A 6-in Sch 80 steel pipe is covered with a 0.1 m layer of 85% magnesia insulation. The temperature of the inner surface of the pipe is 250oC, and the temperature of the outer surface of the insulation is 40oC. Appendix 3 provides dimensions for steel pipes.
a) Calculate the rate of heat loss per meter of pipe and the temperature at the interface (knowing the interfacial temperature is often important to know what materials of construction are needed) between the pipe and the insulation. Be sure to use the log mean area.
b) Often the thermal resistance of the pipe, particularly when it is thin-walled, can be neglected in the overall heat transfer. Calculate your answer both including the steel pipe thermal resistance and neglecting it. Is neglecting it justified?
Useful data:
Steel: thermal conductivity = 44.8 W/m•K 85% magnesia insulation thermal conductivity = 0.066 W/m•K