Analysis of two-phase flow regimes and parameter distribution in 5 x 5 rod bundle using image processing techniques

Abstract

With the recent developments in image processing and analysis, this paper presents bubble characteristics distribution in adiabatic air-water two-phase flow through a 5 × 5 rod bundle. The experiment covered water superficial velocities (Jl = 0.012 m/s – 0.421 m/s) and air superficial velocities (Jg = 0.042 m/s – 0.987 m/s) in which three distinct flow regimes were identified. The flow regime map was compared with existing flow regime transition criteria for vertical rod bundles. Distinct features from the two-phase flow images were extracted to train a classifier model to distinguish between regimes from a separate experiment. The model distinguishes between the bubbly flow regime and others accurately. The void fraction and velocity distributions were also extracted from the R–CCN masked images. Bubble-induced turbulence that was dominant in the subchannel at (Jl = 0.28 m/s) shifted to the outer subchannels and gaps when the flow rate increased (Jl = 0.42 m/s). These methods over-predicted the void faction around the surfaces of the inner rods.