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.
TROUBLE SHOOTING PROCESS Step 1: Identify the Problem In this first step you already know that there is a problem; now you have to identify exactly what it is. This means gathering information. You do this in a few ways: . Question the user. Ask the person who reported the problem detailed questions about the issue. You want to find out about symptoms, unusual behavior, or anything that the user might have done of late that could have inadvertently or directly caused the problem. Of course, do this without accusing the user. If the user cannot properly explain a computer’s problem, ask simple questions to further identify the issue. Identify any changes made to the computer. Look at the computer. See if any new hardware has been installed or plugged in. Look around for an
