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Windows 7: CPU

View Poll Results: Should a CPU Fan be intake or exhuast?
Intake 14 87.50%
Exhuast 2 12.50%
Voters: 16. You may not vote on this poll

23 Mar 2010   #41
cloud8521

 

Experts or not, this is all about Fluid dynamics. let me try to explain this, the blow is more concentrated then the draw, since the draw can be pulled from a larger area, then pushed forward. the weakest part of the fan is the pull of it, the strongest the push, so the push is what you would use. try this simple test, put a card over a fan in the suck direction, notice how there is nearly no force? now try the opposite, you will notice much more force. that is why you use the blow to cool. as for case fans, it is about getting air-though the case, you would use the small case fan as intake, this is because it is smaller, your exhaust needs to be bigger tho since you have a much lower force draw.


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23 Mar 2010   #42
mpcrsc562

Windows 7 Ultimate x64
 
 

Quote   Quote: Originally Posted by win7clutz View Post
I think Intel and AMD certainly have more...
Agreed.
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23 Mar 2010   #43
YTBOY83

Windows 7 64Bit Ultimate Edition SP1
 
 

The hot air is getting exhausted by a top exhaust and back exhaust fans, therefore alot of heat is getting sucked from plenty of directions whilst the cpu is still getting air. There is also plenty of other ways to take air to the cpu etc.

There should be more cold air than what there is hot.

Also, when air is blown towards the HS some heat might get blown in different directions and that is where the back and and top exhaust fans would also come in handy.
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23 Mar 2010   #44
mpcrsc562

Windows 7 Ultimate x64
 
 

Look at an automobile cooling system... I have never seen a fan suck air from a radiator. If that were the case, the car would over heat.
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23 Mar 2010   #45
Product FRED

Windows 7 Enterprise 64-bit
 
 

Quote   Quote: Originally Posted by rmw020 View Post
The hot air is getting exhausted by a top exhaust and back exhaust fans, therefore alot of heat is getting sucked from plenty of directions whilst the cpu is still getting air. There is also plenty of other ways to take air to the cpu etc.

There should be more cold air than what there is hot.

Also, when air is blown towards the HS some heat might get blown in different directions and that is where the back and and top exhaust fans would also come in handy.
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?
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23 Mar 2010   #46
seekermeister

W7x64 Pro, SuSe 12.1/** W7 x64 Pro, XP MCE
 
 

[QUOTE=CommonTater;643602]
Quote   Quote: Originally Posted by CarlTR6 View Post
Quote   Quote: Originally Posted by rmw020 View Post
I agree that the CPU needs cool air and I personally think the the fan vlowing toward the heatsink and CPU is the most efficient. However, even if the fan is exhausting - blowing away from the heat sink, cooler air is still being drawn across the heatsink and CPU. I just don't think doing so is as efficient.
It's about the way air moves... If you stand behind a fan you don't actually feel the air motion, because 90% of it occurs very close to the fan in a very disorganized way as local air pours in to fill the vaccuum behind the blades.

This same air becomes the air stream you feel from a goodly distance in front of a fan. You feel it, because it's organized... it penetrates and travels.

This is what they call the Bernouli effect... moving air gathers more moving air along with it. The problem is that Bernouli's effect only works with pressure, not decompression of air (or fluids). The blowing on the palm example is one simple demonstration another is to bundle a garbage bag and blow it up like a baloon... it's going to take a lot of huffing and puffing to blow it up. But if you hold the end open and simply blow into the bag, you can inflate it with one good blast of breath. Because the air you blow into the bag gathers other air with it and causes a momentary pressure burst.

This relates to fans in that the front of the fan (which normally faces the heatsink, blowing air into it) creates pressure inside the fins, forcing air deeply into the blades getting far more heat conduction, whereas reversing the fan counts on a vaccuum to cause an air inrush which is mostly going to happen immediately behind the fan, with little or no penetration into the fins themselves. It will simply take the path of least resistance to fill the small pocket of reduced pressure right near the blades.

An odd confirmation of this is that a fan will spin faster when drawing air off a heatsink than when blowing air in... because the Bernouli effect causes pressure which causes resistance against the fan blades... and it's that pressure that drives cool air across the entire fin surface of the heatsink.

WHEW... does that help?
While I think that I agree with most of what you have said, your definition of the Bernouli effect leaves something to be desired. This is the effect of either a gas or liquid that is forced through a restricted aperture, causing it to speed up. When it speeds up, the pressure is reduced, This is what occurs in a carburetor, where the throat creates a restriction, which causes the air to speed up and lose pressure, which in turn causes fuel to be pulled from the jets by the lower air pressure.

Actually, it doesn't require an aperture as such, because the same effect occurs over the wing of an airplane, where the upper surface of the wing is curved in a fashion that requires to air to travel at a greater speed than the air below, creating a low pressure above the wing, producing lift and keeping the aircraft aloft.
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23 Mar 2010   #47
mpcrsc562

Windows 7 Ultimate x64
 
 

Quote   Quote: Originally Posted by mpcrsc562 View Post
Look at an automobile cooling system... I have never seen a fan suck air from a radiator. If that were the case, the car would over heat.
Product Fred should know about this being in Brooklyn... Even in the cold winter, an engine fan that would suck air across the radiator would cause that automobile to overheat--even in the coldest of winters.
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23 Mar 2010   #48
CommonTater

XP Pro SP3 X86 / Win7 Pro X86
 
 

Quote   Quote: Originally Posted by Product FRED View Post
So basically, exhaust.
I don't know what you mean by "exhaust"....

The fan on the cpu cooler should blow air into the fins of the heatsink. As I explained with the simple demonstration in my first message, this is at least 10 times more effective than counting on a vaccuum to draw air out of the fins.
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23 Mar 2010   #49
Product FRED

Windows 7 Enterprise 64-bit
 
 

Quote   Quote: Originally Posted by mpcrsc562 View Post
Quote   Quote: Originally Posted by mpcrsc562 View Post
Look at an automobile cooling system... I have never seen a fan suck air from a radiator. If that were the case, the car would over heat.
Product Fred should know about this being in Brooklyn... Even in the cold winter, an engine fan that would suck air across the radiator would cause that automobile to overheat--even in the coldest of winters.
From Wikipedia:
Quote:
In automobiles, a mechanical fan provides engine cooling and prevents the engine from overheating by blowing or sucking air through a coolant-filled radiator. It can be driven with a belt and pulley off the engine's crankshaft or an electric fan switched on or off by a thermostatic switch.
Quote:
Desktop computers typically use one or more fans for heat management. Almost all desktop power supplies have at least one fan to exhaust air from the case. Most manufacturers recommend bringing cool, fresh air in at the bottom front of the case, and exhausting warm air from the top rear.

Do you see how the sucking motion draws the hot air out and creates a lower pressure zone to draw in cool air?
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23 Mar 2010   #50
YTBOY83

Windows 7 64Bit Ultimate Edition SP1
 
 

Quote   Quote: Originally Posted by mpcrsc562 View Post
Quote   Quote: Originally Posted by Product FRED View Post

Oh please. Listen, I know you don't mean to judge or anything, and I don't expect you to believe me when I say this, but he is an expert on these things. Besides, just look at the laws of physics, specifically a vacuum. Overall, the system will be cooler if you just suck the air out from every fan. Why would you have two conflicting fans (rear and CPU)? This thread is over anyways, he'll try it out and we'll see.
A rear out-blowing case fan and a heatsink-blowing fan are not conflicting. If anything, the rear case fan would help draw in cool air from the front--and over the cpu fan to aid in cooling the heatsink.

I agree with this.

Air coming in from the front and side is also going to get sucked passed the cpu by the back and top exhaust fans which will also help keep the cpu cool etc.

For example, when i am to hot in the summer i use a fan to cool me down, not to exhaust the heat off me lol, if i did that i would not cool down what so ever.
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