Two-flux and diffusion methods for radiative transfer in composite layers
- NASA Lewis Research Center, Cleveland, OH (United States)
Temperature distributions and heat fluxes are predicted in composite semitransparent layers heated or cooled on both sides by radiation and convection. Two approximate methods were used for performing spectral calculations, and the results were validated by comparison with `exact ` numerical solutions of the radiative transfer equations. The composite layers have refractive indices larger than one, and isotropic scattering is included. The two-flux method for multilayer composites gave good agreement with numerical solutions for the conditions considered. For a composite with an optically thick layer, the theory was developed to use the diffusion method and join it to the two-flux method in an adjacent layer. Convergence is improved over using the two-flux method in the optically thick layer. When the hot surroundings are at a different temperature than the gas on the hot side, large temperature gradients can occur near the hot boundary that can cause thermal stresses. If the surroundings are at a higher temperature than the gas on the hot side, the maximum temperature can be within the material rather than at the surface. This is important if the material is operating near its upper temperature limit for adequate strength. 8 refs., 4 figs.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 249636
- Journal Information:
- Journal of Heat Transfer, Journal Name: Journal of Heat Transfer Journal Issue: 1 Vol. 118; ISSN JHTRAO; ISSN 0022-1481
- Country of Publication:
- United States
- Language:
- English
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