Measurements of local droplet velocities in horizontal gas-liquid pipe flow with low liquid loading

Abstract

New data on streamwise droplet velocity profiles for low liquid loading pipe flows are reported. The fluids used in the experiments are SF6 (gas-phase) and Exxsol D60 (oil-phase). Experiments are conducted in a 10 cm pipe diameter high-pressure (∼780 kPa, absolute) flow loop to reproduce gas-condensate field conditions. Instantaneous streamwise velocity data, obtained using the non-intrusive Laser Doppler Anemometry (LDA) technique, are used to calculate mean and root-mean-squared (RMS) local velocities. Asymmetric droplet velocity profiles with respect to the pipe center-line are observed especially for the stratified low atomization flow conditions. However, as the flow momentum increases, the droplet velocity profiles seem to become more symmetric. Also, these data suggest that, irrespective of the conditions studied, the single-phase gas flow characteristics are preserved closer to the top pipe wall. The data from the LDA imply that the bottom pipe half region is highly influenced by the gas-liquid interfacial characteristics. This results in high streamwise turbulence intensity in the region influenced by the interfacial waves (interfacial turbulence). An isokinetic sampling instrument is also used to measure the local instantaneous dynamic pressure. The dynamic pressure and the locally extracted liquid (droplets) volume rate under isokinetic conditions are used to calculate local fluid velocity. Excellent agreement has been obtained when comparing this calculated local velocity from the isokinetic instrument to the LDA data.