An Accurate and Reliable Computational Approach for the Mechanical Stress Analysis of Planar SOFC Stack
The method is tested with a 5-cell planar stack. The 5-cell stack is chosen so that the stress analysis with fine grids for all stack components is also affordable. The stack is of practical dimensions and material components such as the cells, frame, interconnects and glass-ceramic sealants, etc. For typical material combinations of SOFC stack and operation conditions, the stack temperature profiles were generated by a high resolution multi-physics numerical model. The test shows that the error for the maximal stress using coarse grids is limited to the order of 10% in comparison with that with fine grids for all stack components. In other words, the grid matching scheme is confirmed to be a computationally efficient and satisfactorily accurate method for the stress analysis. However, the maximal stress of a stack component evaluated with the commonly adopted method using a free boundary condition for the interested component is one order of magnitude smaller than the correct result. On the other hand, the stress of a stack component evaluated with a stiff boundary condition can be a few orders of magnitude higher than the true result. Clearly, the conventional stress analyzing approach with isolated stack components is prone to produce misleading results.
The proposed stress analysis method is valuable for reliably identifying stack components susceptible to mechanical damage. It can be used to improve the design of SOFC stack and to make informed selections of operating conditions.