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The fan on a personal computer draws 8.6 L/s of air at 100 kPa and 20...

The fan on a personal computer draws 8.6 L/s of air at 100 kPa and 20 deg C through the box containing the CPU and other components. Air leaves at 100 kPa and 27 deg C. Calculate the electrical power, in kW, dissipated by the PC components.

answer: 0.0719 KW

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Answer #1

▪︎ Givens :

V1 = 8.6 L/s = 0.3 ft3/s

P1 = 100 kPa = 14.5 psia

T1 = 20°C = 528°R = 80.6°F

T2= 27°C = 68°F

Energy balance

Einput - Eoutput = = 0

Therefore,

  

We have,

From ideal gas equation,

  

= 13.49 ft3/lbm

Therefore,

= 0.02224 lbm/s

We have,

Woutput = mcp(T2 - T1)

   = (0.02224 lbm/s)(0.240 Btu/lbm.°R)(80.6-68)Btu/lbm

Woutput = 0.0709 kW

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