For infinite parallel planes having emissivities ε1 & ε2, the interchange factor for radiation from surface 1 to surface 2 is given by__________________?
Correct answer: B. ε1.ε2/(ε1 + ε2 - ε1.ε2)
- A. (ε1 + ε2)/ε1.ε2
- B. ε1.ε2/(ε1 + ε2 - ε1.ε2)
- C. ε1.ε2
- D. ε1 + ε2
Explanation
For two infinite facing gray surfaces, the radiation exchange factor is the reciprocal of the two surface resistances and the space resistance: ε1ε2/(ε1 + ε2 − ε1ε2). This accounts for repeated reflection between the surfaces.
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