Sensitivity analysis of thermal stress in a cathode porous electrode for a planar solid oxide fuel cell

ABSTRACT

A fuel cell is an electro-chemical device capable of converting chemical energy into electricity. High operating temperature of solid oxide fuel cell (SOFC), between 700°C and 1000°C, causes thermal stress. Thermal stress causes gas leakage, structure instability and cease operation of the SOFC before its life time.

The purpose of the current paper is to present a method that predicts the thermal stress distribution in an anisotropic porous cathode of planar SOFC. The coupled governing non-linear differential equations, heat transfer, fluid flow, mass transfer, mass continuity, and momentum are solved numerically. An in-house computer code based on computational fluid dynamics (CFD), computational structural mechanics and finite-element method (FEM) is developed and utilized. The code determines the temperature and stress distribution from the energy, Darcy, Navier–Stokes thermo-fluid model. The code uses the generated data inside the porous cathode in order to obtain the thermal stress distribution.

The numerical results used to determine the areas of high values of stresses were higher than the yield strength of materials. The results show that the highest thermal stress occurs at the upper corners of the cathode electrode and the maximum temperature at the middle of the electrolyte-cathode boundary, where the maximum pressure concentrated at the upper and lower section of the middle part of cathode electrode.

KEYWORDS:

• Solid oxide fuel cell
• computational fluid dynamic
• finite elements method
• thermal stress
• cathode porous electrode