Thermo-Hydraulic Behavior of Inverted Two-Phase Flow

以氟利昂113为实验流体，对不同直径的竖直和水平流道中的倒置两相流进行了实验研究。结果表明：(1)倒置两相流有三种流型，即倒置环状流、液塞流动和过热分散流。(2)在热平衡质量小于零的区域出现倒置环状流，在0~0.1之间出现液塞流动。(3)过热分散流与干涸后条件下的过热分散流相同。(4)液塞流动的努塞尔数与零质环状流的努塞尔数重合，随着热平衡质量的增加而线性增加，并与雷诺数的平方成正比。在n…的本构方程中，从未考虑过热非平衡条件下的热工水力行为对瞬变两相流进行数值分析，这对轻水反应堆的安全分析具有重要意义。在过冷液体和过热蒸汽出口的同一截面上，倒置环状流具有较大的热非平衡态。因此，本文对倒置环状流进行了二次研究，建立了基于热力非平衡条件下热工水力行为的基础数据，并对其进行了模拟。结果表明：(5)对于水平流，倒置环状流的努塞尔数与雷诺数的0.35成正比，而对于垂直流，则与雷诺数无关。(6)水平流的努塞尔数随壁面过热度和热平衡质量的增加而指数下降。随着流动直径的增大，与过热有关的功率绝对值增大，而与热平衡质量有关的功率绝对值减小。(7)建立了汽膜厚度的基础数据，这对于模拟界面的质量、能量和动量传递是非常重要的。(8)倒置环状流与液单相流的摩擦系数不是由汽膜厚度与流径之比决定的，而是由厚度决定的。当厚度小于0.4 mm时，乘数小于1。较少

Inverted two-phase flow was investigated experimentally in vertical and horizontal flow channels with various diameters using Freon 113 as a test fluid.The folloving are clarified:(1) Inverted two-phase flow has three flow regimes, which are inverted annularflow, liquid slug flow and superheated dispersed flow.(2) Inverted annular flow appears in the region where thermally equilibrium quality is less than zero, liquid slug flow occurs in the region where it is between zero and 0.1, and superheated despersed flow is formed in the region where it is more than 0.1.(3) Superheated dispersed flow is the same as the one under post-dryout conditions.(4) Nusselt number of liquid slug flow coincides the one of inverted annular flow at zero quality, increases linearly as increasing the thermally equilibrium quality and is proportion to the square of Reynolds number.The thermo-hydraulic behavior under thermally non-equilibrium conditions has never been understood in the constitute equations for n … More umerical analysis of transient two-phase flow, which is important for safety analysis of light water reactors. Inverted annular flow has thermally large non-equilibrium state in the same flow cross section where subcooled liquid and superheated vapor exit. Therefore, inverted annular flow was taken up secondly to produce the fundamental data base on the thermo-hydraulic behavior under thermally non-equilibrium conditions and to model it.From these results, the following are clarified:(5) Nusselt number of inverted annular flow is proportion to 0.35th of Reynolds number for the horizontal flow but is independent of it for the vertical flow.(6) Nusselt number of the horizontal flow decreases exponentialy as increasing wall superheating and thermally equilibrium quality. As increasing the flow diameter, the absolute values of the power concerning superheating increases but the one concerning thermally equilibrium quality decreases.(7) The fundamental data base on vapor film thickness is produced, which is very important for modeling mass, energy and momentum transfer from the interface. The empirical correlation of the thickness is proposed.(8) The frictional multiplier of inverted annular flow to liquid single phase flow is not correlated by the ratio of the vapor film thickness to the flow diameter but by the thickness. The multiplier is less than 1 lor the thickness less than 0.4mm. Less