$10$A$\mathrm{.}1.$ Heat loss from an insulated pipe. A standard schedule $40,2-$in$.$ steel pipe $($inside diameter

$2\mathrm{.}067$ in and wall thickness $0\mathrm{.}154$ in$.)$ carrying steam is insulated with $2$ in$.$ of $85\%$ magnesia

covered in turn with $2$ in$.$ of cork. Estimate the heat loss per hour per foot of pipe if the inner

surface of the pipe is at $250F$ and the outer surface of the cork is at $90F.$ The thermal

conductivities $($in $Bt\frac{u}{h}r*ft*F)$ of the substances concerned are: steel, $26\mathrm{.}1$;$85\%$ magnesia,

$0\mathrm{.}04$ ; cork, $0\mathrm{.}03.$