Application of Rankine Cycle to Passenger Vehicle Waste Heat Recovery - A Review 2016-01-0178

Rankine cycle (RC) is a thermodynamic cycle that converts thermal energy into mechanical work, which is commonly found in thermal power generation plants. Recently, there are many studies focusing on applying Rankine cycle to recover low-grade waste heat. On-road vehicles, which convert around one third of the fuel energy into useful mechanical energy for propulsion, are moving energy conversion systems that generate considerable waste heat. It was found from many research studies that Rankine cycle has a great potential to be applied to harvest waste heat from automobiles. However, different from other low-grade waste heat sources, vehicles have limited space for the RC system integration and the waste heat is relatively unstable. In the current paper, the efforts in the past few decades related to applying RC to on-road vehicles, specifically passenger cars, are reviewed. Characteristics of the waste heat sources on vehicles and the constraints put on the automotive RC application are identified. Rankine cycle architectures, system components, and working fluids suitable to different vehicle types are summarized to provide a guideline for the future RC system design for automobiles. In the end, an insight into the application of Rankine cycle to vehicle waste heat recovery (WHR) is provided.