Modeling of a Tubular‐SOFC: The Effect of the Thermal Radiation of Fuel Components and CO Participating in the Electrochemical Process

Abstract

A mathematical model based on first principles is developed to study the effect of heat and electrochemical phenomena on a tubul solid oxide fuel cell (SOFC). The model accounts fordiffusion, inherent impedance, transport (momentum, heat and mass transfer) processes, internal reforming/shifting reaction, electrochemical processes, and potential losses (activation, concentration, and ohmic losses). Thermal radiation of fuel gaseous components is considered in detail in this work in contrast to other reported work in the literature. The effect of thermal radiation on SOFC performance is shown by comparing with a model without this factor. Simulation results indicate that at higher inlet fuel flow pressures and also larger SOFC lengths the effect of thermal radiation on SOFC temperature becomes more significant. In this study, the H2 and CO oxidation is also studied and the effect of CO oxidation on SOFC performance is reported. The results show that the model which accounts for the electrochemical reaction ofCO results in better SOFC performance than other reported models. This work also reveals that at low inlet fuel flow pressures the CO and H2 electrochemical reactions are competitive and significantly dependent on the CO/H2 ratio inside the triple phase boundary.

Three-Dimensional Modelling of a Microtubular SOFC: A Multiphysics Approach

“…The DGM will account for Knudsen diffusion, simulating the interaction between species and the pore walls and the associated losses. Interestingly, the Fuller Equation [23] has an error of 5.1% which will result in some deviation (29). Error from experimental data must also be considered.…”

“…However, the diffusivity of the gases is limited by the pores in the anode and cathode. Therefore, an effective diffusivity is used and is given by: [24] The DGM differs by considering an alternative effective diffusivity, combining the binary diffusivity in Equation [23] with the Knudsen diffusivity below: [24] Where d is diameter [m], T is temperature [K], ɛ is porosity [-]. Adjusting for the porosity, ɛ, as well as permeability, τ, in the following weighting equation:…”

“…The SMM is therefore used as a precursor to the DGM implementation for comparison in later research. Equations are solved in the gas channels and the porous electrodes: [21] where D is the diffusion coefficient [m 2 /s], M is the molar mass [kg/kmol], and the diffusivity is given by: [22] The binary diffusivity of the gases are calculated using the Fuller equation for both the anode and cathode gas channel ( 27): [23] where V is the diffusion volume [m 3 ], P is the pressure [Pa], and τ is the tortuosity [-]. However, the diffusivity of the gases is limited by the pores in the anode and cathode.…”

“…However, the diffusivity of the gases is limited by the pores in the anode and cathode. Therefore, an effective diffusivity is used and is given by: [24] The DGM differs by considering an alternative effective diffusivity, combining the binary diffusivity in Equation [23] with the Knudsen diffusivity below:…”

Three-Dimensional Modelling of a Microtubular SOFC: A Multiphysics Approach

“…The DGM differs by considering an alternative effective diffusivity, combining the binary diffusivity in Equation [23] with the Knudsen diffusivity below:…”