The case of a power transistor, which is of length L = 10 mm and diameter D = 12 mm, is cooled by an air stream of temperature T∞ = 25°C as shown in Fig. P15.6.
Under conditions for which the air maintains an average convection coefficient of on the surface of the case, what is the maximum allowable power dissipation Pe if the surface temperature Ts is not to exceed 85°C?