扭曲椭圆管内降膜蒸发特性研究

Research on characteristics of falling film evaporation in twisted elliptical tube

高效换热管有利于提高降膜蒸发器的传热性能,通过FLUENT软件对扭曲椭圆管内降膜蒸发过程进行研究,分析了液膜在扭曲椭圆管内的流动以及分布情况。研究结果表明:液膜在扭曲椭圆管内为螺旋流动,因离心力的作用会在垂直于主流方向产生二次流,从而增强对传热边界层的扰动;从壁面到液膜表面,液膜速度及压力都在逐渐增大,速度的变化率在逐渐地减小;相比于圆管,扭曲椭圆管内的液膜流动更为平稳,且液膜厚度的分布因扭矩的存在而具有一定的周期性变化规律;在扭曲椭圆管内,流体速度场与温度场的协同性相对来说比圆管的好,而速度场与压力场的协同性比圆管的差。

High efficiency heat exchange tube is beneficial to improve the heat transfer performance of falling film evaporator.The falling film evaporation process in a twisted elliptical tube was studied with FLUENT,and the flow and distribution of the liquid film in the twisted elliptical tube were analyzed.The results show that the liquid film flows spirally in the twisted elliptical tube,and the secondary flow perpendicular to the main flow will occur due to the centrifugal force,which can enhance the disturbance to the heat transfer boundary layer.From the wall surface to the liquid film surface,the liquid film velocity and pressure are gradually increasing,and the rate of change of velocity is gradually decreasing.Compared with the round tube,in the twisted elliptical tube,the liquid film flows more smoothly,the distribution of the liquid film thickness has a periodic variation due to the torque,the synergy between the velocity field and the temperature field is relatively better and the synergy between the velocity field and the pressure field is worse.