The heat transfer coefficient between bed and vertical tube wall was measured in three-phase fluidized beds of 12 and 19 cm i. d. Glass spheres of various diameters (particle diameter = 0.52-2.2 mm, particle density =2500 kg · m
-3) and alumina spheres (particle diameter = 3.2 mm, apparent particle density 1620 kg · m
-3) were fluidized by fluid media of air-water or air-aqueous solution of carboxymethyl cellulose. The superficial velocities of gas and liquid were varied in the range of 2.0-16 cm · s
-1 and 0.05-8.0 cm · s
-1, respectively.
The critical liquid velocity,
ul3, of the stable fluidization state was correlated as follows.
ul3/
ut=0.336 (η
l0/η
l)
0.5/ (1.9+
Fr0.9)
where
ut =terminal velocity of particle, η
l3=water viscosity, ηl=liquid viscosity,
Fr=
ug2/
gdp,
ug = superficial gas velocity,
g = acceleration of gravity, and
dp=particle diameter.
The heat transfer coefficient,
h, in the stable fluidization state was correlated as follows.
Nu'= {0.058 (
Re'·
Pr)
0.78+2.3} (
dh/
dh0)
-0.5where,
Nu'=
hdpε
l/ {
kl (1-ε
l)},
Re'=
dpulρ
l/ {η
l (1-ε
l)},
Pr=
cplη
l/
kl, d
h=heater diameter (2.2-6.3 cm),
dh0 =2.2 cm, ε
l =liquid holdup,
kl =thermal conductivity of liquid,
ul=superficial liquid velocity, ρ
l =liquid density, and
cplspecific heat of liquid.
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