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2019
me1212
join:2008-11-20
Lees Summit, MO
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me1212

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Best positions for fans in pc case?

I have two cases, a cooler master haf 932 and a cooler master 343 elite. the 932 has a 200mm intake fan on the front and side. a 200 exhaust fan on the top and a radiator with 2 120mm fans in the rear which is used for exhaust and cpu cooling. the 343 120 mm intake in front, 140mm exhaust in pus on top, and 80mm exhaust in rear. I've been reading about air pressure and apparently positive air pressure, more intake then exhaust, leads to lower temps and less dust. Now I would love both of those, but would it really work? I can see the 80mm fan in the 343 bringing in cool air and lowering temps, but the cool air from outside of the radiator in the 932 would just get hot from running over the radiator and lead to higher temps for all but the cpu wouldnt it? And wouldn't having more intakes lead to more dust inside the case? Anyone know how this really works?

Krisnatharok
PC Builder, Gamer
Premium Member
join:2009-02-11
Earth Orbit

Krisnatharok

Premium Member

Traditionally, you want cool air blowing in the front (HDD array) and side (GPU) with hot air going out the top (hot air rises). Fan number, sizes and RPM will determine overpressure.

Don't turn your exhaust fan around to provide positive pressure--buy higher RPM intake fans or add an additional one (like a side fan). You also want to be able to sketch out your air flow (turbulence--like turning around an exhaust fan) won't result in lower temps.
me1212
join:2008-11-20
Lees Summit, MO
·Google Fiber

me1212

Member

I've already got fans everywhere I can, largest size I can have too.

Just out of curiosity, what would be the effect of me turning my radiator/fan around? I know like the h40/50/60/70/80 all say to have the fans on their radiators used as intake, so I was wondering if you or anyone knew.

signmeuptoo94
Bless you Howie
Premium Member
join:2001-11-22
NanoParticle

signmeuptoo94

Premium Member

Fans forcing air cooler better than fans drawing air, and drawing in air where it should be exhausted will increase the heat inside the case, making for hotter CPU, GPU, AND especially power/chipset parts of mainboard.

Krisnatharok
PC Builder, Gamer
Premium Member
join:2009-02-11
Earth Orbit

Krisnatharok to me1212

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to me1212
As long as you have air blowing in via the side intake, you should have positive pressure.

Where is your radiator mounted? Are you saying you have it over the side vent? If possible, take off the 120/140mm fan in the back of the case and mount the radiator there.
me1212
join:2008-11-20
Lees Summit, MO
·Google Fiber

me1212

Member

No, my radiator is mounted in the back of the case, where an exhaust fan was mounted when I get the case. I kept it in the exhaust position when I put the radiator in, but its a closed loop and I was reading and closed loop manufacturers recommend the fans on the radiator be used as intake. I was worried that would lead to hotter temps like signmeuptoo said, so I thought I should ask to make sure.

Krisnatharok
PC Builder, Gamer
Premium Member
join:2009-02-11
Earth Orbit

Krisnatharok

Premium Member

I would keep it as exhaust.
MrFixit1
join:1999-11-26
Madison, WI

MrFixit1 to me1212

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to me1212
Just a few things to consider .

Positive pressure leading to less dust in case will only hold true if all the intake fans have filters on them .

You want the air flowing over the radiators to be as cold as possible . Normally this means the air flow for the radiators will be into the case . Ideally you would want the air flow for the radiators to be isolated from the air flow over the motherboard . This is not always easy to achieve .

You do not want too much positive , or negative , pressure , What you want is to get as much airflow as possible through the case , but you want that flow to be as " clean " as possible .
Think of a nice cold windy day , do you feel colder out in the open or hiding behind a wall ? Now try and transfer that idea to the airflow in your computer case .
If you can get a nice clean flow with no dead areas , you would be surprised just how little air flow you need .

If your systems have built in thermocouples on the motherboard , make use of them . Also , you can buy indoor outdoor digital thermometers fairly cheaply . As long as you remember that they can be slow responding , they can help you see what is going on inside your cases .
Don't be afraid to try different setups to see what works for you .
As long as you are monitoring system temps , you should not get into trouble .

Krisnatharok
PC Builder, Gamer
Premium Member
join:2009-02-11
Earth Orbit

Krisnatharok

Premium Member

You also need to balance your temps. My Corsair H100 has a push set-up using case air and exhausting it out the top. I get a couple degrees cooler if I push air *into* the case, but it causes my GPU temp to go up 5 C. That's a net loss in cooling capacity, so I can deal with 2 C warmer on the CPU to get the cooler GPU, which is more important to me anyways.
MrFixit1
join:1999-11-26
Madison, WI

MrFixit1

Member

said by Krisnatharok:

You also need to balance your temps. My Corsair H100 has a push set-up using case air and exhausting it out the top. I get a couple degrees cooler if I push air *into* the case, but it causes my GPU temp to go up 5 C. That's a net loss in cooling capacity, so I can deal with 2 C warmer on the CPU to get the cooler GPU, which is more important to me anyways.

Fully agree on the need to balance temps ! That is why it is so important to monitor what is actually happening and not just assume that " X " is the best way to go .
You will be surprised at the little things that can make a difference .
How cleanly are your wires routed ? Are they blocking air flow ?
Are your memory cards parallel or perpendicular to the air flow ?
What do you have for video cards ? Are they active cooled ? can you get good airflow around them ?
And on and on
That is why you have to monitor , and be willing to compromise .

rusdi
American V
MVM
join:2001-04-28
Flippin, AR

rusdi to me1212

MVM

to me1212
Top & bottom.

Hot air rises, cold air sinks.
Draw cold air in from the bottom, blow it out the top.

signmeuptoo94
Bless you Howie
Premium Member
join:2001-11-22
NanoParticle

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Personally (and I apologize if I am ruffling any feathers) I studied gas flow science in tech college (for laboratory vacuum systems). It is my belief that there isn't a significant positive or negative RELATIVE air pressure in a computer case. The case would have to be *sealed well* and a proper roughing pump be attached, such as a rotory or piston or even claw pump. I think it would be a big challenge measuring any perceivable air pressure difference between the exterior and interior of the average computer case.

IMHO, lady's stockings (nylons, panty hose, or whatever you want to call them) cut in squares and placed over the apertures that input outside air will control dust MUCH better and they can be rinsed clean.

My verbiage in previous post sucks, let me try to express myself again (bear with me, I am in the middle of an anxiety attack for some unknown reason) in better terms:

Pushing air through a heat sink with closely spaced fins (almost all heat sinks) will provide better airflow, measurable, versus "drawing" cool air through the fins because these fans aren't built for counteracting resistance and lack of vacuum. The operative value here is a measure of what is known as "static pressure". The shape/size/angle/number of vanes on fans and the structure of the fan housing and the rotational velocity all dictate the static pressure a fan can produce.

In situations where air IS being drawn over rather than blowing forcefully over, a thicker fan, such as a 38mm thick fan, is more desirable.

In all sincerity, your best bet is to measure temps with different configurations and methodically determine what works best, any argument here as to what is best is somewhat suspect without empirical data being taken.

It could be that zero exhaust fans works best, but your mileage WILL vary.

Sorry, I've got the shakes right now so I hope I am understandable...