Detailed Multi‐dimensional Modeling of Direct Internal Reforming Solid Oxide Fuel Cells

Abstract

Fuel flexibility is a significant advantage of solid oxide fuel cells (SOFCs) and can be attributed to their high operating temperature. Here we consider a direct internal reforming solid oxide fuel cell setup in which a separate fuel reformer is not required. We construct a multidimensional, detailed model of a planar solid oxide fuel cell, where mass transport in the fuel channel is modeled using the Stefan‐Maxwell model, whereas the mass transport within the porous electrodes is simulated using the Dusty‐Gas model. The resulting highly nonlinear model is built into COMSOL Multiphysics, a commercial computational fluid dynamics software, and is validated against experimental data from the literature. A number of parametric studies is performed to obtain insights on the direct internal reforming solid oxide fuel cell system behavior and efficiency, to aid the design procedure. It is shown that internal reforming results in temperature drop close to the inlet and that the direct internal reforming solid oxide fuel cell performance can be enhanced by increasing the operating temperature. It is also observed that decreases in the inlet temperature result in smoother temperature profiles and in the formation of reduced thermal gradients. Furthermore, the direct internal reforming solid oxide fuel cell performance was found to be affected by the thickness of the electrochemically‐active anode catalyst layer, although not always substantially, due to the counter‐balancing behavior of the activation and ohmic overpotentials.

A short review on the modeling of solid-oxide fuel cells by using computational fluid dynamics: assumptions and boundary conditions

“…For heat transfer, the assumption commonly made is that the radiation effect in the stack is negligible [16]. Considering that heat transfer occurring in SOFC is significantly in conduction or convection mode, the effect of radiation is usually not considered during simulation, especially in planar SOFCs as the amount is comparatively smaller [22][23][24][25][26]. Moreover, in single planar SOFC, heat radiation does not affect the cell.…”

Temperature influence on internal reforming and methane direct oxidation in solid oxide fuel cells

“…Хотя вопрос механизмов реакций риформинга остается открытым и на данный момент не существует единой теории процессов кинетики внутреннего риформинга в ТОТЭ [14], из имеющихся данных можно заключить, что частичное окисление метана рассматривается как более быстрая реакция, нежели MSR [15]. WGS реакция является значительно более быстрой по сравнению с MSR [11,16]. Кроме того, из уравнения Аррениуса известна следующая зависимость скорости реакции r, моль/м 3 •с от температуры:…”

Effects of Methane Pre-Reforming Percentage and Flow Arrangement on the Distribution of Temperature and Thermal Stress in Solid Oxide Fuel Cell

“…), and its low price [2]. However, SOFC operates under high-temperature conditions for a long time, and factors such as uneven temperature distribution inside the cell due to strong endothermic reforming reactions, carbon deposition from hydrocarbon fuel cracking, repeated oxidation-reduction in porous nickel-based anodes, and mismatch of thermal expansion coefficients of the constituent materials further aggravate the instability of cell life [3][4][5][6][7]. In addition, there are complex multi-phase, multi-scale and multi-field coupled transfer processes in the pores and three-phase boundary sites of micro/nanoporous electrodes where electrons, ions, and gases are combined in SOFC.…”

“…There is a local mismatch between the endothermic methane steam reforming reaction rate and the exothermic electrochemical rate [8]. Tseronis et al [3] conducted several parametric studies on the direct internal reforming SOFC employing numerical simulation. It is shown that the cooling effect of the methane steam reforming reaction leads to a significant local temperature drop near the anode inlet and a large temperature difference inside the SOFC.…”

“…To further optimize the reaction rate distribution inside SOFC, it is necessary to explore the reforming reaction mechanism inside SOFC. Most researchers model global homogeneous methane-steam reforming and water-gas shift reaction within porous anodes by the described global reactions and corresponding kinetic reaction methods [2][3][4]9]. Schluckner et al [14] validated the simulation results with experimental data from an industrial-scale SOFC single cell.…”