Effect of bubble size in turbulent bubbly downflow in a vertical channel

Lu, Jiacai; Tryggvason, Grétar

doi:10.1016/j.ces.2007.02.012

Cited by 64 publications

(27 citation statements)

References 42 publications

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“…Iskandrani and Kojasoy [9] also reported that, in twophase vertical bubbly flows, the presence of voids tends to flatten the liquid velocity profile, thus leading to a homogenous phase distribution across the vertical pipe section. More recently, Lu and Tryggvason [10] reported similar trends through direct numerical simulations.…”

Section: Resultssupporting

confidence: 57%

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Two-phase distribution in the vertical flow line of a domestic wet central heating system

Fsadni

2013

EPJ Web of Conferences

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Abstract. The theoretical and experimental aspects of bubble distribution in bubbly two-phase flow are reviewed in the context of the micro bubbles present in a domestic gas fired wet central heating system. The latter systems are mostly operated through the circulation of heated standard tap water through a closed loop circuit which often results in water supersaturated with dissolved air. This leads to micro bubble nucleation at the primary heat exchanger wall, followed by detachment along the flow. Consequently, a bubbly two-phase flow characterises the flow line of such systems. The two-phase distribution across the vertical and horizontal pipes was measured through a consideration of the volumetric void fraction, quantified through photographic techniques. The bubble distribution in the vertical pipe in down flow conditions was measured to be quasi homogenous across the pipe section with a negligible reduction in t he void fraction at close proximity to the pipe wall. Such a reduction was more evident at lower bulk fluid velocities.

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Section: Resultssupporting

confidence: 57%

“…More recently, Lu and Tryggvason [10] reported similar trends using direct numerical simulations where the full Navier-Stokes equations were solved by a parallelized front-tracking finite-volume method.…”

Section: Introductionmentioning

confidence: 76%

Two-phase distribution in the vertical flow line of a domestic wet central heating system

Fsadni

2013

EPJ Web of Conferences

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“…The changes in the BSD (from bimodal to unimodal) in the counter-current mode were based on the force pushing the small bubbles toward the center of the pipe. This has been confirmed by the numerical studies of Lu et al [246] and Lu and Tryggvason [247,248]. Generally, lot of parameters influence the bubble size distribution, and it is difficult to provide a general rule for BSD prediction.…”

Section: Superficial Gas Velocitymentioning

confidence: 57%

Two-Phase Bubble Columns: A Comprehensive Review

2018

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We present a comprehensive literature review on the two-phase bubble column; in this review we deeply analyze the flow regimes, the flow regime transitions, the local and global fluid dynamics parameters, and the mass transfer phenomena. First, we discuss the flow regimes, the flow regime transitions, the local and global fluid dynamics parameters, and the mass transfer. We also discuss how the operating parameters (i.e., pressure, temperature, and gas and liquid flow rates), the operating modes (i.e., the co-current, the counter-current and the batch modes), the liquid and gas phase properties, and the design parameters (i.e., gas sparger design, column diameter and aspect ratio) influence the flow regime transitions and the fluid dynamics parameters. Secondly, we present the experimental techniques for studying the global and local fluid dynamic properties. Finally, we present the modeling approaches to study the global and local bubble column fluid dynamics, and we outline the major issues to be solved in future studies.

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“…Similarly, numerical studies done by Lu and Tryggvason [17] reported quasi spherical bubbles with diameters of 1.53 m m and slightly ellipsoidal bubbles with diameters of 1.84 m m through the application of direct numerical simulations for bubbly air water two-phase downward flow. In view of the relation between the bubble shape and bubble breakage events as discussed by Hesketh et al [10], whereby breakage events are expected to occur as a result of substantial bubble elongation with the flow, the quasispherical shapes observed in the current study, suggests that bubble breakage can be assumed to be minimal.…”

Section: Resultsmentioning

confidence: 99%

Bubble shape and breakage events in a vertical pipe at the boiler flow line

Fsadni

2014

EPJ Web of Conferences

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Abstract. The theoretical and experimental aspects concerning the typical bubble shape at the flow line of a standard domestic central heating system are investigated. This is done in support of the on-going research on two-phase flows in domestic central heating systems. Bubble nucleation and detachment at the primary heat exchanger wall of a domestic central heating boiler results in a bubbly two-phase flow in the system pipe work. Bubbly flow results in undesired cold spots at higher points in the system, consequently diminishing system performance. An experimental analysis was done on the bubble shape at the exit of the boiler through the application of photographic techniques. The results are presented in terms of the measured bubble aspect ratios at some principal system operating conditions. The dimensionless Eotvos and bubble Reynolds number were calculated and tabulated with the measured mean diameters. The data was subsequently correlated to the bubble shape regime diagram. Results suggest that most bubbles are quasi-spherical in shape with a noticeable elongation at lower bulk fluid Reynolds numbers.

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Effect of bubble size in turbulent bubbly downflow in a vertical channel

Cited by 64 publications

References 42 publications

Two-phase distribution in the vertical flow line of a domestic wet central heating system

Two-phase distribution in the vertical flow line of a domestic wet central heating system

Two-Phase Bubble Columns: A Comprehensive Review

Bubble shape and breakage events in a vertical pipe at the boiler flow line

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