Evaluation of the Net Radiant Heat Transfer between Specularly Reflecting Plates

Radiative exchange often becomes the controlling mode of heat transfer when systems are found to exist at either low or high temperature levels. In the former case, for instance, it often becomes one of the major heat leaks to cryogenic fluids stored in dewars. In the following, the net radiant heat transfer between two parallel infinite surfaces is calculated for behavior in all respects as predicted by the electromagnetic theory of radiation for polished electrical conductors. t Head, School of Mechanical Engineering, Purdue University, Lafayette, Indiana. 1865 18(36 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1962 I I . FORMULATION AND SOLUTION The monochromatic emissivity, absorptivity, and reflectivity are known to be azimuthally symmetric about the normal to a conducting surface. Electromagnetic theory 1 2 indicates that the monochromatic directional emissivity of low-emissivity metals is given by: 60X e(0,) = a(0,) = 1 - i re 60X _ j /30X , 2 2 A cos 0 + cos y re /30X ~ 0 + 2 A/ cos 0 + cos _ re V re 60 cos2 0 _ /30X . . .1 -- 2 A/ -- cos 0 + 1 re y re 60X cos2 0 /30X . . , + 2 A/ COS 0 + 1 re y re