Suck vs. Blow - A Quickie

Why do cooling fans on computers suck air out of the case instead of blowing cool air in?

 

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Well if you look at the logical aspect of Thermal Dynamics it kind of explains itself.

Air is filled with molecules (Gas) and when it's cold. The molecules aren't as active with Thermal resonance. (The molecules are pretty stagnant). When temperature rises it can cause the molecules to become more vibrant and move around, this causes yet more heat and also pressure.

When you look at a hot air balloon, you will see that it's filled with heated air. The heat gives it lift and also expands the balloon out. (The reason it lifts is because there is less molecules confined to a specific volume)

When the air cools it condenses and the weight pushes/pulls it to the bottom of the balloon. (It loses its lift).

I mention this because a computer when it's on, heats up. The heat inside the box rises to the top, and it also has an increased pressure due to the heat. A fan that sucks the heated air out from the top of the box is actually not just cooling but also lowering the pressure.

Of course a ventilation gap located at the bottom would drag cool/room temperature air into the bottom of the box causing a thermal dynamic flow.

Sucking room temperature air and pushing it into the box on the otherhand would increase the pressure and possibly rise the temperature further because it would cause convection.

 

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