Effect of local phenomena on subcooled boiling oscillations in natural circulation boiling loop

In this paper, the authors report the estimations of bubble frequency and oscillation of local void fraction and their role in subcooled boiling oscillations in a low-pressure natural circulation boiling loop. The estimations primarily rely on the measurements of impedance using inductance L-capacitance C-resistance R (LCR) meter. The bubble frequencies determined from the impedance signals and the images are comparable. The effect of inlet subcooling on the bubble frequency and the oscillation of local void fraction has been studied and found to be remarkable. Based on the comparison of the oscillations of local void fraction, local pressure and loop flow rate, the effect of local dynamic phenomena on the system oscillations clearly demonstrates that the oscillations of void fraction trigger high-amplitude flow oscillations with a delay between the oscillations of void fraction and loop flow rate.