View Poll Results: Should a CPU Fan be intake or exhuast?

seekermeister · 23 Mar 2010

CommonTater said:

Yes carbouration is another demonstration of Bernouli's effect as is the wing of an airplane... However, carbouration occures as an inlet to a closed system created by the valve action of an engine's moving piston and is thus not totally analogous to the operation of a fan.

What is causing the air pressure which causes the air to move is not what is the factor in question. Regardless of what causes the primary airflow, it is the reduction in size of the aperture of the carburetor's throat that causes an additional speed factor to be induced, and this in turn reduces the air pressure within that speed zone.

In our example the casing of the fan with the blades spinning in the smallest part of the aperature is what causes the increase in velocity, and the reduction in pressure on one side of the blades. However it is also what causes the increase in pressure on the other... Just like the curvature of a wing causes an increase in pressure underneath the wing... This is not a closed system... one side can (and does) affect the other.

I may be a tad off on the science --it's been 15 years since I designed cooling systems of any account-- but the palm test explains it very well... It is what the heatsink "feels".

Since the fan casing does not have a reduction in diameter, it does not effect air speed. What does increase airspeed is the fan blades, which act just like the wings of an aircraft.

mpcrsc562 · 23 Mar 2010

Product FRED · 23 Mar 2010

CommonTater said:

Product FRED said:

Right, but what I'm saying is that the hot air will leave more concentrated, and cool air will come in more concentrated. By using exhaust, you're making it easier for the air to travel to the rear and top exhaust fans. Why would you scatter it?

To dispurse the heat over the widest possible area allowing it to mix with cooler air causing less temperature increase.

The cool air is coming from the outside. The air inside the case is all warm. The outside air is presumed to be the cool air. The air inside the case is the warm air.

cloud8521 · 23 Mar 2010

Product FRED said:

mpcrsc562 said:

O.k., some aoutomobile radiator fans may suck...

Anyway, look at it like this: what is usually right under the cpu heatsink / fan? A very hot video card. If the cpu fan is exhausting air away from the heatsink, the first batch of air being sucked across the heatsink is the hot air from the videocard--which will NOT aid in cooling the cpu.

You're removing the heat from the card. That's why the air is hot after passing over it. That is the point of cooling the card. Laws of Heat transfer?

ok? but what does not cool the heat sink, the heat sink will store heat, and slowly release it to equalize, yes. but then nothing is really cooling the heat sink quickly enough, the cpu will keep making it hotter and hotter. you are not coolign you are just removal the hot air that surrounds it, compared to moving air over the hot metal at a faster speed, and i dont think i need to explain that

win7clutz · 23 Mar 2010

There is no cool air already inside the case. It's all warm. Suction draws in air from the outside. It may not be as powerful as blowing, but it's definitely cooler. And the heatsink aborbs most of the heat anyways, so the cold air is effect on both.

Not true, look at your own drawing... Air (cool) is being drawn into the case providing the cpu fan to move it to the cpu hestsiknk... It's clear as day...

Product FRED · 23 Mar 2010

win7clutz said:

There is no cool air already inside the case. It's all warm. Suction draws in air from the outside. It may not be as powerful as blowing, but it's definitely cooler. And the heatsink aborbs most of the heat anyways, so the cold air is effect on both.

Not true, look at your own drawing... Air (cool) is being drawn into the case providing the cpu fan to move it to the cpu hestsiknk... It's clear as day...

I should clarify. The inside of the case is not a source of cool air, the outside is.

CommonTater · 23 Mar 2010

Product FRED said:

There is no cool air already inside the case. It's all warm. Suction draws in air from the outside. It may not be as powerful as blowing, but it's definitely cooler. And the heatsink aborbs most of the heat anyways, so the cold air is effect on both.

Heatsinks do not absorb heat... they transfer it.

If all goes well, thermal energy from the chip/transistor/part producing the heat causes heat conduction into the heatsink the heatsink then transfers this heat into the air moving across it (either by convection or compression). The heat does not magically stay in the heatsink... the heatsink is merely a means of dispursing the heat across a very large area where it can be transferred to another medium (air) which in turn dispurses the heat across an even larger area (the inside of the case)... The entire plan is to take X number of thermal watts (BTUs) from a relatively small object (the chip) and dispurse it across as much area as possible.

Product FRED · 23 Mar 2010

CommonTater said:

Product FRED said:

There is no cool air already inside the case. It's all warm. Suction draws in air from the outside. It may not be as powerful as blowing, but it's definitely cooler. And the heatsink aborbs most of the heat anyways, so the cold air is effect on both.

Heatsinks do not absorb heat... they transfer it.

If all goes well, thermal energy from the chip/transistor/part producing the heat causes heat conduction into the heatsink the heatsink then transfers this heat into the air moving across it (either by convection or compression). The heat does not magically stay in the heatsink... the heatsink is merely a means of dispursing the heat across a very large area where it can be transferred to another medium (air) which in turn dispurses the heat across an even larger area (the inside of the case)... The entire plan is to take X number of thermal watts (BTUs) from a relatively small object (the chip) and dispurse it across as much area as possible.

That's what I'm saying. It's used for transfer, not storage. Otherwise, obviously the CPU would eventually melt. Again, I'm not talking about power. I'm talking about efficiency and the quickest way to get the hot air out and cool air in. Sucking prevent it from going back near the CPU, which is the point. Blowing pushes it back. Yes, both methods will cool a CPU one way or another, but an exhaust system is much more efficient.

mpcrsc562 · 23 Mar 2010

And lastly...

I have a HAF932.

One large front intake. Right behind the front fan are the hard drive bays--intake air helps cool the hard drives.

On the side panel, is another large intake fan. It blows directly across the videocards and helps cool the board too.

In the rear is the smallest of the fans, the rear exhaust. No explanation needed.

At the top of the case is another large exhaust fan, because as we all know, heat rises.

Before I got the Hydro H50, I had a Sunbeam Core Contact Freezer. If I'm not mistaken, the fan mounted on the rather large heatsink was mounted to blow air across the fins. Prior to the CCF, the stock AMD hsf had the fan mounted to blow air across the hs.

My case and components stayed nice and "cool." (Which is a relative term anyway)

I'll leave it at that.

Outty 5000

win7clutz · 23 Mar 2010

Product FRED said:

win7clutz said:

There is no cool air already inside the case. It's all warm. Suction draws in air from the outside. It may not be as powerful as blowing, but it's definitely cooler. And the heatsink aborbs most of the heat anyways, so the cold air is effect on both.

Not true, look at your own drawing... Air (cool) is being drawn into the case providing the cpu fan to move it to the cpu hestsiknk... It's clear as day...

I should clarify. The inside of the case is not a source of cool air, the outside is.

No sir, the outside (cool air) is clearly be drawn into the case and is the SAME cool air that gets circulated through the case. C'mon Fred...