Radiation-laminar free convection in a square duct with specular reflection by absorbing-emitting medium |
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Authors: | Ki-Hong Byun Moon Hyuk Im |
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Affiliation: | (1) Department, of Mechanical Engineering, Dongguk University, Jung-Ku, 100-715 Seoul, Korea;(2) Department of A utomotive and Mechanical Engineering, Keimyung University, 704-701 Daegu, Korea |
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Abstract: | The purpose of this work is to study the effects of specularly reflecting wall under the combined radiative and laminar free
convective heat transfer in an infinite square duct. An absorbing and emitting gray medium is enclosed by the opaque and diffusely
emitting walls. The walls may reflect diffusely or specularly. Boussinesq approximation is used for the buoyancy term. The
radiative heat transfer is evaluated using the direct discrete ordinates method. The parameters under considerations are Rayleigh
number, conduction to radiation parameter, optical thickness, wall emissivity and reflection mode. The differences caused
by the reflection mode on the stream line, and temperature distribution and wall heat fluxes are studied. Some differences
are observed for the categories mentioned above if the order of the conduction to radiation parameter is less than order of
10-3 for the range of Rayleigh number studied. The differences at the side wall heat flux distributions are observed as long as
the medium is optically thin. As the top wall emissivity decreases, the differences between these two modes are increased.
As the optical thickness decreases at the fixed wall emissivity, the differences also increase. The difference of the streamlines
or the temperature contours is not as distinct as the side wall heat flux distributions. The specular reflection may alter
the fluid motion. |
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Keywords: | Specular Diffuse Reflection Radiation Free Convection Participating Media Square Duct Direct Discrete Ordinates Method |
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