How Is the Steady State Assumed in Solving the Thermal Diffusion Equation?

[bon]

thermal diffusion equation - URGENT

Homework Statement

Please see attached q

Homework Equations

The Attempt at a Solution

Ok so thermal diffusion equation is DT/Dt = D del squared T

apparently this is a steady state problem, so DT/dt = 0, how am i meant to know? any hints on solving please?

 

[bon]

I've done part (a) how do you do (b) though

 

[bon]

is (b) a steady state too? how do we know..?

 

[bon]

Ok i guess it is...

is the equation i have to solve:

del squared T = alpha/k (T(a) - Tair) - I^2 ro/pi^2 a^4?