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Numerical study on the wall to bed heat transfer in a conical fluidized bed combustor

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Abstract

In this work a numerical investigation of wall to bed heat transfer, and the related flow characteristics, was conducted along a conical fluidized bed combustor with a height of 0.8 m and a cone angle of 30°. A two-fluid Eulerian-Eulerian model was used while applying Kinetic Theory for Granular Flow (KTGF) to a wall-to-bed FB reactor. The heat transfer coefficient and hydrodynamics are discussed for two different drag models, namely the Gidaspow and Syamlal-O’Brien models. Furthermore, computational calculations were carried out for a variety of inlet velocities(1.4Umf~4 Umf) and different particle sizes. The heat transfer coefficient in the bed region was evaluated and compared with that calculated by penetration theory. The bed expansion for the two models was compared with that calculated using correlations from literature in order to validate the numerical calculations. The heat transfer coefficient was found to be increasing with increasing gas velocity and decreasing with increasing particle diameter.

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Abbreviations

CD :

Drag coefficient

CP :

Specific heat (J kg−1 K−1)

ds :

Diameter of the particles (m)

e s :

Coefficient of restitution

H:

Enthalpy (J)

Hgs :

Heat transfer from fluid to solid (J)

h:

Heat transfer coefficient (W m−2 K−1)

hs :

Static (minimum) bed height (m)

I:

Identity tensor

k:

Thermal conductivity (W m−1 K−1)

q:

Diffusive flux

Pr:

Prandtl number

\(\overline{\overline D}\) :

Rate of strain tensor

g:

Gravitational acceleration (m s−2)

go :

Radial distribution function

Nu:

Nusselt number

P:

Pressure (Pa)

R:

Bed expansion ratio

Re:

Reynolds number

r/R:

Radial distance

U:

Gas velocity (m s−1)

Z:

Height above air inlet (m)

ε:

Volume fraction

β:

Interphase exchange coefficient

γ:

Coefficient defined by Eq. (26)

μ:

Viscosity (N s m−1)

Θ:

Granular temperature (m2 s−2)

νr :

Terminal velocity of particles (m s−1)

ρ:

Density (kg m−3)

τ:

Stress tensor

g:

Gas

m:

Mixture

s:

Solid

pen:

penetration

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Authors and Affiliations

  1. Department of Mechanical Design Engineering and Eco-friendly Machine Parts Design Research Center, Chonbuk National University, 567 Baekjedaero, Duckjin-gu, Jeonju, 561-756, South Korea

    Hamada Mohamed Abdelmotalib, Suk Bum Youn & Ik-Tae Im

  2. Department of Mechanical Power and Energy, Faculty of Engineering, Minia University, Elminia, Egypt

    Hamada Mohamed Abdelmotalib, Mahmoud Abdelftah Youssef & Ali Ahmed Hassan

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  1. Hamada Mohamed Abdelmotalib
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  2. Mahmoud Abdelftah Youssef
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Correspondence to Ik-Tae Im.

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Abdelmotalib, H.M., Youssef, M.A., Hassan, A.A. et al. Numerical study on the wall to bed heat transfer in a conical fluidized bed combustor. Int. J. Precis. Eng. Manuf. 16, 1551–1559 (2015). https://doi.org/10.1007/s12541-015-0205-z

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  • DOI: https://doi.org/10.1007/s12541-015-0205-z

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