Research On Heat Transfer Enhancement Of A Heat Exchanger With Different Diameter Tubes' Bundle And Longitudinal Flow

Heat exchangers are universal equipments used in many industrial fields such as chemical industry, petroleum refining industry, power industry, food industry and light industry etc, and the performance directly influence the thermal cost of the process industries. Enhancement technology of heat transfer and the research of new style heat exchangers have made great progress in recent years because of energy crisis.The heat exchanger with different diameter tubes' bundle (HEDDTB) is firstlyintroduced, through studying the structure characteristics, the behaviors laws of fluidflow and heat transfer in the shellside of heat exchangers with longitudinal flow.HEDDTB not only has the advantage of high anti-vibration performance that belongsto rod baffle heat exchanger but also has a compact structure as more tubes aredistributed per unit cross section area. The tubes' buddle of the traditional heatexchangers is composed of tubes with same diameter, which influences its efficiencyat small Reynolds number because of the big fluctuation of the heat transfercoefficient led by the flux fluctuation. Another feature of HEDDTB is that its tubes'buddle is composed of tubes with different diameters, which lead to a smallerfluctuation of heat transfer coefficient in the condition of fluctuating flux than that ofthe heat exchanger with tubes that has the same diameter in the case of low Reynoldsnumber. So, the HEDDTB has an ability of anti-abrupt-fluctuation of heat transfercoefficient, which expands the range of operation flexibility and makes the workperformance of heat exchanger stable in the condition of fluctuating flux. Thesupporting structure in shellside of HEDDTB is composed of waved steel strip, whichcan make the fluid flow in the shellside generate jets and longitudinal vortexes, and asa result it can enhance the heat transfer efficiency of shellside.The shellside fluid flow of HEDDTB is simulated with a periodic unit flow passage model using the software Fluent. The heat transfer correlation formula and pressure drop correlation formula of HEDDTB's shellside are gained by analyzing the...