Simulations of waste heat recovery system using R123 and R245fa for heavy-duty diesel engines

To improve fuel economy, an Organic Rankine Cycle (ORC) system is proposed to recover waste heat from heavy-duty diesel engines. R123 and R245fa were selected as working fluids. Extensive numerical simulations were conducted to find thermal efficiency of the system under different evaporation pressures, mass flow rates of working fluids and temperature of engine exhaust gases. Results show that the system thermal efficiency was increased with the increase in evaporation pressure for both R123 and R245fa. Efficiency of R123 system was found to be greater than that of R245fa system. For Rankine cycle with both R123 and R245fa, mass flow rate range varied with the evaporation pressure. Limited by evaporation rates and thermal decomposition of the working fluid, the range of mass flow rates in R245fa system was narrower than the R123 system. The thermal efficiency with different temperatures of engine exhaust gases was similar under the fixed evaporation pressure.