Latent Heat and Steam Formation - Continued.

Phase 3 (C to D)

At point C, all of the water has been converted into steam. Therefore, water cannot absorb any more latent heat. Any heat absorbed after this point will be sensible heat and will raise the steam temperature. Since the temperature of steam after this point will be greater than the saturation temperature, it will be referred to as “superheated” steam.

Heat added from C to D = (specific heat of steam) x mass x temperature increase.

Specific heat of steam depends upon its pressure. For our purposes, we are assuming the specific heat of steam to be 0.5. Also assume that we want the steam temperature to be increased to 250 deg F. (From 212 to 250 deg F is a temp increase of 38 deg F)

Heat added to create superheated steam = 0.5 x 1 x 38 = 19 BTU

This is sensible heat since a thermometer can sense it.