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 w 1 = w 2 = 100 mm, while the 6 fins are of thickness t = 10mm and pitch S = 18 mm. The fin length is L f = 50 mm, and the base of the heat sink has a thickness of L b = 20 mm. If cooling is implemented by water flow through the heat sink, with u o = 2 m/s and To = 17°C, what is the base temperature Tb of the heat sink when power dissipation by the chips is P elec = 1800 W? Take the increase in temperature of the water as it flows through the heat sink into account. 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, p = 995kg/m3, cp = 4178 J/kg-K, v = 773× 107 m²/s, and P r= 5.2. Assume the water does not escape through the upper surface of the heat sink and that the boundary layers on each fin surface do not merge, allowing evaluation of the heat transfer coefficient using an appropriate external flow correlation. What is the heat transfer resistance of the base material, in K/W? What is the fin efficiency? What is the overall surface efficiency? What is the overall heat transfer - area product, U A, in W/K? NTU =i What is the heat exchanger effectiveness? What is the base temperature, in °C?