Single- and two-phase pressure drop through vertical Venturis

Abstract

An experimental investigation of the pressure drops measurements in a Venturi placed in a vertical pipe is achieved. Venturis with diameter ratios equal to 0.4, 0.55, and 0.75 were employed. Differential pressure transducers were used to measure the pressure drop between the Venturi inlet and the throat sections. The void fraction was measured upstream the Venturi using a conductance probe technique. Air and water superficial velocities ranges were chosen to cover single-phase flow and bubbly, slug, and churn flow regimes. The single-phase pressure drop increases with the liquid superficial velocity. The Venturi pressure drop coefficient increases with decreasing the Venturi area ratio. The discharge coefficient increases slightly with this ratio and approaches a value of unity at high Reynolds number. The two-phase flow pressure drop and the multiplier coefficient increase with the gas superficial velocity and with decreasing the area ratio. Dimensionless pressure drop decreases with increasing the liquid to gas superficial velocity ratio and approaches an asymptotic value at high ratio (greater than 10). This value matches the single-phase flow dimensionless pressure drop value at high Reynolds number. The Venturi with area ratio equal to 0.55 was shown to correlate well the two-phase multiplier and the liquid holdup.

Pressure recovery model for gas-liquid two-phase flow across sudden expansions

“…The separated flow approach remains relatively reliable especially considering its popularity for pressure drop modeling. The latter is notably used for the estimation of frictional pressure drop in the straight pipes (Muzychka and Awad, 2010;Sassi et al, 2020, Arabi et al, 2021a, as well as for the estimation of the pressure drop generated by the presence of different kinds of singularity, such as the bend (Azzi et al, 2000;Azzi and Friedel, 2005;Hayashi et al, 2020), the orifice (Zeghloul et al, 2017), the multi-hole orifice (Zeghloul et al, 2018), the gate and ball valves (Zeghloul et al, 2020), the pump valve (Ma et al, 2020), the Venturi (Messilem et al, 2020) or the static mixer (Hosni et al, 2023). The liquid pressure recovery of the model of Chisholm and Sutherland (1969) is calculated using the Borda-Carnot formula based on the momentum equation.…”