汽气混合流凝结液膜形成机理研究

Study on Forming Mechanism of Condensate Film of Steam-gas Mixed Fluid

汽气混合流体凝结放热过程中凝结所形成的液膜厚度对换热效果的影响较大,因此通过探讨液膜厚度沿管壁的变化,有利于分析强化换热过程。以圆管为例,对汽气混合流体凝结所形成的液膜机理、沿管壁的分布规律及换热性能进行分析,并建立相应的物理及数学模型。通过给定初始条件进行计算,结果表明:液膜沿管壁向下流动过程中其厚度逐渐增加、换热性能逐渐降低;同时分析了管壁温度、汽气混合流体速度及管径等主要参数对液膜的形成及换热性能的影响,为强化凝结换热过程提供了理论基础。

In the condensation heat transfer process of steam-gas mixed fluid, the liquid film formed by the condensation has a great effect to heat transfer; so the discussion of the changes of the liquid film thickness along the wall was conducive to the enhancement of heat transfer. The mechanism of steam condensation of mixed fluid, the distribution of liquid film along the wall and the heat transfer perform- ance were analyzed, and appropriate physical and mathematical models were established. With the given initial conditions, the results of the calculation indicate that the thickness of the liquid film was gradually increased along the wall flowing down and the heat transfer per- formance gradually reduces; meanwhile the effects of tube wall temperature, vapor-gas mixed fluid velocity and tube diameter on the liquid film formation and the heat transfer performance were analyzed, which provided a theoretical basis for the enhancement of condensation heat transfer process.