Experiment on the Excitation of Vapor Behavior and the Vibration by Thermal Flow Under C-Tube Pool Boiling Model

As an important safety equipment in nuclear system, the passive residual heat removal heat exchanger (PRHR HX) with C-tube is responsible for timely removing heat from the reactor core in accident. A C-tube heating device was setup to investigate the flow characteristics of the in-containment refueling water storage tank (IRWST), which is of the PRHR HX shell-side flow field and the vibration characteristics of the heat exchanger tube. The temperature of the flow field and the acceleration signal of the C-tube were measured. The C-tube frequency in the pool boiling condition is 0–0.660 Hz. There is no resonance with the first natural frequency of 8.98 Hz. The IRWST temperature field can be divided into slow-heating period, fast-heating period, and boiling period. Steam vapor exists in three periods, condensation and collapse of vapor concentrate on horizontal tube. The fast-heating period exists the subcooling degree ΔT_sub for the most intense vapor excitation, ΔT_sub is in the range of 13–16 °C. In term of thermal flow excitation vibration, the existence of the cross flow with C-plane direction is in the transition period from the slow-heating period to the fast-heating period, which excites the maximum root mean squares (RMS) amplitude 0.039 mm and 0.034 mm at the midpoint of upper horizontal tube and vertical tube. When the fluid enters fast-heating period, the direction of flow changes into the normal C-plane. Normal RMS amplitude reached maximum 0.02 mm at upper 1/4 of the vertical tube in boiling period. The above research provides important data support for the safety and reliability of PRHR HX.