周向重叠三分螺旋折流板换热器壳侧传热性能

Shell-side heat transfer performance of circumferential overlap trisection helical baffle heat exchangers

探析了周向重叠三分螺旋折流板换热器高效强化传热性能的主要机理,周向重叠三分螺旋折流板换热器除了具备螺旋折流板换热器的一般特点外,还同时具有适合正三角形布管方案和防相邻折流板之间短路的功能;指出周向重叠方案相邻折流板连接处三角区内的一排管束可以有效抑制因上下游通道的压差引起的逆向泄漏;介绍了倾斜角为20°、24°、28°和32°的单头螺旋、32°双头螺旋周向重叠三分螺旋折流板换热器和弓形折流板换热器的试验结果,表明试验范围内的最佳方案是倾斜角20°方案,其平均壳侧传热系数、压降和综合指标(ho/Δpo)与弓形折流板换热器的数值之比分别为1.122、0.566和2.035。

The main mechanism of efficient performance of heat transfer enhancement in circumferential overlap trisection helical baffle heat exchangers is investigated.The heat exchanger possesses not only the general characters of helical baffle heat exchangers but also the features that are suitable for equilateral triangles layout of tubes and avoid the shortcut in triangular zones of adjacent baffles.It is the row of tubes at the junction triangle of adjacent baffles that effectively dampers the reverse leakage driven by differential pressure between upstream and downstream chambers,which makes this type of helix heat exchangers even more efficient than the others.The test results for heat transfer performance are presented for circumferential overlap trisection helical baffle heat exchangers with single thread schemes of baffle tilt angles of 20°,24°,28°,32°,and dual thread scheme of baffle tilt angle 32°,in contrast to a segmental baffle heat exchanger.The results show that the optimum scheme within the testing scope is the one with baffle tilt angle of 20°,and the ratios of the mean values of shell side heat transfer coefficient,pressure drop,and comprehensive index（ho/Δpo）of the helical scheme with baffle tilt angle of 20° over those of the segmental baffle scheme are 1.122,0.566 and 2.035 respectively.The dual thread scheme of baffle tilt angle 32° has higher heat transfer coefficient,pressure drop and the comprehensive index（ho/Δpo）than the single thread one with same tilt angle.