Influence of the Pipe Diameter on the Structure of the Gas-Liquid Interface in a Vertical Two-Phase Pipe Flow

A critical review of flow maps for gas-liquid flows in vertical pipes and annuli

“…Schlegel, et al [54] reported overall relative errors in the resultant void fraction measurements of less than 10% for void fractions between 0.2-0.4 and less than 5% for void fractions greater than 0.4. The accuracy of this technique was also reported by Prasser, et al [57] to be 5% void fraction. This approach has a greater level of complexity but is non-intrusive, and does not obstruct the flow channel which would risk affecting the flow pattern.…”

“…Conductivity or permittivity is measured within the gaps by alternately sending an excitation voltage to each of the sender electrodes [58]. The accuracy of this technique was reported to be 1-4% of the area-averaged void fraction [57]. Rapid calculations are possible with this tool, however, resolution is limited to approximately 3 mm [30].…”

“…Once the relationship between electrical impedance and phase distribution has been established, the cross-sectional averaged void fraction can then be estimated [40]. Prasser, et al [57] reported the accuracy of conductivity probes to be 5% void fraction. Optical fibre probes operate similarly to conductance probes but rely upon differences in refractive index rather than conductivity to measure local void fractions [60].…”

Novel experimental measuring techniques required to provide data for CFD validation

“…The accuracy of the gas fraction measurement is discussed in [3]. Three different methods are available to visualize the resulting gas fraction data: (1) instantaneous gas fraction distributions in the measuring plane, (2) virtual sectional side views and (3) virtual side projections [4].…”

“…Radial gas velocity profiles were obtained by means of a point-to-point cross-correlation between the signals of both sensors placed in a certain distance behind each other [4]. An alternative is a time-offlight analysis of the bubbles crossing both successive measuring planes [5].…”