Which way do you duct?

PingSpike · Feb 20, 2004

http://www.svc.com/ovcokitbl.html

SVC has a cool looking little duct kit for about $15 that I might pick up. But as I was planning out in my head how I would attach it, a question came up.

What would be the best way to setup the direction the duct fans are going? Away from the CPU sink or onto it?

I have a blow hole fan and a side fan that are both 92mm. Attached to the blow hole it seems like away would be the best since hot air rises. Then again, if it was pushing in cool air that might not be a factor.

Vio1 · Feb 20, 2004

i wouldnt use that kit... one reason: the pipe. A pipe like that will reduce the airflow considerably... I know this because i talked to a heating and airconditioning guy once and he said that with that type of piping you cut down half the airflow.

mccoyn · Feb 20, 2004

If the fans blow toward the heatsink, it will cool the CPU more. If the fans pull away from the heatsink it will cool the system more.

PingSpike · Feb 20, 2004

Vio1 can you a eloborate as to why it doesn't work well? Perhaps because the air changes direction so much in the tube?

archilochus · Feb 20, 2004

It has more to due with the inner wall of the pipe. Its not smooth..ie, Resistance / slows air flow.

pelikan · Feb 20, 2004

Its true that there will be a lot of turbulence in that duct, which will slow down the air flow. But cool air from outside the case makes a huge difference so it will still lower your temps. Also the cooling will be more efficient because of the greater difference between air temp and heatsink temp.
I used to have a duct before I went to watercooling. I used a 4" piece of pvc pipe that went straight out through my side panel. My temps dropped 8C. I found that a combination of the duct pulling in cool air and lots of negative case pressure worked really well. The negative case pressure would pull even more air in through the duct.
I was able to cool a 2100+ @2400 MHz and 1.9V with just an 80mm panaflo L1A on my slk-800. Temps were in the mid 40's.

archilochus · Feb 20, 2004

The PVC pipe is smooth on the inside. Hardly any resistance..I saw a guys rig that had a custom setup on his side panel with PVC 4" for DUCTS...I'll see if I can find it.

thinksnow · Mar 13, 2004

Tag-on question here:
Would a duct work as well with the CPU fan in the normal place? That is, simply attaching a duct to an existing fan still on the sink.

I'm curious because, without cutting, I don't have room to mount a duct-specific fan anywhere, and I'm not cutting my SLK3700. So, I was thinking I could mount a grill in one of the 5 1/4 bays and craft a duct from there to the CPU. using the full width of the bay for intake and drawing it using an 80mm fan on the CPU/sink.

Yea/nay?

cstarritt · Mar 13, 2004

i used to use one of those kits a while back. i left my hs fan on, slapped the duct on top, and ran it to the front of my case where i had a smartfan 2. i then set my psu fan, two rear 80mm, a side panel 90mm, and a top 120mm as exaust. after that i taped off any area where air could get in besides the duct intake. the result was the exauhst fans caused alot of negative pressure that drew air through the duct. it worked pretty well.

archilochus · Mar 13, 2004

thinksnow, You never know til you try it..

You can get that duct at Home Depot.Its bathroom exhaust vent flex...The kit above comes with the various flanges though.Test, Experiment...

fhanderson · Mar 13, 2004

Hame Depot has some 3" and 4" flexible ducting tha has a very smooth surface. It cost around $6-8 dollars for 8' length. I made a duct for my work station in an Antec 800 case. I ran from the cpu fan to the front fan opening. I got a 5c drop. I have 4 vantec stealths in this case so the temp drop may not be as high with higher case flow.

pelikan · Mar 13, 2004

thinksnow said:
Tag-on question here:
Would a duct work as well with the CPU fan in the normal place? That is, simply attaching a duct to an existing fan still on the sink.

I'm curious because, without cutting, I don't have room to mount a duct-specific fan anywhere, and I'm not cutting my SLK3700. So, I was thinking I could mount a grill in one of the 5 1/4 bays and craft a duct from there to the CPU. using the full width of the bay for intake and drawing it using an 80mm fan on the CPU/sink.

Yea/nay?

I think ducts work better with the fan still on the heatsink. That way you have more air pressure on the heatsink where it counts.

iLLestOne · Mar 13, 2004

What if you put a fan on the hs, AND on the other side pushing in the air? I was thinking about doing this, but I was going to cut a whole in the side of my case DIRECTLY over the cpu hs. So the duct would only go like 4" straight to the cpu, so no rough edges. Wouldn't this work better?

cstarritt · Mar 13, 2004

if the fan is on the side panel than i would just craft a duct out of cardboard or somthing else rather than that flex stuff and leave the fan off the heatsink. that way you elimenate the dead zone over the middle of the 'sink

pelikan · Mar 13, 2004

4" dia. pvc coupling for duct (they call it a 4" fittting but its actually 4.5" dia.):

Negative case pressure helped pull in quite a bit of extra air through there. That's an slk-800 and an 80mm panaflo L1A. It cooled 1.9V vcore (only 24 cfm and 21dB).

Vio1 · Mar 13, 2004

thinksnow · Mar 14, 2004

woot!

I think I have my first case-mod project...

Edit to add- Vio, am I seeing that right- you've got two fans in the duct?

(and, I'm thinking, to kill the dead-spot issue, I'll core out a fan and mount a second one over that empty/spacer one.)

Vio1 · Mar 14, 2004

Re: woot!

thinksnow said:
I think I have my first case-mod project...

Edit to add- Vio, am I seeing that right- you've got two fans in the duct?

(and, I'm thinking, to kill the dead-spot issue, I'll core out a fan and mount a second one over that empty/spacer one.)

yup two identical fans... one over the cpu and one in the duct.

killem · Mar 15, 2004

Vio1: wow.

I'm floored by that duct, as it's a glowing, amazing implementation of an idea that I tried to construct from PVC and abandoned in favour of a simpler 'rear-intake' duct.

Was it a DIY job or did you have it made professionally?

One of the major factors for taking the other approach, was my concerns about the added weight/drag on my CPU socket, if I attached the duct to the CPU's fan-housing.

NewBldr · Mar 15, 2004

Yeah, that Vio1 ducting pic is using CD cases for the walls. I believe I read it in Case Mods, and thought it was quite inventive

Which way do you duct?

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