Fluid-to-particle heat transfer in fluidized beds

Zabrodsky, S.S.; Martin, Holger

doi:10.1615/hedhme.a.000172

Cited by 3 publications

(3 citation statements)

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“…Fig. 13 shows a comparison of the measured heat transfer coefficients with the predictions of the packet model, using residence/ contact times measured using PEPT, and the correlation for the maximum obtainable heat transfer coefficient from Zabrodsky (1966), and showing fair agreement. The measured heat transfer coefficient at the highest gas velocity/shortest residence time is well below the packet model predictions, presumably because blanketing of the heat transfer surface reduces heat transfer under these conditions.…”

Section: Heat Transfer Coefficientmentioning

confidence: 88%

Particle motion and heat transfer in an upward-flowing dense particle suspension: Application in solar receivers

García‐Triñanes

Seville

Ansart

et al. 2018

Chemical Engineering Science

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OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in : http://oatao. Particle trajectories are determined within a dense upward-moving fluidised bed.Particle-to-wall heat transfer coefficients have been measured experimentally.Heat transfer coefficients are in the range 180-320 W/m 2 K.Particle residence times at the wall were found to be distributed according to a log-normal distribution.Experimentally-obtained heat transfer coefficients were found to be in good agreement with prior predictions. g r a p h i c a l a b s t r a c t a b s t r a c tConcentrated solar power (CSP) plants conventionally make use of molten salt as the heat transfer medium, which transfers heat between the solar receiver and a steam turbine power circuit. A new approach uses particles of a heat-resistant particulate medium in the form of many dense upward-moving fluidised beds contained within an array of vertical tubes within the solar receiver. In most dense gas-solid fluidisation systems, particle circulation is induced by bubble motion and is the primary cause of particle convective heat transfer, which is the major contributing mechanism to overall heat transfer. The current work describes experiments designed to investigate the relationship between this solids convection and the heat transfer coefficient between the bed and the tube wall, which is shown to depend on the local particle concentration and their rate of renewal at the wall. Experiments were performed using 65 mm silicon carbide particles in a tube of diameter 30 mm, replicating the conditions used in the real application. Solids motion and time-averaged solids concentration were measured using Positron Emission Particle Tracking (PEPT) and local heat transfer coefficients measured using small probes which employ electrical resistance heating and thermocouple temperature measurement. Results show that, as for other types of bubbling beds, the heat transfer coefficient first increases as the gas flow rate increases (because the rate of particle renewal at the wall increases), before passing through a maximum and decreasing again as the reducing local solids concentration at the wall becomes the dominant effect. Measured heat transfer coefficients are compared with theoretical approaches by Mickley and Fairbanks packet model and Thring correlation. The close correspondence between heat transfer coefficient and solids movement is here demonstrated by PEPT for the first time in a dense upward-moving fluidised bed.

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Section: Heat Transfer Coefficientmentioning

confidence: 88%

Particle motion and heat transfer in an upward-flowing dense particle suspension: Application in solar receivers

García‐Triñanes

Seville

Ansart

et al. 2018

Chemical Engineering Science

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“…For studies of heat transfer coefficients in drying systems in the period of constant drying rate, it can be assumed that the temperature of the surface particles T p,s is equal to the wet bulb temperature T wb of the inlet air [14,15], since in such a period the product shows a wet surface.…”

Section: Fundamentals Of Gas-particle Heat Transfermentioning

confidence: 99%

Experimental Investigation on Drying of Forest Biomass Particles in a Mechanically Stirred Fluidized Bed

Moreno-Muñoz,

Antolín-Giraldo,

Reyes-Salinas

2024

Drying Science and Technology

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This chapter reflects a review of the results obtained in several investigations on the fluidization process of wet biomass particles in a mechanically stirred fluidized bed equipment. For the experimental purposes, an experimental equipment with a drying column of 300 mm in diameter is used. Using the Ergun equation, the fluodynamic behavior of the bed is analyzed to obtain, from the measurements of pressure drops in the bed and imposed velocities, the specific gas-particle contact surface; such interfacial surface varies between 5758 and 7317 m2 m–3 for dry particles and between 2774 and 4444 m2 m–3 for high humidity particles. Subsequently, the phenomena of heat and mass transfer by convection between the fluidizing gas and the biomass particles during the drying process are studied. The gas-particle heat and mass transfer coefficients are determined, considering stirrer rotation speeds between 1 and 2 rev s–1. The convective coefficients vary between 13 and 25.7 W m–2 K–1 for heat transfer and between 6 x 10–3 and 20 x 10–3 m s–1 for mass transfer; thus, correlations have been obtained between the Nusselt and Reynolds numbers and between the Sherwood and Reynolds numbers, respectively, valid in the Reynolds number range between 102 and 257.

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“…Gunn1 and Kato et al2 showed that the Sherwood number for large particles is equal to the diffusion limit of two plus the convection conveyed in terms of the Reynolds and Schmidt numbers. However, the Sherwood numbers for fine particles are known to be much smaller than those for large particles 3–5. Breault6 and Breault and Guenther7 reviewed that the Sherwood number varies by at least seven orders of magnitude in the literature, i.e., from 10 −5 to 10 2 .…”

Section: Introductionmentioning

confidence: 99%

Measurements and computation of low mass transfer coefficients for FCC particles with ozone decomposition reaction

Kashyap

Gidaspow

2011

AIChE Journal

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in Wiley Online Library (wileyonlinelibrary.com).The mass transfer coefficients and Sherwood numbers for catalyzed fluid cracking catalyst particles were measured and computed in a two-dimensional (2-D) bubbling fluidized bed, with ozone decomposition reaction. The measured and computed Sherwood numbers, using 3-and 2-D kinetic theory based computational fluid dynamics simulations, were of the order of 10 À6 -10 À2. The low Sherwood numbers were in reasonable agreement with the literature data for small particles, at low Reynolds numbers. The computational fluid dynamics simulations showed that it is possible to compute conversions in fluidized bed reactors without using the conventional model with empirical mass transfer coefficients.

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Fluid-to-particle heat transfer in fluidized beds

Cited by 3 publications

References 0 publications

Particle motion and heat transfer in an upward-flowing dense particle suspension: Application in solar receivers

Particle motion and heat transfer in an upward-flowing dense particle suspension: Application in solar receivers

Experimental Investigation on Drying of Forest Biomass Particles in a Mechanically Stirred Fluidized Bed

Measurements and computation of low mass transfer coefficients for FCC particles with ozone decomposition reaction

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