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Heat and Mass Transfer

, Volume 44, Issue 4, pp 421–435 | Cite as

Optimization of a buoyancy chimney with a heated ribbed wall

  • Marco Cavazzuti
  • Mauro A. CorticelliEmail author
Original

Abstract

Heat and mass transfer in natural convection vertical channels was investigated by means of two-dimensional CFD simulations aided by optimization algorithms. The channel was immersed in air, enclosed between an adiabatic smooth wall and an isothermally heated ribbed wall. The ribs were perpendicular to the fluid flow and their height, width, pitch, thermal conductivity and lateral wall inclination were variable. Also the smooth heated wall channel was studied and compared with the ribbed one. The existence of an optimal channel width for a given channel height and rib geometry was shown. A sensitivity analysis was carried out for the ribbed and the smooth channels. Optimization was applied to the ribbed channel problem in order to maximize the heat and the mass transfer through a multi-objective genetic algorithm. It was found that the presence of the ribs penalizes the channel performance so that no ribbed channel over-performed the smooth one.

Keywords

Nusselt Number Mass Flow Rate Channel Height Heated Wall Average Heat Transfer Coefficient 
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.

List of symbols

Ar

channel aspect ratio

Awet

wetted area (m2)

H

channel height (m)

H

non-dimensional channel height

H0

reference channel height (m)

\({\dot{M}}\)

mass flow rate (g/s)

M

non-dimensional mass flow rate

Nu

Nusselt number

Nux

local Nusselt number

\({\dot{Q}}\)

channel heat transfer rate (W)

Ra

Rayleigh number

Rh

rib height (m)

Rn

ribs number

Rp

rib pitch (m)

Rw

rib crest width (m)

S

channel width (m)

cp

fluid specific heat at constant pressure (J/(kg K))

g

gravitational acceleration (m/s2)

h

local heat transfer coefficient (W/(m2 K))

hav

average heat transfer coefficient (W/(m2 K))

s

heated wall curvilinear abscissa measured from the channel inlet (m)

uref

reference velocity (m/s)

x

vertical abscissa measured from the channel inlet (m)

ΔT

ribbed wall to ambient temperature difference (K)

ΔT

non-dimensional temperature difference

ΔT0

reference ribbed wall to ambient temperature difference (K)

α

rib lateral wall inclination (deg)

β

fluid thermal expansion coefficient (1/K)

λ

rib thermal conductivity (W/(m K))

λfl

fluid thermal conductivity (W/(m K))

μ

fluid dynamic viscosity (kg/(m s))

ρ

fluid density (kg/m3)

Notes

Acknowledgments

Financial support for this research was provided by MIUR, PRIN 2005, Grant No. 2005094817. Thanks to Prof. E. Nobile (University of Trieste) and G. Tanda (University of Genova), for the scientific support. Technical support by ES.TEC.O. Srl, Trieste, italy, is gratefully acknowledged.

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Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  1. 1.DIMeC-Università degli Studi di Modena e Reggio EmiliaModenaItaly

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