Turning it all upsidedown ...

fingers · Post by **fingers** » Wed Feb 22, 2006 8:24 am

Hey guys,

I am concidering silencing my fathers noisy as heck pc and thought in the process I would do a little experimenting

It's a Duron 900MHz with a RivaTNT2 gpu.

If I put three/four 120mm (Nexus@12V) fans on the bottom of my case blowing down and sealed the rest of the case except for the PSU and maybe a small (60mm) blowhole at the top of the case, would ...

a) The air being pulled through the PSU be enough to cool it (OEM S12 with fan removed)?

b) Would the air pulled into the case be enough to cool passive the CPU, NB, GPU etc?

c) Am I right in thinking that with some case damping and standing the case on carpet to diffuse the exhaust this would make for a very quiet system?

Any comments?

Thanks

Chris Chan · Post by **Chris Chan** » Thu Feb 23, 2006 6:34 pm

That would not really work because heat rises. By exhausting it out the bottom you're basically going against the laws of thermodynamics. Turn the case upside down and it should be ok, though.

Tibors · Post by **Tibors** » Thu Feb 23, 2006 9:01 pm

Repeated experiments by people on these forums have shown that natural convection is so weak a force you can largely ignore it when you have fans pushing/pulling air around in a case. So most of your proposal would probably work. Except for the PSU. The 120mm fan in a PSU not only make sure that air moves through the PSU, but flows between the hot components. If you take the fan out and reverse the airflow, most of that airflow will just flow through that wide open path you just created instead of between the hot parts.

B.T.W. Thermodynamics is the part of physics that's concerned with things like entropy and enthalpy. Fluid dynamics is the part concerning the flow of gases an liquids.

fingers · Post by **fingers** » Fri Feb 24, 2006 1:48 am

How about if I block the bottom vent on the PSU so it pulls out from the rear of the unit, will that pull across the relevant hot parts of the CPU? Alternatively an Antec Phantom could be aquired, would this be a better alternative?

Thank you for your replys so far

Tibors · Post by **Tibors** » Fri Feb 24, 2006 4:12 am

Modding the PSU to restrict the airflow to between the components would also result in more resistance to airflow in the PSU. So most of the air will then be pulled in through the duct next to it. This would leave the PSU again with an unknown and possibly to low amount of cooling.

Buying an Antec Phantom is never a good idea in my book, as they (and any other fanless ATX12V PSU I have seen) are too expensive. But if you really want to go with a fanless PSU, then check out the Fortron Zen. It is more open to airflow, it is more efficient in the range your computer is operating (<200W) and is generally sold for less.

That said I still think that is a bad deal. You buy a fanless PSU to be able to put three fans on the bottom. If you put two fans on the bottom blowing up (one under the Riva and one under the disks), keep the fan in the PSU and just have an opening where the exhaust fan normally is, then you'll probably have plenty of cooling. Granted, you loose the experimental airflow pattern, but ....

fingers · Post by **fingers** » Fri Feb 24, 2006 5:36 am

Lots to think about!

I don't want the fans blowing up from the bottom as the area under my Dads desk is very dusty

also having the airflow blowing up in the case removes the reason for this experiment, to have the airflow defused by the carpet under the case therefore removing wind noise!

So, the PSU is the only flaw to the plan! How about bottom mounting the PSU above one of the fans blowing out? (clutching at straws now maybe)

Chris Chan · Post by **Chris Chan** » Fri Feb 24, 2006 1:41 pm

Thanks for clearing up the difference in definition. So with lots of fan CFM bottom exhausts would be okay? and Foertron Zen tested well at XbitLabs.

Tibors · Post by **Tibors** » Fri Feb 24, 2006 1:59 pm

There are some posts by IsaacKuo somewhere on the forums where he tells he has the fan in a PSU flipped (for several machines I believe). This gives you the reversed airflow, but still a fan close to the hot parts, insuring some airflow over them. If you really want to try the top down airflow, then you could mount such a flipped fan PSU on the bottom of the case.