Hołyst Robert, Litniewski Marek
Institute of Physical Chemistry, PAS, Kasprzaka 44/52, 01-224 Warsaw, Poland.
J Chem Phys. 2009 Feb 21;130(7):074707. doi: 10.1063/1.3077059.
We performed molecular dynamics simulations of liquid film evaporation into vacuum for two cases: free evaporation without external supply of energy and evaporation at constant average liquid temperature. In both cases we found that the pressure inside a liquid film was constant, while temperature decreased and density increased as a function of distance from the middle of the film. The momentum flux in the vapor far from the liquid was equal to the liquid pressure in the evaporating film. Moreover the pseudopressure (stagnation pressure) was found to be constant in the evaporating vapor and equal to the liquid pressure. The momentum flux and its relation to the pressure determined the number of evaporating molecules per unit time and as a consequence the mass evaporation flux. We found a simple formula for the evaporation flux, which much better describes simulation results than the commonly used Hertz-Knudsen relation.
无外部能量供应的自由蒸发以及平均液体温度恒定的蒸发。在这两种情况下，我们发现液膜内部的压力是恒定的，而温度随着距液膜中部距离的增加而降低，密度则随着该距离的增加而增大。远离液体的蒸汽中的动量通量等于蒸发膜中的液体压力。此外，发现蒸发蒸汽中的伪压力（滞止压力）是恒定的，且等于液体压力。动量通量及其与压力的关系决定了单位时间内蒸发分子的数量，进而决定了质量蒸发通量。我们找到了一个蒸发通量的简单公式，与常用的赫兹 - 克努森关系相比，它能更好地描述模拟结果。
