Isothermal hollow enclosure

Fig. 5.22 Isothermal hollow enclosure for the realisation of a black body. 1 insulation 2 heating 3 copper cylinder 4 reflected radiation 5 polished surface 6 black surface 7 incident beam 8 strongly absorbing surface...

We will now consider a hollow enclosure surrounded by walls consisting of several parts each with an isothermal surface, Fig. 5.55. According to H.C. Hottel... 

If the bodies participating in radiative exchange cannot be assumed to be black bodies, then the reflected radiation flows also have to be considered. In hollow enclosures, multiple reflection combined with partial absorption of the incident radiation takes place. A general solution for radiative exchange problems without simplifying assumptions is only possible in exceptional cases. If the boundary walls of the hollow enclosure are divided into isothermal zones, like in 5.5.2, then a relatively simple solution is obtained, if these zones behave like grey Lambert radiators. Each zone is characterised purely by its hemispherical total emissivity si — whilst at = is valid for its absorptivity, and for the reflectivity... 

Fig. 5.57 Hollow enclosure bounded by isothermal surfaces (zones) each of which is a grey Lambert radiator...

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See also in sourсe #XX -- [ , , , ]

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