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基于环状流流型建立了小管径冷凝管的数学模型.模型考虑了气液界面表面张力的作用,在同一横截面上气相与液相存在压力差.对两相压降的计算,考虑了气液两相间的相互作用,包括摩擦切应力和动量转移切应力.应用该模型,可考察气相与液相压降、液膜厚度、气相与液相平均速度、气液界面切应力以及管内壁换热系数等的沿程变化情况.根据模拟结果可得:两相压降沿管长呈近似线性增加;气相平均速度沿管长先增大后逐渐减小,但变化范围很小,且远大于液相平均速度;动量转移切应力随液膜厚度增加而增大,同摩擦切应力相比不可忽略;管内壁对流换热系数随液膜厚度增加而减小,由于冷凝管的管径很小,即使蒸气冷凝趋于完毕,气液界面接近冷凝管中心线,换热系数仍较大.
Based on the annular flow pattern, a mathematical model of small-diameter condenser is established.The model considers the effect of surface tension on the gas-liquid interface and the pressure difference exists between the gas phase and the liquid phase on the same cross-section. The interaction between gas-liquid two-phase, including friction shear stress and momentum transfer shear stress, can be used to study the relationship between gas phase and liquid pressure drop, liquid film thickness, gas and liquid average velocity, shear stress at gas- Wall heat transfer coefficient, etc. Based on the simulation results, it can be seen that the pressure drop along the two phases increases approximately linearly along the pipe length. The average velocity of the gas phase decreases first along the pipe length but decreases gradually, and Which is much larger than the average liquid velocity. The shear stress of momentum transfer increases with the thickness of the liquid film, which can not be neglected compared with the shear stress. The convective heat transfer coefficient decreases with the increase of liquid film thickness. Small, even if the vapor condensation tends to be completed, the gas-liquid interface close to the centerline of the condenser, the heat transfer coefficient is still large.