A 30-cm-OD pipe with a surface temperature of 90?C carries steam over a distance of 100 m.

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A 30-cm-OD pipe with a surface temperature of 90?C carries steam over a distance of 100 m. The pipe is buried with its center line at a depth of 1 m, the ground surface is ?? 6?C, and the mean thermal conductivity of the soil is 0.7 W/(m K). Calculate the heat loss per day, and the cost, if steam heat is worth $3.00 per 106 kJ. Also, estimate the thickness of 85% magnesia insulation necessary to achieve the same insulation as provided by the soil with a total heat transfer coefficient of 23 W/(m2 K) on the outside of the pipe.GIVENA buried steam pipeOutside diameter of the pipe (D) = 30 cm = 0.3 mSurface temperature (Ts) = 90?CLength of pipe (L) = 100 mDepth of its center line (Z) = 1 mThe ground surface temperature (Tg) = ??6?CThe mean thermal conductivity of the soil (k) = 0.7 W/(m K)Steam heat is worth $3.00 per 106 kJThe heat transfer coefficient (hc) = 23 W/(m2 K) for the insulated pipeASSUMPTIONSSteady state conditionsUniform thermal conductivityTwo dimensional heat transfer from thepipe

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Principles of heat transfer

ISBN: 978-0495667704

7th Edition

Authors: Frank Kreith, Raj M. Manglik, Mark S. Bohn

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