A thick-walled tube of stainless steel(Ks=19.0 W / m.°C) with 2-cm inner diameter (ID) and 4-cm outer diameter (OD) is covered with a 3-cm layer of asbestos insulation ( ka =0 . 2 W / m.°C). If the...

A thick-walled tube of stainless steel(Ks=19.0 W/m.°C)  with 2-cm inner diameter (ID) and 4-cm outer diameter (OD) is covered with a 3-cm layer of asbestos insulation (ka
=0.2 W/m.°C). If the temperatures of  inside wall of the pipe and the outside of the insulator are maintained at 600 and the surface temperature on the insulating material remained constant at 293 °C.

 determine the values of r1,r2,and r3 from the below equation and calculate heat loss per unit lenght .

q/L​=ln(r2​/r1​)/Ks​+ln(r3​/r2​)/Ka​2π(T1​−T2​)​