Two-phase mixing for annular flow in simulated rod bundle geometries

Turbulent mixing rates between adjacent subchannels were obtained at 50 psia for annular flow of air-water mixtures in a simulated square-square rod bundle geometrical array using a tracer technique. The gap spacing was varied by a factor of 5. Mixing rates were found to be flow regime dependent, decreasing exponentially with subchannel mass flux and quality and increasing with gap spacing. Enhanced liquid interchange was measured in the low quality bubble flow regime and high quality annular flow regime. The results presented here are in qualitative agreement with data obtained by other investigators using steam-water at elevated pressures.