Single-loop organic Rankine cycles for engine waste heat recovery using both low- and high-temperature heat sources

•A novel single-loop organic Rankine cycle for engine waste heat recovery (WHR).•Thermodynamic analyses of the novel system in comparison with conventional systems.•Increasing the temperature of engine coolant to increase the net power of the system.•Effects of pressure drop and efficiency of recuperator on performance of the system.•Effects of changes in waste heat sources.

A highly efficient single-loop ORC (organic Rankine cycle) is proposed for engine WHR (waste heat recovery) from a gasoline vehicle. IC (Internal combustion) engines have two waste heat sources—exhaust gas and engine coolant—with similar quantities of energy but different temperatures. Dual-loop systems can obtain the maximum power output from engine WHR; however, the systems occupy large amounts of space and are complex, heavy, and economically unfavorable, particularly for vehicle applications. A highly efficient single-loop system can overcome such limitations. This paper compares the performances of conventional single-loop systems and proposes a novel single-loop ORC system for engine WHR from both low- and high-temperature sources. The novel single-loop system produces approximately 20% additional power from engine WHR when operating under the target engine conditions.