# Heat transfer Using Reynolds Analogy

A circuit board with a dense distribution of integrated circuits (ICs) and the

dimensions of 120mm by 120mm on a side is cooled by a parallel flow of atmospheric air with a velocity of 2 m/s.

From wind tunnel tests under the same flow conditions , the average frictional shear stress on the upper surface is determined to be 0.0625N/m^2. What is the allowable power dissipation from the upper surface of the board if the average surface temperature of the ICs must not exceed the ambient air by more than 25 degrees C ?

Answer given is---14.3 W

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#### Solution Preview

Please see attachment.

Problem.

A circuit board with a dense distribution of integrated circuits (ICs) and the

dimensions of 120mm by 120mm on a side is cooled by a parallel flow of atmospheric air with a velocity of 2 m/s.

From wind tunnel tests under the same flow conditions, the average frictional shear stress on the upper surface is determined to be 0.0625N/m^2.

What is the allowable power dissipation from the upper surface of the board if the average surface temperature of the ICs must not exceed the ambient air by more than 25 degrees C ?

Solution:

According to the Newton's law, the shear at the wall (circuit board) is given by formula:

...

#### Solution Summary

This solution determines the allowable power dissipation from the upper surface of the board assuming that the average surface temperature of the ICs cannot exceed the ambient air by more than 25 degrees C. All steps are shown with full formulas and brief explanations.