Waste heat recovery from heavy-duty diesel engine exhaust gases by medium temperature ORC system

A medium-temperature waste-heat recovery system based on the organic Rankine cycle (ORC) is designed to recover the exhaust energy from a heavy-duty diesel engine. Analysis of the 1st law of thermodynamics for an ORC system is performed. This analysis contains two parts. The first part is an analysis with undefined heat exchangers to gain an understanding of the ORC and find out suitable organic fluid parameters for a better ORC efficiency. The second part of the analysis uses combined engine test results and two designs of heat exchangers. By comparing the two designs, an improved system of heat exchangers is described. This analysis also quantifies the effect of engine parameters on ORC system. The study concludes that the supercritical Rankine cycle is a better approach towards waste heat recovery. The ORC system is found to perform better under part-load conditions if the medium-high power condition rather than rated working point of the engine is used as the design parameter. The ORC system achieves the highest waste-heat recovery efficiency of up to 10-15% for the optimised heat exchanger design.