Analysis and Calculation of Flow-Induced Vibration for Serpentine Finned-Tube Heat Transfer Equipment

In integral fast reactors (IFRs), serpentine finned-tube heat exchangers serve as critical heat transfer components in the decay heat removal system (DHRS), transferring thermal energy from the accident residual heat to ambient air. These serpentine finned tubes function as the critical boundary interface between the sodium coolant and the atmospheric environment, and their structural integrity is paramount to the safe operation of the entire reactor. The heat exchanger tubes in sodium-air heat exchangers are subjected to tube bundle vibration induced by external cross-flow gas impingement, potentially leading to wear, fatigue failure, and even rupture of the serpentine finned tubes. To ensure reactor safety and reliability, flow-induced vibration (FIV) analysis of the heat transfer equipment must be conducted during the design phase. Flow-induced vibration in tube bundles is primarily governed by the flow medium and velocity, tube geometry, and support structure configuration. Currently, three design codes—GB/151, ASME, and TEMA—are available for analyzing flow-induced vibration in tube bundles operating in gaseous environments. However, the computational methods in these codes were developed primarily for conventional working fluids such as water inside heat exchanger tubes, whereas the serpentine finned tubes in this application contain liquid metal sodium. Consequently, the applicability of these codes to sodium-air heat exchangers requires further evaluation. This study employs both design code methodologies and numerical simulation approaches to conduct flow-induced vibration analyses of turbulent buffeting and Kármán vortex shedding for the sodium-air heat exchanger in an integral fast reactor. The vibration frequencies of serpentine finned tubes, external flow velocities, and tube bundle vibration responses are determined to ensure that flow-induced vibration instability will not occur in the sodium-air heat exchanger.