To fan shroud or not to fan shroud

To fan shroud or not to fan shroud
That is the question.

Ok I'm gearing up on fhinishing my upcoming upgrades.
After days of researching layouts of cases and component placement to price / performance, I have settles on the Gigabyte 3D Mars case.
I will be slapping my old school 2x120 Swiftech radiator (this is the orignal one that came out with their first kit, probably really outdated by now) on the back of the case (externally, but without the radbox, god I fucking hate that thing).
I have 4 120mm fan shells that I can use as "shrouds" for the fans if needed.

So the 2 big questions:
Should I do 2 fans push and 2 fans pull or stick with just 2 fans push or pull?
And on top of that should I use shrouds?
Shouldnt be a problem with space, but I'm wondering if it will even give me any performance advantage on my rad.

Other thing is does anyone know where to find screws long enough to thread through 2 25mm thick fans and into the switftech rad? I remember looking before and my local hardware store couldnt match the threads, would I have better luck with Home Depot, Lowes, etc?

Almost forgot will be cooling either a q9450 or q6600 and I don't want my current WCing loop to let me down before the chip maxes out. CPU block will be the D-Tek Fuzion with quad nozzles and will be the only thing in the loop.

Thanks

If you're cooling only the CPU, don't bother shrouding or push/pulling it.

Home depot will carry screws in the 6-32 thread you require, up to about 2.5" long.

2 fans pull, shroud would be best but I don't like the idea of the fan shells as shroud, the idea of a shroud is to spread out the area of low pressure caused by the fans so air is pulled through the entire surface of the rad. I am concerned fan housings will still tend to localize the airflow through the rad to the basic area/footprint of the fan, loosing cooling at the edges. You most likely would have to make a shroud from an al baking pan, now thats old school.

push pull has been show to be of little improvement and the bulk (especially if properly shrouded) is excessive. Does not hurt, just does not help nearly as much as one would think. Tons of old school testing but hard to find now.

Great, thanks for the replies. Ordered my case and will just be putting 2 fans on rad, if it performs poorly I'll look at a shroud or triple rad. I remember back when I built my WCing rig and reading about the shrouds/push pull etc but some of that stuff is just downright hard to find now.

BillParrish said:

2 fans pull, shroud would be best but I don't like the idea of the fan shells as shroud, the idea of a shroud is to spread out the area of low pressure caused by the fans so air is pulled through the entire surface of the rad. I am concerned fan housings will still tend to localize the airflow through the rad to the basic area/footprint of the fan, loosing cooling at the edges. You most likely would have to make a shroud from an al baking pan, now thats old school.

push pull has been show to be of little improvement and the bulk (especially if properly shrouded) is excessive. Does not hurt, just does not help nearly as much as one would think. Tons of old school testing but hard to find now.

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I thought the purpose of a shroud was to mainly lessen the dead spot created by the fan motor While I agree that an empty fan shell would not be ideal, I think it would be better than nothing.

I think that typically using a properly sized fan shroud can net at least a 10% improvement in cooling simply due to the loss of dead space where the fan motor is.

mainly lessen the dead spot created by the fan motor

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we are saying basically the same thing, just in different ways, and keep in mind the fan is round and the rad is rectangular so unshrouded and close to the rad air will be pulled or pushed mainly through the fan blade footprint. You are exactly correct about the center hub but dont forget the edges of the rectangle too.

To expand on the idea a bit, the way a fan moves air is twofold, there is the mechanial force on the air by the fan blades but also due to their "pitch" or curve, like an airplane wing, they form a low presurre area at the intake that helps suck air through the fan. Thats why good fans do not have flat blades. So standing the fan away from the rad (more than 3/4 of an inch is not needed from the data "back in the day", no idea if new studies have been done") lets that low pressure work for pulling air through that would be masked by the fan hub and the outer edges of the rad not directly under the fan blades.

All that said, in day to day operation the difference is probally just barely measurable. My fans are only about 1/4-3/8 away from the rad, being mounted to the rad flange, and I have been too lazy to do anything about it because it works just fine that way on my system. So splitting hairs with a razor, but you asked and it is fun to discuss the fine details So perhaps I was a little to hard on the fan shells, in theory they would be better than no shroud at all because of the hub issue but not quite (in threory) as good as a full regular shroud. Guess the main point is you have the fan casings so it certainly would not hurt a thing to use them and would probally help a bit.

For what it's worth, your hated RadBox uses 2 1/4" 6-32 bolts and 1 small nylon washer to attach it (with spacer) going through an already positioned rear fan of 25 mm thickness.

I think the same would work without the RadBox, if you put two fans back to back. The Dual 120 Swiftech Rads are threaded for 3M or 6-32 bolts depending on whether you think in metric or American bolt sizes.