Experimental study on transient flow fluctuation characteristics in a 3 × 3 rod bundle under rolling condition

Abstract

Abstract Experimental investigation on adiabatic transient flow fluctuation characteristics in a 3 × 3 rod bundles subjected to rolling motion in normal pressure and temperature was carried out. Single-phase flow as well as gas parameters under stagnant liquid condition were concerned. Ranges of liquid Reynolds number and gas flow rate were 657–3 328 and 0.079–0.2 m3/h, respectively. Rolling period and amplitude range from 8 s to 16 s and from 5° to 15°, respectively. Fluctuation amplitudes of transient parameters such as flow rate, pressure drop, void fraction and gas rising velocity were focused on this study. The results indicate that flow rate and frictional pressure drop present obvious fluctuations after rolling motion, and the fluctuation amplitudes decrease with the decrease of bypass valve opening. Flow rate reaches to peak at the positive rolling amplitude and it reaches to trough at the negative rolling amplitude, and there is no obvious phase difference between the fluctuation and rolling angle. Periodical fluctuation of gas flow rate was weakened with the increase of gas inlet pressure and valve opening under experimental conditions, while the variations of void fraction and gas rising velocity were limited. Transient parameter fluctuations correspond to the rolling period at low gas flow rate, whereas their periodical fluctuations are inconspicuous in relative high gas flow rate. Amplitudes of void fraction and gas rising velocity increase with increasing the rolling amplitude while the amplitudes of void fraction and gas rising velocity are nearly invariable with the rolling period no matter if gas flow rate oscillates.