Comparison of disturbance wave parameters with flow orientation in vertical annular gas-liquid flows in a small pipe

Thin film thickness measurements in two phase annular flows using ultrasonic pulse echo techniques

“…Increasing gas flowrate increases the interfacial shear and the frequency and velocity of these small waves resulting in a higher degree of coalescence and the formation of a higher frequency of disturbance waves. These results are consistent with the the work of Chu and Dukler [50], Azzopardi [46] and Vasques et al [9]. The ultrasonic technique and concentric conductance probe technique also showed excellent agreement in term of the mean film thickness measurement with a relative deviation less than ±5% between them.…”

“…Annular flow generally features a base film and the presence of disturbance waves. The amplitude and frequency of these disturbance waves increases as either the gas velocity or volume of water increases [9]. We believe the effects of inclination angle on reflected ultrasonic signals will therefore be less when there are less or smaller disturbance waves which is often the case when the films are thinner and the flow less turbulent.…”

“…When the gas and liquid meet at the inlet section the liquid phase is broken down into high frequency, low amplitude waves due to the shearing of the gas phase. These waves have irregular velocities and will coalesce with other low amplitude waves as the flow develops [9]. Increasing gas flowrate increases the interfacial shear and the frequency and velocity of these small waves resulting in a higher degree of coalescence and the formation of a higher frequency of disturbance waves.…”

“…The previous research has focussed on studying the annular thin film thickness and the features of the disturbance waves (frequency, amplitude/height and velocity). The features of the disturbance waves have received interest as they have significant effects on heat and mass transfer between the gas and liquid phases which is essential to understand, for industrial applications such as condensers and evaporators [9]. The measurement methods used to study the film and wave features have been classified by Clark [6] as film averaged methods, localised methods and point methods.…”

“…Pan et al [13] used high speed photography in vertical upward gas liquid annular flow to show that increases in gas velocity reduced the film thickness. Vasques et al [9] studied upward and downward gas/liquid annular flow and used measurements from a brightness based laser induced florescence technique to demonstrate that the disturbance wave behaviour was dependent on flow direction. Wang et al [14] used Near-Infrared measurements at two points to study the velocity of disturbance waves at different gas pressures in vertical upwards gas/liquid flow.…”