Droplet transport in oil/gas and water/gas flow at high gas densities

An isokinetic probe has been built to obtain samples of the gas/droplet flow in oil/gas and water/gas flow. Experiments have been performed at gas densities from 22 to 47 kg/m(3), at superficial gas velocities from 3.5 to 7 m/s, but at only one superficial liquid velocity of 0.25 m/s. Samples obtained show an exponential distribution of droplets above the liquid layer in stratified flow. The liquid distribution along the vertical axis through the pipe centre is remarkably smooth in both cases, and no discontinuity in liquid flux is seen at the transition from the gas/droplet zone to the wave/bubble zone. The determination of the gas-liquid interface is the major source of uncertainty when local droplet fluxes are integrated to give a total droplet mass flow and entrained fraction. However, the wave tops can be detected from quickly increasing pressure fluctuations at the probe tip. The entrained fraction increases with the gas density to the first order and with the gas velocity to the third order. The entrained fraction is almost two times higher in the case of oil/gas than water/gas flow. Velocity profiles are obtained from stagnation pressures indicating a significant increase in gas wall friction due to droplets deposited on the wall, thereby increasing the wall roughness. (C) 2000 Elsevier Science Ltd. All rights reserved.