System Emulation And Numerical Simulation Of The Ship Waste Heat Recovery Based On TEG-ORC Combined Cycle

As a means of transport for maritime transport,ships have a huge demand for energy while the energy utilization rate of them is still at a low level.When the ship’s main engine is running,a large part of the heat is directly released into the environment as waste heat without being used.Not only does it cause the energy waste,but a lot of carbon emissions also have a huge impact on the environment.Therefore,waste heat recovery(WHR)has gradually become one of the research focuses in the field of energy saving because of its high cost performance and obvious energy saving effect.Now,the most widely studied WHR technologies include thermoelectric generation(TEG)and organic Rankine cycle(ORC).However,it is difficult to recover the waste heat of various types and multiple temperature ranges of the ship by means of a single WHR technology.After analyzing the advantages and disadvantages of TEG and ORC,referring to the characteristics of ship waste heat,a ship WHR system based on TEG-ORC combined cycle is proposed.Firstly,after the design of TEG-ORC combined cycle system,based on the theoretical model of TEG and ORC,the thermodynamic model and thermal economic model of TEG-ORC combined cycle are established.Secondly,based on MATLAB and REFPROP,the system emulation of TEG-ORC combined cycle system was conducted.In the emulation,the TEG unit,the evaporation pressure and the flow of the ORC working fluid are set as variables.Five parameters including the net output power,the thermal efficiency and the cost are set as the performance parameters of the system.Then the law of parameters’ variation is investigated.After that,the solutions of simulation are filtered to obtain the optimal one.The emulation results show that at the optimal system economy,the number of thermoelectric module is 22,the ORC working fluid flow is 0.44kg/s,the evaporation pressure is 2.2MPa,the power generation cost is 1.77 Y/kW ·h,and the net output power is 2520.30W.Finally,after the design of the TEG-ORC experimental system,based on the optimal solution obtained by the system emulation,the numerical simulation of the heat transfer process in the TEG unit,the second preheater,the third preheater and the evaporator is conducted.The simulation results show that under the optimal working condition in theory,in the TEG unit,the average temperature of the TEG hot and cold side is 536.20K and 314.28K,respectively,and the TEG output power is about 51.20W.Passing through the TEG unit,the exhaust temperature is about 554.75K,the waste heat utilization of the exhaust is about 402.20W,and the ORC working fluid temperature is about 312.03K;In the second preheater,the temperature of the ORC working fluid rises to 332.23K after preheating,and the utilization of the jacket water waste heat is 433.82W;In the third preheater,the temperature of the ORC working fluid reaches 397.66K after preheating,and the utilization of the pressurized air waste heat is 1363.26W;In the evaporator,the ORC working fluid absorbs heat and evaporates to 399.86K.The final outlet temperature of the exhaust is 479.46K,and the utilization of the exhaust waste heat is 1568.47W.The study shows that the TEG-ORC combined cycle can realize the cascade recovery and utilization of many kinds of ship waste heat It also has high net output power and high thermal efficiency.The addition of the TEG unit can effectively reduce the temperature of the exhaust before entering the evaporator,so the cracking of the ORC working fluid at high temperature can be avoid and the system reliability can be improved.The advantages of TEG-ORC combined cycle prove that it has a broad prospect in the recovery of ship waste heat,and has research value and practical application value.