Numerical study of detecting crack initiation in a planar solid oxide fuel cell

Abstract

Converting chemical energy into electricity is done by an electrochemical device known as a fuel cell. Thermal stress is caused by high operating temperature, between 700 and 1,000 C, of solid oxide fuel cell (SOFC). Thermal stress is the main cause of crack initiation and crack propagation. This phenomenon may cause gas leakage, structure instability and cease operation of the SOFC before its lifetime. The aim of this study is to present a method that predicts the initiation of cracks in an anisotropic porous planar SOFC. The coupled governing nonlinear differential equations are solved numerically as for heat transfer, fluid flow, mass transfer, mass continuity, and momentum. An in-house computer code which is based on computational fluid dynamics, computational structural mechanics and extended finite element method is utilized and developed. This code, according to Darcy and Navier-Stokes thermofluid model, determines the temperature and stress distribution. The results show that the highest thermal stress occurs at the upper corners of cathode and at the lower corners of the anode. The maximum temperature occurs at the middle of the electrolyte cathode and electrolyte anode, while the maximum pressure occurs at the middle of the upper and lower section of the anode and cathode. In addition, the thickness of the cathode electrode at the left side is increased by 1.5%. Finally, the crack initiation occurs at the left side between the upper and lower corners of the cathode.

Optimized design of planar solid oxide fuel cell interconnectors

“…In this paper, considering that the gas flow rate in the SOFC fuel gas channel is low and the corresponding Reynolds number is small, the flow state of the fuel gas in the channel can be regarded as laminar flow. In order to depict the momentum conservation in the fuel channel, the Navier-Stokes equations [ 38 ] are used in this paper: where is the divergence of the flux j i for species i , ρ is the density of the medium, is the convective transport term for the species i , and R i is the net production rate of species i due to chemical reactions.…”

Distribution of SOFC thermal stress via helium gas (He) based cooling system

“…One of the different types of fuel cells are solid oxide fuel cell (SOFC). Lately, they drew more attention as a result of their performance and elasticity 2,3 . In addition to that, they function in a wide range of high temperatures, 700°C up to 1000°C.…”

“…M. Promsen et al, 20 studied a novel perception of cooling SOFC stacks with phase variation heat transfer of saturated water with small parasitic energy consumption. Fahs and ghassemi 21 studied thermal stress distribution as well as temperature distribution in the porous electrodes of SOFC in order to detect the site of crack initiation and the type of electrode it acts on. The study was based on matching the temperature and thermal stress.…”