- #1

shyta

- 56

- 0

I understand that for a grey body sphere confined within a blackbody spherical shell, the general forumla for the net power radiated from inner sphere should be

P

_{rad}= kAe(T

^{4}-T

_{surr}

^{4})

where k=stefan boltzman's constant

However recently, I was given a question which made me really confused.

For the case where 2 plates are separated by a gap and the left plate has a higher temp, T

_{1}and emissivity, e

_{1}= 1, as compared to the right plate having T

_{2}and emissivity e

_{2}. Then the net rate of power transferred from the left to the right is?

P

_{rad by left plate}= kAe

_{1}T

_{1}

^{4}

P

_{rad by right plate}= kAe

_{2}T

_{2}

^{4}

which all of it is absorbed by the left plate since emissivity is 1

then fraction absorbed by right plate is e

_{2}

and fraction reflected by right plate is 1-e

_{2}(all absorbed by the left plate)

P

_{net flow from left to right}= kA (e

_{1}T

_{1}

^{4}e

_{2}- e

_{2}T

_{2}

^{4})

But how??