An experimental study of two-phase flow in slightly inclined pipes—II. Liquid holdup and pressure drop

Pressure drop, flow pattern and hold-up measurements of gas–liquid flow in pipes

“…As shown in Figure 9(b), in downward stratified flow at pipe inclination -1°, the liquid hold-up becomes independent of mixture velocity over a wide range of the gas flow rate and is a function of liquid flow rate. This shows a good agreement with the results presented by Kokal and Stanislav [5]. However, the liquid hold-up increases as mixture velocity increases for downwardly inclined flow at pipe inclination -5°.…”

“…However, lower hold-up values are recorded at lower mixture velocities for downwardly inclined flow at pipe inclination -5°. In general, the measured hold-up data shows a good comparison with the results presented by Kokal and Stanislav [5], Andritsos and Hanratty [6]). It must be noted that the experimental procedure for measuring hold-up will give slightly biased results for transient flows, like slug flow in upwardly inclined pipes.…”

Liquid layer characteristics in gas–liquid flow in slightly inclined pipes: Effect of non-ionic surfactant additives

“…As the subjective judgement of the researcher affects the definition of each flow pattern, different researchers may recognize different types of flow regimes under the same flow conditions (Taitel and Dukler, 1976;Kokal and Stanislav, 1989). The flow pattern determination is considered a first step towards developing two-phase flow models that predict liquid layer characteristics.…”

“…The experimental studies of Barnea et al (1980), Kokal and Stanislav (1989) and Grolman et al (1996) indicate that lower liquid flow rates are required to generate slugs in upflows compared to the horizontal case. The stratified region in a flow regime flow map (using the superficial gas and liquid velocities as coordinates) shrinks to a small bell-shaped area for an inclination of only 1 • (Grolman et al, 1996), while for inclination angles larger than 10 • , stratified flow is not observed (Barnea et al, 1980).…”

Bubble shape in horizontal and near horizontal intermittent flow

“…More researchers, such as Nicholson et al (1978), Kokal and Stanislav (1989), Taitel and Barnea (1990) improved the steady state slug flow models by employing the unit cell concept. It is assumed that liquid slugs and gas bubbles have constant lengths.…”