A parametric study of the heat and mass diffusion dimensionless parameter in SOFC with DIR by lattice Boltzmann method
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A parametric study of the heat and mass diffusion dimensionless parameter in SOFC with DIR by lattice Boltzmann method Mehdi Rahimi Takami1 · Davood Domiri Ganji1 · Mojtaba Aghajani Delavar1 · Shahriar Bozorgmehri2 Received: 21 December 2019 / Accepted: 29 August 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract In the present study, the lattice Boltzmann method (LBM) is employed to study the diffusion phenomenon in solid oxide fuel cell (SOFC) with direct internal reforming (DIR). The main focus of this work is to correlate and estimate the diffusion coefficient through dimensionless numbers, i.e., Schmidt and Prandtl. This work tries to reveal the importance of reforming and electrochemical reactions on these dimensionless numbers in active and inactive zones. In addition, the effects of inlet velocity (Re number), steam-to-carbon ratio (S/C) of inlet flow, current density, and porosity were investigated to disclose their importance on diffusion phenomena. A lattice Boltzmann method is used for numerical simulation of diffusion phenomenon in porous media of anode. Our results show that the Schmidt and the Prandtl numbers could be used for high precision estimation of the diffusion process in SOFC. It is also found that the molar ratio variation in hydrogen and water is highly effective since their diffusion characteristics are significantly different from other gases. By changing in operating parameters, the variation in the Prandtl number is much greater than the reforming reactions due to electrochemical reactions. Our results indicate that the Schmidt number of hydrogen increases by 53%, and the Prandtl number decreases about 45% at the center of SOFC when the porosity decreases about 25%. Keywords Heat and mass transfer · Porous media · Solid oxide fuel cell · Lattice Boltzmann method · Schmidt number · Prandtl number List of symbols c Discrete lattice velocity C Molar concentration (mol m−3) Di,eff Overall effective diffusion coefficient of species (m2 s−1) Di,j Diffusion coefficient between species i and species j (m2 s−1) Di,m Mass diffusion coefficient for species i in the mixture (m2 s−1) Dk Knudsen diffusion (m2 s−1) E Equilibrium voltage (V) Eo Reversible potential (V) Eact,a Activation energy of anode (J mol−1) Eact,c Activation energy of cathode (J mol−1) fk Distribution function * Mehdi Rahimi Takami [email protected] 1
Department of Mechanical Engineering, Babol Noshirvani University of Technology, Babol, Iran
Renewable Energy Department, Niroo Research Institute (NRI), Tehran, Iran
2
fk Local equilibrium distribution function F Faraday constant (9.6485 * 104 C mol−1) Fk External force jo Exchange current density (A m−2) k Lattice model direction K+ Velocity coefficient of forward reaction K− Velocity coefficient of backward reaction Keff Effective thermal conductivity (W m−1 K−1) Kf Fluid media heat conductivity coefficient (W m−1 K−1) Ks Porous media heat conductivity coefficient (W m−1 K−1) L Thickness of electrolyte (μm) M Molecular mas
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