Research On Tube Heat Exchanger For Engine Waste Heat Utilization

Energy saving and emission reduction is the eternal goal pursued by the economy and society,and the exhaust gas emitted by automobile engines contains a large amount of heat energy.In order to improve the fuel utilization rate,this paper conducts research on the utilization of tube heat exchangers for vehicle engine exhaust heat,analyzes the factors affecting the comprehensive performance of tube heat exchangers,and optimizes the structure of the heat exchanger to improve the comprehensive heat exchange performance.First of all,check the literature to understand the domestic and foreign research status of tube heat exchangers in the utilization of vehicle waste heat.Study the working fluid flow and heat transfer theory in the heat exchanger,and summarize the heat transfer calculation method of the heat exchanger.On this basis,the work performance evaluation criteria of the heat exchanger and the basic control equations and turbulence characteristics involved in the flow field of the heat exchanger are analyzed.Then,the coiled-tube heat exchanger model was established and verified,and the influence of structural parameters and operating parameters on the performance of the heat exchanger was studied using numerical simulation methods.Based on the single-variable method to analyze the influence of structural parameters on the comprehensive performance of the heat exchanger,the results show that: when the spiral diameter of the heat exchange tube is 120 mm,the comprehensive performance of the heat exchanger is the best,and as the tube diameter and pitch increase,the The overall performance of the heat exchanger decreases;in terms of operating parameters,as the engine exhaust gas at the inlet of the heat exchanger decreases and the temperature increases,the Q/△P evaluation index of the coil heat exchanger increases.After that,the structural parameters and operating parameters that affect the tubular heat exchanger are studied through modeling and simulation;the results show that the comprehensive heat transfer performance is the best when the heat exchange tubes are equilateral triangle distribution,and the inlet temperature of the cold working fluid is reduced and increased.The exhaust gas flow rate can improve the Q/△P evaluation index of the heat exchanger.Finally,the research on heat transfer enhancement of heat exchangers was carried out,and the ways of enhancing heat transfer were analyzed based on the basic heat transfer equations.Two structures of baffle and variable curvature heat exchange tube are adopted to improve the coil heat exchanger.The surface heat transfer coefficient of the baffle structure heat exchanger is increased by 9.47%,and the surface heat exchange of the variable curvature heat exchange tube heat exchanger is increased by 9.47%.The thermal coefficient has increased by 14%.Two structures of bellows and spiral tubes are used to improve the tubular heat exchanger.The results show that the overall performance of the bellows heat exchanger is the best.The heat exchanger based on modeling has conducted a comparative study on the types of heat exchange and cold working fluids,and the results show that: water is suitable for heat exchange systems that mainly recover heat,and ethanol is suitable for systems that heat up and do work.