air circulation

[subdismal]

It's common knowledge to most everyone that heat rises and cool air stays at the bottom. It's a principle I learned at a very early age but recently was reminded of when thinking about how to cool down my rig.

My idea was (and I'm sure I'm not the first to think of this) to put some high-flow fans at the lower portion of the case, blowing cool air in, which will circulate through and since heat rises, you need to get the heat out of the top of the case. I've saw PCI exhaust setups and whatnot, but they don't seem logical to me since it seems like they would be taking the cold air out, right? My plan for getting the hot air out of the top would be to put a high-flow fan in backwards(making it suck air from inside and blow it out instead of suck air from out and blow in). You could mount this fan (reverse rotation fan) at the highest mount in your case or if you're into more modification work, cut some sort of hole in the top of the case to vent it from the top.

Basically, I'm wondering two things. Have any of you tried this? Results? Ever read anything about it? Results? Another thing I was wondering, and this ties into any of you ever hearing/doing this, is the size of the case big enough for the process of rising air temperatures to take place enough to effect anything at all?

I realize this isn't something that's going to drastically improve cooling, but if it worked, it couldn't hurt, right?

 

[Sentinel]

it wouldnt hurt and is a good idea, providing i had a case i could do that with i would try it as well

 

[gotensan01]

Your idea is called a blowhole. It isn't a new idea and many companies, like coolermaster, have long added these blowhole fans in as a standard feature to there cases. As for having fans on the bottom to push it up while the top blows it out, seems the same as having fans on the front to intake and fans in back to exhaust.

I personally think having an 80mm fan on top is as effective as having one in the rear.

 

[subdismal]

sentinel, if you try this before I do, let me know how it worked!

Originally posted by: gotensan01
Your idea is called a blowhole. It isn't a new idea and many companies, like coolermaster, have long added these blowhole fans in as a standard feature to there cases. As for having fans on the bottom to push it up while the top blows it out, seems the same as having fans on the front to intake and fans in back to exhaust.

I personally think having an 80mm fan on top is as effective as having one in the rear.

It seems to me that you missed the whole science of my idea; I don't think having fans in the front and PCI exhaust fans in the back is the same. Simply because the hot air is lingering at the top and not escaping. My idea was to have the cool air go to the bottom, flow upward, and the hot air at the very top would be exhausted out of the highest point of your fan in reverse rotation? See what I mean?

 

[Navid]

You are right, having a PCI fan that exhausts air from the case is not efficient.

It is always advised to have exhaust fans at the top rear, right under the PSU. That is a standard place for an exhaust fan and many cases come with those fans or at least with a place holder.

It is always advised if you want to have an intake fan to have it at the front bottom. Many cases come with place holders for such a fan.

The reasoning is exactly what you mentioned; warm air is lighter than cold air.

 

[effee]

There is a great article on overclockers.com under tips & techniques. It involves creating a channel for the air to flow directly to your component, maybe you'd want to try that

 

[MEDISIN]

subdismal I don't see how your idea is any different from how 90% of the cases out there operate. Cool room air is sucked into the front lower portion of the case and hot air is exhausted out of the top/rear. This allows for an "S" pattern of air flow i.e. in, up, and out.

The blowhole design is great for exhausting the hot air that gathers at the top of a case. Most PSU's mounted at the top also contain dual fan designs to help exhaust the hot air so adding a blowhole is often not needed.

The important thing is to have smooth, unobstructed, FLOW with as little turbulance as possible. Accomplish this and you will have both a cool AND quiet case.

 

[HeroOfPellinor]

You mean have the fan in the bottom front of the case bring air in and the fan in the top back of the case exhaust it? This is common sense and is what everybody is already doing. Am I missing something to this idea?

 

[subdismal]

I'm not sure if you guys are missing something or what, but for some reason my idea didn't seem exactly like what people do commonly. Yeah, it's common sense, but I didn't realize it had actually been widely applied.

I'll try to elaborate a bit more.

A typical case has intake fans in the front bottom to pull the cool air in, and some fans have exhaust systems right under the PSU, and I realize this and take this into consideration. What I was trying to explain would be to use the intake fans all over the bottom, pushing the cool air into the lower portion of the case. Then, since warm air is heavier (as Navid said) it will rise. Standard exhaust fans under the PSU is still allowing the hot air to linger at the top, correct? Well, a reverse rotation fan, in my theory, mounted at the top of the case, horizontally flush or whatever with the top of the case, would allow almost all the hot air to escape from every portion of the case.

It may not work, or work just not be effective, which is why I posted this here trying to get some feedback. Even if you know it won't work or whatever the case, do you at least understand what I'm saying?

You 1337 people here at AnandTech may think I'm dumb for this idea or any of my ideas or anything I post here, but I'm very interesting in modding, and trying to learn. I admit I've only fully built one computer from scratch, and I am in no way an expert. That's why I lurk these forums, trying to get more information about things.

 

[Navid]

OK, wait a minute.
So, you want to have intake fans all around? That would be new.
And you want to have exhaust fans the same level as the power supply instead of under it. This would be an improvement. But, some people put exhaust fan at the top of their cases. So, the fan in installed on the upper surface of the case. That is the best position to ensure that the air that is removed is the warmest.

I don't see anything wrong with what you want to do. Just keep in mind that it's not just cooling. You want to cool it without making it sound like a jet engine.

By the way, the PCI fans are really meant for cooling down a graphics card. But, they may screw up the overall cooling. But, they are not meant to be used in order to cool down the case.

 

[subdismal]

Navid, it seems like you have my idea grasped! Awesome! Now I don't feel like such an idiot.

Yes, I would put the intake fans all the way around the bottom of the case, in certain increments of space. Then, have the fan atop the case with a flow-through like you mentioned, but have the fan upside down so it grabs air from inside the case and pushes it out instead of the other way around. Having this fan somewhat close to the power supply would also pull some of the power supply's heat out too, would it not?

Yeah, I know what you mean about the jet engine thing. I wanted to cool down my rig and had the bright idea of hooking up three Vantec Tornado fans; two 80mm and one 120mm. I tried it without a fan controller (like an idiot) and almost drove myself insane. I bought the Nexus controller, and haven't had time to fool with getting things hooked up. I need to get a three-pin to four-pin adapter cable before I can hook it up, though.

 

[Navid]

A fan at the top of the case must be an exhaust fan. An intake fan at the top makes no sense. I have never seen anyone doing that. Have you?

I think that is a part of this disscussion that has confused almost everyone. You keep saying that you want to install a fan at the top that would remove warm air from the case instead of blowing air in as if that is a new idea. And everyone keeps telling you that it is not!

 

[subdismal]

Haha, I guess that makes sense, then. I had no idea that it was common knowledge and common technology. And here I had thought I had stumbled across something new. =( Way to bust my bubble, Navid!

 

[stardust]

Wait till you see BTX..

 

[HeroOfPellinor]

Okay, so you're proposing a blow hole. I didn't get that at all from your first post.

People do mod their case like this and some cases come with blow holes already in place. It was a novel idea in it's time, but I think it proved to offer little advantage and has several disadvantages which is why it's not widely used today.

And you keep referring to "reverse rotation fans". If you want a fan to blow the opposite way, you just need to flip it over. Or are you referring to a fan which spins reverse from how it was designed in which case I think all you'd do is drastically decrease the CFM.

Keep working on the ideas. The latest trend seems to be isolating the PSU from the rest of the case so that the two don't share heat.

 

[subdismal]

I meant to just flip the fans over, thus putting them in reverse rotation in relation to their function. Sorry for the confusion.

Also, that's a damned good idea! Isolating the PSU... ::wheels in head start turning::

 

[ApacheChief]

This is an excellent idea, if I understand what you're saying.

Fans on the BOTTOM of the case, blowing UP, to a couple blowhole fans, pulling out all the hot air?

I don't see how the temperature in the case could rise at all with that kind of a setup... if you had a constant supply of fresh air.

 

[mickles]

Seems logical.

 

[MEDISIN]

I THINK I understand what you're getting at.

Just make sure the lower fans all cause air to flow in the SAME direction (in your case, UP). Fans at right angles to each other cause turbulance, which disrupts flow and adds noise. And of course try to balance intake with exhaust i.e. X cfm in = X cfm out.

Those Chieftec cases, if I remember correctly, have two or three front 80mm intakes and two rear 80mm exhaust by the mobo - is that correct?

 

[Painman]

Originally posted by: MEDISIN
I THINK I understand what you're getting at.

Just make sure the lower fans all cause air to flow in the SAME direction (in your case, UP). Fans at right angles to each other cause turbulance, which disrupts flow and adds noise. And of course try to balance intake with exhaust i.e. X cfm in = X cfm out.

Those Chieftec cases, if I remember correctly, have two or three front 80mm intakes and two rear 80mm exhaust by the mobo - is that correct?

Yup, that's the Chieftec/Antec arrangement. The airflow/fan arrangements in these cases are excellent IMO, aside from cutting out the perforated sections of the sheet metal where the fan mounts are, I don't think there's much to improve on. The temps inside of my Antec are superb and it's completely stock.

 

[Blain]

Look... it's a bird... it's a plane... NO, IT's A CUBE