Two-phase redistribution in horizontal subchannel flow—turbulent mixing and gravity separation

The redistribution of two-phase flow in two horizontal interconnected subchannels caused by gravity separation and turbulent mixing has been investigated experimentally using an air—water loop. The measured redistribution data included the axial distribution of void fraction and liquid and gas flow rates in the two subchannels. The redistribution data exhibited an asymptotic behaviour, approaching certain flow distributions independent of the inlet distribution. The observed equilibrium distributions were explained as a balance between gravity forces (which tend to cause flow stratification) and turbulent diffusion (which tends to homogenize the two-phase mixture). A constitutive equation for transverse vapour drift, to account for both gravity separation and turbulent diffusion, was presented and a turbulent mixing coefficient was identified. The experimental data were used to obtain the best estimate of the empirical constants.