Modeling bubble distribution and heat transfer in polydispersed gas-liquid flow in a backward-facing step

Abstract

Abstract The numerical results on the flow, bubble distributions and heat transfer in a bubbly polydispersed flow in a horizontal duct with a backward-facing step are presented. The numerical model uses the Eulerian approach taking into account the back effects of bubbles on the mean and turbulent characteristics of the carrier fluid phase. The model takes into account the interphase momentum transfer, bubble break-up and coalescence processes. The set of 2D RANS equations is used for modeling two-phase bubbly flows. Turbulence of the carrier fluid phase is predicted using the second moment closure. The method of δ-function approximation is employed for simulation of gas bubble break-up and coalescence. The effect of the gas volumetric flow rate ratios on the flow structure and heat transfer in the two-phase flow is numerically studied. An increase in the gas volumetric flow rate ratios leads to a significant increase in the wall friction coefficient (almost 1.5 times in comparison with the single-phase flow regime). The addition of air bubbles results in a significant increase in the heat transfer rate (up to 50%).