Overkill fans for 3U rack server (experimental)

[Phas3L0ck]

Two points; we all know that the 3U rack size is the least liked by many server enthusiasts and manufacturers, and even hated by some for its odd size; many large servers use axial fans in 80, 92, and 120mm sizes, but very few beyond the 1U format will have squirrel-cage/blower fans for full system cooling.  Even in the rare case which such fans are used, the air is always drawn in from the front of the chassis for obvious reasons.

 

I have a random idea to design a chassis in 3U form factor that dedicates all of it's front-panel space to a pair of 8" HD (old HD, not 1080) screens for system telemetry, maintenance, and casually observing running workloads... but how to cool it? Through the top, of course!  (my rack has an open 3U space in the top, so this works perfectly) But I couldn't just pick an axial fan to mount on the top and blindly believe it would work, no, I needed a more strategic approach to the issue-- so I looked at datasheets from the few manufacturers known to make high-speed fans, and found something perfectly fitting as well as energy efficient from San-Ace under their C133 line, model 9TJ48P0H01.

To those of you wondering why I'd do such an odd configuration and with powerful centrifugal fans, the simple answer is; I was bored. (and I have a mad obsession with fans!)

 

Because the fans I intend to use are proprietary in shape, the only way to mount them and effectively direct the airflow in a full-scale server chassis is to design a custom base and shroud to affix the fans and the inlet nozzle uniformly to the target chassis. I ran the numbers several times, and while at first I didn't think it would all fit, I made it work just barely staying within mechanical tolerances. Needless to say this is going to be ludicrously dense.

Overall dimensions are 420mm wide, 140mm deep, and 107mm total height. Each fan (133mm wheel diameter) is separated at the midpoint by 140mm, leaving effectively 2mm of running space between each wheel and the walls of the shroud. Vertically it has about 5mm from the base plate to the bottom of the wheel, and some odd 12-13mm from underneath the cover plate to the top of the wheel. 

 

Am I concerned about the fan wheel rubbing against the side walls?

Well first off that's what the screw holes on the base plate are for since that's how the fan is expected to be mounted, and second, as Linus would say; YOLO!

 

Also a little side comment here; the numbers weren't quite what I expected, so I plan to split my 3U design idea internally; the system itself will live on a 2U upper-deck area (the effective cooling path for this fan model only covers 2U vertical area) inline with the custom fan assembly, while the power supply and other components will be in the bottom 1U of the chassis' usable space, making it possible to create a monster of a system!

Here are renderings of the semi-final assembly I've made so far:

[artuc]

Could you not have a 4RU, have the screens extended out ans suck air around the screens on the front ?

 

 

[Phas3L0ck]

3 hours ago, artuc said:

Could you not have a 4RU, have the screens extended out ans suck air around the screens on the front ?

First of all, YUCK. Second, the last thing I need is bezel-shock in which an extra part needlessly extends the front of the chassis beyond the uniform borders of what is currently present and intended to be installed.

 

And third... well... after a cascade of conflicting ideas on how to use the top 3U of space efficiently, (the only space to be fully available in the end) I decided to try putting them all together and see what happened. At first it wasn't going to work because of mechanical conflicts between available hardware, but then I found a few things that happened to fall in line with most of my ideas extremely narrowly and pushing the boundaries of what can be assembled without a major issue.

And you won't believe the motherboard I chose to use in the event I'm able to design a full chassis and have it manufactured.

 

One other thing-- the fans I found are surprisingly efficient, and I'm interested to see what kind of cooling capacity they have to offer on a tremendously powerful system (or maybe I'll be lazy in testing and do something with watercooling stuff... meh.)

[artuc]

9 hours ago, Phas3L0ck said:

First of all, YUCK. Second, the last thing I need is bezel-shock in which an extra part needlessly extends the front of the chassis beyond the uniform borders of what is currently present and intended to be installed.

 

I mean depends on current clearances, some racks are super deep and viable 

 

A current aesthtic on some exhaust fans is a round or rectangular plate gapped out slightly and sucking air through the gap all round the edge. They are very high CFM so seems plausible, looks nicer than a grille.

 

So the thinking was with a very sturdy front plate there could be options for drawing air around screens while still looking good.

 

I think overall there could be some interesting cooling designs with more space to work with and unusual configurations where front to back with minimal space used is the usual goal.

[Phas3L0ck]

1 hour ago, artuc said:

I mean depends on current clearances, some racks are super deep and viable 

 

A current aesthtic on some exhaust fans is a round or rectangular plate gapped out slightly and sucking air through the gap all round the edge. They are very high CFM so seems plausible, looks nicer than a grille.

 

So the thinking was with a very sturdy front plate there could be options for drawing air around screens while still looking good.

 

I think overall there could be some interesting cooling designs with more space to work with and unusual configurations where front to back with minimal space used is the usual goal.

I get what you meant, but tolerances are already maxed out by my calculations, and I'm kinda OCD about mechanical uniformity.

 

Big CFM may sound good, but 40-100CFM from the average fan means nothing without pressure. The San Ace fan I'm looking into combines airflow, pressure, and a far more predictable flow pattern in a dense area where the high air volume must be focused.  In other words, it's not what I had planned, but San Ace's C133 series shows a great deal of respect for common 2U equipment layouts (by a great deal of coincidence in it's design) although requiring a 3U enclosure. Funny how the fan itself looks like it was intended to be mounted in a position slightly above the surface of a motherboard, and hang just under a chassis roof so as to fully cover multiple 2U CPU heatsinks with the most effective use of space!

 

Finding a screen model with a decent image quality and reasonable pixel size that would actually fit onto the front of a 3U chassis was a nightmare! The only good Full-HD model known to be available requires a proprietary adapter to use the full display area, and most other models are too basic.