Research Of Dual-loop Organic Rankine Cycle Of Engine Waste Heat Recovery

With energy crisis of the world getting more and more serious,the current important issue is improving energy efficiency and finding new energy.Saving energy is important to internal combustion engine which consumed much energy.Only about one-third of the energy released by combustion of the combustion of the internal combustion engine is converted into effective power,the rest of energy converted into heat,and 40%?80%of the heat are took away by engine exhaust and coolant which has a huge recovery possibility.For the characteristics of waste heat of internal combustion engine,first,professional software is used to establish two different dual-loop organic Rankine cycle system(including high temperature loop and low temperature loop)to recover the engine exhaust waste heat,coolant heat and high temperature loop waste heat.The difference between these two systems is the recovery of the exhaust heat,and the system for recovering two times of exhaust waste heat is defined as system A,and the system for recovering only one time of exhaust waste heat is defined as system B.Then,by four performance evaluation index(net output power Wnet,exergy efficiency ?e,the product of heat exchanger's heat transfer coefficient and heat transfer area UA,electricity production cost of system EPC)of the simulation,compare the performance of this two systems,and analyze the impact of the parameter of high temperature loop(the evaporating pressure and turbine inlet temperature of working fluid)on system performance,and the impact of working fluid(Water,methanol,toluene,R245fa and n-pentane)of high temperature on system performance.The results show that the system B,with the high-temperature loop evaporation pressure is 7Mpa and the high-temperature loop turbine inlet temperature is 752K has the best performance,the net output of the system is 117.46kW,exergy efficiency is 57.15%,UA is 65.02kW·K-1,EPCis 0.0532?·(kW h)-1.In order to improve the heat transfer capacity of the coolant,two kinds of nanoparticles were added to the coolant,reserch the effects of different concentrations of nano-coolant on the system performance.The results show that when put 0.5%.wt carbon nanotubes,improve 350%of the heat transfer capacity of the coolant,system gains best performance,net output power increase 7.78kW,the exergy efficiency is 53.89%,UA is 93.992kW·K-1,EPC is 0.05376$·(kW·h)-1.