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Quiz 1 08

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

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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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