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A study on mass transfer modelling in SOFC anode: Comparison of diffusion mass transfer models for estimation of diffusion overpotential

Ramakrishnan P., Sahoo Abanti

Chemical and Process Engineering : New Frontiers

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2023

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Vol. 44, nr 1

art. no. e4

EN

The mathematical approach to SOFC modelling helps to reduce dependence on the experimental approach. In the current study, six different diffusion mass transfer models were compared to more accurately predict the process behavior of fuel and product diffusion for SOFC anode. The prediction accuracy of the models was extensively studied over a range of parameters. New models were included as compared to previous studies. The Knudsen diffusion phenomenon was considered in all the models. The stoichiometric flux ratio approach was used. All the models were validated against experimental data for a binary (CO-CO2) and a ternary fuel system (H2-15 H2O-Ar). For ternary system, the pressure gradient is important for pore radius below 0.6 μm and current density above 0.5 A/cm2. For binary system, the pressure gradient may be ignored. The analysis indicates that the MBFM is identified to be the best performing and versatile model under critical SOFC operating conditions such as fuel composition and cell temperature. The diffusive slip phenomenon included in MBFM is useful in SOFC operating conditions when fuel contains heavy molecules. The DGMFM is a good approximation of DGM for the binary system.

2

Parametric sensitivity of a CFD model concerning the hydrodynamics of trickle-bed reactor (TBR)

Janecki D., Burghardt A., Bartelmus G.

Chemical and Process Engineering

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2016

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Vol. 37, nr 1

97--107

EN

The aim of the present study was to investigate the sensitivity of a multiphase Eulerian CFD model with respect to relations defining drag forces between phases. The mean relative error as well as standard deviation of experimental and computed values of pressure gradient and average liquid holdup were used as validation criteria of the model. Comparative basis for simulations was our own data-base obtained in experiments carried out in a TBR operating at a co-current downward gas and liquid flow. Estimated errors showed that the classical equations of Attou et al. (1999) defining the friction factors Fjk approximate experimental values of hydrodynamic parameters with the best agreement. Taking this into account one can recommend to apply chosen equations in the momentum balances of TBR.

3

Oscillating magnetohydrodynamic flow past a rigid plane wall

Poria S., Mazumdar H. P.

Journal of Technical Physics

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2002

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Vol. 43, no 3

343-350

EN

In this paper, the effects of a magnetic field acting perpendicularly to the direction of an oscillatory, viscous, conducting, incompressible fluid stream past a fixed plane wall is investigated. The problem is first converted to the Stokes second problem by introducing a new coordinate system and prescribing the appropriate forms for the pressure gradient corresponding to two sets of boundary and initial conditions. Solutions to the problem are then obtained by invoking an invariance principle, and computed numerically for different values of a magnetic parameter. The effects of the transversal magnetic field on the velocity profiles are finally discussed.

4

Linked S2 and S1 design with experimental and CFD verification

Waggott J., Maier W.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

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1999

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nr 115

405--412

EN

A precise method of deriving advantageous meridional (S2) flowpath shapes is presented. This design method eliminates radial, or "potential surface" pressure gradients, refines secondary flow, and improves efficiency. The derivation is based on two-dimensional (S1) airfoil or vane shapes and can be applied to most types of turbomachinery. The elimination of radial pressure gradients in high specific speed machines allows the use of airfoils or vanes with less hub to shroud variation. Both CFD calculations and experimental results show that aerodynamic improvements extend far beyond flowpath regions where this design technique is applied.