Experimental Study of Adiabatic Two Phase Flow in an Annular Channel Under Low Frequency Vibration

Abstract

In order to investigate the possible effect of seismic vibration on twophase flow dynamics and thermalhydraulics of a nuclear reactor, experimental tests of adiabatic airwater twophase flow under lowfrequency vibration were carried out in this study. An eccentric cam vibration module operated at low motor speed (up to 390 rpm) was attached to an annulus test section which was scaled down from a prototypic boiling water reactor (BWR) fuel assembly subchannel. The inner and outer diameters of the annulus are 19.1 mm and 38.1 mm, respectively. The twophase flow operating conditions cover the ranges of 0.03 m/s ≤ م€ˆjgم€‰â€‰â‰¤â€‰1.46 m/s and 0.25 m/s ≤ م€ˆjfم€‰â€‰â‰¤â€‰1.00 m/s and the vibration displacement ranges from آ±0.8 mm to آ±22.2 mm. Steadystate areaaveraged instantaneous and timeaveraged void fraction were recorded and analyzed in stationary and vibration experiments. A neural network flow regime identification technique and fast Fourier transformation (FFT) analysis were introduced to analyze the flow regimes and void signals under stationary and vibration conditions. Experimental results reveal possible changes in flow regimes under specific flow and vibration conditions. In addition, the instantaneous void fraction signals were affected and shown by FFT analysis. Possible reasons for the changes include the applied high acceleration and induced void/flow structure changes at certain ports under the specific flow and vibration conditions.