水平管外降膜流动液膜厚度的测量及分析

MEASUREMENT AND ANALYSIS OF THE THICKNESS DISTRIBUTIONS OF FALLING LIQUID FILMS AROUND HORIZONTAL TUBES

应用双极电导探针技术对水平管外无传热时的降膜流动的液膜厚度分布及其变化特性进行了实验研究。试验段水平管管径为φ25.4 mm,长为300 mm,液膜流量范围为Q=50～250 L·h^(-1),水平管之间的垂直管间距分别为25mm、32 mm、40 mm。测量了不同流量、管间距变化条件下的液膜厚度分布,重点分析了流量变化、管间距变化、周向角度变化以及轴向距离变化对水平圆管外液膜厚度分布的影响。

An experimental investigation on the flow characteristics of falling liquid film outside horizontal tubes under conditions of no heat exchange have been performed in the present study.A bi-polar type conductivity probe was constructed based on the conductance theory,and was used to measure the film thickness distributions of the falling film around horizontal tubes under different conditions.The test section was made up of copper tube with a diameter of 25.4 mm,and a length of 300 mm.The experimental conditions were as follows：the flow rate Q = 50～250 L·H^（-1） and the vertical gap between horizontal tubes h=25,32,40 mm,respectively.Effects of the film flow rate,the vertical gap between tubes,the circumferential positions and the axial positions on the falling film thickness distribution around horizontal tubes were verified,and some conclusions were reached.