Simulation of diesel engine conditions on a medium temperature ORC system

Two medium temperature ORC systems based on different exhaust temperature of a heavy duty diesel engine were designed. Simulation results of working fluid evaporation rate, node temperature, efficiency and output power of the systems were compared. Effects of engine exhaust flow rate and temperature on ORC system efficiency were also studied. Results show that, the ORC system can extend the operating range and give better performance under the part-load conditions if the medium-high power condition rather than the rated working point of engine is used as the design condition. The ORC system flow rate range varies with exhaust temperature, and the higher the temperature is, the wider the flow rate range is. The ORC system gives waste heat recovery efficiency by 10 percent or even 15 percent by the optimized design of the heat exchanger under engine medium-high load conditions.