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

Abstract

Non-isothermal liquid evaporation in micro-pore structures is studied experimentally and numerically using the lattice Boltzmann method. A hybrid thermal entropic multiple-relaxation-time multiphase lattice Boltzmann model (T-EMRT-MP LBM) is implemented and validated with experiments of droplet evaporation on a heated hydrophobic substrate. Then liquid evaporation is investigated in two specific pore structures, i.e. spiral-shaped and gradient-shaped micro-pillar cavities, referred to as SMS and GMS, respectively. In SMS, the liquid receding front follows the spiral pattern; while in GMS, the receding front moves layer by layer from the pillar rows with large pitch to the rows with small one. Both simulations agree well with experiments. Moreover, evaporative cooling effects in liquid and vapour are observed and explained with simulation results. Quantitatively, in both SMS and GMS, the change of liquid mass with time coincides with experimental measurements. The evaporation rate generally decreases slightly with time mainly because of the reduction of liquid–vapour interface. Isolated liquid films in SMS increase the evaporation rate temporarily resulting in local peaks in evaporation rate. Reynolds and capillary numbers show that the liquid internal flow is laminar and that the capillary forces are dominant resulting in menisci pinned to the pillars. Similar Péclet number is found in simulations and experiments, indicating a diffusive type of heat, liquid and vapour transport. Our numerical and experimental studies indicate a method for controlling liquid evaporation paths in micro-pore structures and maintaining high evaporation rate by specific geometry designs.

Tricoupled hybrid lattice Boltzmann model for nonisothermal drying of colloidal suspensions in micropore structures

“…(8) while δt is the time step in numerical time discretization. For spatial discretization, isotropic central schemes are employed to evaluate the first-order derivative and the Laplacian [66,67]. To model nonisothermal evaporation, the extended temperature equation [ETE, Eq.…”

“…With the coupling model, nonisothermal drying of liquid in various geometries under different temperatures is simulated and compared with experimental and theoretical data in [67], showing high accuracy and stability.…”

“…The temperature difference is dT = T p − T sat = 0.01T c , which is a quite low value. We mention that our model can deal with a tenfold larger temperature difference and remain stable [67]. The reason we use the small temperature difference is to ensure drying mechanisms similar to what occurred in the experiment, i.e., where the capillary force is much more dominant than the viscous force.…”

“…The mechanisms of pure liquid drying have been discussed for similar SMSs in [67] in detail. The nondimensional numbers that describe the mechanisms are Reynolds number for liquid (Re L ) and air (Re V ), and capillary number (Ca) and Péclet number for vapor transport (Pe V ).…”

Viscous Dissipation and Apparent Permeability of Gas Flow in Nanoporous Media

“…LBM is a newly developed mesoscale simulation method which can be derived from the Boltzmann equation. It has been widely used in many areas, such as multiphase and multicomponent flow (Chen et al, ; Huang et al, ; Qin et al, ; Qin et al, ; Qin et al, ; Qin et al, ; Zhao et al, ), reactive flow (Kang et al, ), and thermal flow (Kang et al, ). Due to the high computational efficiency and kinetic physical basis, LBM has also been adopted to simulate pore‐scale shale gas flow in recent years.…”