Thermal performances of saturated porous soil during freezing process using lattice Boltzmann method
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Thermal performances of saturated porous soil during freezing process using lattice Boltzmann method Yiran Hu1 · Donghao Zuo1 · Yaning Zhang1 · Fei Xu1 · Bingxi Li1 · Shuang Liang1 Received: 21 September 2019 / Accepted: 6 November 2019 © Akadémiai Kiadó, Budapest, Hungary 2019
Abstract A stochastic growth method for generating the porous soil structure is proposed, and an enthalpy-based lattice Boltzmann phase transition model is introduced. Thermal performance of phase transition in saturated porous soil during freezing is investigated. The effects of thermal diffusivity ratio of porous medium to fluid, difference in specific heat capacity between liquid and solid phase, and porosity of porous medium are investigated. The results show that higher thermal diffusivity ratio will promote the low-temperature propagation and phase interface movement while higher specific heat capacity difference and porosity will hinder the temperature propagation and phase transition from liquid to solid. The solid–liquid interface moves from 39 to 51 mm with the ratio increasing from 2 to 5; the interface position decreases from 51 to 26 mm with the difference increasing from 2000 to 26,000; the interface moves from 59 to 47 mm when the porosity increases from 0.2 to 0.8. Keywords Stochastic growth method · Lattice Boltzmann method · Thermal diffusivity · Specific heat capacity · Porosity List of symbols cs Sound speed Cp Specific heat (J kg−1 K−1) e Discrete velocity f Density distribution function fflu Fluid volume fraction in calculation unit f Body force per unit mass F Force (N) g Temperature distribution function g Gravitational acceleration (m s−2) h Enthalpy distribution function H Total enthalpy ΔH Latent heat in calculation unit L Latent heat of the fluid p Pressure (Pa) q Heat source term R Radius S Specific surface area (m−1) t Time (s) * Yaning Zhang [email protected] * Bingxi Li [email protected] 1
School of Energy Science and Engineering, Harbin Institute of Technology (HIT), 92 West Dazhi Street, Harbin 150001, Heilongjiang, China
T Temperature (°C) u Velocity vector of fluid (m s−1) Greek symbols β Volume expansivity η Thermal diffusivity λ Thermal conductivity (W m−1 K−1) μ Dynamic viscosity (N s m−2) ν Kinetic viscosity ρ Density (kg m−3) ϕ Porosity τ Dimensionless relaxation time ω Mass coefficient Ω Collision term Subscripts b Boundary f Fluid l Liquid phase m Freezing s Solid phase 0 Initial state i Lattice velocity direction eq Equilibrium state ref Reference liq Liquidus pm Porous medium sol Solidus
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Introduction Natural soil is a multi-dispersive porous medium with its particles composed of minerals and organic matter of different shapes and sizes. Relevant studies show that the phase transition of pore fluid during soil freezing is correlated with the pore characteristics of soil [1, 2]. In order to describe the effect of soil pore structure characteristics on the phase transition of soil pore fluid, the pore-scale soil structure
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