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No case fans,closed, 1.4ghz T-Bird, 100%cpu 45c

Last response: in CPUs
July 2, 2001 1:31:47 AM

No intake or exhaust fans, case is closed, only the Power Supply exhausting air and the cpu fan exhausting air through a specially designed port. 1.2ghz T-Bird overclocked to 1.4ghz on a Iwill KK266, Radeon64 Retail at stock speed, 512mb of Crucial cas2 ram, 40gb 7200 RPM IBM drive (Deskstar), Alpha 6035 HSF (this fan sucks air through the cpu heat sink), medium tower case. Test results, 100% cpu usage for 20 min:

<b>Case open</b>

Ambient: 74F
System Temp: 28c
CPU Temp: 46c

<b>Case closed</b>

Ambient: 74F
System Temp: 29c
CPU Temp: 45c (interesting)

When the case is closed the cpu temperture actually went down by 1c. I believe that the cpu fan exhaust port actually allows a greater flowrate due to less turbulance on the discharge side of the fan in addition of isolating the hot air from also being inadvertantly sent back through the HSF again. Note that the system temperture actually went up 1c with the case closed which would be expected. I am very impressed with these results and wanted to share this discovery with you guys. In fact with this setup I don't even need any intake or exhaust fan on my system.

Can anyone give me a good reason to install a intake fan? I havn't installed my 120mm fan yet and during these test I unplugged the 80mm intake fan that was in the case.

<P ID="edit"><FONT SIZE=-1><EM>Edited by noko on 07/01/01 10:19 PM.</EM></FONT></P>
July 2, 2001 1:43:09 AM

Very impressive - any idea where the air that the cpu fan is exhausting is coming in from? Is there a vent or holes in the case for air to naturally be drawn in? There is a lot to be said for venting cpu air directly outside - the same concept as having a water cooler basically - very very neat. It's a good job the alpha is designed for suck and not blow - I wonder whether similar effects would be seen with other brands of HS?

Also - with your ducted exhaust - do you find that that alone helps supress CPU fan noise?

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July 2, 2001 2:06:18 AM

The case has many holes in the back plus I have one pci card slot open. In the front where the 80mm fan is, is another path for air to come in. Having the case closed significantly reduces the Alpha fan noise to a more acceptible level. The vent port has louvers on it which helps to isolate the noise through the exhaust port, in these tests I removed the louvers to allow maximum air flow. I am very startled with the results especially with the cpu temperture going down with the case closed.

Now if the fan on a heat sink blows into the heat sink then fresh air outside the case could be ported to the HSF but in this case the hot air will remain in the case. The Alpha cooler has short fins and a high volumetric flowrate fan (Delta) which I believe is a 38cfm rated fan which was made for the fan to suck. In other words the Alpha was designed for tight space considerations. I just capitalized on the way the air flow through the HSF out through the fan on the Alpha.

<P ID="edit"><FONT SIZE=-1><EM>Edited by noko on 07/01/01 10:23 PM.</EM></FONT></P>
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July 2, 2001 2:18:33 AM

That's great!

How did you arrange/build the duct from the delta to the outside of the case - I may consider something similar if it is possible to shroud a standard heatsink...

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July 2, 2001 2:43:48 AM

My case power supply does not interfere with the HSF for the cpu:

<A HREF="" target="_new">Case lay out</A>

I cut a hole in the side panel:

<A HREF="" target="_new">View of cut hole and cpu HSF beneith</A>

How it looks when completed:

<A HREF="" target="_new">Installed on case</A>

Here are the parts top view: <i>Note: I havn't installed the 120mm fan yet.</i>

<A HREF="" target="_new">Parts</A>

The cost of the port was $5.95, it is a dryer exhaust kit which I picked up at Home Depot. The ducting I measured and cut with scissors to a height about 1/16" above the cpu fan. I wanted to be able to install and remove the case cover. In fact I could have extended it around the fan since the clearance of the vent ducting would be sufficient. Also consider this, the Delta fan is moving around 38cfm, but as it discharges air through the port, the actual flowrate of the exhaust port will be higher since it will entrap and entrain air surrounding the exhaust air from the Delta Fan. So the flowrate out of the computer will be more then the discharge rate of the Delta fan by itself. Something to think about. Hope this helps.
July 2, 2001 4:23:25 AM

Right now with 10% cpu usage (watching TV with the VideoIn on the Radeon) my cpu temperture is 38c with 26c system temperture. This is working out well for me so far. Can anyone think of a good reason for me to install my 120mm fan?

<P ID="edit"><FONT SIZE=-1><EM>Edited by noko on 07/02/01 00:23 AM.</EM></FONT></P>
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July 2, 2001 11:33:45 AM

"Can anyone think of a good reason for me to install my 120mm fan?"

yep, dust etc. install fan as a filtered intake.
my case (macase ka80) has a removable fine mesh filter in front of intake fan, result - no dust inside whenever i open her up

ps do the voltage mod to the fan if noise is a concern.

however, we all start at the end and finish at the begining
July 2, 2001 2:37:53 PM

Thanks for the response and that is an excellent point. Could I use a volume control (variable resister) to control the DC motor fan to the speed that ensures positive pressure in the case? That way I will be able to adjust to ensure positive pressure and the least amount of noise easily outside the case. That is a very important point since I have to rountinely remove the dust from my Alpha cooler heat sink as well as from the Radeon chip heat sink. It gets bad after about 6 weeks. Thanks. Anyone else have suggestions?
July 2, 2001 8:21:24 PM

To control the speed of a DC fan can a volume control or variable resister work good? Where would be the best place to place the adjustable speed control? Front, side or back? Obviously it will be a manual adjustment. Will this work?? Please let me know.
July 2, 2001 8:53:45 PM

<font color=blue>okdoke. Cool stuff man. One thing. Reason it is cooler IS absolutely because you are getting fresh air to the proc instead of what is called short-circuiting when the case is off. (I design ventialtion systems for a living, albeit for buildings not comp). Anyway, there are more advantages to more fans than just filters (although that is a very good one) but being realistic the main goal here is higher clock speeds and I don't know how many more oc mhz you will get past 1.4. Old tom only got 1.6 out of the kryo job on the 1.2. I get 1.533, but there is a hurricane in there. Maybe all you would get is just a cooler proc and how great is that <i>really.</i>

Personally, I am not sure the 120 would be worth the noise. Of course, do as I say, not as I do. :smile:

:cool: <i><font color=blue>on company time....</i>
July 2, 2001 9:14:11 PM

Well my cpu will go up to 1.46 pretty reliably as it stands and the 120mm fan I was going to control the speed to minimize the noise. Actually the noise of the 120mm fan is less then the Delta fan on the cpu but still adding more noise is not what I really want to do if I can help it. I think keeping the air inside the computer clean would just help to ensure the longevity of the system. So will the variable resistor do the trick in controlling the fan speed properly? I am not to worried about higher clock speeds, I have a cool setup as it stands so now I like to minimize dust and noise as much as possible. I may even place sound tiles inside the machine for the ultimate in quietness as an experiment. Sounds kinda dramatic since my computer now is not overbearingly loud with the case closed. 27c system temp 38c cpu temp right now.
July 2, 2001 9:22:51 PM

<font color=blue>Cool. I am going to put my 2 120's in series and to reduce my noise. I figure I could stand to lose a couple of cfm's. Since your noise is coming from your hsf sound tiles inside of you case would ordinarliy make a huge difference, but with the duct and all, well that is where your noise is emitting from. Try lining the duct with insulation. That will make the biggest difference. (its works on air handling units for theaters - insulating the inside instead of the outside.)

:cool: <i><font color=blue>on company time....</i>
July 3, 2001 12:21:43 AM

Thanks, I will try that. The vent has louvers which when installed cuts down the noise transferred through the duct except when installed increases the temperture about 2c. So I will try out your idea and thanks for the info.
July 3, 2001 1:24:46 AM

Well that worked really well, I installed thin foam rubber inside the cpu exhaust port and the noise reduction it caused was remarkable. My computer is almost as quiet now as the Pentium2 450 at work. First I tried some thick foam rubber which even cut the noise down a little bit better but my cpu temperture went up 4c. So I had to find thinner stuff which I happend to have (packing foam). Thanks again for the suggestion, it worked.
July 3, 2001 3:13:33 AM

hey noko... do u live in the states?
i was thinking if in winter the temps get down to below freezing,
you could drill a hole thru your wall, put a filter over it and pipe crispy clean freezing air into your computer! to combat condensation you could make the outside intake the ONLY source of air, thus its very dry and wont cause condensate on the internals of your computer :) 

whatcha think?

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My Hamster doesnt like sarcasm. He may very well bite you in your hard to reach places!
July 3, 2001 5:07:46 AM

Let me know how it works out, besides I live in Florida, not to chilly down here.
July 3, 2001 5:52:36 AM

i was suggesting someone else try it!
i live in oz and it gets VERY hot here. besides... i would probably get possums nesting in the duct lol

My Hamster doesnt like sarcasm. He may very well bite you in your hard to reach places!
a b à CPUs
July 3, 2001 11:26:55 AM

hey Noko, those temps are pretty impressive... Do you know where i could get that whole Duct System thing you got? Is it a package or something? And if so, can i get you to tell me who makes it?

If you're getting the thing really quiet with the insulation, why don't ya try a Delta and see how much louder it is? Ultimately i want to get a Delta but i am easily annoyed by the noise so i have been looking for ways to cut it down... I am buying a new case soon, not sure which yet, but it'll be a full tower...

So anyway yeah, who makes the vent? and also, what kinda case do you guys reckon i should get?

<b><font color=blue>Who needs drugs when you got <font color=black><i>BasS?</i></font color=black></font color=blue></b>
July 3, 2001 1:19:33 PM

Virtually any hardware store and basically it is a dryer vent kit. I paid $5.95 for the whole assembly. Above are images of what it is if you want to use the links. The inside sound insulation (thin foam rubber) actually cuts a significant amount of noise from my Delta fan through the cpu exhaust port. Hardest part was cutting the hole and making sure it was right over the cpu HSF, everything else is straight forward. If you buy a case and plan on removing the heat generated by the cpu so that the rest of the case remains cool, make sure that the cpu is open for the exhaust port, in other words the Power Supply isn't to low or over the CPU HSF. Also you need a HSF which sucks air through the heat sink, actually the other way around may work just as good in keeping the cpu cool because you will be drawing cool air from outside the case to the cpu except the heat will be discharged inside the case. In the last case a exhaust fan will probably be needed then also.

<P ID="edit"><FONT SIZE=-1><EM>Edited by noko on 07/03/01 09:23 AM.</EM></FONT></P>
July 3, 2001 1:27:15 PM

Actually your idea has merrit but instead of drawing air from outside the building just draw air from an air conditioning vent or duct, that would definitely keep the system cool. Just don't turn on the heater in the winter or disconnect ducting for winter use when you really don't need it. Just a thought.
July 3, 2001 3:12:17 PM

<font color=blue>great to hear it noko. Another way to reduce noise is put a 90º bend in the duct. That will also make a huge difference. But if it is pulling a lot of cfm, use turning vanes in the bends. Also, don't run the air faster than 700 feet per minute. (cfm/crossectional face area=air velocity)
<font color=black>
i was thinking if in winter the temps get down to below freezing,
you could drill a hole thru your wall, put a filter over it and pipe crispy clean freezing air into your computer! to combat condensation you could make the outside intake the ONLY source of air, thus its very dry and wont cause condensate on the internals of your computer :) 

<font color=blue><font color=red>Note to poobaa. <font color=blue><b>NEVER</b> bring in untreated air to the comp. Asking for trouble. Putting a heatsink outdoors, especially those of you who live where it's cold, you betcha. Characteristics of OA (outside air) is very unpredictable when it comes to humidity. One really doesn't want even the chance to bring in humid air, ever. Maybe if I lived in the desert in Mexico. If your thinking well, I live in North Dakota. realize that the air may not have that much water in it, but it is near 100% humidity often. What does that matter? Say one day the temp jumps up and you bring in air at 20º/95%. That night, air drops back to 3º. Bad situation. The water in the air in your case can't handle the drop and you hit dewpoint. Ever see footprints in the grass in the morning? Hate that to be fingerprints in your case, man. Anyway - if you try it - let me know how long it takes to corrode the components.

:cool: <i><font color=blue>on company time....</i>
July 3, 2001 3:24:38 PM

Outside air could also be a great bug trap especially here in Florida. Well having a bend would be interesting except I don't want the increase air drag plus anything sticking out of the side if I can help it. Your idea for sound insulation inside the duct worked like a charm. I added another acostic device to my setup and that is a piece of 1/4" foam rubber on my computer desk directly opposite of the exhaust port which cuts down on the noise bouncing off my workstation desk. Most of the low noise now is from the case and not the port. Compared to what I had before this is like a whole new computer.