Vapor flows caused by evaporation and condensation on two parallel plane surfaces: Effect of the presence of a noncondensable gas
Vapor flows caused by evaporation and condensation on two parallel plane surfaces: Effect of the presence of a noncondensable gas
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两个平行平面上蒸发和冷凝引起的蒸气流：不可冷凝气体存在的影响
DOI：
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
S. Kosuge
中科院分区：
文献类型：
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作者：
K. Aoki;S. Takata;S. Kosuge
如果另一种既不蒸发也不在表面上凝结的气体(比方说不可凝结气体)也包含在空隙中，则考虑在其凝聚相的两个平行平面表面之间的空隙中可能发生蒸发或冷凝的蒸汽。在动力学理论的基础上，研究了蒸发面和冷凝面的定常流动以及不凝性气体的行为。首先，通过对Boltzmann方程的系统渐近分析，阐明了较小的Knudsen数(与蒸汽-蒸汽碰撞有关)时的流场基本特征。然后，用直接模拟蒙特卡罗方法对该问题进行了数值分析，得到了在较大的克努森数范围内蒸汽和不凝性气体的稳态行为(如宏观量的空间分布)。特别是，在克努森数趋于零时的极限(关于蒸汽的连续极限)，根据不可凝结气体的量，存在两种不同类型的极限行为，只有当不可凝结气体的平均密度比蒸汽的平均密度小得多时，才能发生蒸发和凝结。
A vapor in a gap between two parallel plane surfaces of its condensed phase, on which evaporation or condensation may take place, is considered in the case where another gas that neither evaporates nor condenses on the surfaces (say, a noncondensable gas) is also contained in the gap. The steady flow of the vapor caused by evaporation on one surface and condensation on the other and the behavior of the noncondensable gas are investigated on the basis of kinetic theory. First, fundamental features of the flow field are clarified for small values of the Knudsen number (associated with vapor–vapor collisions) by a systematic asymptotic analysis of the Boltzmann equation. Then, the problem is analyzed numerically by means of the direct simulation Monte Carlo method, and the steady behavior of the vapor and of the noncondensable gas (e.g., the spatial distributions of the macroscopic quantities) is clarified for a wide range of the Knudsen number. In particular, it is shown that, in the limit as the Knudsen number tends to zero (the continuum limit with respect to the vapor), there are two different types of the limiting behavior depending on the amount of the noncondensable gas, and evaporation and condensation can take place only when the average density of the noncondensable gas is vanishingly small in comparison with that of the vapor.