Modeling the thermal stress of heat transfer tubes with tube support plate gaps in a steam generator

This work presents a three-dimensional “unit pipe” model with and without gaps between tubes and associated tube support plates in a steam generator. The model is used to simulate the thermal-hydraulic characteristics of the steam generator and obtain the distributions of key parameters of the heat transfer tubes, the primary and secondary sides. Using this model, we pass fluid calculation results to the structure through a flow-heat-solid coupling in workbench, conduct thermal stress calculations of the heat transfer tubes, and analyze the influence of gaps on the system's thermal-hydraulic characteristics and resulting thermal stress. The results indicate that there is a rapid change in the secondary side's velocity and heat transfer coefficient at the tube support plates, and that the steam quality and fluid velocity in the gaps is higher and lower, respectively, than in the flood holes. Moreover, the resulting thermal stress experienced by the heat transfer tubes shows a periodic fluctuation around their circumference at the tube support plates, while the thermal stress without gaps at the tube support plates is greater than the thermal stress seen with gaps, and its circumferential volatility is approximately twice the volatility with gaps present.