| Because limited by the working principle, the fuel convert into effective power less than 45%, yet the exhaust emission take away more than 30% in the automobile. If exhaust heat was recovered, the thermal power of the engine will increase. Exhaust waste heat utilization as a car "energy-saving" technology, this paper puts forward the conception and design of fluctuate water heating system for automobile exhaust heat recovery, which opens a new way to achieve the effective heat utilization of exhaust waste heat.Based on the working process of the electrelectric fluctuate circulation heating system, the working principle of fluctuate water heating system for automobile exhaust heat recovery has been establishment, and complete the system and each component basic design. According to the special request of on-board and heat exchange system, and based on the analysis of convective heat transfer theory, the core component heat exchanger performance parameters has been confirmed with theoretical calculation, and ultimately determine the shell and tube heat exchanger arrangement and structure parameters. Has completed the tee branch pipe of exhaust system design and 3D drawings according to the basic theory of fluid mechanics and combined with the actual needs of the system.For the sake of make sturcture design optimization, by using the method of numerical simulation and analysis, two aspects have been deep research which are tube heat exchanger and tee branch pipe in the system.(1) In order to reduce the local pressure loss in tee branch pipe, a numerical simulation based on FLUENT and GAMBIT software was carried out for the dispersed flow and interflow characteristics of the tee branch pipe, with the influence analysis on the total pressure loss coefficient under different conditions of the flow area ratio, angle, mass flow ratio and fluid temperature of the branch and main pipes. The numerical simulation and experimental results are compared with previous studies, showing the same trend and high accuracy of calculation. Through numerical simulation and analysis, the structure of tee branch pipe is recommended that angle of branch-main pipe is 45°, and flow area ratio A3/A1 of branch and main pipes is within the appropriate range of 0.8 to 1.(2) A numerical simulation based on FLUENT software was carried out for airflow distribution uniformity of tube side, which in the tubular heat exchanger with double tube side, with the influence analysis on the maldistribution under different conditions of split range channels height h, distance of tube side L, tube columns number r, internal diameter of tube d and tube spacing S. The orthogonal design theory was used to design numerical experiments. The simulation results showed that d have an important influence on the maldistribution, is the dominant factor, followed by r and h by the range analysis and variance analysis. The optimal combination structure of the tube side within the scope of the simulation is that h=60mm, L=20mm, r=4. To further increase the distribution uniformity, taking into account the energy loss is analyzed split range channels with different tube permutations and longitudinal section angle, the best structure is recommended for the left and right longitudinal section angle are 78.7°, maldistribution and energy consumption are reduced. By comparing the different structure of split range channels heat transfer coefficient of deviation, it’s not affected by the flow uniformity which under the condition of constant heat exchange tube wall temperature and no heat exchange with the environment for the gas-water medium of shell and tube heat exchanger. |
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