气汽混合流体凝结液膜传热特性研究

Research of condensation heat transfer of liquid film for gas-vapor mixtures

中文关键词: 气汽混合流体  凝结 传热  管型 液膜厚度

英文关键词: gas-vapor mixtures  condensation  heat transfer  tube type  liquid film thickness.

中文摘要:

      液膜厚度对凝结传热具有较大影响,且传热管管型影响着凝结液膜形成及排除,为了通过改变管型降低液膜厚度达到强化传热的目的,对圆管、椭圆管及滴形管等三种管型凝结液膜建立了相应的物理及数学模型,并计算了液膜沿管壁的厚度分布及传热系数。分析了三种管型对液膜传热的影响。结果表明,在气汽混合流体凝结传热过程中,不同管型其凝结液膜厚度差别较大；壁面温度和混合流体速度对液膜传热均有影响；相同条件下滴形管管壁上所形成的液膜,其平均厚度较薄,传热系数较高,因此滴形管传热性能优于其它管型。

英文摘要:

      Film thickness has a great impact on the condensation heat transfer and the type of heat exchange tube affects the condensing film formation and liquid drainage. In order to enhance heat transfer by reducing the film thickness via changing the tube type, appropriate physical and mathematical models of the liquid film outside three special tube types of circular, oval and drop-shaped tubes were established. The liquid film thickness distribution and heat transfer coefficient along the tube wall were calculated. The effects of three kinds of tube type on the liquid film heat transfer were analyzed. The results show that the tube type has enormous influence on film condensation heat transfer characteristics in the condensation heat transfer process of gas-vapor mixtures. Both tube wall temperature and gas-vapor mixture velocity have significant influence on the heat transfer. On the drop-shaped tube wall, there is a thin film thickness and a high heat transfer coefficient, thus the drop-shaped tube has the best heat transfer characteristics.