation. The specific volume of superheated steam is considerably higher than that of the saturated steam at the same pressure