An array of electronic chips is mounted within a sealed

Chapter , Problem 7.29

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An array of electronic chips is mounted within a sealed rectangular enclosure, and cooling is implemented by attaching an aluminum heat sink (k 180 W/m K). The base of the heat sink has dimensions of w1 w2 100 mm, while the 6 fins are of thickness t 10 mm and pitch S 18 mm. The fin length is Lf 50 mm, and the base of the heat sink has a thickness of Lb 10 mm. If cooling is implemented by water flow through the heat sink, with u 3 m/s and T 17 C, what is the base temperature Tb of the heat sink when power dissipation by the chips is Pelec 1800 W? The average convection coefficient for surfaces of the fins and the exposed base may be estimated by assuming parallel flow over a flat plate. Properties of the water may be approximated as k 0.62 W/m K, 995 kg/m3 , cp 4178 J/kg K, 7.73 107 m2 /s, and Pr 5.2.