Calculating Steady State Heat Transfer

[dzkl]

A straight, uniform circular pipe of internal diameter of 88.43 mm and external diameter of 118.38 mm carries hot water at 63.67 deg cel. The pipe has a thermal conductivity of 247 Wm^-1 K^-1.

how to calculate the steady-state rate of heat transfer per unit length, in W m^-1, when the outside temperature is 30.59 deg cel.

What I have done so far:-

Temperature Gradient = (T1-T2)/d, where d is the diff in radius of cylinder = (63.67-30.59)/(0.5*(118-88.43)*0.001) = 2209.015025

So,heat transfer = 247*3.142*0.08843*2209.015025 = 151581 Wm^-1

Is the method right?

 

[rock.freak667]

You'll need to use the formula for a hollow cylinder (which is what a pipe is)

http://en.wikibooks.org/wiki/Heat_Transfer/Conduction#A_hollow_cylinder