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. 2020 May 18;10(1):8143.
doi: 10.1038/s41598-020-64905-5.

Evaporation coefficient and condensation coefficient of vapor under high gas pressure conditions

Kotaro Ohashi  1 , Kazumichi Kobayashi  2 , Hiroyuki Fujii  1 , Masao Watanabe  1
Affiliations

Evaporation coefficient and condensation coefficient of vapor under high gas pressure conditions

Kotaro Ohashi et al. Sci Rep. .

Erratum in

Abstract

We investigated the evaporation and condensation coefficients of vapor, which represent evaporation and condensation rates of vapor molecules, under high gas pressure (high gas density) conditions in a system of a vapor/gas-liquid equilibrium state. The mixture gas is composed of condensable gas (vapor) and non-condensable gas (NC gas) molecules. We performed numerical simulations of vapor/gas-liquid equilibrium systems with the Enskog-Vlasov direct simulation Monte Carlo (EVDSMC) method. As a result of the simulations, we found that the evaporation and condensation fluxes decrease with increasing NC gas pressure, which leads to a decrease in the evaporation and condensation coefficients of vapor molecules. Especially, under extremely high gas pressure conditions, the values of these coefficients are close to zero, which means the vapor molecules cannot evaporate and condensate at the interface. Moreover, we found that the vapor molecules behave as NC gas molecules under high gas pressure conditions. We also discussed the reason why NC gas molecules interfere with evaporation and condensation of vapor molecules at the vapor/gas-liquid interface.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Molecular mass fluxes at a vapor/gas–liquid interface. Jcallω denotes the colliding molecular mass flux, Joutω is the outgoing molecular mass flux, Jevapω is the evaporating molecular mass flux, Jcondω is the condensing molecular mass flux, and Jrefω is the reflecting molecular mass flux. ω=V denotes the molecular mass fluxes for vapor molecules at the interface, and ω=G those for NC gas molecules.
Figure 2
Figure 2
(a) Schematic of the present simulation condition (steady vapor/gas–liquid equilibrium). At the center of the system, there is a thin liquid film; (b) Schematic of the molecular fluxes in the vicinity of vapor/gas–liquid interface. We can count the number of molecules using mixture gas and liquid boundaries; Jevapω denotes the evaporating molecular mass flux for ω component molecules, Jrefω the reflecting molecular mass flux, and Jcondω the condensing molecular mass flux.
Figure 3
Figure 3
Number density profiles of each simulation case: (a) vapor component, nVσ3; (b) NC gas component, nGσ3; (c) non-dimensional NC gas pressure pˆG=pGσ3/kT0 as a function of molar fraction of dissolved NC gas molecules μ. Each number near the symbols denotes each case number. The dotted line shows the eye guide (linear relation of the Henry’s law). Macroscopic quantities of Case 8: (d) number density, velocity, and temperature fields; (e) mean-field forces of vapor and NC gas molecules.
Figure 4
Figure 4
Molecular mass fluxes, evaporation coefficient, and condensation coefficient of vapor and NC gas molecules as a function of μ: (a) outgoing, evaporating, and reflecting vapor molecules; (b) colliding, condensing, and reflecting vapor molecules; (c) outgoing, evaporating, and reflecting NC gas molecules; (d) colliding, condensing, and reflecting NC gas molecules; (e) evaporation and condensation coefficients of vapor molecules; (f) evaporation and condensation coefficients of NC gas molecules; (g) evaporating and condensing molecular mass fluxes as the function of Nl−gNC; and (h) schematic of JevapV and JcondV. Due to the collision of molecules between the liquid and mixture gas boundaries, the backscattering for JevapV and JcondV increases.
Figure 5
Figure 5
Molecular velocity distribution function (VDF) normalized to unity at the mixture gas boundary (the position to impose KBC): (a) vapor of Case 1; (b) NC gas of Case 1; (c) vapor of Case 8; and (d) NC gas of Case 8.
Figure 6
Figure 6
Non-dimensional number of reflecting molecules at the interface: (a) definition of reflect position of reflecting molecules between mixture gas and liquid boundaries; (b) non-dimensional number of reflecting molecules in Case 1; (c) non-dimensional number of reflecting molecules in Case 8; (d) non-dimensional stall time of reflecting for vapor and NC gas molecules in Case 1; (e) non-dimensional stall time of reflecting vapor and NC gas molecules in Case 8.
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