120mm Fan, and case mod

[pickxx]

I am looking for a 120mm fan, i have 1 120mm fan already and i am looking for an intake. or i could switch it around and make it an exhaust. I would prefer something relitivly quiet but i dont need a 10Db fan.

Also, i dont know if this would be practical or not, but i would like to put a case fan on the top of my case. something small and quiet. I am looking at the airflow of my case and the space between the optical drives and the PSU has a spot where warm air can linger. I think a small case fan blowing out of the case at the top might lower the ambient temp. I guess it could blow the air down and then be blown out the back by the 120mm fan.
I dont have a hot case but preventive measures are always nice. when i get my 3rd HD, 2nd optical drive, and a video card upgrade in there the temps will rise a little. and why spend spend all that money for parts and then not spend 25-30bucks to keep it cool.
thanx

 

[Coyote]

I put hole in the top of one of my pc's too. It's blowing out. It's in a tight space and I wanted to be sure the hot air was getting out. Works well.



Mobile XP 2600+ (11X200)
Abit NF7-S v 2.0
Maxtor 60GB ATA 133 7200RPM
512MB Corsair Twinx 3200LL
BBA 9800 Pro
Enermax Noisetaker 420 watts
Win98SE

 

[Mr5oh]

I have heard mixed things about fans in the top of PC cases, generally it seems many people say they disrupt airflow.

It is my understanding that you want to try and create more exhuast than intake, intake being low and in the front, and a more powerful exhaust near the top rear of the case. This should create a "wind-tunnel" effect. I at one time found a very good article about this, but I can't seem to find it anymore.

I was trying to figure out your message, where do you currently have fans, and are they intakes or exhauasts

 

[pickxx]

I have one 120mm fan for an exhaust. I am looking for something an intake. I was readint that fans with temp sensors work best as an exhaust because otherwise they would just be running faster or slower depending on the outside air and not the case temp. In that case i could bump my fan to the front and use my new fan for exhaust.

Wouldn't a stronger fan in the rear create a small Neg. Preasure in my case? if the exhaust is stronger then the intake it will pull air from the seals in the case. And with a slightly Neg. preasure case wouldn't the heatsink fan have to work harder to blow air down on the heatsink?

I dont know, i know enough about physics to know what SHOULD happen but practical experiance is better then theories.

How much should my 120mm fan blow? and noise should be below ~30Db..right?
Thanx

 

[Mr5oh]

Yeah I was thinking about it and you are right it would create a negative pressure, I think the effect would be minimal though.

That was just sort of a vague memory, I found a really interesting article by a college professor one time on this subject, but I can't seem to find it anymore.

 

[pickxx]

That sounds interesting and i would like to have read that. and the reasons for not having it and the reccomendations for airflow.
i am a physics major but i am merely a Sophmore so i havn't gotten to Thermodynamics and Aerodynamics to the extent that i could figure this out.

 

[_WW_]

First of all, I doubt that your case is airtight enough to really concern yourself with pressure differences. The object here is to <i>move</i> air through your case...exhausting the warmer air and replacing it with cooler air. Your CPU fan is going to move air no matter the pressure, so what you want is to provide it with the coolest air you can.

A blow-hole at the top can certainally help to exhaust the warm air. Add all the fans you want...until the noise drives you bonkers. Just remember, at a certain point you will reach maximum efficiency and any more added fans are pointless.

Don't over analyze it...this ain,t rocket science.



....WW (5.0)

 

[Stickx]

I found the following site to have some good ideas. This is just one of his case mods, so look around for other ideas. This guy seems to do quite a bit of modding for good airflow.

http://www.coolcases.com/catalog/case_cclx6a_cat.htm