新型旋流布液器成膜性能实验研究

布液器是降膜蒸发器的关键部件。文章针对现有布液器存在的不足,开发了一种新型旋流布液器。该布液器为切向开槽结构,槽一侧与管内壁相切,另一侧延伸一定长度与管内壁形成导流结构,下端与换热管通过螺纹连接。在有机玻璃实验装置内对新型旋流布液器和切向槽型布液器形成液膜等性能进行了系统的对比研究。实验结果表明:只要合理控制流量,两种布液器均能连续稳定成膜,不会出现“干管”现象;新型旋流布液器的最小成膜流量更小,成膜的流量范围更广,说明其操作弹性更大;在相同流量下,新型旋流布液器比切向槽型布液器形成的液膜厚且流速小,因此液膜稳定性更好,同时液膜在换热管内的停留时间更长,换热效果更好。

Liquid Flow Field on Evaporator of Wiped Short Path Distillation——Experimental Results and Computer Simulation

Short path distillation (SPD) is a kind of high vacuum distillation method, which is suitable for the separation of high boiling, heat sensitivity and viscidity products.In this paper,through measuring the phase-averaged velocity distributions with a conditional sampling method of the particle imaging velocimetry (PIV), the liquid flow field that affects the heat and mass transfer of evaporating thin-film in an SPD evaporator is investigated.Measured results show that the flow velocities decrease rapidly apart from the wiper at different wiper velocities, the maximum velocity appears before wipers, and the quicker the wiping, the larger the flow velocity. Meanwhile, the evaluation of numerical calculations is carried out.The measured velocity distributions indicate clearly the effect of the wiper both on the flow field along its moving direction and on the vortices behind the wiper.Simulation data show that the performance of liquid flow field on the heating surface not only agrees with the experimental results well,but also can give further more information, such as the distribution of turbulent kinetic energy.In this study,turbulent kinetic energy mainly distributes before wipers and laminar flow appears far away from the wipers.

新型窗式布液器设计及降膜流动性能

窗式布液器是用于降膜蒸发装置液膜分布的关键部件,其流道结构及数量直接影响液体在降膜管内的流动均匀性。然而工程应用中布液器流道的结构参数难以确定,缺乏布液器流道设计的依据。利用平板切向狭槽为研究对象,开展液体降膜性能研究,通过理论分析,建立了平板狭槽液体流动轨迹方程,确定了最小成膜流量下的狭槽流道结构尺寸与流道数量。通过实验研究及数值模拟,验证了平板狭槽液体流动轨迹方程可用于圆管布液器的优化设计,以获得最小成膜流量下最佳的降膜流动性能,为工程应用提供了极其重要的理论依据。