Hydro-thermo-mechanical analysis on high cycle thermal fatigue induced by thermal striping in a T-junction

Turbulent mixing in a T-junction causes thermal striping which is irregular and frequent fluctuation of thermal layer. Thermal striping is a significant thermal problem because it causes unpredicted high cycle thermal fatigue and fatigue cracking in piping systems. Since this phenomenon is hardly detected by common plant instruments due to high frequency and complex mechanism, numerical approaches are indispensable for a precise evaluation. This research was carried out to define a suitable and effective numerical method for evaluating thermal stress and fatigue induced by thermal striping. A three-dimensional hydro-thermo-mechanical analysis was performed based on one-way separate analysis method to find out the characteristics of stress components and its results were compared to the results of a one-dimensional simplified analysis. It was found that the detailed three-dimensional analysis is indispensable because one-dimensional simplified analysis can overestimate or underestimate according to the assumed heat transfer coefficient and cannot estimate the considerable mean stress effects.