Numerical Simulation And Optimization Research On Bus’s Heating Equipment Recovering Exhaust And Coolant Energy

With the development of kinds of high technologies,especially in electronic technology,automobile with engine as power has obtained a certain achievement in energy saving and environmental protection,but people still have an expectation in revolutionary breakthrough.Plenty of energy is wasted in the process that fuel’s chemical energy is transformed into useful mechanical energy,and massive heat energy is carried away by exhaust gas and cooling water in this process.There is a great social benefit and economic benefit in recycling the automobile waste heat energy.Traditional automobile warm-air-conditioner uses engine’s coolant heat or independent oil heater’s combustion heat to get warm.But engine’s coolant heat energy which can be recovered is low and can’t satisfy large and medium bus’s heating demand.So large and medium bus need independent heat source to get enough warm.But independent heat source’s cost is high,and the independent oil heater’s exhaust emission will cause environmental pollution.The bus’s water-exhaust heating system studied in this thesis not only uses part energy of coolant heat,but also uses exhaust heat exchanger to recover exhaust heat energy.This heating system has high heating amount and doesn’t consume fuel,so it has advantages of energy saving and environmental protection.Heat load calculation model for computing bus’s heating demand is established in this thesis,and the computatiOnal program is compiled using VB software.The exhaust heat exchanger is the most important part of the water-exhaust heating system.The characteristics of coil type exhaust heat exchanger are firstly analyzed,and shortcomings of such heat exchanger are pointed out.In order to solve the existing problems of the water-exhaust heating system,a new kind of water-jacket and tube type heat exchanger is designed.Such heat exchangers use water-jackets and tubes as composite heat exchanging structure.Hydraulic expanding and welding technology which is hot in the heat exchanger industry is used to connect tubes and tube sheets.The coil type exhaust heat exchanger and water-jacket and tube type heat exchanger are simulated with the CFD software FLUENT.Heat transfer and flow resistance characteristics are analyzed,and the simulation results show that the water-jacket and tube type heat exchanger has better performance.In addition,structure parameters of the water-jacket and tube type heat exchanger are optimized and adjusted through the numerical simulation results.Based on the numerical simulation,a prototype of water-jacket and tube type heat exchanger was trial produced.The prototype is numbered SL30.Heating performance experiments were conducted on the prototype SL30.In order to make the experiments more persuasive,performance experiments were also carried on the coil type heat exchanger SXB30, and the experimental results of the two heat exchangers were compared. The comparison shows that the whole performance of SL30 is better than SXB30.Moreover,the SL30’s simulation results and experimental results were also compared in this paper.Although there are deviations between simulation results and experimental results,they still have good consistency.So the numerical simulation can be well used to guide heat exchanger’s structure design and optimization.At last,a special exhaust triple valve was designed according to the SL30’s exhaust bypass control.And the intelligent control methods of the water-exhaust heating system are discussed.