Air at 27°C with a free stream velocity of 10 m/s is used to cool electronic devices mounted on a printed circuit board. Each device, 4 mm × 4 mm, dissipates 40 mW, which is removed from the top surface. A turbulator is located at the leading edge of the board, causing the boundary layer to be turbulent.
(a) Estimate the surface temperature of the fourth device located 15 mm from the leading edge of the board.
(b) Generate a plot of the surface temperature of the first four devices as a function of the free stream velocity for 5 ≤ u∞ ≤ 15 m/s.
(c) What is the minimum free stream velocity if the surface temperature of the hottest device is not to exceed 80°C?