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基于双边界层理论,考虑气膜内诱导速度、气液界面剪切力和压力梯度等因素的影响,建立了在水平管外汽-气凝结换热过程中所形成气膜厚度的数学模型,并讨论了气膜分离情况.结果表明:沿管壁向下,气膜厚度逐渐增大;当气膜发生分离时,气膜厚度在分离点处急剧增大,且随流速增大而减小;当气膜不发生分离时,气膜厚度在管壁底部附近急剧减小,且随流速增大而增大;气膜厚度随壁温升高而增大,随不凝结气体质量分数增大而增大;气膜厚度及气膜分离对换热特性有一定的影响.
Based on the theory of double boundary layer, considering the influence of in-film velocity, gas-liquid interface shear force and pressure gradient, the mathematical model of the gas film thickness formed during the horizontal tube vapor-air condensation heat transfer was established. And the situation of gas film separation is discussed.The results show that the thickness of gas film increases along the downward direction of the pipe wall.When the gas film is separated, the thickness of gas film increases sharply at the separation point and decreases with the increase of flow rate When the gas film does not separate, the thickness of the gas film decreases sharply near the bottom of the tube wall and increases with the increase of the flow rate. The thickness of the gas film increases with the increase of the wall temperature. With the increase of the non-condensable gas mass fraction While the thickness of the gas film and the separation of the gas film have a certain influence on the heat transfer characteristics.