Numerical Analysis of Thermal Stress for a Stack of Planar Solid Oxide Fuel Cells

Abstract

In this work, a 3D multi-physics coupled model was developed to analyze the temperature and thermal stress distribution in a planar solid oxide fuel cell (SOFC) stack, and then the effects of different flow channels (co-flow, counter-flow and cross-flow) and electrolyte thickness were investigated. The simulation results indicate that the generated power is higher while the thermal stress is lower in the co-flow mode than those in the cross-flow mode. In the cross-flow mode, a gas inlet and outlet arrangement is proposed to increase current density by about 10%. The generated power of the stack increases with a thin electrolyte layer, but the temperature and its gradient of the stack also increase with increase of heat generation. The thermal stress for two typical sealing materials is also studied. The predicted results can be used for design and optimization of the stack structure to achieve lower stress and longer life.

Thermo-Electro-Chemo-Mechanical Coupled Modeling of Solid Oxide Fuel Cell with LSCF-GDC Composite Cathode

“…The heat generated is predominantly conducted through metallic ribs owing to their large thermal conductivity [ 27 ], and the heat is in turn transported to the inlet gases carried by them. It is also noted that there is a significant temperature difference between the cell and the outside environment, which also causes some of the heat to be radiated from the outer walls through electromagnetic waves [ 23 ]. Thus, the thermal energy balance among heat generated, conduction, convection, and radiation induce inhomogeneities from the midst of the cell towards the surrounding walls.…”

“…Most researchers analyze the stress field of SOFC by comparing the first principal stress because the first principal stress is applied to the analysis of ceramic and metallic systems and can distinguish the maximum tensile and compressive stresses (positive and negative values of stress values represent tensile and compressive stresses) [ 17 , 23 ].…”

“…The momentum transfer process refers to the transfer of momentum from the high-velocity fluid layer to the low-velocity fluid layer or the wall boundary layer. The Navier-Stokes equation is used to describe the momentum transfer process of the gas species inside the SOFC [ 23 ], which is expressed as: where the ρ eff and μ eff are the average density and average kinematic viscosity of the gas mixture, respectively, U is the velocity vector, and S d is the source term.…”

“…As reported by Khan et al [ 22 ], highly coupled fluid flow, chemical/electrochemical reactions, and heat/mass transfer processes complicate the temperature field inside the cell, which could induce thermal stress resulting from the temperature gradient and the mismatch of the TEC (thermal expansion coefficient). Research on thermal stress behaviors of SOFC with the typical Ni-YSZ/YSZ/YSZ-LSM configuration has been carried out with varying degrees of model complexity [ 1 , 23 , 24 , 25 ]. Xu et al [ 24 ] have numerically examined the thermal stress of SOFC (Ni-YSZ/YSZ/LSM) and found that the functional buffer layers can affect the stress between different components and inhibit the extent of degradation.…”

Solid Oxide Fuel Cells with a Thin Film Electrolyte: A Review on Manufacturing Technologies and Electrochemical Characteristicses

“…It was concluded that the cell gas tightness had to be enhanced to increase the lifespan. Moreover, thermal stresses caused by mismatch of thermal expansion between cell components and thermal gradients, which were shown to be significant in the planar SOFCs, can lead to microstructural changes, fractures, and delamination [104][105][106].…”