Effects of compressibility and wetting on the liquid-vapor transition in a confined fluid

TL;DR

This paper develops an analytic model to understand how compressibility and wetting influence the liquid-vapor transition in confined fluids, extending previous numerical approaches to include partial wetting effects.

Contribution

It introduces a new analytic formulation valid for any fluid and wetting condition, incorporating the Berthelot-Laplace length to quantify finite volume effects on phase equilibrium.

Findings

The model captures the effects of compressibility and wetting on phase stability.

A single non-dimensional parameter determines the finite volume effects.

The approach generalizes previous numerical corrections to an analytic framework.

Abstract

When a fluid is constrained to a fixed, finite volume, the conditions for liquid-vapor equilibrium are different from the infinite volume or constant pressure cases. There is even a range of densities for which no bubble can form, and the liquid at a pressure below the bulk saturated vapor pressure remains indefinitely stable. As fluid density in mineral inclusions is often derived from the temperature of bubble disappearance, a correction for the finite volume effect is required. Previous works explained these phenomena, and proposed a numerical procedure to compute the correction for pure water in a container completely wet by the liquid phase. Here we revisit these works, and provide an analytic formulation valid for any fluid and including the case of partial wetting. We introduce the Berthelot-Laplace length $\lambda=2\gamma\kappa/3$, which combines the liquid isothermal compressibility $\kappa$ and its surface tension $\gamma$. The quantitative effects are fully captured by a single, non-dimensional parameter: the ratio of $\lambda$ to the container size.