Mixed convection from an isolated spherical particle

Bhattacharyya, S.; Singh, Ashok

doi:10.1016/j.ijheatmasstransfer.2007.05.033

Cited by 29 publications

(21 citation statements)

References 34 publications

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“…The rear vortex will vanish if buoyancy force is strong enough. The collapse of rear vortex due to density stratification was also observed by Torres et al (2000) and Bhattacharyya and Singh (2008) for an assisting convective flow [18,32]. The buoyancy force is determined by the density difference which results from the nonuniform temperature field.…”

Section: Flow Fieldmentioning

confidence: 74%

“…They found that the acceleration of the flow due to buoyancy considerably stabilized the flow and pushed the onset of instabilities. Bhattacharyya and Singh (2008) studied the aiding flow from an isolated spherical particle with moderate range of Reynolds number (1 ≤ Re ≤ 200) and Grashof number (0 ≤ Gr ≤ 10 4 ) [18]. They revealed that the decrease in drag coefficient with increase of Reynolds number is due to the increase of the wake size, and the heat transfer is dominated by the convection effect at higher Reynolds number.…”

Section: Introductionmentioning

confidence: 99%

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Numerical Study on the Mixed Convection Heat Transfer between a Sphere Particle and High Pressure Water in Pseudocritical Zone

Wei

2013

Advances in Mechanical Engineering

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Mixed convection heat transfer between supercritical water and particles is a major basic problem in supercritical water fluidized bed reactor, but little work focused on this new area in the past. In this paper, a numerical model fully accounting for thermophysical property variation has been established to investigate heat transfer between supercritical water and a single spherical particle under gravity. Flow field, temperature field and Nusselt number are analyzed based on the simulation results. Results show that buoyancy force has a remarkable effect on flow and heat transfer process. When the direction of gravity and flow are opposite, the gravity enhances the heat transfer before the separation point and inhibits the heat transfer after the separation point. When gravity is incorporated in calculation, a higher temperature gradient and a thinner boundary layer in the vicinity of the particle surface are observed before separation point, and the situations are just the reverse after separation point. Variation of specific heat and conductivity plays a main role in determination of heat transfer coefficient.

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Section: Flow Fieldmentioning

confidence: 74%

Section: Introductionmentioning

confidence: 99%

Numerical Study on the Mixed Convection Heat Transfer between a Sphere Particle and High Pressure Water in Pseudocritical Zone

Wei

2013

Advances in Mechanical Engineering

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“…Data for the velocity field taken from Bagchi and Balachandar (2004) for a fixed sphere in uniform flow at + á ñ = Re 610 t , •Re=107, and data from the temperature field taken from Bagchi and Kottam (2008) for a fixed sphere in uniform flow at á ñ = Re 250 t , and Pr=1.0 ×. Bhattacharyya and Singh (2008) and Bagchi and Kottam (2008). The amplitude of this peak decreases for for Ga=150, 170 and 200 and then slightly increases for the last Galileo number.…”

Section: Structure Of the Scalar Field And Influence Of The Density Rmentioning

confidence: 99%

Heat and water vapor transfer in the wake of a falling ice sphere and its implication for secondary ice formation in clouds

et al. 2019

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We perform direct numerical simulations of the settling of an ice sphere in an ambient fluid accounting for heat and mass transfer with the aim of studying in a meteorological context the case of falling graupel in humid air. The study is motivated by the fact that falling graupels in clouds are heated by the latent heat released during the accretion of liquid water droplets. They may therefore be considerably warmer than their surrounding and evaporate water vapor, which mixes with the surrounding air in the wake of the graupel, thereby creating transient zones of supersaturation there. The problem of a falling graupel is modeled as that of a heated sphere falling in a quiescent ambient fluid under the action of gravity. The coupling between the temperature and velocity fields is accounted for by the Boussinesq approximation. This problem can be parameterized by four parameters: the particle/fluid density ratio r r ¥ p , the Galileo number Ga=u g D/ν (where D is the diameter of the sphere, ν the viscosity of the fluid, r r = -¥ |( ) | u gD 1 g p , and g the gravitational acceleration), the Prandtl number Pr=ν/D T (where D T stands for the thermal diffusivity), and the Richardson numberbetween the sphere and the ambient fluid and β the thermal expansion coefficient of the fluid. A separate scalar transport equation accounts for the vapor transport. Typical cloud conditions involve small temperature differences between the sphere and the surrounding, yielding relatively small Richardson numbers for both heat and mass transport. We give a special emphasis to the Galileo numbers 150, 170, 200 and 300 in order to analyze the specificities of each settling regime. The questions addressed in this study are mainly methodological and concern the influence of the settling regime and the mobility of the sphere on the structure of the scalar fields, the possible influence of modest Richardson numbers on the structure of the wake, and the possible application of this simulation framework to the investigation of the saturation in the wake of a falling graupel. We observe that the body behaves similar to a body with infinitely large density. Buoyancy effects upon the wake at the values of the Richardson number corresponding to the atmospheric context are found to be negligible. We discuss the necessity to distinguish between the diffusivity of temperature and vapor content and for this the requirement to solve both scalar transport equations separately. The simulations reveal the structure of the saturation field which features zones of supersaturation that might indeed be the sites of secondary ice nucleation (formation of additional ice crystals). The potential error in not solving both fields separately is relatively low but affects the regions of the flow that feature the largest supersaturation, such that it could be preferable to separate both transport equations depending on the future questions addressed.

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“…Several authors [30][31][32] have observed that the transition from a steady axisymmetric flow to a steady non-axisymmetric wake flow occurs at a Re number of 211. Below this critical Re number, the exact numerical results obtained for a rigid sphere can be approximated rather well by the following relation [33,34]:…”

Section: Introductionmentioning

confidence: 99%

Magnetic actuation of catalytic microparticles for the enhancement of mass transfer rate in a flow reactor

Lisk

Bonnot

Rahman

et al. 2016

Chemical Engineering Journal

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Permanent WRAP URL:http://wrap.warwick.ac.uk/81857 Copyright and reuse:The Warwick Research Archive Portal (WRAP) makes this work by researchers of the University of Warwick available open access under the following conditions. Copyright © and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable the material made available in WRAP has been checked for eligibility before being made available.Copies of full items can be used for personal research or study, educational, or not-for-profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP URL' above for details on accessing the published version and note that access may require a subscription. AbstractThe effect of periodic changes in particle velocity on mass transfer to the reacting surface of a magnetic particle with a diameter 225 m in laminar flow has been investigated in a microfluidic reactor. The periodic particle motion in a fluid was investigated under a sinusoidal magnetic field generated by a quadrupole arrangement of electromagnets around the reactor. The effect of operating frequency of the rotating magnetic field, intensity of the magnetic field, and phase shift between the two sets of magnets on particle dynamics has been studied. Three particle motion modes have been observed depending on the frequency of the applied field. The mass transfer rate was estimated under steady velocity and variable velocity of the particle using a mass transfer correlation by Feng and Michaelides (Int. J. Heat Mass Transfer 44 (2001) 4445). The validity of this correlation for the case of variable particle velocity has been confirmed with a 2D numerical model, describing actual hydrodynamics and mass transfer towards the particle surface. The mass transfer coefficient *Revised Manuscript (clean for typesetting) Click here to view linked References 2 depends both on the mean particle velocity and the deviation of velocity from the mean value.The periodic movement with variable particle velocity reduces the mass transfer coefficient by 7.6% as compared to steady state motion with the same mean velocity.

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Mixed convection from an isolated spherical particle

Cited by 29 publications

References 34 publications

Numerical Study on the Mixed Convection Heat Transfer between a Sphere Particle and High Pressure Water in Pseudocritical Zone

Numerical Study on the Mixed Convection Heat Transfer between a Sphere Particle and High Pressure Water in Pseudocritical Zone

Heat and water vapor transfer in the wake of a falling ice sphere and its implication for secondary ice formation in clouds

Magnetic actuation of catalytic microparticles for the enhancement of mass transfer rate in a flow reactor

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