Comparison of Conventional and Advanced Exergy Analysis for Dual-Loop Organic Rankine Cycle used in Engine Waste Heat Recovery

Abstract

At present, the dual-loop organic Rankine cycle (DORC) is regarded as an important solution to engine waste heat recovery (WHR). Compared with the conventional exergy analysis, the advanced exergy analysis can better describe the interactions between system components and the irreversibility caused by economic or technical limitations. In order to systematically study the thermodynamic performance of DORC, the conventional and advanced exergy analyses are compared using an inline 6-cylinder 4-stroke turbocharged diesel engine. Meanwhile, the sensitivity analysis is implemented to further investigate the influence of operating parameters on avoidable-endogenous exergy destruction. The analysis result of conventional exergy analysis demonstrates that the priorities for the components that should be improved are in order of the high-temperature evaporator, the low-temperature turbine, the first low-temperature evaporator and the high-temperature condenser. The advanced exergy analysis result suggests that the avoidable exergy destruction values are the highest in the low-temperature turbine, the high-temperature evaporator and the high-temperature turbine because they have considerable endogenous-avoidable exergy destruction. The sensitivity analysis indicates that reducing the evaporation pinch point and raising the turbine efficiency can decrease the avoidable exergy destruction.