Research On Performance Of Finned Tube Heat Exchanger In The Exhaust Heat Recovery System Of Passenger Car

When the bus engine is working,more than 30% of the total heat of the fuel is discharged into the atmosphere through the tail gas.If the wasted heat can be recovered,it will greatly make the fuel burn more fully and achieve energy conservation and consumption reduction.The purpose of environmental protection is to use exhaust heat exchanger to recover exhaust heat from passenger car engine exhaust gas is an effective way to achieve the above purpose.This paper aims at the heat transfer performance of Yutong's 12 m traditional passenger car with finned tube exhaust gas heat exchanger,using experimental methods and numerical simulation methods to study its heat transfer performance from two aspects of fluid medium and structural parameters.In the experimental process,the heat transfer effect of the finned tube type exhaust gas heat exchanger was tested by the effects of the exhaust gas temperature,the exhaust gas flow rate,the cooling water temperature,and the cooling water flow rate on the heat recovery amount and the heat recovery rate.In the numerical calculation process,the structure of the fin-tube exhaust gas heat exchanger is optimized by the influence of the fin height,pipe diameter,longitudinal pipe spacing,and arrangement on the heat exchanger outlet temperature and Nu,in order to develop a highly efficient tail gas heat exchange for the subsequent development.The device laid the foundation.The results show that: in the fluid medium,the exhaust gas temperature and the exhaust gas flow rate have a great influence on the heat recovery and the heat recovery.The cooling water temperature and the cooling water flow rate have little effect on the heat recovery and the waste heat recovery.Increasing the tail gas temperature,waste heat recovery The increase in the amount of waste heat will increase the recovery rate;increase the flow of exhaust gas,increase the amount of waste heat recovery,and reduce the recovery of waste heat;the maximum heat recovery amount obtained in the experiment was 8.7 k W,and the maximum heat recovery rate was 30.7%.The heat transfer performance of the fin-tube exhaust gas heat exchanger needs to be further improved.In terms of optimizing the structural parameters,for the same structural parameters,Re increases,the exit temperature and Nu of the heat exchanger increase.With the same Re conditions,as the fin height increases,the pipe diameter increases,and the pipe pitch increases,The exit temperature of the exhaust heat exchanger decreases and Nu increases.When the tube bundles are transposed,the heat exchange performance of the exhaust gas heat exchanger is obviously better than that of the row.The minimum temperature at the outlet of the heat exchanger is 504.91 K and the maximum Nu is 197.54.In the numerical calculation range of this paper,the fin height is 8.5mm,the pipe diameter is 26 mm,and the longitudinal pipe distance is 74 mm.When the tube bundles are arranged in transposition,the heat transfer effect of the fin-tube exhaust gas heat exchanger is better.