Airflow pressure equalization

cozumel · Apr 20, 2006, 03:39 PM

I've read a lot of stuff about the importance of equalizing pressure between air intake and blowers. The importance of a good airflow from front to back and side to side ensures that all components stay cool all of the time. I understand what equalizing means but not why. Although I plan to ensure that equalization is correct on next build I hate doing things "just 'cos I was told to". Please could someone explain?

Some of things I have read also suggest ideal ratios of air coming into and leaving the case and was wondering whether their are any difinitive rules for this carved in stone. ie 2:1 or 1:2 etc, etc...

I plan to be permanently overclocking next week when new case arrives and to upgrade mobo and other components (all to be overclocked) later this year. Is important that I have the understanding to ensure adequate cooling.

Thanks

H3X4D3C1M4L · Apr 21, 2006, 09:01 AM

I would say more airflow is more important than even air pressure.

Having 1:1 intake:exhaust doesn't help that much. You'd be better off to just have as much air as possible flowing through, intaking at the front bottom area and exhausting at the rear top area. If you have to create a vacuum of air then do it.

Sandok · Apr 21, 2006, 09:06 AM

i can just take a guess but to be honest, the best way is to test yourself (just takes a few minutes to unscrew and switch fan directions).

If you have too much intake, the air pressure is postif and as a bonus, dust doesn't like getting into the case that easily and all but air isn't exhausted as fast and thus, temps build up.

On the other hand, too much exhaust and not enough intake means that heat is disapated faster but less cool air is taken in to cool the case anyways and dust gets in happily

Me I have a perfect ratio of 1:1 and the thing is, dust will get in but stays neutral (doesn't want to get in more or less than the other fan settings) but when it comes to air mouvment, it's a perfect amount. Cool comes in and warm leaves out in the same techincal quanitities...

dipstick · Apr 21, 2006, 03:14 PM

From what I have seen what helps the most is exhaust flow. Whenever I add more intake than exhaust my temps always go up. For example my case had;
two 120mm fans(intake-front) Removed 1
one 80mm(intake-side panel) Removed/Sealed
one 80mm(exhaust-top) Removed/Sealed
one 120mm(exhaust-back)

Removing all fans except for the rear and front 120mm along with sealing up the openings on the side and top panels has dropped my temps by 4c+ degrees on cpu, mobo and gpu. My X1900 went from 54c idle to 47-48c!! Yes, I now only have two fans and it works A LOT better. So, more is not always better, and at least with my case side and top fans actually hurt cooling..

H3X4D3C1M4L · Apr 21, 2006, 03:22 PM

Quote:

Originally Posted by dipstick

From what I have seen what helps the most is exhaust flow. Whenever I add more intake than exhaust my temps always go up. For example my case had;
two 120mm fans(intake-front) Removed 1
one 80mm(intake-side panel) Removed/Sealed
one 80mm(exhaust-top) Removed/Sealed
one 120mm(exhaust-back)

Removing all fans except for the rear and front 120mm along with sealing up the openings on the side and top panels has dropped my temps by 4c+ degrees on cpu, mobo and gpu. My X1900 went from 54c idle to 47-48c!! Yes, I now only have two fans and it works A LOT better. So, more is not always better, and at least with my case side and top fans actually hurt cooling..

You didn't use powerful enough fans or you just have a really poorly designed case then

Asmoday · Apr 21, 2006, 03:41 PM

Quote:

Originally Posted by H3X4D3C1M4L

You didn't use powerful enough fans or you just have a really poorly designed case then

I wouldn't say that the CM stacker is poorly designed...

cozumel · Apr 21, 2006, 03:50 PM

It think it appears Hex and yourself more or less agree on the principal below:

Quote:

Originally Posted by dipstick

Removing all fans except for the rear and front 120mm along with sealing up the openings on the side and top panels has dropped my temps by 4c+ degrees on cpu, mobo and gpu. My X1900 went from 54c idle to 47-48c!! Yes, I now only have two fans and it works A LOT better. So, more is not always better, and at least with my case side and top fans actually hurt cooling..

How can this be? Were there any hot-spots? Are HDD's and optical temps up or down in this setup?

Has anyone else out there in DHLand had similar experiences when blocking/removing intakes and exhausts from case? Or theories on what causes this effect.

Edit: May have been wrong about Hex and dipstick having agreed on the prinicpal, though unsure!!!

Sandok · Apr 21, 2006, 03:53 PM

The only thing I can say is that a side intake = horrible. My mobo and CPU temps went up like hell and it's all because air flow was disturbed. As long as it's nice and smooth, you'll have good temps.

H3X4D3C1M4L · Apr 21, 2006, 03:56 PM

Quote:

Originally Posted by Sandok

The only thing I can say is that a side intake = horrible. My mobo and CPU temps went up like hell and it's all because air flow was disturbed. As long as it's nice and smooth, you'll have good temps.

Not so, it was more likely because the side panel intake screwed with the exhausting and intake by blowing cold air back to the front. The turbulence is what gets the heat off of the heatsink.

I still say running it like a vacuum is best. Towers work best with more of a vacuum and desktop machines work better with positive air pressure excluding the more dense hot air out the back.

I've done every possible thing with fans and a vacuum always works provided you have some form of vent somewhere in the case and some form of air intake

Sandok · Apr 21, 2006, 03:57 PM

Really? well there was an article recently (I can post the link) with the new Coolermaster 830 which can have FOUR intake side fans but the guy said more than two actually made the cooling worse... Sorta like me.

H3X4D3C1M4L · Apr 21, 2006, 04:35 PM

Quote:

Originally Posted by Sandok

Really? well there was an article recently (I can post the link) with the new Coolermaster 830 which can have FOUR intake side fans but the guy said more than two actually made the cooling worse... Sorta like me.

Because it adds too much positive air pressure

cozumel · Apr 21, 2006, 06:03 PM

Thanks for your input everyone.

Using 'keywords' from your discussion I went 'Googling' as there is an obvious difference of opinion.

Most forums and cooling guides agreed that (if I understand correctly):

Negative pressure improves cooling as long as airflow is not obstructed by cables etc. Dust is drawn into case though.
Side intake will improve cooling provided negative pressure is maintained via top blowhole or adjusting fan voltages/configuration.
Positive pressure reduces intake of 'dirty' air although temperatures are a little higher.

Some sites/forums do feel that equal pressure is the way to go although most go with the 'vacuum' theory.

I hope that this is correct. Please come back to me with any thoughts on this 'cos I am a newbie and want to be able to get good overclock by pickin' your brains!!!

Just to touch on another thread on this forum that was highlighted during my 'Google', the acrylic case (and I have one) has very poor thermal conductivity. God, I hate acrylic......

dipstick · Apr 21, 2006, 06:43 PM

Quote:

Originally Posted by H3X4D3C1M4L

You didn't use powerful enough fans or you just have a really poorly designed case then

Yup, that can definitely be true as I run all my fans at 70-80% except for the rear exhaust which is always at 100% but the case it not too bad

I can see the temp differences going back and forth between setups every single time so i know im not imagining it lol

Scargo · Apr 22, 2006, 12:33 PM

I haven't done the research that coz' or others have but I am reminded of the cars that I have raced and the basic principles. They do a lot of damn testing when they design a cooling system on a race car. You want plentiful, smooth flow to carry the heat away.
I have seen the effects of negative pressure and it is not pretty! Do you want dust crawling in at every crack? That is why my Lian case has a huge filter covered hole in its bottom. They want air to come in there if the balance is not right. The next thing you want is flow, not just a lot of fans blowing. Stirring heat doesn't do much if it can't get out fast enough. After you have equalized the temperature of the case, it doesn't do that much for you as a heat sink, since it doesn't have a bunch of fins sticking off it. Hmmmmmmm?

Most good case designs use the front to rear and bottom to top flow. Some bring fresh air in just for the CPU. Many have a 120mm fan in front of the hard drives, so they get cooling first. I believe in having some positive air pressure. An exhaust fan is like a hole. If you have a lot of pressure it will go out the hole and help the exhaust fan spin that is over "the hole". It doesn't hurt, IMHO.

Has anyone evaluated their flow with smoke? I may fire up some incense and check it out. I will replace the side cover with clear acrylic or saran wrap first, so I can view the smokes path. I wonder; if you have a big CPU heatsink fan, whether it will cause so much air blasting every which-way that it will become invisible? I know mine directs air up and down as it bounces off the board due to the orientation of the fins. This is good...
I suspect a lot of cooling efficiency could be had if the case designers were to add ducts or deflection plates inside the case. Similar to the idea of compartmentalization the Antec has done with some of their cases.
Let's all grab some cardboard and play!

H3X4D3C1M4L · Apr 22, 2006, 10:05 PM

Scargo the dust isn't that bad... believe me from experience, the difference between balanced/positive/negative in terms of dust is negligable. Use dust filters on all big holes with anything and you negate the dust thing.

Cleaning out your PC once in a while is good practice anyway

Apr 20, 2006, 03:39 PM	#1
cozumel I'm dangerous but cute... Join Date: Apr 2006 Location: Under the waves... Posts: 3,619 Rep Power: 42 System Specs	Airflow pressure equalization I've read a lot of stuff about the importance of equalizing pressure between air intake and blowers. The importance of a good airflow from front to back and side to side ensures that all components stay cool all of the time. I understand what equalizing means but not why. Although I plan to ensure that equalization is correct on next build I hate doing things "just 'cos I was told to". Please could someone explain? Some of things I have read also suggest ideal ratios of air coming into and leaving the case and was wondering whether their are any difinitive rules for this carved in stone. ie 2:1 or 1:2 etc, etc... I plan to be permanently overclocking next week when new case arrives and to upgrade mobo and other components (all to be overclocked) later this year. Is important that I have the understanding to ensure adequate cooling. Thanks __________________ Don't worry about money - Be a beach bum! Scuba Rocks Last edited by cozumel; Apr 20, 2006 at 03:40 PM. Reason: bad spelling

Apr 21, 2006, 06:03 PM	#12
cozumel I'm dangerous but cute... Join Date: Apr 2006 Location: Under the waves... Posts: 3,619 Rep Power: 42 System Specs	Thanks for your input everyone. Using 'keywords' from your discussion I went 'Googling' as there is an obvious difference of opinion. Most forums and cooling guides agreed that (if I understand correctly): Negative pressure improves cooling as long as airflow is not obstructed by cables etc. Dust is drawn into case though. Side intake will improve cooling provided negative pressure is maintained via top blowhole or adjusting fan voltages/configuration. Positive pressure reduces intake of 'dirty' air although temperatures are a little higher. Some sites/forums do feel that equal pressure is the way to go although most go with the 'vacuum' theory. I hope that this is correct. Please come back to me with any thoughts on this 'cos I am a newbie and want to be able to get good overclock by pickin' your brains!!! Just to touch on another thread on this forum that was highlighted during my 'Google', the acrylic case (and I have one) has very poor thermal conductivity. God, I hate acrylic...... __________________ Don't worry about money - Be a beach bum! Scuba Rocks Last edited by cozumel; Apr 21, 2006 at 06:04 PM. Reason: typing errors

Apr 22, 2006, 12:33 PM	#14
Scargo DriverHeaven Lover Join Date: May 2005 Location: Connecticut Posts: 100 Rep Power: 0	This is thermodynamics: not so simple! I haven't done the research that coz' or others have but I am reminded of the cars that I have raced and the basic principles. They do a lot of damn testing when they design a cooling system on a race car. You want plentiful, smooth flow to carry the heat away. I have seen the effects of negative pressure and it is not pretty! Do you want dust crawling in at every crack? That is why my Lian case has a huge filter covered hole in its bottom. They want air to come in there if the balance is not right. The next thing you want is flow, not just a lot of fans blowing. Stirring heat doesn't do much if it can't get out fast enough. After you have equalized the temperature of the case, it doesn't do that much for you as a heat sink, since it doesn't have a bunch of fins sticking off it. Hmmmmmmm? Most good case designs use the front to rear and bottom to top flow. Some bring fresh air in just for the CPU. Many have a 120mm fan in front of the hard drives, so they get cooling first. I believe in having some positive air pressure. An exhaust fan is like a hole. If you have a lot of pressure it will go out the hole and help the exhaust fan spin that is over "the hole". It doesn't hurt, IMHO. Has anyone evaluated their flow with smoke? I may fire up some incense and check it out. I will replace the side cover with clear acrylic or saran wrap first, so I can view the smokes path. I wonder; if you have a big CPU heatsink fan, whether it will cause so much air blasting every which-way that it will become invisible? I know mine directs air up and down as it bounces off the board due to the orientation of the fins. This is good... I suspect a lot of cooling efficiency could be had if the case designers were to add ducts or deflection plates inside the case. Similar to the idea of compartmentalization the Antec has done with some of their cases. Let's all grab some cardboard and play! __________________ ASUS A8N32-SLI Deluxe motherboard AMD Athlon 64 X2 4400+ Toledo: 2,600+ Mhz on air- Thermalright XP-90C with 92MM Thermoflow temperature sensing fan 4 Gig of OCZ Titanium DDR400 (PC3200) dual channel, unbuffered RAM MSI NX6600-TD256E video card & dual 21” CRT screen setup 2X - WD 250Gb 7200RPM SATA main drive, w. 16Mb cache 2X - Fujitsu MAU3036NP (15K RPM drives running SCSI 0 [striped]) in their own (optional) bay Lian 7077A - full tower case with optional 120mm fan in top and 120mm added in side, facing MB Antec TP2 550 (watt) power supply Windows XP Pro/Windows X64 Pro MS Digital Media Pro Keyboard Wacom Intuos II Tablet

Apr 21, 2006, 09:01 AM	#2
H3X4D3C1M4L DriverHeaven Extreme Member Join Date: May 2005 Posts: 6,818 Rep Power: 0	I would say more airflow is more important than even air pressure. Having 1:1 intake:exhaust doesn't help that much. You'd be better off to just have as much air as possible flowing through, intaking at the front bottom area and exhausting at the rear top area. If you have to create a vacuum of air then do it.

Apr 21, 2006, 09:06 AM	#3
Sandok DriverHeaven Extreme Member Join Date: Jul 2004 Posts: 9,501 Rep Power: 53	i can just take a guess but to be honest, the best way is to test yourself (just takes a few minutes to unscrew and switch fan directions). If you have too much intake, the air pressure is postif and as a bonus, dust doesn't like getting into the case that easily and all but air isn't exhausted as fast and thus, temps build up. On the other hand, too much exhaust and not enough intake means that heat is disapated faster but less cool air is taken in to cool the case anyways and dust gets in happily Me I have a perfect ratio of 1:1 and the thing is, dust will get in but stays neutral (doesn't want to get in more or less than the other fan settings) but when it comes to air mouvment, it's a perfect amount. Cool comes in and warm leaves out in the same techincal quanitities...

Apr 21, 2006, 03:14 PM	#4
dipstick DriverHeaven Extreme Member Join Date: May 2002 Location: USA Posts: 3,565 Rep Power: 53 System Specs	From what I have seen what helps the most is exhaust flow. Whenever I add more intake than exhaust my temps always go up. For example my case had; two 120mm fans(intake-front) Removed 1 one 80mm(intake-side panel) Removed/Sealed one 80mm(exhaust-top) Removed/Sealed one 120mm(exhaust-back) Removing all fans except for the rear and front 120mm along with sealing up the openings on the side and top panels has dropped my temps by 4c+ degrees on cpu, mobo and gpu. My X1900 went from 54c idle to 47-48c!! Yes, I now only have two fans and it works A LOT better. So, more is not always better, and at least with my case side and top fans actually hurt cooling..

Apr 21, 2006, 03:53 PM	#8
Sandok DriverHeaven Extreme Member Join Date: Jul 2004 Posts: 9,501 Rep Power: 53	The only thing I can say is that a side intake = horrible. My mobo and CPU temps went up like hell and it's all because air flow was disturbed. As long as it's nice and smooth, you'll have good temps.

Apr 21, 2006, 03:57 PM	#10
Sandok DriverHeaven Extreme Member Join Date: Jul 2004 Posts: 9,501 Rep Power: 53	Really? well there was an article recently (I can post the link) with the new Coolermaster 830 which can have FOUR intake side fans but the guy said more than two actually made the cooling worse... Sorta like me.

Apr 22, 2006, 10:05 PM	#15
H3X4D3C1M4L DriverHeaven Extreme Member Join Date: May 2005 Posts: 6,818 Rep Power: 0	Scargo the dust isn't that bad... believe me from experience, the difference between balanced/positive/negative in terms of dust is negligable. Use dust filters on all big holes with anything and you negate the dust thing. Cleaning out your PC once in a while is good practice anyway