Thermodynamic Simulation of Organic Rankine Cycle (ORC) for Electricity Generation from Low-Grade Waste Heat

Abstract

This paper proposes the simulation model of Organic Rankine Cycle (ORC) system based on an actual data. The ORC system was installed to recovery waste heat from exhaust gas and jacket water of natural gas engine. The working fluid of ORC is R245fa. Thermodynamic analyses are conducted with variation of evaporating pressure in ORC loop to observe efficiencies and expansion powers of ORC system. The simulation results indicate that about 20% and 80% of the total heat absorption are from jacket water and exhaust gas, respectively. The system gives the maximum expansion power of 326 kW and the maximum exergy efficiency is 21.45% at 26 bar of evaporating pressure. The maximum recovery efficiency is 8.74% in which it occurs at 27 bar of evaporating pressure due to the dramatic drop of R245fa flow rate. From the simulation model, the ORC system should be operated at 26 bar of evaporating pressure to gain the highest benefit with constant waste heat loss.