A 4 in-OD pipe is to be used to transport liquid metals and will have an outside surface temperature of 1400F under operating conditions. Insulation is 6 in. thick and has a thermal conductivity expressed as, k = 0.08(1-0.003T) where k is in Btu/h*ft*F.

a) What thickness of insulation would be required for the outside insulation temp to be no higher than 300F.

b) What heat flow rate will occur under these conditions.