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An accurate 3D model of the relevant components needs to be constructed. If there is enough distance between components, isolated models can be constructed in order to reduce complexity and calculation time.
What is the temperature distribution within the vessel? Do significant local thermal gradients occur or are there large differences between components? Determining the (transient) heat transfer boundary conditions, and thereby the actual temperature distribution is a key part of most FEA analyses. Here we take care to ensure a conservative but credible case, which is either based on flow calculations with CFD, analytical formulas or HTRI results.
The calculated temperature distribution can be used as a boundary condition in the FEA model, together with the other loadings such as pressure and nozzle loads. With an elastic material model, the calculated stresses need to be categorized, it needs to be considered which load is primary (or weight driven) or secondary (displacement limited). It is important to consider which loads should be combined, for instance what is the range for the startup/shut down, or the operating cycle, or does the pressure load always act simultaneously with the thermal loading.
The results from a DRG analysis will always be documented in a detailed technical report. This will include all of the boundary conditions, details of the model setup and the analysis approach, and will be suitable for a rigorous review by a notified body. The report will also make sure that the results are explained to the client in a concise manner to build up to conclusions and practical recommendations.