搭接量对螺旋折流板换热器壳程性能的影响

对螺旋折流板换热器进行数值模拟,研究相同螺旋角时搭接量对壳程对流传热充分发展段流动与传热性能的影响。结果表明,随搭接量的增大,同流量下壳程传热系数与压降均增大,而同压降下的传热系数降低。连续搭接时,轴向速度沿壳体径向逐渐降低;交错搭接后,轴向速度在搭接点前后变化趋势不同,分布均匀性变差。三角区漏流的切向速度方向与主流相反,强化了中心区域传热;而搭接区漏流的切向速度方向与主流相同,会增大螺旋旁流,不利于传热。搭接量越大,换热管表面换热量沿径向的不均匀性越强。

Influence of Overlap Size on Shell-side Performance of Heat Exchangers With Helical Baffles

Numerical simulation of heat exchangers with helical baffles was carried out.The study focused on the effects of overlap size on shell-side flow and heat transfer characteristics under the same helix angle in fully developed regions.The results show that,with the increase of overlap size,both the heat transfer coefficient and pressure drop increase at identical mass flow rate,whereas the heat transfer coefficient decreases at identical pressure drop.When the adjacent baffles are arranged in a continuous manner,the axial velocities gradually decrease along the radial direction.When the baffles are connected in an overlapped manner,the variation trends of axial velocities are different before and after the overlap point,and the distributions get non-uniform.The direction of leakage’s tangential velocities in triangle zone is opposite to that of the bulk flow’s,which will enhance the heat transfer in central region.The direction of leakage’s tangential velocities in overlapped zone is the same with that of the bulk flow’s,which will increase the spiral-flow leakage and make against with the heat transfer.The bigger overlap size is,the more non-uniform radial distributions of heat transfer on tubes are.