Here's my latest effort at clean cpu cooling using an external filter, two 80mm spacers, one pctoys crystal maxx fan, one Zalman 5700 shroud.
The shroud is attached to the case fan, not the cpu fan.

This setup sucks external ambient air through the filter (powercare #165-036), through two 80mm shells, by the fan. The air is bent 90 degrees by the Zalman shroud and is blown directly on an Alpha heatsink.(Celeron 2.0)

Using this setup only the cpu idles about 4C over ambient....stays around 40C at maximum usage.

For a redundent backup to this system, I have a small 60mm fan sitting on the top of the Alpha, which is turned on by a DigiDoc sensor should the temp go over about 40C. Normally the air just blows thru this small fan.

As you can see the internal duct is wrapped in a sheet of sound-deadening material. Over- all this setup is quiet, clean-running and was a rather easy install.

http://photos.yahoo.com/bluefront100

Could you tell me where you purchased the Zalman shroud/duct. I ordered one from ChipCooler.com only to be informed that the Zalman duct is no longer available.

I got it with the fan and heatsink from CompUSA...about $39. I wasn't pleased with the setup, so I got an Alpha heatsink and used the Zalman shroud as you see in the pictures. I heard you could buy the shroud separate from Zalman, but cannot confirm it.

I have always been under the impression that a duct over the cpu should be an exhaust rather than an intake. The reason being is that you're taking air, warming it via the heatsink, and dispersing it within the case. Thus raising overall temperature. I am no expert, and this is what I've read/hypothesised.

I'd be curious to see the temp differences if you turned the fans around..

Brice

Of course the filter would have to be removed to blow the air out.

This is a positive pressure setup, designed to keep the case clean. Both the front and rear fans blow in, through filters.

This is the exact direction Dell uses with most of their cases....blowing into the case directly onto the CPU. You know how quiet most Dells are...this type of setup is one reason.

You can eliminate the CPU fan doing it like this. I have a DigiDoc5 with eight sensors hooked up....so I am 100% certain everything is running plenty cool.

Bluefront,

I am about to install a duct over my CPU (w/ a Zalman Flower) in order to cool it w/o the CPU fan. I've always thought to use this fan as an exhaust. I'm also cutting a hole in the top of the case, directly above the PSU, and will have it exhaust there. This is a rackmount case.. and most of the air will be pulled in from the rear side (which I could probably fit cheesecloth / foam to filter). If I were to turn these exhaust fans to intake fans (thus air would move out of the side vent) .. would you believe I'd achieve better thermal results, not to mention the fans would likely be less noisy b/c of unconstricted airflow to the intake.

Brice

I guess the answer would depend on your particular setup. But think about it....at the same fan speed your cpu would be cooled with ambient temp air using my setup (say 23C air). If you suck the air out, the cpu is cooled with internal case temp air (usually 27C or more). If the fan speeds are equal, my setup, Dell's setup, give you a benefit of at least 4C.

When filtering intake air, be very careful to use a big enough filter with a large surface area. I cannot stress this enough. Those little foam filters you usually see are way too restrictive.

Measuring the P/S output temps gives you a pretty good idea if your setup
is working ok. That setup in the pictures has a P/S output temp of about 29.4C at an idle.

The link to your pictures (http://photos.yahoo.com/bluefront100) only shows the three pictures of your external air filter. Is there somewhere else to see the pictures of your CPU shroud?

Humm...All the pictures are there, in three different folders. Perhaps the page didn't load properly and you were viewing a cached page. Try clearing the browser cache and try again.

I guess I should add something about the 80mm case fan used in this setup. As I said it's a PCToys Crystal Maxx, with a variable fan speed. An external sensor on a long wire makes this fan unique. The sensor wire is long enough to place it in the Alpha heatsink......the result is a rear case fan that varies it's speed as the CPU heats up.

I guess you could try a constant speed fan with this setup....but I think the Crystal Maxx is the correct approach. The cpu heats up, the fan spins faster.....

so its like a reverse dell fan duct? using the fan as intake instead of exhaust. It looks cool, I like it

Been a lurker for a while, but thought I would point out a place that has the separate ducts. Caveat is that they are OOS.

http://www.sharkacomputers.com/newzal80fand.html

Hey thanks for the link. I did try setting the duct up like they suggest in the link.......blowing air off the heatsink directly at the rear exhaust fan. But when I reversed the airflow, as you see in my picts, my temps went down quite a bit. Plus I eliminated the CPU fan, and had filtered intake air.