quiz 1 07 without key doc

# quiz 1 07 without key doc - at 27°C A What is the rate at...

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PTFE 3210 Quiz #1 Spring 2007 CLOSED BOOK NAME:____________________________ 1. Define: (5 points each) a) Heat Flux b) Blackbody c) Steady State d) Thermal Radiation e) Forced Convection

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2. The temperature distribution through a plane wall (thickness of 0.1 m) with constant thermal conductivity of 1.0 W/ (m . K) is T = [100 + 100x /m + (150x 2 /m 2 ) ] 0 C where x is the distance measured from the left wall. (a) Determine the heat flux at the mid-point of the wall. (11 points) (b) In which direction does the heat flow at the mid-point of the wall? (3 points) (c) Where does the absolute value of heat flux in the wall occur? What is the heat flux there? (11 points)
3. A gray body sphere with an area of 0.5 m 2 , an emissivity 0.8, and a temperature of 127°C is placed in a large, evacuated chamber whose blackbody walls are maintained

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Unformatted text preview: at 27°C. A. What is the rate at which radiation is emitted by the surface? (10 points) B. What is the net rate at which radiation is exchanged between the surface and the chamber walls? (10 points) Note: The Stefan-Boltzmann constant is 5.670 x 10-8 W/ m 2. K 4 . 4. A square isothermal chip is of width w = 10 mm on a side and is mounted in a substrate such that its side and back surfaces in a substrate such that its side and back surfaces are well insulated, while the front surface is exposed to the flow of a coolant at T ∞ = 15 o C. From reliability considerations, the chip temperature must not exceed T = 115 o C. If the coolant is air and the corresponding convection coefficient is h = 200 W/m 2. K, what is the maximum allowable chip power? (25 points)...
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quiz 1 07 without key doc - at 27°C A What is the rate at...

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