Radiation Heat Transfer in Nonisothermal Nongray Gases

Experimental measurements of absorption and emission by nonisothermal CO2 and H2O gases are reported. Analytical formulations and calculations of radiant heat transfer using a simple nongray gas model are presented. It is found that a gray gas model cannot predict even qualitatively the experimental results, while the band model method of calculation yields results in quantitative agreement for total emission and absorption in a band. Effects of line structure are shown to be of secondary importance compared to band envelope structure for line-width-to-spacing ratios above 10−2 in saturated bands. An analytical solution for coupled convection and radiation in a plane-parallel-wall duct is derived to illustrate the utility of the exponential band model for analysis of radiant transfer in nonisothermal, nongray gases.

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Radiant Heat Transfer From Isothermal Dispersions With Isotropic Scattering

Journal of Heat Transfer ◽

10.1115/1.3614389 ◽

1967 ◽

Vol 89 (4) ◽

pp. 300-308 ◽

Cited By ~ 20

Author(s):

R. H. Edwards ◽

R. P. Bobco

Keyword(s):

Heat Transfer ◽

Approximate Solutions ◽

Radiant Heat ◽

Second Order ◽

Isotropic Scattering ◽

Radiant Heat Transfer ◽

Approximate Methods ◽

First Order ◽

Order Solution ◽

Radiant Transfer

Two approximate methods are presented for making radiant heat-transfer computations from gray, isothermal dispersions which absorb, emit, and scatter isotropically. The integrodifferential equation of radiant transfer is solved using moment techniques to obtain a first-order solution. A second-order solution is found by iteration. The approximate solutions are compared to exact solutions found in the literature of astrophysics for the case of a plane-parallel geometry. The exact and approximate solutions are both expressed in terms of directional and hemispherical emissivities at a boundary. The comparison for a slab, which is neither optically thin nor thick (τ = 1), indicates that the second-order solution is accurate to within 10 percent for both directional and hemispherical properties. These results suggest that relatively simple techniques may be used to make design computations for more complex geometries and boundary conditions.

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A New Method for Direct Exchange Area Calculation in Zonal Method of Radiant Heat Transfer Modeling in Combustion Furnaces

Volume 8A: Heat Transfer and Thermal Engineering ◽

10.1115/imece2014-36983 ◽

2014 ◽

Author(s):

G. Malikov ◽

V. Lisienko ◽

A. Titaev ◽

R. Viskanta

Keyword(s):

Heat Transfer ◽

Radiation Heat Transfer ◽

Radiant Heat ◽

New Method ◽

Computational Time ◽

Test Case ◽

Radiant Heat Transfer ◽

Zonal Method ◽

Direct Exchange ◽

Exchange Area

A new method based on the discrete transfer modeling technique for calculating the direct exchange areas (DEA) in zonal methods of radiation heat transfer is presented. The key feature of this method is a fast DEA matrix evaluation. The computational time was found to be short in comparison to other methods for direct exchange areas calculation based on numerical quadrature integration. The accuracy of the procedure is assessed by comparing the predictions with those based on the numerical integration for a test case (IFRF furnace).

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