Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : Solid


A Study of Chaotic Behavior of Heat Transfer In Gas-Solid Fluidized Bed

e Al-Rubeai; Jamal Mane; Nabeel Majid Aliwi

Engineering and Technology Journal, 2010, Volume 28, Issue 10, Pages 2027-2042

Fluidized beds are characterized by high heat transfer rates between the
bed and internal surfaces and have uniform temperature distribution that can be
achieved in fluidized bed systems. In the same time there is a chaotic behavior of
hydrodynamic and heat transfer in gas-solid fluidized bed.
Experimental work was carried out in gas-solid (air – sand) fluidized bed to
investigate the steady state heat transfer coefficient. The bed column used was
(172) mm in diameter and (1000) mm height, fitted with immersed cylindrical
heating element of (25.4) mm in diameter. The fluidizing medium was air flowing
at different velocities from fixed bed to fluidized bed of (0.006-0.078)m/s, and
three different sizes of fine sand particles were used (i.e. 63, 112, and 145 μm),
these average particles diameters were estimated by two methods (Wide and
Narrow Range Solids).
A comparison have been done with values of the minimum fluidizing velocity that
calculated analytically, empirical, and which got experimentally. The results show
a chaotic behavior of hydrodynamic gas-solid fluidized bed.
The heat transfer coefficient and the bed viodage increase with increasing gas
fluidizing velocity and the heat transfer coefficient decreases with an increase in
particle diameter.
Two empirical correlations are proposed which can calculate wide range solids and
narrow range solids based on experimental data. The Nusselt number presented
with some dimensionless groups as follows:-
For Wide Range Solids Nu = 0.81Re0.94 Pr0.35
Where the correlation coefficient (R) was equal to (0.92) and the average absolute
relative error was (12.62 %).
For Narrow Range Solids Nu = 0.45Re0.65 Pr0.33
Where the correlation coefficient (R) was equal to (0.86) and the average absolute
relative error was (24.2 %).

Heat Transfer from an Immersed Heater in Liquid – Liquid – Solid Fluidized Beds

Asrar A. Al-Obaidy; Majid I. Abdul-Wahab; Balasim A. Abid

Engineering and Technology Journal, 2009, Volume 27, Issue 10, Pages 1901-1914

Heat transfer from an immersed heating surface to a liquid-solid and liquid-liquidsolid fluidized beds have been studied. The experiments were carried out in a (0.22) m column diameter fitted with an axially mounted cylindrical heater heated electrically. The fluidizing medium was water as the continuous phase and kerosene as the dispersed phase. Low density (Ploymethyl-methacrylate) particles were used. Previous
published heat transfer correlations, obtained for fluidized beds containing highdensity particles, gave significant deviations compared with the present data. New correlations were developed to predict the heat transfer coefficients in liquid-solid and liquid-liquid-solid fluidized beds. The new correlation is,

The heat transfer coefficients obtained from the present work were compared with those estimated from other correlations reported in the literature. The comparison shows a good agreement with the data obtained for the gas-liquid-solid fluidized beds using low-density particles.