双壳程管壳式换热器的传热和阻力特性

Heat Transfer and Flow Resistance Performance of a Double Shell-Pass Shell-and-Tube Heat Exchanger

针对弓形折流板管壳式换热器流动死区大,压降高的不足,提出外螺旋折流板内斜百叶折流板的双壳程管壳式换热器结构,外螺旋角为15°～40°,内斜百叶折流板倾角为45°。通过三维数值模拟,研究其传热和阻力特性,获得其局部流场,并与传统弓形折流板换热器进行了对比,同时分析了外壳程螺旋折流板不同倾角对其性能的影响。结果表明:双壳程管壳式换热器的壳侧流场分布均匀,流动死区减小,综合性能高于相同壳径和管束布置的弓形折流板管壳式换热器,外螺旋角为30°时,单位压降下的传热系数平均提高了24. 4%。当外螺旋角为20°时,该换热器具有最好的综合性能。

The shell side in the traditional shell-and-tube heat exchanger with segmental baffles has large dead zone and pressure drop.In order to overcome these disadvantages,a novel double shell-pass shell- and-tube heat exchanger combined with discontinuous helical baffles in the outer shell pass and louver baffles in the inner shell pass is proposed in this paper.With the three-dimensional numerical simulation, the heat transfer and flow resistance performance of the novel double shell-pass shell-and-tube heat ex- changer were investigated.It was found that the flow field is evidently uniform and has less dead zones. Compared to the shell-and-tube heat exchanger with segmental baffles,the novel double shell-pass shell- and-tube heat exchanger has 24.4%higher heat transfer coefficient per pressure drop.Six different incli- nation angles of the helical baffles in the outer shell pass were investigated,which is,15°,20°,25°,30°, 35°and 40°.The result indicates that the novel double shell-pass shell-and-tube heat exchanger has the best overall performance when the inclination angle of the helical baffles is 20°.