Merte Herman
Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109-2125, USA.
Ann N Y Acad Sci. 2006 Sep;1077:629-49. doi: 10.1196/annals.1362.017.
Pool boiling experiments were conducted in microgravity on five space shuttle flights, using a flat plate heater consisting of a semitransparent thin gold film deposited on a quartz substrate that also acted as a resistance thermometer. The test fluid was R-113, and the vapor bubble behavior at the heater surface was photographed from beneath as well as from the side. Each flight consisted of a matrix of three levels of imposed heat flux and three levels of initial bulk liquid subcooling. In many of the total of 45 experiments, steady nucleate boiling was observed from 16-mm movie films, where a large vapor bubble formed and remained slightly removed from the heater surface, with small vapor bubbles growing on the heater surface, and on contact coalescing with the large bubble. Computations of the forces associated with the momentum transfer in this process, which counters the Marangoni convection effects tending to impel the large bubble toward the heater surface, have been completed for all cases where applicable. The modes of pool boiling observed with successive increases in levels of heat flux in microgravity are categorized as: (i) minimum or incipient nucleate boiling; (ii) nucleate boiling with vigorous motion of the bubbles adjacent and parallel to the heater surface, impelled by Marangoni convection effects; (iii) nucleate boiling followed by coalescence with a neighboring large vapor bubble; (iv) partial dryout of the heater surface, in parallel with nucleate boiling; (v) complete dryout. The boundaries between these modes are delineated graphically as a function of the imposed heat flux and initial bulk liquid subcooling, together with the levels of the forces holding the large bubbles, acting as vapor reservoirs, away from the heater surface for the steady nucleate boiling mode.
在五次航天飞机飞行中进行了微重力池沸腾实验，使用的平板加热器由沉积在石英基板上的半透明薄金膜组成，该石英基板还用作电阻温度计。测试流体为R - 113，从加热器表面下方和侧面拍摄了蒸汽泡行为。每次飞行由三个施加热流水平和三个初始整体液体过冷水平的矩阵组成。在总共45次实验中的许多实验中，从16毫米电影胶片中观察到稳定的核态沸腾，其中形成了一个大蒸汽泡，并与加热器表面保持轻微距离，加热器表面上有小蒸汽泡生长，并在接触时与大蒸汽泡合并。对于适用的所有情况，已经完成了与该过程中动量传递相关的力的计算，该力抵消了倾向于将大蒸汽泡推向加热器表面的马兰戈尼对流效应。在微重力条件下，随着热流水平的连续增加观察到的池沸腾模式分类如下：(i)最小或初始核态沸腾；(ii)由马兰戈尼对流效应推动的、与加热器表面相邻和平行的气泡剧烈运动的核态沸腾；(iii)核态沸腾后与相邻大蒸汽泡合并；(iv)加热器表面部分干涸，与核态沸腾同时发生；(v)完全干涸。这些模式之间的边界以图形方式描绘为施加热流和初始整体液体过冷的函数，以及在稳定核态沸腾模式下将作为蒸汽储存器的大蒸汽泡保持在远离加热器表面的力的水平。
