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arXiv · 2201.13060

Defining the pressures of a fluid in a nanoporous, heterogeneous medium

Olav Galteland·Michael T. Rauter·Kevin K. Varughese·Dick Bedeaux·Signe Kjelstrup
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Abstract

We describe the thermodynamic state of a single-phase fluid confined to a porous medium with Hill's thermodynamics of small systems, also known as nanothermodynamics. This way of defining small system thermodynamics, with a separate set of control variables, may be useful for the study of transport in non-deformable porous media, where presently no consensus exists on pressure computations. For a confined fluid, we observe that there are two pressures, the integral and the differential pressures. We use molecular simulations to investigate and confirm the nanothermodynamic relations for a representative elementary volume (REV). For a model system of a single-phase fluid in a face-centered cubic lattice of solid spheres of varying porosity, we calculate the fluid density, fluid-solid surface tension, replica energy, integral pressure, entropy, and internal energy.

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Olav Galteland, Michael T. Rauter, Kevin K. Varughese, Dick Bedeaux, Signe Kjelstrup. 2022-01-31. Defining the pressures of a fluid in a nanoporous, heterogeneous medium. https://arxiv.org/abs/2201.13060

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