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Wärme - und Stoffübertragung

, Volume 14, Issue 3, pp 173–182 | Cite as

Characteristics of heat transfer between particles and fluid in aggregative fluidized bed

  • N. Seki
  • S. Fukusako
  • K. Torikoshi
Article

Abstract

Measurements are made on the heat-transfer coefficients between particles and fluid in the aggregative fluidized bed. In order to evaluate the heat-transfer coefficients, a proposed model takes into account of the variation of the particles-temperature and the fluid-temperature distributions throughout the bed is developped on the basis of an experimental investigation of the fluidizing behavior. The heat-transfer coefficients obtained by conforming the outlet-air temperature profile to be predicted with the one measured are found to be varied significantly depending on the static bed height, as well as particle diameter and fluid velocity.

Keywords

Experimental Investigation Temperature Profile Apply Physic Particle Diameter Fluid Velocity 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Nomenclature

a

surface area of particles per unit volume of bed

Cp

specific heat

d

diameter

g

gravitational acceleration

hp

heat-transfer coefficient between particles and fluid

I0

modified Bessel function of the first kind of zero order

L

bed height at fluidization

Lmf

bed height at minimum fluidization

Ls

static bed height

n

natural integer

Nup

Nusselt number, hpdpf.

ΔP

pressure difference between static pressure in bed and atmospheric pressure

Rep

Reynolds number, Ufdpf.

t

time

T

temperature

Tfi

inlet-fluid temperature

Tfo

outlet-fluid temperature

Tfoin

initial outlet-fluid temperature

Tpin

initial particle temperature

Tps

particle-surface temperature

Ub

rise velocity of a bubble

uf

interstitial fluid velocity

Uf

superficial fluid velocity

Umf

superficial fluid velocity at minimum fluidization

up

downward particle velocity

x

coordinate along bed distance from distributor

Greek Symbols

α

thermal diffusivity

α′,β′,γ′

dimensionless variables, (1+ψ)e−ψ and (-hpat/ρpCppɛf)

ψ

dimensionless variable, hpy a(x/uf)/ρfCpfɛf

ϕ

dimensionless variable, hpa(t-x/uf)/ρpCpp(1-ɛf)

ξ

dimensionless variable, ψ · ϕ

η

dimensionless variable, (-hpat)/ρpCpp(1+hpaL/ρfCPpUf)

ζ

ratio of the volume of wake dragged upward behind a rising bubble to the volume of a bubble

δ

volume fraction of bed consisting of bubbles

ɛf

average voidage of the overall bed

ɛmf

voidage at minimum fluidization

ɛfx

voidage at a distance x in bed

ɛfafb

local voidage in A zone and B zone, respectively

λ

thermal conductivity

ν

kinematic viscosity

ρ

density

Subscripts

f, p

refer to fluid and particle, respectively

Wärmeübertragung zwischen Teilchen und Fluid im Fließbett

Zusammenfassung

Wärmeübertragungskoeffizienten zwischen Teilchen und Fluid im Fließbett wurden gemessen. Das benutzte Rechenmodell berücksichtigte die Änderung der Teilchentemperatur und der Fluidtemperaturverteilung im Bett, wie sie aus den Versuchen ermittelt wurden. Die Wärmeübergangskoeffizienten, die durch Anpassung der Austrittstemperaturverteilung an die gemessenen Werte erhalten wurden, ändern sich stark mit der statischen Betthöhe, ebenso mit dem Teilchendurchmesser und der Fluidgeschwindigkeit.

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Copyright information

© Springer-Verlag 1980

Authors and Affiliations

  • N. Seki
    • 1
  • S. Fukusako
    • 1
  • K. Torikoshi
    • 1
  1. 1.Department of Mechanical Engineering Faculty of EngineeringHokkaido UniversitySapporoJapan

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