A small sphere(d1= 0.4) is placed within a spherical enclosure (d2= 2.0) and supported with insulated struts such that it is concentric with the outer wall. The space between the sphere is evacuted. The small sphere is maintanied at a temprature of T1= 450 k and teh wall of the spherical enclosure are maintained at a temprature of T2= 300 k. There is no Heat transfer due to struts.
a) If the surface act as black bodies, what is the net rate of radiation exchange the two spheres.
b) what is the net radiation exchange between the surfaces if they are diffuse and gray with E1= 0.5 and E2=0.05?
c) what is the net radiation exchnage between the surface if the diameter of the enclousre is increased to d2= 20m and the other parameter remain the same (d1=0.4, E1=0.5 and E2=0.05)?
d) What error would be introduced for the value calculated in part (c) if the assumption was made that the outer surface act as a black body (E2=1)
e) Explain your answer for part (d).