Poll: Airflow configuration

[pbox]

What do you think guys what is the best airflow configuration. Please do not just post yours, I really want to know why do you think that is the best.

Here is my 2c:

Power Supply: Exhaust (It needs to draw off the hot air from the TOP of the case (Hot air tends to rise according to 2nd grade physics).

CPU Fan: Obviously blow onto the heatsink. More effective then pulling air off.

Rear Case Fan: Intake. CPU Fan needs cool air to blow onto the CPU (this is somewhat contradictory to the most common setups, if I read your posts properly). This also helps to prevent the hot air rising from the video and PCI cards to reach the CPU.

Front Case Fan: Intake. Hard disks need serious cooling (I got two IBM 45GB in RAID0, I cannot touch their surface after a defrag)

Blowholes: I got no idea, I have none.

Other: I am planning on cutting a hole on the top panel (96 mm) with a superquiet fan as exhaust to remove the hot air. I also have a Plextor CDRW woking in there and I do not want it to fail because of heat...

Peter

 

[mechBgon]

The conventional wisdom is for all the rear fans to blow out, and all the front fans to blow in. If you have the power-supply fan blowing out, and the 80mm fan directly underneath it blowing in, they may tend to recirculate some of the same (heated) air. You could get a Radio Shack digital thermometer and try some different configurations. Nothing like actual testing to figure out what works.

For Alpha heatsinks, the fan is recommended to be pulling air away from the sink, while others are conventionally set to blow air onto the sink. Alphas usually show a performance gain when oriented in the recommended direction. If you run a high-output fan for a while and then put your finger in the center of the label, you are likely to find that it is HOT. Makes sense to me to blow the fan's own heat production away from the heatsink, although that is probably splitting hairs...

I tested both directions for side blowholes and found that intake worked best at cooling my system. Power supplies produce heat so people like to see them blowing out the back.

 

[pbox]

Any other thoughts? Does everyone takes the front intake back exhaust for granted?

Peter

 

[darth maul]

"CPU Fan: Obviously blow onto the heatsink. More effective then pulling air off."

I don't agree with this. Try putting a box fan in your window, you will get much better airflow thru your house when you are exhausting air, then trying to force air in. Some heatsinks might perform better blowing on to the heatsink, but most don't...including Alphas.

Also, rear fans should blow out, other wise you could have ricirulation problems from your PS fan. Where the air goes out your PS fan, then back in, thru a endless loop.

IN low/front, OUT high/rear makes the most sense.

Hmmmm, how many times is this question asked in a months time?

 

[pbox]

Sorry if this is a repeated thread, I check back a few pages and there was none, I am also new here.

A few thoughts:

1) Hot air rises, therefore if the PS fan exhausts, it will rise away from the rear fan. Ok this might be a little weak.

2) Rear intake will blow fresh air (lets say theoretically) into the case, and the CPU fan blows this roomtemp air onto the heatsink. This is ideal if true.

3) Front intake air will go through your hard disks (that can be really hot) then through you PCI and video card (30-50W) and then this nice and warm air gets pulled off off your CPU heatsink to be exhausted by the rear fan. Hmmm, see my point?

4) I really think the top should have an exhaust fan. That would be ideal but requires cutting. What are your thoughts?

Peter

 

[Jwyatt]

The CPU fan blowing in will rais the temp on the MB components. The heat will spread from the bottom of the CPU to the components around it. Does it not make sense to pull the heat away fromt he CPU which will also pull the fresh air across the MB components?


Blow hole: I dont have one. Really dont like the idea of having a HUGE fan sitting on top of my case where lil fingers and drinks will end up ruining the system!

Front lower: This should pull fresh air in. Directing it across the PCI/ISA boards.

PS/Rear top: OUT. This should really be the only place to have the air exhaust. The PS usually sits in the very top of the case. In most cases there is nothing above the PS, unless you have a full tower or server case.

Another reason to have this setup is to keep the dust to a minimum. You should have one filter in front of the front lower fan. If you put 2 or 3 fans blowing in you should then filter all of them.


These are just my opinions. Take them or not.

Why redesign the wheel? If you check out what others are doing and it works then try it. If your not happy with that then try some other ideas.

 

[Duvie]

I think that fans work better sucking air in and across fins of heatsink on the cpu because the other way the mass of the heatsink limits the air to pull out...It like putting the fan up against the wall...

Blowholes are highly recommended warm air gets trapped up between ps and ide devices....Due to cables and devices the case doesn't have very good circulating characteristics

Don't forget about the ability of side fans that can intake air and blow it onto the mobo...I know you didn't want to here about our configs but I have two fans pulling air on the side blowing across pci cards and across harddrives.

Also I have devised a way to have the fan of the cpu to pull in air directly from the outside...not warmer case air but ambient room air...not fully installed yet but minor testing has shown me temps 4 degrees celsius cooler...my 750 t-bird oc'd to 840 was running at 32 degrees celsius under very minor cpu load.

 

[pbox]

Thanks for the info, great tips. Duvie, maybe I was not clear, I am interested in your configs, but even more interested in the reason why you have it set up in that particular way.

I agree with you that blowing onto the fans is more effective. I have also seen that most benchmarks on Alpha coolers do gain by sucking air through the fins. Again that is true only for the Alpha coolers with Delta fans (I guess that the high CFM helps to overcome the fin-block. I also suspect this is the reason for the extremely loud and screaming noise. 46bD is not for me...)

Thanks again,

Peter

 

[Duvie]

I think the reason for sucking ambient room air onto cpu versus internal case air is obvious...

Blow holes...If you look at you system from the side you can get really get a sense for the nooks and crannies were hot air can collect...now if the cross flow was strong enough which it is not it could pull that air out like a vaccum. In my case the PS at the upper rear and the full load of ide devices FDD below that and 2 HDD'd below taht make my intake at lower bottom ineffecive in scouring out that air.

The side fans step in where the above is defficient...Stagnant air between two HDD's is a serious concern of overheating the HDD's as well as the pci cards that expend heat off the top and the bottom of the cards creating pockets. Also round cables I need to get as 40 pin ribbons really hamper smooth air circulation, another reason of the side blowers.

 

[smp]

<< Power Supply: Exhaust (It needs to draw off the hot air from the TOP of the case (Hot air tends to rise according to 2nd grade physics). >>


I disagree with this comment. AMD states that the best power supplies to use with their processors are the kind that pull air from the bottom of the powersupply and out the back.. the reason for this is because it would pull any hot air (rising) off of the cpu and push it out the back...
Also.. if you feel blowing fan.. the area in the center is practically dead of wind.. there are no fins in the center.. now, if you blow onto the heatsink.. the air is being blown onto the outside parameters of the sink and then out and away from it.. so the middle of the sink is not getting any fresh air.. and the middle it the part that would (by my estimate) be the hottest.. Don't get fooled into thinking that positive pressure is stronger than negative..
Also, it's a good idea to have the same amount of fans blowing in, as blowing out.. if the idea of case cooling is air CIRCULATION then that would be the way to get it.. try attaching a fan to the top of a empty tin can and see if it blows in real good.. see what I mean.. ?? I like blowholes myself.. and for hdd cooling, I think that those bay fans are a good idea, even though I don't have any myself.
I probably missed some stuff.. feel free to correct me..
Oh, about the fan blowing on or off of the heatsink.. my comment maybe made you think that I think that pulling air off is better.. I think that is the case if the fan is mounted sideways ala alpha.. from the top I think the same problem as I outlined with it blowing down would be the case.. or similar.. fans seem to blow a 'ring' of air.. not a solid wall..

 

[pbox]

> AMD states that the best power supplies to use with their processors are the kind that pull air from the bottom of the powersupply and out the back.. the reason for this is because it would pull any hot air (rising) off of the cpu and push it out the back...

Absolutely agree with that. All PS should have grill in the bottom... or in top cases that install it upside down.

> the air is being blown onto the outside parameters of the sink and then out and away from it.. so the middle of the sink is not getting any fresh air.. and the middle it the part that would (by my estimate) be the hottest..

That is true that the fan does not push air in the middle, if mounted on a proper heatsink the fins will interfere with the airflow (that is turbulent and rotating with the axis of the fan) so some of the blow can be directed through the inside fins also. And yes that must be the warmest, since the die is relatively small in the middle of the heatsink.

> Also, it's a good idea to have the same amount of fans blowing in, as blowing out.. if the idea of case cooling is air CIRCULATION then that would be the way to get it.. try attaching a fan to the top of a empty tin can and see if it blows in real good.. see what I mean.. ?? I like blowholes myself.. and for hdd cooling, I think that those bay fans are a good idea, even though I don't have any myself.

I agree, actully that the total CFM going in and out should be the same. Not neccessarily the number of fans. And by CFM I mean the actual one, not the ratings, since that can be drastically reduced by air flow blockings (such as grill filters etc.

And I also like the ideas of the blowholes (specially over the HDDs) it can be omitted if you get some good HDD coolers (the kind that sucks air form the front of the case).

Peter