Evaporation with the formation of chains of liquid bridges

Abstract

OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in : http://oatao. The objective of the present work is to study the drying of a quasi-two-dimensional model porous medium, hereafter called the micromodel, initially filled w ith a pure liquid. The micromodel consists of cylinders measuring 50 µm in both height and diameter, radially arranged as a set of neighbouring spirals and sandwiched between two horizontal flat p lates. A s d rying p roceeds, a ir i nvades t he p ore space and elongated liquid films t rapped b y c apillary f orces f orm a long t he s pirals. These films c onsist o f ' chains' o f l iquid b ridges c onnecting n eighbouring c ylinders. They provide hydraulic connectivity between the central bulk liquid cluster and the external rim of the cylinder pattern, where evaporation takes place during a first constant-evaporation-rate drying stage. The first g oal o f t he p resent p aper i s to describe experimentally the phase distribution during drying, notably the evolution of liquid films, w hich c ontrols t he e vaporation k inetics ( e.g. t he d epinning o f t he films from the external rim signals the end of the constant-evaporation-rate period). Then, a viscocapillary model for the drying process is presented. It is based on numerical simulations of a liquid film c apillary s hape a nd v iscous fl ow wi thin a fil m. The model shows a reasonably good agreement with the experimental data. Thus, the present study is a step towards direct modelling of the effect of films o n t he drying of more complex porous media (e.g. packing of beads) and should be of interest for multiphase flow a pplications i n p orous m edia, i nvolving t ransport w ithin l iquid films.

Drying of a Compressible Biporous Material

“…Since here there are no small pores, this signal likely finds its origin in some liquid films remaining along the previously emptied pores, and ensuring the hydraulic connection between filled pores and the free surface of the sample. Such a connection is indeed necessary to ensure a constant drying rate [30]. Although here the shape of the hydraulic network is more complex, the drying process observed is finally similar to the drying of a single channel (filled with liquid) taking the form of a progressive penetration of a large air finger leaving liquid films behind along some channel walls [24,31,32].…”

Lattice Boltzmann Modeling of Drying of Porous Media Considering Contact Angle Hysteresis

“…Liquid films at corners of porous media can enhance the drying process (Yiotis et al 2004;Prat 2007;Wu et al 2020;Laurindo and Prat 1998). Pore size and its distribution affect without surprise the drying pattern and drying rate significantly (Pillai et al 2009;Chen et al 2018;Qin et al 2019a;Wu et al 2016;Lehmann et al 2008). Surface conditions, such as air velocity, affect the diffusive boundary layer thickness, which significantly influences the drying rate (Shahraeeni et al 2012).…”

Study of non-isothermal liquid evaporation in synthetic micro-pore structures with hybrid lattice Boltzmann model

“…When smaller-pore layer was exposed, both the smaller-pore layer (due to evaporation) and larger-pore layer (due to capillary pumping) dried out and the evaporation rate was bilinear. Most recently, Chen et al (2017Chen et al ( , 2018) studied how to control drying kinetics by designing three different pore size distributions in micro-sized porous media. They demonstrated two types of control, i.e.…”