Characterization of Liquid‐Vapor Interfaces in Pores During Evaporation

Abstract

Liquid-vapor (l-v) interfaces are ubiquitous in porous media under variably saturated conditions and are inevitably engaged in pervasive processes such as multiphase flow, heat and mass transport, the phase change of water during evaporation or freezing. For instance, the competing effects of capillarity and flow viscosity control the percolation pattern of interface distribution between invading and defending fluids in geological CO 2 sequestration and enhanced oil/gas recovery (e.g., Hu et al., 2018;Kazemifar et al., 2015); the local thermocapillary flow occurred on the interfaces in process of liquid evaporation from nanopores plays an important role in natural practices of transpiration in plants and industrial procedures of water desalination (e.g., Lu et al., 2015;Plawsky et al., 2008).In particular, the fundamental mechanism of soil water evaporation is still unconcluded. The enhanced vapor diffusion found in the soil water evaporation process under thermal gradient is highly related to the l-v interface and is of significant importance in hydrology and land-atmosphere interaction (e.g., Philip & deVries, 1957;Shokri et al., 2009). Yet the role of the interface in the vapor transport enhancement mechanisms remains elusive and controversial to be determined (e.g.,

Morphology Characteristics of the Liquid–Vapour Interface in Porous Media

“…a l-v has a small value of 0.058 at the beginning of evaporation (S w = 85.0%) and it keeps increasing nonlinearly until it reaches the peak value of 0.176 around the saturation of 31.7%. The same trend was also found in our experiments with glass beads [10]. The evolution of the internal interface during evaporation of sandy soils is directly investigated and its effect on the evaporation rate can be discussed in relation to the curvature of the interface.…”

“…A single grayscale image is referred to as a slice, and the complete set of slices constitutes a stack. Unlike materials with high purity and smooth surfaces, such as glass beads [10], Ottawa sand is characterized by its irregular shape and rough surface [33,35]. Accurately extracting the liquid-vapour interface requires precise identification of the phase boundaries, where traditional watershed and top-hat techniques struggle to yield ideal results.…”

“…Previous research has extensively investigated interface characteristics such as surface area, curvature, phase morphology, and phase connectivity during processes like CO 2 injection or oil/gas displacement in oil/water or CO 2 /salt interface [7][8][9]. Dong et al [10] utilized interface characteristics to describe the evaporation process of pore water in glass beads. Lin et al [11] employed Gaussian curvature to characterize the evaporation process, using curvature to delineate interface morphologies in oil-wet reservoir rocks, thereby providing pore-scale insights into the dynamics of two-phase fluid flow during oil and gas displacement.…”

“…Therefore, saline solutions are commonly used instead of pure water to enhance contrast and image quality. Dong et al [10] accurately characterized the liquid-vapour interface during evaporation using glass beads as an ideal soil material. In heterogeneous materials, results may show film-like artifacts.…”

Exact Solution for Water Evaporation During CO2 Injection

“…The net rate of transfer of water molecules across the gas‐liquid interface will depend on the interfacial area, a dynamic quantity during evaporation. Descriptions of the interfacial area can be derived from geometric considerations (Niessner & Hassanizadeh, 2009), from percolation/pore network modeling (Tsimpanogiannis et al., 1999), or more recently by direct measurement using X‐ray micro tomography (Dong et al., 2022). The change in the interfacial area over the course of evaporation will result in a transient evaporation rate, which must be accounted for in the mathematical model.…”