Quiz 1 08 - ( 2 5 p o i n t s ) 3. An electric resistance...

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PTFE 3210 QUIZ #1 Spring 2008 Name _______________ Closed Book Quiz and No calculators are allowed!! 1. Define the following terms: (3 points each) a. heat transfer Transfer of Energy Due to a Temperature Difference b. blackbody An ideal surface having the following properties: Absorbs all incident radiation For a given temperature and wavelength, emits the maximum amount of energy Emits diffusely c. steady state No changes with time d. gray surface Suppose a real body is at the same temperature as a blackbody. If the body emits a constant fraction of blackbody emission at each wavelength, the body is called a gray body. e. transient Changes with time 2. A heat rate of 3 kW is conducted through a section of an insulating material of cross- sectional area of 10 m 2 and thickness of 2.5 cm. If the inner (hot) surface temperature is 415 ° C and the thermal conductivity is 0.25 W/m-K, what is the outer surface temperature?
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Unformatted text preview: ( 2 5 p o i n t s ) 3. An electric resistance heater is embedded in a long cylinder of diameter 100 mm. When water with a temperature of 25 ° C flows over the cylinder, the power per unit length required to maintain the surface at a uniform temperature of 125 ° C is 31.4 kW/m. Calculate the convective heat-transfer coefficient for the water flowing over the cylinder. ( 2 5 p o i n t s ) 4. An overhead, uninsulated industrial steam pipe of 1/ π∗ mm diameter is routed through a building whose walls and air are at 27 ° C. Pressurized steam maintains a pipe surface temperature of 127 ° C, and the heat transfer coefficient associated with natural convection is h = 10 W/m 2 . K. The surface emissivity is ε = 1/5.67. What is the rate of heat transfer loss per unit length from the steam line? (25 points) Note: The Stefan-Boltzmann constant is 5.670 x 10-8 W/ m 2. K 4 . * π = 3.1416 (35 points)...
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This note was uploaded on 08/11/2011 for the course PTFE 3210 taught by Professor Dr.carr during the Spring '11 term at Georgia Institute of Technology.

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Quiz 1 08 - ( 2 5 p o i n t s ) 3. An electric resistance...

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