Pore-Scale Simulation of Water Vapor Adsorption in Silica Gel Using the Lattice Boltzmann Method

Articles in Press

Document Type : Full Length Research Article

Authors

1 Applied Multi-phase Fluid Dynamics Laboratory, Iran University of Science and Technology, Tehran, Iran

2 School of Mechanical Engineering Iran University of Science & Technology, Tehran, IRAN

Abstract

This study presents a pore-scale numerical investigation of water vapor adsorption in silica gel using the lattice Boltzmann method (LBM). Five distinct geometric configurations with nearly identical porosity values (~0.56) were simulated to ensure consistent flow conditions and enable a focused analysis of adsorption dynamics. The results demonstrated that fluid flow behavior remained uniform across geometries, with permeability values showing minimal variation. The adsorption process was then examined under varying particle sizes (1.6 to 4.57 μm), inlet concentrations (20 to 40 mol.m^(-3)), and Langmuir isotherm parameters. Among all the examined factors, particle size had the most pronounced influence on adsorption dynamics. Smaller particles (1.6 μm) achieved complete adsorption within 17 μs , while larger particles (4.57 μm) required up to 95 μs, about 5.5 times longer. This delay in larger particles is attributed to their higher internal diffusion resistance, whereas smaller particles, with their greater area-to-volume ratio, enabled faster adsorption and higher mass flux. Conversely, changes in inlet concentration and the absolute values of the Langmuir adsorption and desorption rate constants (adsorption rate k_a altered from 1.47×〖10〗^6 to 1.47×〖10〗^8 with constant adsorption to desorption rate K) had negligible effects on the overall dynamics. These findings highlight that solid-phase diffusion is the dominant mechanism governing adsorption in silica gel, while the influence of isotherm kinetics and external concentration gradients is of second importance. This work contributes to a deeper understanding of mass transfer limitations in porous adsorbents and offers insights for optimizing material design and operating strategies in adsorption-based systems.

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Journal of Heat and Mass Transfer Research

Articles in Press, Accepted Manuscript
Available Online from 08 November 2025

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History

  • Receive Date: 18 August 2025
  • Revise Date: 08 November 2025
  • Accept Date: 08 November 2025

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