Consider the chip cooling scheme of Problem 3.134, but with an insulated top wall placed at the pin tips to force airflow across the pin array. Air enters the array at 20°C and with a velocity V that may be varied but cannot exceed 10 m/s due to pressure drop considerations. The pin fin geometry, which includes the number of pins in the N x N square array, as well as the pin diameter Dp and length Lp, may also be varied, subject to the constraint that the product N_D p not exceed 9 mm. Neglecting heat transfer through the board, assess the effect of changes in air velocity, and hence 11 0 , as well as pin fin geometry, on the air outlet temperature and the chip heat rate, if the remaining conditions of Problems 3.134 and 3.27, including a maximum allowable chip temperature of 75°C, remain in effect.

Recommend design and operating conditions for which chip cooling is enhanced