A steel tube having a inner diameter of 45 mm and outer diameter of 75 mm is covered by a thick insulation (asbestos) ha

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A steel tube having a inner diameter of 45 mm and outer diameter
of 75 mm is covered by a thick insulation
(asbestos) having a thickness of 28 mm. The thermal conductivity of
asbestos is 0.2 W/m.k. The hot gas having
a temperature of 550 °C is flowing in the steel tube with heat
transfer coefficient of 300 W/m'.C. The outer
surface of the steel pipe is exposed to the atmosphere at 25 oC
with the heat transfer coefficient of 15 W/m^2.K.
Calculate the heat loss and also the interface temperature and
surface temperature. Take the thermal
conductivity of the steel tube as 7 W/mK .