Modelling of a batch sonochemical reactor

Naidu, Deepak; Rajan, Rahul; Kumar, R.; Gandhi, K. S.; Arakeri, V.H.; Chandrasekaran, Srinivasan

doi:10.1016/0009-2509(94)80024-3

Cited by 126 publications

(53 citation statements)

References 10 publications

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“…The physics of cavitation is a classical subject, tracing back to the 19th century. Here we summarize the equations that describe cavitating bubbles (18,19). Acoustic waves traveling in a liquid can be modeled as longitudinal pressure waves.…”

Section: Modelmentioning

confidence: 99%

“…Plesset (21) introduced effects of viscosity, surface tension, and variable external pressure. The generalized Rayleigh-Plesset (R-P) equation neglects mass transfer and is derived from the Navier-Stokes equation as (19,21) …”

Section: Modelmentioning

confidence: 99%

“…The flow field vðr; tÞ in the fluid is simply vðr; tÞ ¼ V ðtÞRðtÞ 2 ∕r 2 . We use model paramaters representative of typical sonication conditions (19), R i ¼ 10 nm, ω ¼ 20 kHz, and P A0 of 1,500 and 4,500 kPa for single and double-cycles bubbles.…”

Section: Modelmentioning

confidence: 99%

See 2 more Smart Citations

Competing mechanisms and scaling laws for carbon nanotube scission by ultrasonication

Pagani

Green

Poulin

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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Dispersion of carbon nanotubes (CNTs) into liquids typically requires ultrasonication to exfoliate individuals CNTs from bundles. Experiments show that CNT length drops with sonication time (or energy) as a power law t −m . Yet the breakage mechanism is not well understood, and the experimentally reported power law exponent m ranges from approximately 0.2 to 0.5. Here we simulate the motion of CNTs around cavitating bubbles by coupling Brownian dynamics with the Rayleigh-Plesset equation. We observe that, during bubble growth, CNTs align tangentially to the bubble surface. Surprisingly, we find two dynamical regimes during the collapse: shorter CNTs align radially, longer ones buckle. We compute the phase diagram for CNT collapse dynamics as a function of CNT length, stiffness, and initial distance from the bubble nuclei and determine the transition from aligning to buckling. We conclude that, depending on their length, CNTs can break due to either buckling or stretching. These two mechanisms yield different power laws for the length decay (0.25 and 0.5, respectively), reconciling the apparent discrepancy in the experimental data.T he dispersion of carbon nanotubes (CNTs) in liquids is critical for the use of CNTs in applications ranging from biomedical sensors to structural composites (1). However, CNTs form insoluble bundles and ropes during production due to van der Waals attraction. Commonly, CNTs are exfoliated and dispersed in liquids by sonication, where energy is supplied to the system as ultrasonic waves. These waves induce cavitation, which leads to progressive exfoliation of bundles into individual CNTs. Understanding dispersion by sonication is critical for the use of CNTs in biological and materials applications (2).Prior studies have monitored the effects of sonication on CNT dispersion quality and length (3-7). Most of these studies sonicated a sample under controlled conditions and monitored bundle diameter and length. Although sonication decreases bundle diameter at short times as individual CNTs are exfoliated, it also cuts the CNTs. Shortening has been observed for both singlewalled and multiwalled CNTs (SWNTs and MWNTs) (4, 5).Similar shortening occurs during sonication of polymer solutions (5,(8)(9)(10)(11)(12), where the mechanism is well established; cavitation induces high strain rates in the liquid, stretching polymer molecules to failure. Although the mechanism of CNT shortening remains unclear, there are some similarities between sonicated polymers and CNTs. Like polymers, CNTs show a nonrandom cutting pattern; i.e., they break near their center of mass (CoM) (5). Similar to polymers, the kinetics of CNT shortening are length-dependent, and sonicated CNTs approach a limiting length, below which no shortening occurs (6, 13). Evidence suggests that thermal effects (due to local temperature rise during bubble collapse) are negligible and mechanical effects dominate (6,14,15).Experiments consistently report a power law relation between CNTs' average length and sonication time L ∼ t −m . Th...

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Section: Modelmentioning

confidence: 99%

Section: Modelmentioning

confidence: 99%

See 1 more Smart Citation

Competing mechanisms and scaling laws for carbon nanotube scission by ultrasonication

Pagani

Green

Poulin

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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“…These low rates of cavity collapse do not sufficiently explain the substantial liberation of iodine observed during the decomposition of aqueous KI solution using the above equipments. For these reactions to occur, very severe conditions should exist in these systems [6]. Also, the dynamics of the individual cavities are affected by the neighboring cavities due to the generation of shock waves as a result of the neighboring cavity collapse.…”

Section: Mathematical Modelingmentioning

confidence: 99%

Modeling Hydrodynamic Cavitation

Kumar

Pandit²

1999

Chem. Eng. Technol.

135

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A simplified and unified model has been proposed to study the cavitation phenomena in hydraulic devices, with emphasis on the venturi tube and high-speed homogenizer. A turbulence model analogous to the acoustic cavitation has been developed and the dynamics of the cavities as a cluster has been considered. The prediction of the cavitation inception number has been made for various operating conditions and has been compared with the experimental observations. The effect of operating parameters, such as inlet pressure and fully recovered downstream pressure, has been studied numerically and compared with the data in the literature for the case of the venturi. The predicted cavitation intensities were compared indirectly with the experimental results. It has been found that optimum operating conditions do exist at which the observable cavitational effect is maximum. In the case of the high-speed homogenizer, the predicted effects as a function of rotational speed have been compared with the results of the aqueous KI decomposition reaction and have been found to match well. The study concludes with the recommendations and methods for possibly optimizing hydrodynamic cavitation phenomena for maximum effect.

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“…2, 3). Naidu et al (1994) also observed an increase in iodine liberation in solutions with higher KI concentrations sonicated at 25 kHz. However, a higher cavitation yield was observed with sonication frequency of 574 kHz in both cases of KI concentration.…”

Section: Effect Of Power Supplied and Ki Concentrationmentioning

confidence: 75%

Towards the development of cavitation technology for upgrading bitumen: Viscosity change and chemical cavitation yield measurements

Kirpalani

Mohapatra

2017

Pet. Sci.

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Among the different methods used for reducing viscosity of bitumen, acoustic cavitation during sonication is well recognised. Several chemical methods were used to detect the production of reactive species such as hydroxyl radicals and hydrogen peroxide during acoustic cavitation processes. However, quantification of cavitation yield in sonochemical systems is generally limited to low frequencies and has not been applied to bitumen processing. An empirical determination of the cavitation yield in midto high-frequency range (378, 574, 850, 992, and 1173 kHz) was carried out by measuring the amount of iodine liberated from the oxidation of potassium iodide (KI). Further, cavitation yield and the effects of different sonic operating conditions such as power input (16.67%-83.33%) and solute concentration on cavitation yield were carried out in KI solution and sodium carboxymethyl cellulose-water mixture to obtain benchmark changes in rheology and chemistry using these two model fluids. The findings were then applied to bitumen upgrading through sonication. Through this study, it was found that the chemical cavitation yield peaked with a sonication frequency of 574 kHz. It was also found that cavitation yield and viscosity change were correlated directly in bitumen and a 38% lower bitumen viscosity could be obtained by acoustic cavitation.

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Modelling of a batch sonochemical reactor

Cited by 126 publications

References 10 publications

Competing mechanisms and scaling laws for carbon nanotube scission by ultrasonication

Competing mechanisms and scaling laws for carbon nanotube scission by ultrasonication

Modeling Hydrodynamic Cavitation

Towards the development of cavitation technology for upgrading bitumen: Viscosity change and chemical cavitation yield measurements

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