Heat Recovery from Internal Combustion Engine with Rankine Cycle

For an internal combustion engine, 30% to 40% of the fuel energy is carried away by exhaust. Recovering a portion of the heat loss can increase the brake power and reduce the fuel consumption and CO₂ emission of the engine. This paper shows how Rankine cycle is used to recover the exhaust heat. Total heat recovery efficiency is used to measure the performance of heat recovery system. The thermodynamic properties of the working fluids are analyzed. The results show that among the working fluids investigated, water has the highest total heat recovery efficiency when the exhaust temperature is high. In comparison to water, organic fluids are advantageous when the exhaust temperature is low and/or variable. Water is the fluid with the smallest variations from the power output at the evaporating pressure of 3 Mpa. This characteristic leads to the possibility of simplifying the compression and expansion component.