三维变形管MVR蒸发器的强化传热数值研究

Numerical Study on Heat Transfer Enhancement of MVR Evaporator with 3D-Deformation Tube

蒸发器的换热性能对MVR (mechanical vapor recompression)系统有着重要影响。利用FLUENT软件,以水为介质,在雷诺数13000 <Re <110000,研究了三维变形管的不同结构参数对管内传热与压降性能的影响,拟合出了计算准则关联式。模拟结果显示:由于受到离心力的作用,流体在三维变形管内产生了垂直于主流方向上的二次流,促进了边界层与主流区的径向混合,强化了传热;三维变形管的扭距S越小,长短轴比A/B值越大,强化传热效果越好,但同时压降也会增大;综合换热性能在13000 <Re <60000随着雷诺数Re的增大迅速减小,在60000 <Re <110000随雷诺数Re增大而逐渐趋于平稳,但仍然优于光滑直圆管,减小扭距S值比增大长短轴比A/B值更有利于提高管内综合强化传热性能。将三维变形管应用于MVR蒸发器中,节材效益显著。

Heat transfer performance of evaporators has significant influence on MVR(mechanical vapor recompression)systems.Effects of structure parameters of3D-deformation tubes on heat transfer and pressure drop were investigated with FLUENT under Reynolds number13000<Re<110000using water as the medium,and a correlation equation of heat transfer was presented.The results show that secondary flow perpendicular to the main flow direction forms in the3D-deformation tube due to centrifugal force,which promotes radial mixing of boundary layer and mainstream areas and enhances heat transfer.Heat transfer increases with the decrease of twisted pitch and increase of axial ratio.Meanwhile,the pressure drop also increases.The comprehensive heat transfer decreases rapidly with the increase of Reynolds number in13000<Re<60000.When studied at60000<Re<110000,it gradually becomes stable with the increase of Re,which is still better than straight circular tubes.Reduction of twisted pitch values is more efficient than increase of axial ratio to improve comprehensive heat transfer performance.A noticeable benefit of material saving can be achieved by applying3D-deformation tube to MVR evaporators.