The Never Exhausted Debate About Computer Air Exhaust

[MERRICK]

One of the biggest debates in the discussion of computers is cooling. There are as many different philosophies as there are people. In my experience I have found that air intake fans in a computer rig are actually counter productive. This was first brought to my attention at the AMD website in their .pdf on cooling entitled: "AMD Athlon™ System Cooling Guidelines"

http://www.amd.com/us-en/Processors...39_2983,00.html

http://www.amd.com/us-en/assets/con...oling_guide.pdf

“8. A front cooling fan does not seem to be essential. In fact, in some extreme situations, testing showed these fans to be recalculating hot air rather than introducing cool air.”

I tried this and sure enough I brought the CPU temp down 1 degree C. I spoke with an associate who worked for years on hi tech military electronic systems and he confirmed that military cooling systems are always exclusively exhaustive.

[Thrax]

Yep. I run all my fans on exhale. Dust be damned.

Better temperatures than 2 exhaust, 2 intake.

[dodo]

It seems the major reason for intake fans is to introduce outside (typically cooler) air directly onto the main heat producing components of the board (cpu, vc, hdd, etc). In the case of a side intake fan that blows fresh air on the cpu, the temperature differences are certainly lower with that fan blowing in.

~dodo

[tycho]

For my rig, I have a bank of three small fans in one of my CD bays and i find that without them my CPU temp will be about 1-2 degrees higher... but i also know that my case has horrible airflow and nearly no space for naturally air intake... just my experience

[FudgePacker]

I run all 4 of my systems without intake fans. The exhaust fans pull all the air they need. It's also quieter without the additional noise from intake fans.

[Clutch]

Interesting guys. In my main rig, I have one 80mm intake fan and 2 80mm exhaust fans, along with the psu fan. I did have a side intake also, but once I cut out my window, it eliminated that. On my next rig, I am going to try the no intake, only exahust method to see how things stack up.

[MERRICK]

I would propose that people using intakes take a temp reading and then try all exhaust. You'd have to do it within a reasonable time frame since outside room temperature makes a difference. Surprisingly I found on my rig that taking the roof off did not change the temp (you'd think it would with hot air rising). One mod that was posted on Icrontic mentioned someone cutting a hole in the case right behind the CPU connection to the MB and putting a small exhaust fan for the REAR of the CPU. They said that there was a 2 degree (?) improvement. Anyone try that?

[mmonnin]

I have one side-intake and 2 rear exhaust plus PSU.

I thought about adding a front fan.

[Clutch]

MERRICK said
One mod that was posted on Icrontic mentioned someone cutting a hole in the case right behind the CPU connection to the MB and putting a small exhaust fan for the REAR of the CPU. They said that there was a 2 degree (?) improvement. Anyone try that?


I don't recall seeing that, sounds interesting though. The hole behind the motherboard tray right?

[MERRICK]

Another sad reminder of the "lost" Icrontic archives :rolleyes: but yes the original poster had made the hole in the case right behind the motherboard tray. Makes sense. There must be a bitchin' amount of heat back there!

[leishi85]

just to throw in some info

after reading this thread, i tried to put all my fans on my rig to exhaust, and it brought my system and CPU up by like 2C,

my setup is 2 80mm side intake, and one rear top exhaust, and one exhaust on the PSU.

[Omega65]

Thrax said
Yep. I run all my fans on exhale. Dust be damned.

Better temperatures than 2 exhaust, 2 intake.

Dust be damned is right. I just cleaned a dust carpet out of one of my computers......:aol:

And I was wondering why it was crashing :shakehead

[MERRICK]

All I can say in my defense is that my 'puter I refer to has:

Case: Full Tower w Leadman/400W PSU

1]CPU Cooler: Swiftech MC462w/Delta 80mm fan

2] Lian LI MF-699 mini 3 fan Hard drive coolers on all 5 HD's (fans modified for exhaust)

3] (1) 90mm rear exhaust fan

4](1) 80mm rear exhaust fan.

No intake fans.

I've actually seen it fly up a few inches lol. I'm a bit of a cooling freak.

But I respect anyone who disagrees with me. BTW I have one of those neat little cheap mini vacs that I don't use. Did I mention I'm researching my next rig. "Why clean the house when ya can move out?"

[Gargoyle]

Do you think the hard drives near the front of the case would still be properly cooled just by the air pulled by the exhaust fans? I have my front fan on (Sunon 120mm) to keep my four hard drives from glowing red :).

Edit -> And when you all say all exhaust, is that only the rear fans and perhaps a blowhole, or do you also have a front fan on exhaust? And if so, where is it sucking in the air? Some cases have ventilated side panels that would be good for an all-exhaust application, but my case doesn't. Damned Noblesse. Looks sexy, but impractical as hell. :banghead:

[panzerkw]

The one intake fan I have is for blowing air right over the hard drives.

[dodo]

panzerkw said
The one intake fan I have is for blowing air right over the hard drives.

Same with me....I wonder if this is why some people get higher CPU temps when using an intake fan, the air is heater over the hard drives. Of course, this intake fan probably cools the hard disks better, so its a tradeoff i guess. I personally would stick with a front intake fan over the hard disks and let my CPU temps raise 1C. I dont think an exhaust fan would cool the hard disks properly. Think about it, do you have your CPU fan blowing out?

~dodo

[panzerkw]

I have mine blowing air downard into the heatsink.

Way I figure it, warm air rises, and the exhaust fans are up high. So whatever warm air the hard drives and CPU make will eventually be sucked out as it rises. The intake is down near the floor where the air is cooler. But the difference it makes is probably negligble.

[profdlp]

One thing I have found during my personal adventures in cooling is that you can't make a blanket statement to cover every situation.

There is such a variety of cases out there that what is terrific for one might be awful for another.

The one constant I have found is that an intake fan on the side of the case blowing directly onto the CPU/Video Card area is a good idea, provided your exhaust fans are up to snuff.

My main rig is a full tower (generic) with gobs of places pre-drilled for installing fans. I went on a fan binge a few years back and at one point had 16 fans going! (This included two hard drive coolers which had 3 fans each, a bay cooler with 2 fans, as well as the chipset, cpu and ps fans, a slot cooler fan, twin exhaust fans on the back, an intake fan on the front, and the side fan blowing onto the cpu).

With the exception of the mandatory fans (cpu, etc) I found that the side fan did more good than all of the rest of them put together (and I tried many, many combinations).


Prof

PS: My side fan is a 120V 5" fan made by a German company - it really moves the air!):cool:

[Clutch]

Gargoyle said
And when you all say all exhaust, is that only the rear fans and perhaps a blowhole, or do you also have a front fan on exhaust?


Rear fans, blow hole, and a side fan if any. I would think it would be to impractical to have a front exhaust fan. Although air does get inside your case in the smallest cracks possible, it still would be the same.

I myself would trade 1c for my hard drives to be cooled down, especially if I had over 2 hdd's.

[MERRICK]

One thing I have found during my personal adventures in cooling is that you can't make a blanket statement to cover every situation.

That's the truth. the particular case of my case (pun) is that it came with many vents as well as predrilled fan holes. I feel the vacume created by my exhuast system has plenty of free air inlet oppertunity.

On the subject of the exhaust hard drive coolers: My hard drives (7200rpms) are "stacked" one over the other 5 high in the front bays. Now since heat rises, that is one hot totem pole. But the moment heat disapates off each individual hard drive it is whisked away and out the case. This minimizes the upper HD's catching the heat from the lower HDs. I had to reverse the mini Lian-Li fans to do this. I honestly can' see how making these fans intake would be better. It would be blowing that hot air into the case.

I did debate making a blow hole but I first removed the top of the case and took temps. there was no change:scratch: I couldn't believe it but I reckon it was because of the fact that I have so many fans and it is a full tower with many upper rear vents. A smaller case would probably yeild different resultd (?).


I don't have the typical low front intake fan or any fan their for that matter. I allow those vents to be for intake.

One thing I'll change on my next rig: I have a single fan PSU. (yeah I know). I'll go for the extra bucks next time and get a unit that has an internal intake. :cool:

[MarkTAW]

Prof - I agree, if your side fan aims directly at your CPU, getting more air to blow directly over that thing may be a good idea. From behind as well.

I have an interesting (?), off-topic anecdote here.

I've always been interested in air... We need it to breath, yet so many of us close all our doors and windows for much of the year.

As I kid, I had this very powerful, all-metal window fan that was probably outlawed when someone got their finger chopped off in one. I'd stick it in the window and within moments the room would cool off... I've never had another fan like it.

So as a kid, I experimented with it (and I still have all my fingers). I stuck it in the window and put towels in the doorway and tried to experience the changes in atmospheric pressure. Well, I can tell you first hand - you can feel it, and it does have an effect on you.

Sticking the fan on exhaust, I felt like I was in the mountains. I'd get a little light headed and noticed things more, or like on a cold winter morning. When it was on intake, the atmosphere got a little more oppressive, and my mood showed it as well.

I know you think I'm crazy or on drugs, but something happened today to make me think otherwise... I was blowing air into the apartment to get it to cool off, but the air outside was hot and sticky, so I flipped the (cheap plastic low power) fan around in the window and the moment I did it, the cats started running around chasing each other. Now, I think they hunt at dawn or dusk or something, and dawn and dusk are often accompanied by changes in atmospheric pressure. Could this change have told them that it was time to hunt? I think so. I might try it again to rule out concidence.

Back on topic, I'd be interested in seeing some stats here ont he effect of a vacuum on case tempreture. If anyone has a barometer that can be read from outside the computer, something to insulate with (tape or something) to prevent air from getting in and some powerful comptur fans, I think it would be fun to see what effect a bit of a vacuum has on the temperature inside the case and on the CPU. I guess the barometer isn't completely necessary, but it adds some extra numbers to back up any other evidence.

Is anyone up for the challenge?

[Camman]

old topic I see, but I figured I'd hit the ol' Search button before posting a new one, maybe one of you can answer me this question.

I was thinking about installing a blow hole in my case to exhaust heat, but, I've been told by someone that blow holes can actually destroy PSU's by not letting the PSU fan pull the hot air out, so the blow hole pulls all the hot air back over the components inside of it, is this true?

[Al_Capown]

My Thoughts:
If that was true why woudl lian li and coolermaster install blowholes on their cases?

From my experience, my blowhole has not killed my psu, yet...

If i was you i'd install a side intake near the cpu socket. Be sure it pushes plenty of air. It would cool down the cpu considerably.

[TheLostSwede]

ALL air that is inside the case is hotter than ambient or room temps, heat rises and to duct the warm air out is a great advice. I can´t understand why this would kill a psu though, it should be the opposite. It will still pull the air out, but the air might be cooler which would be concidered a plus. To reach good or great temps with blowholes/ducting, off course you need an intake of fresh air, and the most effective place to have that is at the front, low front the best.

[SimGuy]

Here's a question about air flow for all the Antec/Chieftec/Chenming SX1080 users out there.

Everyone knows the came I'm talking about and it has 5 fans: 2 80mm intakes stacked vertically in the front of the case. The Antec SX1080 has a dust filter to prevent those awful dustbunnies from being sucked in.

Installed in the rear are 2 80mm vertically-stacked exhaust fans.

Installed in the left-hand side panel is 1 80mm.

I picked up a couple of Panaflo 120mm U1A 115 CFM case fans and plan on mounting them horizontally along the base of the left-hand side panel, eliminating the 80mm intake fan located there.

AFAIK, you are supposed to balance exhaust with intake. The location of the 2 new 120mm Panaflo's will be directly over the expansion cards and just lower than the CPU.

Here's the question: Would having the 4 remaining 80mm case fans work as exhaust fans only instead of 2 exhaust, 2 intake fans work better with the dual 120mm's intaking? Is it wise to have that much intake pressure? Thoughts?

[Camman]

sounds good fellas, thanks for the responses.

A long time ago I got this 120mm monster from "3dfxcool.com" , cant remember the name of the site now, like 2coolcpu or osmething? but anyway, I think I might try that for a side intake.

[Mt_Goat]

What about putting all case fans to exhaust as mentioned but adding a "cold air induction" for the CPU so all the cool incoming air goes over the HS. In addition I would conclude that having a 120mm fan for the intake and gradually tapering down the tunnel to the size of the fan on the HS so as to increase velocity of the incoming air and there fore cooling it slightly.

[Leonardo]

Principle. It's all about physics. The more air, up to a point, that you can pass over a heated solid object, the more heat will be washed away. Assuming you have a case that has zero drag at the intakes - zero obstructions, then yes, it would seem logical that an intake fan would not be necessary. Due to most case designs, air exhausts with much less restriction than air can passively enter the front. Without the front case fan(s) most of our computers will have negative air pressure relative to the environment outside the case. I don't have any data, but it just seems like even a slight vacuum would allow for pockets of hot air in the case that wouldn't get flushed out.

Again, not talking about a rule here, but a principle. As a couple other posters said, I think you just have to experiment with every case setup. I've got homemade airfilters at the front of both of my home computers. Without the air intake fans, case and CPU temps are elevated.

[danball1976]

Seeing as how I see a lot of LRU's on the B-52, other than the air duct cooling system thats on the B-52 for most of the larger LRU's, most smaller ones have a fan the pulls air out of the LRU.

[Geeky1]

Actually, the G5's case is almost ideal from an airflow standpoint. I've been trying to design something somewhat similar for an ATX computer... If you were to set up a computer case with several large fans blowing across the motherboard and CPU at a 90* angle (e.g. a blowhole) and had the rest of the case open enough for the air to escape, you could keep the MB and cards near room temperature. I've run boards outside of the case, and if you put one or two of those rotron 6.75" fans blowing across the board, everything drops to a few degrees above ambient, except for the CPU, chipset, and video card (although if you have a really good cooling setup on them, they'll drop a great deal too.

I just haven't found a design I'm happy with yet...

[Straight_Man]

Typically, the traditional case flow is from low in front to high in back.

Where you have a hyper hot CPU and the best heatsink and thrmal compund you can get (Arctic Silver Ceramique after about 200 hours of runtime comes to mind), and you still have an overheat problem, I woudl try this:

Put an extra or higher CFM back exit fan, and move the case so it has 8-10 inches between it back and the wall so the heat can rise up and flow away from computer.

Then, if still having problems, put a blowhole fan of about 20-25 CFM aligned with CPU cooler to vent air from the CPU fan exhaust.

If you still have issues, check your voltages real versus right with a voltage\heat monitor software and see if the CPU is misvoltaged or the 3.3 or 5 volts lines are misvoltaged. If they are test your surge strip and the wall outlet. running too much juice through CPU will heat it up big time, and PSUs can vary high or low, so sometimes you have to compensate with the BIOS settign to allow for a cronic under or overvoltage from the wall outlet or give the box the present of a UPS that will chop to batery at +\- 8% or so. If a UPS is present and you still get lots of misvoltaging, probably time for anew bigger PSU.

The other reason for a blowhole is sometimes a cheap PSU mfr will make it vent INTO the case, or misassmble the fanning and get a fan blowing into case, and in that case (especially with the nice insulation of a plastic or polycarbonate window compared to a heat-conductive metal case side) a low to mid volume outward venting blowhole fan is nice to both make up for the extra heat holding of a plastic window AND to help compensate where some idiot has a computr that blows heat from PSU right on CPU heatsink instead of sucking air AWAY from heatsink.

NOTE, you do not want a high volume blowhole fan, instead use high volume exhaust fans in back-- otherwise, the effects of the exhaust fan in blowhole on side interfere with the normal front/low to back/high airflow. blowhole should only supplement if NEEDED.

John.

[muddocktor]

SimGuy had this to say
Here's a question about air flow for all the Antec/Chieftec/Chenming SX1080 users out there.

Everyone knows the came I'm talking about and it has 5 fans: 2 80mm intakes stacked vertically in the front of the case. The Antec SX1080 has a dust filter to prevent those awful dustbunnies from being sucked in.

Installed in the rear are 2 80mm vertically-stacked exhaust fans.

Installed in the left-hand side panel is 1 80mm.

I picked up a couple of Panaflo 120mm U1A 115 CFM case fans and plan on mounting them horizontally along the base of the left-hand side panel, eliminating the 80mm intake fan located there.

AFAIK, you are supposed to balance exhaust with intake. The location of the 2 new 120mm Panaflo's will be directly over the expansion cards and just lower than the CPU.

Here's the question: Would having the 4 remaining 80mm case fans work as exhaust fans only instead of 2 exhaust, 2 intake fans work better with the dual 120mm's intaking? Is it wise to have that much intake pressure? Thoughts?

SimGuy, I have the air exhausting in the lower fron of my Antec 1240 from the radiator and I found that the louvers on the front of the case held a lot of back pressure and caused considerable flow noise. I ended up making a 120mm vent hole in the louvers by cutting the plastic and making an extention that goes into the front faceplate up to the fan to direct all that heat outside of the case, which is considerable as that is a dual XP machine. Putting the vent hole also cut the flow noise down considerably.

[MediaMan]

Here's my 2c on the issue:

Airflow and Heat: A cooling guide. (http://www.short-media.com/article.php?111.0)

It's in that other area of SM...that non-forum area... :rolleyes:

[Geeky1]

WHOAH... There's ANOTHER area of SM? :eek: ;D

[MediaMan]

Yah....I clicked a wrong link on the forum page and I was in this whole other area. Some dude was talking about computer stuff and there was a whole buncha pictures.

Some cool stuff too about how to mod and all that. Dude...I was blown away.

I wonder if anyone else has thoughta doin that?







We know return you to your regular hot air thread.

[Leonardo]

MM, this thread is an independent study to the seminal work found at Short-Media main. The effort here was to hopefully arrive at the same conclusions, without knowledge of the other study, hence lending credibility to the first study.

Yeah, that's what we were doing. :eek3:

[automaton]

:Rocker:
i just redid my fans

skyhawk al psr series
intake
front 48cfm ys tech 80mm [obstructive fan case] cools raid hds
evercool triple fan bay cooler 18cfm under cd bay blows right thru case
window galaxy clear w led 80mm 53cfm w al filter :banghead:

exhaust
duct 50cfm sunon 80mm bx
60mm delta black label 37 cfm
pci slot 25 cfm
got my temps down 4-5c degrees :grr:

sound isnt as bad as i feared not much louder new pitch
spark7+ is already loud on full
with the delta as an added tone

i feel ive gotten :celebrate good results

[bothered]

I always imagine a fan blowing air in would be warmer than ambiant because the fan produces heat. A fan sucking air out would only draw ambiant air in so surly it would be cooler inside the case.

[Gobbles]

I've run boards outside of the case, and if you put one or two of those rotron 6.75" fans blowing across the board, everything drops to a few degrees above ambient, except for the CPU, chipset, and video card (although if you have a really good cooling setup on them, they'll drop a great deal too.

I just haven't found a design I'm happy with yet...

LOL everything drops a few degrees except all the parts...
:wow2:

[automaton]

hi
i tried the window as exhaust was not cooler :rarr:

im trying to get air front to back :hitit2:

cooling guides :clap:

http://www.tweak3d.net/tweak/airflowtweak/

http://www.overclockers.com/articles578/

http://www.sysopt.com/articles/casecooling/

http://www.speedy3d.com/articles/case_cooling/

http://www.overclockersclub.com/?re...ppZZpuZCxjnbYEJ

http://www.nordichardware.com/artic...03/luftkylning/

http://www.ocforums.com/showthread.php?t=70679

http://www.tweakers.com.au/articles...part2/page1.asp

http://www.short-media.com/review.php?r=230

http://firingsquad.com/guides/hdcasecooling/
http://www.firingsquad.com/guides/cooling/default.asp

http://forums.overclockers.co.nz/sh...=&threadid=7042

http://www.gamers-depot.com/guides/...g_guide/001.htm

http://www.heatsink-guide.com/

http://www.heatsink-guide.com/casecool.htm

http://www.tech-pc.co.uk/cooling.php

http://forums.extremeoverclocking.c...ead.php?t=92559

:rarr:

[Tex]

I always did better with intake blowing through the side driectly onto the cpu's hsf. front intakes only help with hard drive temps. It's generally believed you want more exhaust then intake if its not equal and as far as cpu temps that hasnt played out for me. the more cold air I blow right onto teh cpu hsf the better. I typicaly use one top and one back exhaust but in general they blow much less exhaust then the intake fan does

[fudgam]

My current setup is 2 intake on front, 1 intake on side, and 2 outtake on back (and the psu fan blowing out). What if I turned the 2 front intake around, so Id have 2 outtake in front, one intake on side, 2 outtake on back and then the psu? Would that mess up the fans because there is only one fan blowing in and 5 blowing out? I figure I'd leave the side intake alone since thats blowing on the video card.

[EyesOnly]

My setup is the only possible for a Antec Sonata (man it was long since i wrote that word). One 120 mm PAPST in the front blowing in and the stock 120 mm fan in the rear blowing out all running on the lowest voltage thanks to a fancontroller.

Whilest reading i though of turning off the front fan but then i realized that the case doesn't have alot of flow in it and having no intake would prolly kill the harddrive. The temps right now are 49C for the cpu and 28C for the mobo. Room temp is 26C.

The highest temps measured was: Cpu 53C, 33C mobo. That was during a heatwave about a month ago where room temps where around 30-33. Still i've got fah running at full speed (which bothered can verify) :fold: so i'm pleased with my temps.

When gaming i turn on the fan for the graphics card (an 80 mm zalman) and i can't understand how many of you have fans like that or even louder on all the time. :eek2:

In other word. My quest for a silent, modern gaming computer was a success. :)
It's not that hard as long as you don't listen to what anyone has to say and just go your own way.

If my case had better flow i would atleast consider it.

[][v][AGIC]

with every case ive had ive tried about all fan configs. i figure that you just need more outtake than intake, you just cant have any lingering air around high heat componentes.

[entropy]

One side intake, one exhaust, plus 2 on psu (one going into it and one leading out of case). Temps average at around 24-26*C (YES, that's correct, don't even bother challenging it, because I already have ;) ) Ambient varies - tends to stay around 20 to 25. Right now ambient is about 20*C, and my CPU is at 24*C, and it's idling. SF2 on temp-sense over SLK-947. Btw, how safe would it be to remove my psu's intake fan...?

[KINGPIN]

if intake and outlet are at opposite sides it circulates air better

[Leonardo]

One thing I have found during my personal adventures in cooling is that you can't make a blanket statement to cover every situation. Prof, I agree completely. In my experience though, the principle of rear exhaust being the most important cooling component is correct. I've tried many different setups with many different PCs (way to many fan configurations to list here). Sometimes a front intake fand made no difference at all to either case or CPU temperatures. I have found though, that with intake air filtering, an intake fan is almost mandatory with my setups, generally causing a 2*C case temp lowering and 1*C CPU temp lowering.

[automaton]

:Rocker: :banghead: :Rocker:
got my fans in

intake
48cfm 80mm
triple fan bay cooler
window 53cfm

exhaust
38cfm 60mm
duct 50cfm
pci slot 20cfm :celebrate
dropped cpu temp 4-5c degrees

noise not as bad as feared
window as intake also quieter :rarr:

[if pix 2 much delete]

[JChretien]

Hmmm i have one side intake, two front intake, two back exhaust and one top exhaust, all 80mm. add my PSU's one exhaust.. and i have negative pressure... its not as noisy as i thought it would be.. and even with my O/Ced barton, the Vantec Aeroflow keeps my CPU folding@100% in the mid 40s (Celcius). During the recent summer heatwave, its hit 56C max... its not too bad really considering i got the fans for 2$ each =D

[TheGr81]

I have next to no experience with this, as I've only built one computer where there were fans other than the one(s) in the PSU. My current setup is 1 rear exhaust+psu exhaust 1 side intake and 1 front intake, all 80mm. I didn't notice any difference when I installed the front intake. I hate the noise it makes though, my case sucks.

Great thread so far, I'll try and keep this stuff in mind whenever I get a new case and fans.