Simulation of waste heat recovery from a heavy-duty diesel engine with a medium temperature ORC system

A medium temperature organic-fluid Rankine cycle (ORC) system was designed to recover the waste heat from a heavy-duty diesel engine. R123 (CF₃CHCl₂) is used as the working fluid in the ORC system. Efficiency simulation was carried out under different circulating pressures, mass flow rates of R123 and engine exhaust temperature. The results show that the system efficiency increase with increasing circulating pressure, and supercritical Rankine cycle is better for waste heat recovery due to its higher circulating pressure. The ranges of mass flow rate of working fluid vary with circulating pressure. There is a maximum efficiency within the mass flow rate range under a fixed circulating pressure. The mass flow rate corresponding maximum efficiency decreases as circulating pressure increases. The maximum efficiency with different exhaust temperature is similar under the fixed circulating pressure. The mass flow rate under most efficient conditions reduces as the exhaust temperature decreases.