Quote:

But the shape of the air's path under the case is bounded by the edges of the case (a square, or at least rectangle!)). I just moved the "square" to right under the fan where it's area would be the smallest and hence the required area would be the largest.. I suppose the calculations could be done with the surface area of a tube (120 mm, etc) but this is was just an exercise in approximation.Originally Posted by

The airflow into a fan is the circumference, not a square the size of fan, times the clearance.

120mm fan's circumference is 37.7cm

120mm square's circumference is 48cm

Circumference of square is almost a third bigger than the fan.

**doyll**Quote:

Originally Posted by

A simple calculation would be extend an imaginary box that's the size of the fan from the bottom of the case to the surface the case is setting on.

If the area of the four sides of the box is, Oh, let's say 1-1/2 times the area of the fan (ie, area of 120mm, 80mm, etc. diameter) then restriction should be minimal.

That works out to a height of about 1-1/2 inches for a 120 mm fan.

**billbartuska**A simple calculation would be extend an imaginary box that's the size of the fan from the bottom of the case to the surface the case is setting on.

If the area of the four sides of the box is, Oh, let's say 1-1/2 times the area of the fan (ie, area of 120mm, 80mm, etc. diameter) then restriction should be minimal.

That works out to a height of about 1-1/2 inches for a 120 mm fan.

The airflow into a fan is the circumference, not a square the size of fan, times the clearance.

120mm fan's circumference is 37.7cm

120mm square's circumference is 48cm

Circumference of square is almost a third bigger than the fan.

What do you come up with?