细竖管内流动凝结的换热特性

为探讨小尺度条件下管内流动凝结换热的特性，针对１～５ｍｍ的细圆管，考虑凝结液膜的弯曲、气液界面剪切力与液膜表面张力的影响，建立起柱坐标系下竖直管内受迫流动凝结换热物理数学模型；利用数值求解的结果，对小尺度条件下管内凝结换热的规律进行预测性分析．研究表明，细管径条件下，气液界面切应力与液膜表面张力对流动凝结过程的影响增大，使重力的影响处于相对微弱的地位；与Ｎｕｓｓｅｌｔ换热关联式的预示值相比，小尺度圆管有明显的强化凝结换热的效果．上述结果有助于深化对小尺度下凝结换热规律的理解

Heat Transfer Characteristics for Flow Condensation in Vertical Thin Tube

In order to explore the flow condensation heat transfer characteristics for thin tube, an analytical model was established in cylindrical coordinate system under consideration of the bend effect of condensed film, shear stress on the vapor liquid interface and surface tension of liquid film. With the numerically solved results, the effcts of tube diameter, gravity, shear stress and surface tension on liquid vapor interface on flow condensation were discussed. The analyses indicate that, under small diameter tubes, shear stress and surface tension have greater effects on flow condensation than that of gravity. Also, compared with Nusselt's prediction, thin tube can enhance the condensation heat transfer obviously.