p1.6-6 - pin fins will provide the best performance. Plot...

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1.6-6 Your company has developed a technique for forming very small fins on a plastic substrate. The diameter of the fins at their base is D = 1 mm. The ratio of the length of the fin to the base diameter is the aspect ratio, AR = 10. The fins are arranged in a hexagonal close packed pattern. The ratio of the distance between fin centers and to the base diameter is the pitch ratio, PR = 2. The conductivity of the plastic material is k = 2.8 W/m-K. The heat transfer coefficient between the surface of the plastic and the surrounding gas is h = 35 W/m 2 -K. The base temperature is T b = 60°C and the gas temperature is T = 35°C. a.) Determine the number of fins per unit area and the thermal resistance of the unfinned region of the base. b.) You have been asked to evaluate whether triangular, parabolic concave, or parabolic convex
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Unformatted text preview: pin fins will provide the best performance. Plot the heat transfer per unit area of base surface for each of these fin shapes as a function of aspect ratio. Note that the performance of these fins can be obtained from the EES functions eta_fin_spine_parabolic_ND , eta_fin_spine_parabolic2_ND , and eta_fin_spine_triangular_ND . Explain the shape of your plot. c.) Assume that part (b) indicated that parabolic convex fins are the best. You have been asked whether it is most useful to spend time working on techniques to improve (increase) the aspect ratio or improve (reduce) the pitch ratio. Answer this question using a contour plot that shows contours of the heat transfer per unit area in the parameter space of AR and PR ....
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This note was uploaded on 08/11/2008 for the course ME 364 taught by Professor Rothamer during the Summer '08 term at Wisconsin.

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