Measurement of local two-phase flow parameters of downward bubbly flow in mini pipes

Abstract

In order to extend a precise database on local two-phase flow parameters in mini pipes, experiments were conducted for adiabatic gas-liquid bubbly flows flowing down in vertical mini pipes with inner diameters of 1.03, 3.00, and 5.00 mm. A stereo image-processing was applied to observe the phase distribution characteristics in pipe cross-section. The local flow parameters including profiles of void fraction, Sauter mean bubble diameter, and interfacial area concentration in pipe cross-section were obtained at three axial locations in the test pipes with various flow conditions: superficial gas velocity of 0.00508-0.0834 m/s and superficial liquid velocity of 0.208-3.00 m/s. The axial developments of the local flow parameters were discussed in detail based on the obtained data and the visual observation. It was confirmed that the core peak distributions were formed at low liquid flow rate conditions in which the buoyancy force dominated while the wall peak distributions were formed at high liquid flow rate conditions in which the body acceleration due to the frictional pressure gradient dominated. The result indicated the existence of lift force pushing the bubbles towards the pipe wall even in vertical downward flows. The database obtained through the present experiment is expected to be useful in modeling the interfacial area transport terms, the validation of the existing lift force models as well as the benchmarking of various CFD simulation codes.

Void Fraction of Two-Phase Flow of Air – Emulsion of Water and Oil in Horizontal Mini Pipe

“…Two-phase flow on mini pipes differs from pipes of larger diameter [7]. In mini tubes, the surface tension is found a lot, while in heat transfer, it is not found, and it can be said that no phase change occurs in mini pipes [8][9][10]. Dibek and Demir [11] say the void fraction is the ratio of the gas's crosssectional area to the tubes.…”

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

“…Gas-liquid two-phase flow in macro pipes are widely encountered in the industry as oil and gas production and transportation (Arabi et al, 2022, Boutaghane et al, 2023, nuclear power plants (Yeo, 2019;Hibiki, 2019), wastewater industry (Hundshagen et al, 2021) or in chemical and biochemical applications (Wang et al, 2021, Levitsky et al, 2022. These kinds of flows are also found in mini pipes such as those used in high-power electronic devices, heat exchangers and airconditioning systems (Hazuku et al, 2020) Due to the complexity of industrial installations, many parts of fluid transport systems are constituted by singularities, or fittings. These geometrical 'anomalies' lead to a change of the flow behavior and static pressure.…”