A comprehensive review of waste heat recovery from a diesel engine using organic rankine cycle

ORC has gained attraction in diesel engines due to its outstanding capability in improving thermal efficiency and fuel economy by recovering heat from low-temperature waste heat sources. This review paper initially discusses the engine–ORC system based on the trade-off between parameters such as weight, backpressure, space, and cost versus thermal efficiency and fuel economy. Working fluid, configuration, and process parameter selections are analyzed based on the steady-state ORC model. Based on the analysis, Isentropic working fluids are suggested for engine–ORC systems as they undergo complete dry expansion and simultaneously enters the condenser with minimum superheat. The steady-state ORC model has thermal efficiency and exergy efficiency up to 25% and 36% for single-loop systems respectively. Exergetic efficiency for combined recovery system are observed upto 46%. Single loop ORC systems generate about 25% lower power output than dual loop ORC systems. Single loop ORC configurations are suggested for vehicular-based diesel engine applications as they utilize waste heat from multiple sources ensuring weight, space, and cost concerns. Dual loop ORC configurations are proposed for stationary diesel engine applications due to lower weight and space constraints. Steady-state ORC models are suitable for analyzing stationary diesel engine applications, highway and marine-based vehicular diesel engine applications due to nearly steady exhaust conditions. Dynamic ORC models are discussed for in-city-based vehicular diesel engine applications due to transient exhaust conditions and compared for dynamic analysis based on computational time, cost and accuracy.