水平管外冷态降膜流动特性研究

Study on flow characteristics of cold-state falling film outside horizontal tubes

采用VOF(volume of fluid)方法建立水平管外冷态降膜流动的计算模型,对冷态液膜流动条件下水平管外的液膜厚度分布以及流体速度分布规律进行研究,分析喷淋密度、流动截面位置及壁面距离对速度场的影响。数值计算结果表明:液体喷淋密度越大,水平管外液膜的流动速度越快;在降膜液柱所在的截面处,液膜周向速度随周向角的增大而增大;在相邻降膜液柱的中间截面处,液膜周向速度随周向角的增大而增大,在30°~110°周向角内液膜周向速度快速增加,在120°~150°周向角内液膜周向速度变化较为平缓。

The calculation model of cold-state falling film flow outside horizontal tubes is established by volume of fluid（VOF）method. The distribution rules of liquid film thickness and velocity outside horizontal tubes under the flowing cold-state falling film condition are studied. Effects of sprinkle density, cross section position and distance from wall on velocity field are analyzed. The results of numerical calculation show that the flow velocity of liquid film outside horizontal tubes increases with the increasing sprinkle densities. The circumferential velocity of liquid film increases with the increasing circumferential angle at the cross section of falling film column. Moreover, the circumferential velocity of liquid film at middle cross section between adjacent falling film columns shows an ascending tendency with the increasing circumferential angle. The circumferential velocity of liquid film increases fast with the angle in the range of 30° to 110°, while the circumferential velocity of liquid film is smoothly changed in the range of 120° to 150°.