Experiments and modelling of near-horizontal bubbly flow

Abstract

This work aims to establish a fast and robust mechanistic model framework for predicting phase fraction profiles in bubbly flows. The main motivation is that the associated closure laws can in the future be used as a basis for a more general gas entrainment model in multiphase flows. Two-phase gas-liquid experiments were conducted in a 212 meter long pipe with an inner diameter of 56.3 mm and a pipe angle of 0.13°. The experiments were conducted with Exxsol D60 oil and Argon gas. The system was pressurized to 12 bara, yielding a gas density of 19 kg/m3. Phase fraction profiles were measured using a vertically traversing gamma densitometer, and bubble sizes were obtained using a CANTY InFlow Particle Sizer system. In addition, pressure transmitters were connected to the pipe facilitating pressure drop measurements. The experiments were performed in the bubbly flow region, where the gas was dispersed as bubbles in the liquid. The model presented in this paper is based on a gravity/turbulent diffusion balance, where the measured bubble size distributions are used as input to the model. The agreement between the model and the data was found to be good, although some discrepancies could be seen. A key model ingredient was found to be the effect of turbulence on the bubble drag. It was also found that the Sauter mean bubble size could be used in place of the bubble size distribution without significant loss of accuracy.