Modeling the effect of bubbles on a pattern and heat transfer in a turbulent polydisperse upward two-phase flow after sudden enlargement in a tube

In this work, the numerical modeling of the flow pattern and heat transfer in a polydisperse bubbly turbulent flow after sudden enlargement in a tube is performed. The pattern of average and fluctuation two-phase flows at small volumetric gas flow rate ratios $(\beta \le 10\%)$ is qualitatively similar to the one-phase liquid flow pattern. It is shown that small bubbles are present almost throughout the entire cross section of a tube, while great bubbles generally pass through the flow core and the shear mixing layer. The addition of air bubbles to a one-phase liquid flow appreciably intensifies heat transfer (up to two times), and these effects become stronger with an increase in the diameter of bubbles and the volumetric gas flow rate ratios gasratios.