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Unformatted text preview: Midterm Progress Assessment ECH 3223, Fall 2008 Monday, October 20 Directions: • Two hours. • Open book. • No notes. • Calculator needed. • Start each problem on a new page. • Maximize your score by showing all work. • Good luck to you!! Problem #1: Quick questions (15 points) a) The thermal diffusivity α = k/ρc p has what units? b) By performing a change of variable, determine c in each case: ∂φ ∂x = c ∂φ ∂z 1) z = x/L 2) z = 1 / √ x 3) z = x 2 c) If the effectiveness of a cylindrical pin fin of length L and radius R is 2, what is the efficiency of the fin? Problem #2: Non-uniform generation (20 points) The exposed surface ( x = 0) of a plane wall of thermal conductivity k is subjected to microwave radiation that causes volumetric heating to vary as ˙ q ( x ) = ˙ q 1- x L , where ˙ q (W/m 3 ) is a constant. The boundary at x = L is perfectly insulated, while the exposed surface is maintained at a constant temperature T . If the temperature far from the wall is...
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This note was uploaded on 01/08/2010 for the course ECH 3223 taught by Professor Asthigiri during the Spring '08 term at University of Florida.
- Spring '08