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Research Papers: Radiative Heat Transfer

Coupled Thermal Radiation and Mixed Convection Step Flow of Nongray Gas

[+] Author and Article Information
M. Atashafrooz

Mechanical Engineering Department,
Sirjan University of Technology,
Sirjan, Iran

S. A. Gandjalikhan Nassab

Mechanical Engineering Department,
School of Engineering,
Shahid Bahonar University of Kerman,
Kerman, Iran
e-mail: Ganj110@uk.ac.ir

K. Lari

Mechanical Engineering Department,
Graduate University of Advanced Technology,
Kerman, Iran

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received June 7, 2015; final manuscript received February 19, 2016; published online April 19, 2016. Assoc. Editor: Zhuomin Zhang.

J. Heat Transfer 138(7), 072701 (Apr 19, 2016) (9 pages) Paper No: HT-15-1405; doi: 10.1115/1.4033095 History: Received June 07, 2015; Revised February 19, 2016

The main goal of this paper is to analyze the thermal and hydrodynamic behaviors of laminar mixed convection flow of a nongray radiating gas over an inclined step in an inclined duct. The fluid is considered an air mixture with 10% CO2 and 20% H2O mole fractions, which is treated as homogeneous, absorbing, emitting, and nonscattering medium. The full-spectrum k-distribution (FSK) method is used to handle the nongray part of the problem, while the radiative transfer equation (RTE) is solved using the discrete ordinate method (DOM). In addition, the results are obtained for different medium assumptions such as pure mixed convection and gray medium to compare with the nongray calculations as a real case. The results show that in many cases, neglecting the radiation part in computations and also use of gray simulations are not acceptable and lead to considerable errors, especially at high values of the Grashof number in mixed convection flow.

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References

Figures

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Fig. 1

Schematic of problem geometry

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Fig. 2

Distribution of absorption coefficient across the spectrum at T = 900 K

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Fig. 3

k–g distribution and weight function at T = 900 K

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Fig. 4

Distribution of nondimensional radiative heat flux along the bottom wall obtained from the LBL and FSK methods

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Fig. 5

Effect of Gr on the streamlines contours in nongray medium, β=30 deg, εw=0.8: (a) Gr = 5000, (b) Gr = 7500, and (c) Gr = 10,000

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Fig. 6

Effect of Gr on the U-velocity in different media: (a) Gr = 2500, (b) Gr = 5000, (c) Gr = 7500, and (d) Gr = 10,000

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Fig. 7

Effect of Gr on the friction coefficient along the bottom wall in different media

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Fig. 8

Distributions of isotherms contours: Gr = 5000, β=30 deg, εw=0.8. (a) gray medium, (b) nongray medium, and (c) pure mixed convection.

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Fig. 9

Effect of Gr on the temperature distributions along Y-axis in different media: (a) Gr = 2500 and (b) Gr = 10,000

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Fig. 10

Effect of Gr on the Nusselt number distributions along the bottom wall in different media: (a) convective Nusselt number, (b) radiative Nusselt number, and (c) total Nusselt number

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