Modeling of thermal stresses in a microtubular Solid Oxide Fuel Cell stack

• No cracking of anode and electrolyte was predicted for temperatures lower than 750 °C at the voltage of 0.7 V.
• Risk of cracking damage for the cathode layer was confirmed for working temperature of 750 °C at the voltage of 0.7 V.
• The largest total axial stress of 212 MPa was found for cathodes of the fuel cells at the outer row.

A modeling study was carried out to analyze thermal stresses in a microtubular Solid Oxide Fuel Cell (mSOFC) stack and to estimate thermal expansion of the fuel cells inside the stack. A joint analysis by Computational Fluid Dynamics (CFD) and Computational Structural Mechanics Finite Element Method (FEM) was performed. Temperature profiles generated by the thermo-hydrodynamic model were applied in the thermo-mechanical model to calculate thermal stress distributions in the mSOFC stack. The results yield maximum thermal axial elongation equal to 1.34 mm for the mSOFC stack, while the maximum radial elongation was equal to 0.496 mm. Modeled maximum equivalent (von Mises) stress was equal to 538 MPA in the contact areas of the cylindrical housing and manifold on the fuel inlet side. Based on comparison of the total axial stresses and the residual ones with the material strength it was noticed that the anode and electrolyte layers should not be critically deformed, but there is a risk of damage for cathode layers at chosen fuel cell configurations. A high risk of damage was also noticed for the outer housing, near contact points with manifolds as well as at the air distributor due to large number of cut-outs in the material.