相比于光管，外波纹管的壁面凹凸结构可增加换热面积，从而提高水平管降膜蒸发器的传热特性。准确预测溶液管间流型是提高传热传质性能的关键步骤。建立了水平管降膜实验装置，研究管间距、溶液浓度、管型对降膜流动过程管间流型转变的影响。结果表明：随着雷诺数（Re）的增加，管间流动形态依次出现滴状流、滴柱状流、柱状流和柱片状流和片状流；对于每一种流型转变所对应的Re，外波纹管明显低于光管，并随管间距的增大而增大，随NaCl溶液质量分数的增大而减小；相较于光管，两种外波纹管更易在较低Re下获得各稳定流型。流型转变边界可以通过流体Re与伽利略数（Ga）之间的函数关系式描述。通过拟合实验数据，得到了3种管的流型转变关系式。

Compared with the smooth tube,the external corrugated tube can increase the heat transfer area and improve the heat and mass transfer performance of the horizontal tube falling film evaporator.Accurate prediction of flow patterns between solution tubes is a key step to improve heat and mass transfer performance.In this paper,the tube spacing,solution concentration and tube type flow pattern transition between tubes during falling film flow are studied by establishing a horizontal tube falling film experimental device.The results show that with the increase of Re number,following flow patterns between the tubes appear in sequence: droplet flow,droplet columnar flow,columnar flow,column sheet flow,and sheet flow.For each flow pattern transition,the Re number is clearly lower in the external corrugated tube than in the smooth tube,and increases with the increase of the tube spacing and decreases with the increase of the mass fraction of NaCl solution.Compared with light tube,it is easier for two external corrugated tubes to obtain stable flow patterns at lower Re number.The transition boundary of flow pattern can be described by the function relation between Re number and Ga number of fluid.By fitting the experimental data,the flow pattern transition relation of three kinds of tubes is obtained.

TK213

河北省科技计划项目（14273105D）