An array of 10 silicon chips, each of length l = 12 mm on a side is insulated on one surface and cooled on the opposite surface by atmospheric air in parallel flow with t

[infinity]

= 25

o

c and u

[infinity]

= 35 m/s. when in use the same electrical power is dissipated in each chip, maintaining a uniform heat flux over the entire cooled surface.

a) if the temperature of the chip may not exceed 85

o

c, what is the maximum allowable power per chip?

b) would it be preferable to orient the array normal, instead of parallel, to the air flow. explain your answer.

Aloaded platform of total mass 500 kg is supported by a dashpot and by a set of springs of effective stiffness 72 kn/m. it is observed that when the platform is depressed through a distance x = 12.5 cm below its equilibrium position and then released without any initial velocity; it reaches its equilibrium position in the shortest possible time without overshoot. find the position and velocity of the loaded platform 0.10 sec. after its release. if a further load of 400 kg is added to the platform, find, i) the frequency of damped vibrations, and i) the amplitude of vibration after 2 complete oscillations, given that the initial amplitude is 15 cm.

During a steady flow process, the change of energy with respect to time is zero. a)- true b)- false

Ajournal bearing has a journal diameter of 3.250 in with a unilateral tolerance of 20.003 in. the bushing bore has a diameter of 3.256 in and a unilateral tolerance of 0.004 in. the bushing is 2.8 in long and supports a 700-lbf load. the journal speed is 900 rev/min. find the minimum oil film thickness and the maximum film pressure for both sae 20 and sae 20w-30 lubricants, for the tightest assembly if the operating film temperature is 160°f. a computer code is appropriate for solving this problem.