Radiation Exchange Between Multiple Gray Surfaces

10 Radiation Exchange Between Multiple Gray Surfaces 

As Equation (7.45) indicates, knowledge of the view factor allows for the calculation of the net radiation between any two blackbodies as 

For non-black surfaces, the net interchange must account for the reflected radiant energies from other surfaces. For refractory material surfaces encountered in rotary kilns, perhaps one can assume that all surfaces are gray, diffuse, and opaque, that is, 

Equation (7.51) can be interpreted either algebraically or electrically as was done for Newton s Law of cooling in convection or for Fourier s Law of conduction through composite materials. The electrical analogy for Equation (7.51) can be made by comparing ( 5, —/,) to the driving potential difference and Q, as the electrical current. 

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