The schematic diagram of ORC system with an internal heatexchanger is shown in Fig. 1. At first, Organic vapor of the workingfluid from the evaporator outlet expands in the turbine to producepower. Then, organic vapors in the exhaust gases of the turbine iscondensed to liquid water in the condenser after passing through the high temperature side of internal regenerator. Afterwards, theliquid organic working fluid from the condenser is pumped intolow temperature side of internal regenerator to absorb heat. Ultimately,the working fluid passes through the preheater and evaporator,where it is converted into saturated or superheated vapor,and repeats the same process over and over again.