Rankine cycle system, a method of operating a cogeneration system and a Rankine cycle system

Rankine cycle system (20A), the pump (23), the evaporator (24), and a expander (21), the condenser (22) and the internal heat exchanger (25). Internal heat exchanger (25), and a working fluid discharged from the expander working fluid discharged from (21) and a pump (23) is heat exchanged. As the temperature of the working fluid at the outlet of the expander (21) is higher than the saturation temperature at the high pressure side of the cycle, the temperature of the working fluid at the inlet of the expander (21) is set.