The structure of bubbly flow through venturis

Thắng, Nguyễn Tất; Davis, M. R.

doi:10.1016/0301-9322(79)90003-x

Cited by 40 publications

(19 citation statements)

References 10 publications

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“…The findings of the present study are also in agreement with studies done by Thang and Davis [2], Van der Welle [3], Michiyoshi and Serizawa [4], Winterton and Orby [5] and Winterton and Munaweera [6] who assumed a spherical shape for bubbles flowing in vertical pipe bubbly flow. 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.…”

Section: Resultssupporting

confidence: 93%

“…The studies done by Thang and Davis [2], Van der Welle [3], Michiyoshi and Serizawa [4], Winterton and Orby [5] and Winterton and Munaweera [6] in vertical two-phase bubbly flow, have assumed a perfectly spherical bubble shape. However, Liu [7] reported that bubble elongation along the flow is observed with the presence of larger bubbles, with minimal elongation observed with smaller sized bubbles.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Resultssupporting

confidence: 93%

Section: Introductionmentioning

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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“…The gas velocities were averaged as follows: The data obtained from the optical fiber probe also yields the average bubble size which is of interest for two-fluid models. An analysis of the average bubble sizes was performed by Thang and Davis (1979). It was assumed that for a truly spherical bubble in bubbly flow there is an equal probability of the probe tip hitting the bubble along any chord subtended by its surface.…”

Section: Resultsmentioning

confidence: 99%

Experimental investigation of cocurrent two‐phase flow in a vertical rectangular channel

Moujaes

Dougall

1987

Can J Chem Eng

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New time averaged data of two‐phase flow in bubbly and slug regimes are presented. A modified dual spherical tipped optical fiber probe is used to measure local void fractions, gas velocity and bubble sizes. Hot film anemometry was used to measure the local mean liquid velocity axially. The void fraction, gas and liquid velocities values were presented as averages over the long and short dimensions respectively. Also core values of these variables are presented along the smaller dimension of 12.7 mm, near the plane of symmetry of the longer dimension, to show the most general trend of the different bubbly and slug flow runs. Bubble sizes obtained experimentally were compared with predictive models applied to circular geometries and were found to have a reasonable agreement. It was also interesting to find that local void fractions measured using hot film anemometers were comparable to those found by optical fiber probes. Frequencies of interfacial passage of bubbles and slugs are presented which show rather flat profiles across the channel. It is hoped that these data can be further used in predictive two‐phase two‐fluid models in the future. Lastly of interest is the fact that slip values near the boundaries were shown to be less than 1.0 for some cases in bubbly flow similar to those observed in circular geometries.

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“…Neve [18] also identifies this and suggests that the decrease in pressure recovery with increased void fraction is caused by nonuniformity of density in the diffuser, because liquid is pulled towards the centre and gas towards the walls due to streamline curvature. This hypothesis seems plausible and the non-uniformity of density described can clearly be seen in the experimental results of Thang and Davis [19].…”

Section: Diffuser Designmentioning

confidence: 64%

Hydraulic air pumps for low-head hydropower

Howey

Pullen

2009

Proceedings of the Institution of Mechanical Engineers, Part A:

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Abstract:Hydropower is a proven renewable energy resource and future expansion potential exists in smaller-scale, low-head sites. A novel approach to low-head hydropower at run-of-river and tidal estuary sites is to include an intermediate air transmission stage. Water is made to flow through a siphon, rather than a conventional water turbine, and at the top of the siphon the pressure is sub-atmospheric and air is entrained into the water. The siphon forms a novel, hydraulically powered vacuum pump or 'hydraulic air pump' (HAP). Air is pumped by the HAP through a separate air turbine and generator. This arrangement offers dramatic increases in turbine-generator speed and allows better control and matching of components and lifecycle cost reductions due to reduced maintenance costs and the use of smaller rotating machines.This study builds on previous work on such systems by showing why the pumping process can be treated as isothermal. Also, initial test results with a small siphon are presented and compared to existing models. These show a discrepancy between predicted and measured pressure ratios and therefore an overprediction of efficiency and power output using simple mathematical models.

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The structure of bubbly flow through venturis

Cited by 40 publications

References 10 publications

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

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

Experimental investigation of cocurrent two‐phase flow in a vertical rectangular channel

Hydraulic air pumps for low-head hydropower

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