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) A computer CPU chip operates at steady state with D-C electrical input of 4.5

ID: 1860717 • Letter: #

Question

) A computer CPU chip operates at steady state with D-C electrical input of 4.5 amps

at 9 volts. To prevent the chip from overheating, a small fan blows air over metal fins

fused to the chip to transfer heat by convection. The metal fins are at approximately

uniform temperature. The fan power and heat transfer by other paths are negligible.

The metal fins have a total surface area of 0.05 m2

and a convective coefficient of

0.040 kW/m2

-K. The air temperature is 300 K.

A computer CPU chip operates at steady state with D-C electrical input of 4.5 amps at 9 volts. To prevent the chip from overheating, a small fan blows air over metal fins fused to the chip to transfer heat by convection. The metal fins are at approximately uniform temperature. The fan power and heat transfer by other paths are negligible. The metal fins have a total surface area of 0.05 m2 and a convective coefficient of 0.040 kW/m2-K. The air temperature is 300 K. Ans: Tsurface = 320 K The electrical work input needed for 24 hours of operation = kJ The surface temperature of the metal fins = K

Explanation / Answer

electric work input = 400 kJ

we have ,, 400 = .040 * .05 (T-300) *10^3

this gives T = 320 K