Numerical Simulation of Gas-Liquid Two-Phase Flow in a Horizontally Placed Hydrophobic Rectangular Channel (Part 1, Influence of Abrupt Expansion)

Ueda, Y.; Nakajima, T.; Ishii, T.; Tsujino, Ryoji; Iguchi, Mitsuko

doi:10.1515/htmp-2012-0074

Cited by 2 publications

(9 citation statements)

References 17 publications

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Section: Introductionsupporting

confidence: 83%

“…Here, r L and r G are the densities of liquid and gas, σ the surface tension and g the acceleration due to gravity. Similar to the associated study [1], the present setting of the duct thickness is 2 mm which is smaller than the calculated Laplace constant of about 2.7 mm in the present situation.As the preliminary step, this paper computationally visualizes twophase flow patterns through an abrupt contraction of a hydrophobic or hydrophilic rectangular duct with the narrow thickness. …”

supporting

confidence: 83%

Section: Computational Proceduresmentioning

confidence: 99%

“…To design such twophase flow systems, we need to investigate the influence of abrupt change of a duct area, i.e., abrupt expansion and contraction. The influence of the abrupt expansion has been investigated in the coupled study [1], and so the investigation on the abrupt contraction is required. In particular, a narrow thickness of the rectan gular duct affects the nature of the twophase flow, i.e., if the duct height (not a hydraulic diameter) would be smaller than the Laplace constant…”

Section: Introductionmentioning

confidence: 99%

“…GAMBIT 2.2.30 was employed for the establishment of the threedimensional computational grid. The detailed description about the actual setting of the FLUENT code is given in the associated study [1].The computational grids were made up of struc tured elements and a total of 100,320 cells were employed for a given flow domain in the millimeterscale rectan gular channel with the thickness of 2 mm (see Fig. 1).…”

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confidence: 99%

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Numerical Simulation of Gas-Liquid Two-Phase Flow in a Horizontally Placed Hydrophobic Rectangular Channel (Part 2, Influence of Abrupt Contraction)

Ueda¹,

Nakajima

Ishii

et al. 2012

High Temperature Materials and Processes

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This paper computationally visualizes two phase flow patterns through a horizontally placed hydro philic or hydrophobic rectangular channel with an abrupt contraction. The rectangular duct used in this study has a thickness narrower than the Laplace constant so that the surface tension governs the fluid system rather than the inertia force. In particular, the computed bubble behavior at the abrupt contraction seemed to be a similar nature against the preliminary experimental result. Keywords I IntroductionTwophase flow in a channel is an intriguing issue to control flow systems in complicated piping geometries of nuclear energy plant and steelmaking plant, etc. To design such twophase flow systems, we need to investigate the influence of abrupt change of a duct area, i.e., abrupt expansion and contraction. The influence of the abrupt expansion has been investigated in the coupled study [1], and so the investigation on the abrupt contraction is required. In particular, a narrow thickness of the rectan gular duct affects the nature of the twophase flow, i.e., if the duct height (not a hydraulic diameter) would be smaller than the Laplace constantL G g σ r r − , the surface tension governs the fluid system rather than the inertia force. Here, r L and r G are the densities of liquid and gas, σ the surface tension and g the acceleration due to gravity. Similar to the associated study [1], the present setting of the duct thickness is 2 mm which is smaller than the calculated Laplace constant of about 2.7 mm in the present situation.As the preliminary step, this paper computationally visualizes twophase flow patterns through an abrupt contraction of a hydrophobic or hydrophilic rectangular duct with the narrow thickness. II Computational procedureThe FLUENT numerical code ver. 6.2.16, a commercially available CFD software package, was employed for all numerical predictions on Intel Core 2 Quad 2.66 GHz pro cessor with 3.25 GB RAM. GAMBIT 2.2.30 was employed for the establishment of the threedimensional computational grid. The detailed description about the actual setting of the FLUENT code is given in the associated study [1].The computational grids were made up of struc tured elements and a total of 100,320 cells were employed for a given flow domain in the millimeterscale rectan gular channel with the thickness of 2 mm (see Fig. 1). The

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Section: Introductionsupporting

confidence: 83%

supporting

confidence: 83%

Section: Computational Proceduresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Numerical Simulation of Gas-Liquid Two-Phase Flow in a Horizontally Placed Hydrophobic Rectangular Channel (Part 2, Influence of Abrupt Contraction)

Ueda¹,

Nakajima

Ishii

et al. 2012

High Temperature Materials and Processes

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Review on Microbubbles and Microdroplets Flowing through Microfluidic Geometrical Elements

et al. 2020

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Two-phase flows are found in several industrial systems/applications, including boilers and condensers, which are used in power generation or refrigeration, steam generators, oil/gas extraction wells and refineries, flame stabilizers, safety valves, among many others. The structure of these flows is complex, and it is largely governed by the extent of interphase interactions. In the last two decades, due to a large development of microfabrication technologies, many microstructured devices involving several elements (constrictions, contractions, expansions, obstacles, or T-junctions) have been designed and manufactured. The pursuit for innovation in two-phase flows in these elements require an understanding and control of the behaviour of bubble/droplet flow. The need to systematize the most relevant studies that involve these issues constitutes the motivation for this review. In the present work, literature addressing gas-liquid and liquid-liquid flows, with Newtonian and non-Newtonian fluids, and covering theoretical, experimental, and numerical approaches, is reviewed. Particular focus is given to the deformation, coalescence, and breakup mechanisms when bubbles and droplets pass through the aforementioned microfluidic elements.Micromachines 2020, 11, 201 2 of 22 droplets through a sudden/gradual expansion/contraction, several numerical and experimental works considered the flow through horizontal pipes, but they are mainly focused on pressure drop [6][7][8][9].The heat and mass transfer can be significantly enhanced in a microsystem due to the high surface volume ratio. Currently, bubble/droplet-based microfluidics has been successfully applied in chemical and biological analysis [10,11], the synthesis of advanced materials [12], sample pretreatment [13], and the encapsulation of cells [14]. Droplets are liquid entities that flow in a immiscible liquid continuous phase, and bubbles are gas entities also flowing in a liquid fluid. The use of droplets as microreactors presents a lot of advantages when compared with single-phase microfluidics, such as: confinement of reactants or prevention of longitudinal dispersion, and cross contamination between samples [15]. The reduction of unwanted adhesion/absorption of the material confined in droplets at the microchannel walls, the possibility of varying, in each droplet the physicochemical conditions under which chemical or biological process develop, and the facilitated heat/mass transport due to the fast mixing promoted by droplets are other benefits [15,16]. The use of bubbles might be interesting to produce contrast agents in medical applications [17], as a source of reactants in the gas phase to promote reactions in liquid or solid (i.e., microchannel wall) phases [18], and to study in vitro gas embolisms [19].Microfluidic devices (length scales lower than one millimeter) comprise microfluidic elements, analogous to their macroscale counterparts, to transport and distribute fluids, to promote mixing, reaction, and mass transfer. In the case of multiphase flows, ...

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Numerical Simulation of Gas-Liquid Two-Phase Flow in a Horizontally Placed Hydrophobic Rectangular Channel (Part 1, Influence of Abrupt Expansion)

Cited by 2 publications

References 17 publications

Numerical Simulation of Gas-Liquid Two-Phase Flow in a Horizontally Placed Hydrophobic Rectangular Channel (Part 2, Influence of Abrupt Contraction)

Numerical Simulation of Gas-Liquid Two-Phase Flow in a Horizontally Placed Hydrophobic Rectangular Channel (Part 2, Influence of Abrupt Contraction)

Review on Microbubbles and Microdroplets Flowing through Microfluidic Geometrical Elements

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