One hundred electrical components, each dissipating 25 w, are attached to one surface of a square (0.2 m 0.2 m) copper plate, and all the dissipated energy is transferred to water in parallel flow over the opposite surface. a protuberance at the leading edge of the plate acts to trip the boundary layer, and the plate itself may be assumed to be isothermal. the water velocity and temperature are u 2 m/s and t 17 c, and the water’s thermophysical properties may be approximated as 0.96 106 m2 /s, k 0.620 w/m k, and pr 5.2. ch007.qxd 4/14/11 8: 23 pm page 471

(a) what is the temperature of the copper plate?

(b) if each component has a plate contact surface area of 1 cm2 and the corresponding contact resistance is 2 104 m2 k/w, what is the component temperature? neglect the temperature variation across the thickness of the copper plate.