Radiation in participating media

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The investigation of radiative transfer so far has contained the assumption that the radiative transfer between and among surfaces is unaffected by any medium that exists between the surfaces. Often this is a good assumption; however, in important cases the radiation is attenuated on its path between an emitting and an absorbing surface. In addition, the medium between the surfaces may emit energy, adding to the radiation incident on enclosing surfaces. The effect of a participating medium is especially important in combustion systems, where combustion products and ash and soot particles cause significant attenuation within the medium as well as emission from high-temperature flames and gas mixtures. Other systems where medium effects are important are in shock-layer emission to the surface of reentry heat shields for spacecraft; attenuation by interstellar dust clouds that affect observations; emission from the hot gases at the surface of the sun; the damage to lenses in optical systems due to even very small absorption of energy from a high-intensity laser beam; absorption in the Earth's atmosphere by the "greenhouse gases" that affects global warming; cancer detection by monitoring of skin-temperature anomalies due to submerged tumors; and attenuation of laser energy by the skin and organs that affects everything from treatment of cataracts in the eye to tattoo removal.


Faghri, A., Zhang, Y., and Howell, J. R., 2010, Advanced Heat and Mass Transfer, Global Digital Press, Columbia, MO.

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