If insulation having a thermal conductivity of 0:060 Btu/h ft F is added to the outside of the steam pipe described in Problem 20.40, what thickness will be necessary if radiation losses from the...

If insulation having a thermal conductivity of 0:060 Btu/h ft
F is added to the outside of the steam pipe described in Problem 20.40, what thickness will be necessary if radiation losses from the outside surface of the insulation account for no more than 15% of the total? The surroundings may be considered black at 70F. What is the temperature at the outside surface of the insulation under these conditions?

Problem 20.40

Steam at 400 psi, 800F flows through a 1-in. schedule140 steel pipe at a rate of 10; 000 lb_m/h: Estimate the value of h that applies at the inside pipe surface.