Flow field simulation and fluid-structure coupling analysis of C-tube pool boiling two-phase flow model

As a heat exchanger is an important energy transfer equipment in chemical and nuclear power, the fluid induced vibration (FIV) of the tube bundle becomes an important factor to induce the tube bundle rupture. So the safety and reliability of the tube bundle becomes especially important. In order to study the flow induced vibration response of C-tube in the passive residual heat removal heat exchanger (PRHR HX), the in-containment refueling water storage tank (IRWST) and C-tube were simplified, and the numerical simulation of the flow field and vibration response were carried out. Simulation results showed that the intersection of natural and forced convection in the temperature field caused by the velocity disruption, due to the loss of flow velocity, vapor bubbles can not be flushed, combined and wrapped with tube, resulting in transition boiling, the boiling reduces the heat flux to produce the phenomenon of thermal stratification. According to the fluid flow characteristics, the flow field can be divided into three regions:gas-liquid two-phase hot flow region, hot flow region, cold flow region. Among them, there was high turbulence energy in the gas-liquid two-phase hot flow region, and the steam volume fraction reaches 50%, which made the rapid growth and collapse of steam to provide the disturbance, and the damping ratio of C-shaped tube structure was reduced, so the upper bend at the end away from the solid support became the region with the largest induced vibration. Based on the vibration results, the vibration direction is the C-tube plane, and the position of the upper bend vibrates were most strongly impacted by the gas-liquid two-phase hot flow. Therefore, the tube bundle at this position in PRHR HX was prone to wear with the support and anti-vibration components, and there was a potential risk of tube bundle rupture. © 2023 Chemical Industry Press. All rights reserved.