Hot engine oil is being transported in a horizontal pipe (k = 15 W/m∙K, Di = 5 cm) with a wall thickness of 5 mm. The pipe is covered with a 5-mm-thick layer of insulation (k = 0.15 W/m∙K). A length of 2 m of the outer surface is exposed to cool air at 10°C. If the pipe inner surface temperature is at 90°C, determine the outer surface temperature. Hint: The pipe outer surface temperature has to be found iteratively. Begin the calculations by using a film temperature of 50°C.

Hot engine oil is being transported in a horizontal pipe (k = 15 W/m∙K, Di = 5 cm) with a wall thickness of 5 mm. The pipe is covered with a 5-mm-thick layer of insulation (k = 0.15 W/m∙K). A length of 2 m of the outer surface is exposed to cool air at 10°C. If the pipe inner surface temperature is at 90°C, determine the outer surface temperature. Hint: The pipe outer surface temperature has to be found iteratively. Begin the calculations by using a film temperature of 50°C.

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter6: Forced Convection Over Exterior Surfaces

Section: Chapter Questions

Problem 6.4P: An electrical transmission line of 1.2-cm diameter carries a current of 200 amps and has a...

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Clothing made of several thin layers of fabric with trapped air in between, often called ski clothing, is commonly used in cold climates because it is light, fashionable, and a very effective thermal insulator. So it is no surprise that such clothing has largely replaced thick and heavy old-fashioned coats. Consider a jacket made of five layers of 0.1-mm-thick synthetic fabric (k = 0.13 W/m·K) with 1.5-mm-thick air space (k = 0.026 W/m·K) between the layers. Assuming the inner surface temperature of the jacket to be 28°C and the surface area to be 1.25 m2, determine the rate of heat loss through the jacket when the temperature of the outdoors is 0°C and the heat transfer coefficient at the outer surface is 25 W/m2·K. What would your response be if the jacket is made of a single layer of 0.5-mm-thick synthetic fabric? What should be the thickness of a wool fabric (k = 0.035 W/m·K) if the person is to achieve the same level of thermal comfort wearing a thick wool coat instead of a…
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