Thermal Analysis of the necessity of A CPU Heat sink fan

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Thermal Analysis of the necessity of A CPU Heat
sink fan

• Shaun Heldt and Tyler Merrell

2
Background

• Most common type of cooling method
• Keeps CPU at a safe operating temperature
• Has fan to improve overall heat transfer of fins
  by introducing forced convection.

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Materials

• 1 Intel I7-26000K Processor heat sink
• 1 Fluke 51 Thermometer with K-thermocouple
• 1 Soldering Iron
• 1 Hot Glue Gun

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Experiment

• Used glue gun and soldering iron to simulate a
  hot CPU
• Measured temperature of the center of the heat
  sink and the fin tip while heating
• Measured time to cool after heated
• Compared with theoretical calculations to solve
  for Qout and the required air velocity for forced
  convection

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Data
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Natural Convection

• Solve for Qout from natural convection of the
  heat sink to find if cooling due to natural
  convection is sufficient for cooling CPUs
• Note Qin from CPU equals 80W
• Therefore, Qout must be greater than or equal to
  80W for natural convection to be sufficient

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Natural Convection



Calculated Properties Calculated Properties Calculated Properties

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Thermal Circuit
 
 
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Compiled Calculations
Thermal Circuit Method Thermal Circuit Method Thermal Circuit Method



Qout 6.77W Therefore, natural convection is not
sufficient
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Forced Convection

• Used forced convection calculations to solve for
  required airspeed from fans to have a Qout 80W
• Using previous calculations, an h value of
  143.138 W/m2 would be required to sufficiently
  cool the CPU
• Using Hilperts equation for cross flow of a
  square geometry and thermophysical properties we
  found that the required airspeed velocity is
  2.913 m/s

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Conclusion

• Approximations were made to form the model used
  in calculating the presented values, however, we
  believe that this model was a reasonable
  approximation of the system.
• We found that forced convection through a heat
  sink is necessary in CPU cooling