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.
![114_20a5cbef-d5a3-43d7-9995-466dfb0d80ef.png](https://secure.tutorsglobe.com/CMSImages/114_20a5cbef-d5a3-43d7-9995-466dfb0d80ef.png)
(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?