Robert McClelland

Instead blowing air in the back of the case in going go blow it out. To see how cool it will get on mobo. On my guardian 921 case

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Takaharu

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Robert McClelland

I guess you don't know my English lol. What I was staying Case has in take back fan. I took and flip the fan backword so the hot air go out along with my psu instead case fan blow air inword. Because the top psu fan heat is drawing heat out then it goes in with my case fan blowing inword. So far it's working very good having rare case blowing outword instead inbound.

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IvanV

I thought that the "rule of thumb" was that fans at the back of the case were supposed to blow the air out, while the front ones suck the air in, to create a directed flow of air through the case (also, that bottom and side fans generally blow inwards and the top ones blow the air out).

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steves6403

i cut a hole in mine at the top that blows out and 1 on the side bottom that blows air in.The cpu box cooler blows the air upwards.....One at the back blowing in is not a good idea

Robert McClelland

Ya but some reason on my 921 case they have back case fan blow inword. I do have 3 case fans on 921 case. One in front blows air in and side of the case blow in. And back case was blow air in then go threw out PSU fan. But I don't think it would make sence have blow in air back of the case because PSU fan goes out then hot air goes back into your back case in right? It's just better have back case fan blowing out?

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synthesis204

It is a rule of thumbs, but fuck thumbs. I have a 200mm pointed directly at my motherboard in the side and tops with vents in the front and back taking air out.

Or you can do it like my 65 year old father and just put them ALL pointing in "so it's cooler, duh."

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WxMan1

Back in the day all my gear-head friends always said: "Injection is nice, but I'd rather be blown."

My thinkin' is that hot air rises; let physics take car of its own. Forget 'bout air "injection", blow the hot air out the back of the case. Case intake inlets usually will be in front towards the bottom. If the case lives on the floor, you will need a filter for intake ports to keep dust bunnies out of the box.

That notwithstanding, its my opinion that ALL intake ports should be filtered (including side-port CPU-snorkel duct).

The newer boxes are nice in that they allow the PSU to be installed so that the fan faces the bottom of the case. A decent CFM case fan installed above the PSU would complement most contemporary PSU's having 120mm fans. These two fans blowing hot air out should be sufficient to keep a case moderatly warmer than ambient.

This philosophy is based on the principle that most modern CPU coolers alone are quite suitable to stir up case internal airspace; they suck air in axially and blow it out radially.

blibbax

As long as you have slightly more intake than exhaust, and air passes over components to get from intake to exhaust, it doesn't hugely matter.

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WxMan1

You're totally correct, inject external case air into the box and let it escape however it wants to and whereever it can.

One thing that bothered me concerning being simultaneously injected / blown was that of hydrodynamic pressure at the fan; most especially from the perspective of the CPU fan relying on side-case intake snorkel. That's why my druthers have - so far - been blow the hot air out the top; rely on the CPU / GPU fan(s) to thoroughly mix the internal case volume.

It may be more efficient from the fan's perspective to inject colder, i.e., denser, air into the case rather than blow hot, less dense, air out.

Possibly could result in lower fan noise?



If the intake has larger CFM than the exhaust, the case would become positively pressurized, no? If the exhaust has higher CFM than intake, the case would become negatively presurrized, no. It is plausible that a negatively pressurized case may be deleterious to thermal resistance to the fans internal to the case, e.g., CPU and/or GPU. Pressurization entails an increase in mass of the air contained w/in the case; albeit either Charles or Boyle would have something to say about the corresponding internal ambient temp.



Dunno if anything is to be gained one or the other way.



I think somebody should run the numbers and then run objective empirical metrology to ascertain the soundness of any of these conjectures. That's what I think.

blibbax

Positive pressure is considered preferable mostly because it is better with dust (if intakes are filtered) and because it prevents unwanted air paths (e.g. air coming in right next to the exhaust it comes out on). The difference in the effectiveness of coolers caused by denser air is negligible.

And yes, those CPU fan intake tubes will reduce CPU temp and thus fan noise in some systems. However, if they are used instead of (rather than as well as) a conventional intake fan, some other components will be hotter than they would otherwise be. Also, those intake tubes are rarely filtered.

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WxMan1

Of course one would not want to rely on CPU side-snorkel / PSU exhaust fan only.

Intuitively my perspective is that when cold room-air is injected into the case via the front / bottom ports, the side snorkel should be blocked (with exception - obviously - if its actually being used).

IF the side-snorkel CPU-duct is implemented, then the air shouid be ripped out from the top rear aspect of the case; all other air inlets, i.e., side or rear, should be blocked.

That notwithstanding, it may be efficacious to actively vent hot air near the video card; that should be easily accomplished with a small 50mm exhaust-fan. The idear is to prevent the CPU from sucking in any of the hot GPU / PCI air.

One doesn't want to exhaust TOO much air out from that particular region as it might interfere with the CPU fan sucking air in through the snorkel side-duct; peripherals to its south are designed to run warm; they'll be happy.

Its far more important to ensure your CPU, RAM & HDD are adequately cooled. If one's HDD's are running around 37 Deg. C. they're doing fine. Most HDD are rated at 65 Deg. C. (if your HDD is running that hot: you've got other prollems).

It doesn't need to be said that dust-bunnies have a vicious Deg. C/ w thermal resistance; one does NOT want their components coated in dust. Since it doesn't need to be said is exactly why I'm not getting into that.

When one gets down to it: its about as important as defragging the HDD regularly, e.g. weekly.

blibbax

Why?

The side snorkel effectively turns the CPU cooler into an extra intake. Two intakes and one exhaust is fine.

You should keep the exhaust at the top-rear as an exhaust, as you say, then have the intake at the bottom-front and the snorkel intake. That way, everything gets air passing over it, and the PSU and exhaust fan between them ensure that it all flows in the right direction.

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