The analytical model was established for organic Rankine cycle(ORC)system for power generation from geothermal energy.Three typical types of organic working fluids were selected for the ORC performance analysis.At different heat source outlet temperatures

change laws of the work output

work output per unit area

evaporation pressure

thermal efficiency and exergy efficiency with the heat source outlet temperature were investigated.Moreover

the optimal operation condition for each working fluid was obtained.The results show that

the work output(with and without internal heat exchanger(IHX))and work output per unit area(with IHX)reached the maximum value with the variation of heat source outlet temperature.For geothermal with temperature below 135 ℃

subcritical ORC was more suitable for power generation than supercritical ORC.The introduction of IHX can increase the thermal efficiency and exergy efficiency

but has little effect on cycle optimum evaporation pressure.