液氢空间贮存过程膜态沸腾数值模拟

Numerical simulation on subcooled pool film boiling of liquid hydrogen in microgravity

为实现液氢在空间中安全高效应用,针对微重力条件下液氢膜态沸腾现象,建立了加热细丝浸没在过冷液氢池中的数值计算模型。采用VOF方法捕捉相界面,相变模型选取Lee模型,利用文献中的实验数据验证了模型的准确性。从气泡运动行为和换热特性两方面开展研究,结果发现液体过冷度和重力水平是影响换热机理的两个重要因素。在高重力水平、低液体过冷度的条件下,加热细丝上方持续产生气泡并脱离,随着重力水平的降低,气泡脱离直径和气泡生长时间逐渐增大,流体与壁面间换热量随之降低。在低重力水平、高液体过冷度条件下,气膜附着在加热丝表面不断晃动,没有气泡的产生与脱落现象。对于液体过冷度为2 K,壁面过热度为30 K的工况,气泡是否脱落的临界重力在0.1 g至0.15 g之间。

In order to achieve the safe and efficient application of liquid hydrogen in space,a numerical calculation model for the subcooled film boiling of liquid hydrogen under microgravity is established.The VOF method combined with the Lee model is adopted,and the accuracy of the model is verified by the experimental data in the literature.The results are analyzed from the aspects of bubble behaviors and heat transfer characteristics,and it is found that liquid subcooling and gravity level are two important factors that affect the heat transfer mechanism.Under the conditions of high gravity level and low liquid supercooling,bubbles continue to be generated and detached over the wire.As the gravity level decreases,the bubble detachment diameter and bubble growth time gradually increase,and the heat flux between the fluid and the wall is reduced.Under the conditions of low gravity level and high liquid supercooling,the gas film keeps shaking on the heating wire during the subcooled film boiling,without the generation and release of bubbles.For the condition where the liquid supercooling is 2 K and the wall superheating is 30K,the critical gravity is between 0.1 g and 0.15 g.