Insulated steam lines in power plants are lagged to protect the insulation from damage to prevent...
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Insulated steam lines in power plants are lagged to protect the insulation from damage to prevent absortion of moistuire into the insolation. Cavas cloth or thin aluminum sheet is currently used. The aluminum is typically 1.5 mm thick, whereas the cloth may be 1.5 to 3 mm thick. Use aluminum, with its lower emittance, reduces the heat loss but increases the surface temperature by 5 to 15°C . To avoit skin burns, it is recomended that maximun safe lagging surface temperatures are 40°C for metalic jackets and 60°C for cavas jackets. A 36 cm-0.D., 7 cm wall-thickness steel steam line is insulated with a 10 cm thickness of calcium cilicate. The steam temperature is 560°C, and the ambient temperature is 26°C. The inside convective resistence is negligible and the outside convective heat transfer coeficient can be taken as 10 W/m² K. a) Calculate the rate of heat loss per meter and surface temperature for a 1.5 mm-thick aluminum sheet lagging. b) Calculate the rate of heat loss per meter and surface temperature for a 3 mm-thick cavas lagging. Take ɛ = 0.9 for cavas. c) If aluminum is painted with an oil-based paint with a emittance of 0.9 calculate the increase in heat loss and the reduction in surface tempearure. %3D Use e = 0.1 for the aluminum, k 0.04 W/m K for cavas, and k 0.085 W/m K for calsilite insulation. Insulated steam lines in power plants are lagged to protect the insulation from damage to prevent absortion of moistuire into the insolation. Cavas cloth or thin aluminum sheet is currently used. The aluminum is typically 1.5 mm thick, whereas the cloth may be 1.5 to 3 mm thick. Use aluminum, with its lower emittance, reduces the heat loss but increases the surface temperature by 5 to 15°C . To avoit skin burns, it is recomended that maximun safe lagging surface temperatures are 40°C for metalic jackets and 60°C for cavas jackets. A 36 cm-0.D., 7 cm wall-thickness steel steam line is insulated with a 10 cm thickness of calcium cilicate. The steam temperature is 560°C, and the ambient temperature is 26°C. The inside convective resistence is negligible and the outside convective heat transfer coeficient can be taken as 10 W/m² K. a) Calculate the rate of heat loss per meter and surface temperature for a 1.5 mm-thick aluminum sheet lagging. b) Calculate the rate of heat loss per meter and surface temperature for a 3 mm-thick cavas lagging. Take ɛ = 0.9 for cavas. c) If aluminum is painted with an oil-based paint with a emittance of 0.9 calculate the increase in heat loss and the reduction in surface tempearure. %3D Use e = 0.1 for the aluminum, k 0.04 W/m K for cavas, and k 0.085 W/m K for calsilite insulation.
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a Steel pipe Nith Aluminrum sheet lagring Ob 36 Cm d 22 cm Alumniunm t z7em Calerun 2 36 cm d 364 ... View the full answer
Related Book For
Fundamentals of Thermodynamics
ISBN: 978-0471152323
6th edition
Authors: Richard E. Sonntag, Claus Borgnakke, Gordon J. Van Wylen
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