Drift-flux model for dispersed adiabatic and boiling two-phase flows in rectangular channels

Numerous industrial components and production processes encounter two-phase flows in rectangular channels. The drift-flux model, mathematically expressed in terms of the drift-flux parameters, such as the drift velocity and distribution parameter, is often utilized to solve two-phase flow problems. The constitutive equations of the drift-flux parameters have been limitedly developed and assessed for dispersed two-phase flows in rectangular channels. This study discusses the effects of geometrical parameters, such as the characteristic length and aspect ratio of a rectangular channel, on dispersed two-phase flow parameters. For the flow conditions of collected data in rectangular channels, it was observed that the hydraulic diameter was appropriate as the characteristic length scale for the drift velocity calculation since the drift flux correlation using the hydraulic diameter correlated better with experimental data. The asymptotic distribution parameters in the constitutive equation of the distribution parameter were approximated to be 1.35 and 1.20 for rectangular channel aspect ratios less than 0.25 and greater than 0.33, respectively. Due to the lack of data, the asymptotic distribution parameters were tentatively determined based on a linear interpolation scheme between 1.35 and 1.20 for the aspect ratios between 0.25 and 0.33. The constitutive equations of the drift-flux model were assessed using the collected data with various fluids, pressures, and flow conditions. The constitutive equations of the drift-flux model could predict the void fractions with negligible bias and random uncertainty of +/- 0.0358 and +/- 0.0434 (absolute value measure) and +/- 13.9 % and +/- 8.72 % (relative value measure) for adiabatic and boiling two-phase flows in rectangular channels, respectively.