Abstract: A method was proposed to enhance the single phase convective heat transfer. A stainless mesh cylinder was inserted into the tube concentrically to divide its cross section into an annular region and a central region. As the fluid passes the mesh cylinder, most of it enters the annular region because of resistance, modulating the flow field. Hot fluid in the annular region and cold fluid in the central region mix with each other more intensely through the mesh surface, enhancing the heat transfer. The heat transfer and pressure drop characteristics in the vertical upward flow with inserted mesh cylinder were investigated experimentally to validate the method. The mean and local Nusselt numbers and pressure drop data were obtained from the mesh cylinder tube and a smooth tube with water as the working fluid. The Reynolds numbers cover the range of 2392-20175 and the heat flux is in the range of 50.18-282.88 kW·m^-2. The experimental results from the smooth tube are validated by using the well known equations in literature. Inserting a mesh cylinder increases the heat transfer and pressure drop considerably compared with the smooth tube. The heat transfer enhancement factors range from 1.21 to 1.84. In the entrance region or thermal developing region, the heat transfer enhancement factor is up to 2.64. Meanwhile, the pressure drop is 6.1-10.6 times larger than that of the smooth tube.

Key words: mesh cylinder, flow field modulation, convection, heat transfer, experimental validation

摘要： 提出在传热管内插入圆柱状丝网管调控流场进而强化传热的方法。通过在管内同心插入圆柱状丝网管，将流通截面分成中心区和环隙区，流体流经丝网入口处时受到阻力较大，大部分流体流向环隙区，使得速度场受到调控。环隙区与中心区内冷热流体掺混，强化传热。为验证这一思想搭建强制对流换热实验台，以去离子水为工质，Reynolds数为2392～20175，热通量为50.18～282.88 kW·m^-2。通过对局部、平均Nusselt数及摩擦压降数据的研究，结果表明：同光管传热相比，插入丝网管后平均Nusselt数提高，传热强化系数为1.21～1.84，且最大强化系数发生在过渡流内。入口段强化效果明显，局部传热强化系数最高可达到2.64。而强化传热的同时摩擦压降增大6.1～10.6倍。同时对该结构的传热强化机理进行分析：流场受到丝网管的调控作用，进而强化传热。

关键词: 丝网管, 流场调控, 对流, 传热, 实验验证