Fig. 11.5 shows temperature entropy diagram for 1 kg of water. At ooc the entropy is zero(arbitrarily chosen). The steam is generated at constant pressure. if shows the heating constant pressure. The area under the curve ‘if’ represents heat transferred to during the process of heating from 0°C to saturation temperature of water. The of entropy is S1during ‘if’. The entropy change Sfg occurs during change of phase about by the heat flow during evaporation. All datas regarding steam is available at ‘steam table’ – (interpolation may be done to get exact value).