# Emissivity, radiation and heat transfer

1. Jul 7, 2012

### CeeCoops

1. The problem statement, all variables and given/known data
A space station in outer space (far from the sun) has a total surface area of 580 m^2 with emissivity of .62. The temperature of the outside surface is 156 K. the walls are .25 m thick with an average thermal conductivity of .038 Wm^-1K^-1. Find the temperature of the inner wall of the space station, assuming that the outside surface radiates into an environment that is very cold - essentially at 0.0 K.

2. Relevant equations

P= σA(T^4 - To^4) and P= kA ((Th-Tc)/L)

3. The attempt at a solution Just not too sure where to start...does the outer surface of the wall lose some of its heat to the surroundings and then we try to determine how much heat will be transfered to the inner wall? thanks for any help :)

Last edited by a moderator: Jul 9, 2012
2. Jul 7, 2012

### rude man

Heat obviously travels from the inside to the outside wall. The space station is generating heat which flows thru the wall to deep space at 0K.

Your emissivity equation is for a black body (α=1). If α < 1 how should that equation go?

So all that's left is to realize that power flowing out of the platform by conduction = power dispersed by emission to cold, cold space!

Last edited: Jul 7, 2012