Computing Chimney?

ddrueding1 · Post by **ddrueding1** » Wed Oct 24, 2007 12:16 pm

What is better than cooling a computer with just one fan? Cooling several computers with just one fan.

I'm sure I'm not the only one with more than one computer at/near my desk, and I've decided to take a holistic approach to cooling them.

Basic concept:

Wooden Chimney, approx 7 feet tall, ~14" on a side internally.

Starting from the bottom:

1. Intake
2. Filter
3. Sound baffle
4. 36cm fan
5. Suspended hard drives
6. Surface mounted motherboards with passive tower heatsinks
7. Sound baffle
8. Exhaust

Pretty simple, really. The concept is to create an acoustically isolated windtunnel, and put all the stuff in it. A very simple model of a single-computer version might look like this:

My first question is, where can I buy a really quiet 36cm fan?

I welcome any thoughts on this project before I begin in a week or so.

ddrueding1 · Post by **ddrueding1** » Wed Oct 24, 2007 12:19 pm

Based on this old thread, I was also thinking of pre-cooling the air going into the chimney with a TEC somewhere between the filter and the hard drives.

FlorisNielssen · Post by **FlorisNielssen** » Wed Oct 24, 2007 12:49 pm

That's looking pretty big.
I think your overdoing the depth and width of the chimney. There's enough space to make it a little smaller.

If you use a TEC you'll have to dissipate mÃ³re heat. Because one side gets cold, but to do so, the other side gets a lot hotter. It's good for getting (extreme) low temperatures on a certain point, for example for overclocking. (Also said in the thread you mentioned.)

Were you planning to use that much HD's by the way?

A quiet 360mm fan. Hmm. Quite big. You could try and acquire a car's fan. (It probably runs on 12V, because that's what a large car battery (called an accu in Dutch, don't know the English word..) provides you of.) You could probably undervolt it. Don't know how low you can go though. The fan's will probably have a high(er) start-up voltage because they have more mass than say a 120mm fan.
But I don't know of a computer-fan of 360mm. You have cases with a built in 360mm fan. But I don't know of seperate ones.

Good luck with this one.

protellect · Post by **protellect** » Wed Oct 24, 2007 1:53 pm

couldn't you take 9 120mm fans, and make a 3x3 square of them? lol

ddrueding1 · Post by **ddrueding1** » Wed Oct 24, 2007 2:12 pm

protellect wrote:couldn't you take 9 120mm fans, and make a 3x3 square of them? lol

I was thinking about it actually. That's likely what I will end up doing.

ddrueding1 · Post by **ddrueding1** » Wed Oct 24, 2007 2:23 pm

FlorisNielssen,

Thanks for the response.

Size:

The reason for it's dimensions is that ATX motherboards are about 12" wide, and I want to be able to mount one on each side at the same height. Including tower-style heatsinks (Ninjas, of course) and full-height expansion cards on at least 2 of them, this is the size I come to. Also, I don't need to make it small. This is a piece of furniture; shrinking an inch here or there won't make a difference, so I may as well have some wiggle-room. Why 7' tall? Why not? It will consume 256sq.in. of floor space, and I want it to fit in a room with 8' tall ceilings.

TECs:

It is just a thought. The heat isn't an issue because that would be dissipated outside the chimney using massive aluminum heatsinks. Cooling the air another 10+ degrees before it hit the components would make any overclocking that much easier. I also like the idea because it is optional, it could be turned on or off depending on ambient temp or gaming sessions

Hard Drives:

My current main data array is 8 750GB hard drives in RAID-5. I also have a RAID-0 of 2 74GB Raptors for the OS/Apps and 4 independent 36GB Raptors for my virtual machines. Then there is some wiggle-room

Fans:

Based on my research so far, no other field puts as much effort into quiet airflow as computers. So it makes sense to use computer fans in the rig. A 3x3 array of 120mm fans makes a lot of sense, and should provide the airflow I need.

ddrueding1 · Post by **ddrueding1** » Wed Oct 24, 2007 2:28 pm

Questions:

I know that not giving sound a direct path out is a "good thing". I also know that having an airflow path of uniform cross-section is a "good thing". How can I make these two concepts work in a chimney?

With 9 fans, I would want their speed to be dependant on the hottest computer at the time, whichever it happened to be. Is this a case for a t-balancer with lots of sensors?

scdr · Post by **scdr** » Wed Oct 24, 2007 3:08 pm

So how many machines do you figure to put in there?
If multiple levels, then the lower ones will be dumping heat
on the upper ones.
If you go for multiple 120 fans (instead of 1 360) - it
might be easier to cool them giving each set of motherboards
its own set of 120fans (not necessarily 9 - maybe 4 fans per pair) and starting with room temp air then to try to share it.

Obviously the I/O connections for the computers will be a bother.
How will you muffle them so sound doesn't come out (dust come in, etc.)
with minimal airflow blockage.

I assume you selected that motherboard orientation so that I/O cards would be in line with the air-flow.
Will there then be a cross-bar or something to support the cards?

Might want a dust cover at the top as well. Or will it be on all the time.

ddrueding1 · Post by **ddrueding1** » Wed Oct 24, 2007 3:24 pm

scdr,

I'm currently planning 2 high-powered machines and one low-powered one, all on the same level. The hard drives will be on a lower level because they are more sensitive to heat. 9 120mm fans just works too well to pass up, if any component isn't getting enough airflow, I can put on a larger heatsink.

I/O won't be that big an issue. All cables will be run down an inside corner and out the bottom. There will be a gigabit switch, KVM switch, and UPS inside to reduce cabling issues.

A cross-bar to keep the cards in place is a good idea. I hadn't gotten to that detail yet.

I actually planned on the top being a solid piece, with exhaust out the sides just below.

Thanks for all the ideas so far, I appreciate it!

ddrueding1 · Post by **ddrueding1** » Wed Oct 24, 2007 4:17 pm

Pictures of the new model. If anyone wants the full google sketch-up model, I can post it somewhere.

Picture 1

Picture 2

NyteOwl · Post by **NyteOwl** » Thu Oct 25, 2007 10:33 am

Not to naysay innovation or DIY initiatives, but wouldn't it be easier to just get a shallow and/or short rack case and cooling module?

ddrueding1 · Post by **ddrueding1** » Thu Oct 25, 2007 5:34 pm

NyteOwl wrote:Not to naysay innovation or DIY initiatives, but wouldn't it be easier to just get a shallow and/or short rack case and cooling module?

How would that be quiet?

CoolColJ · Post by **CoolColJ** » Thu Oct 25, 2007 10:49 pm

it would be wise to add some curves to the horizontal bits to aid aerodynamic airflow, but a good idea in any case

you might run into resonance issues though... I mean speakers with transmission tunnels use it to amplify the bass....

CyberDog · Post by **CyberDog** » Fri Oct 26, 2007 1:22 am

I would recommend that you put some foam on walls. You should also read a book of silencing air supply units on houses or some book of noise control on buildings. There is lot of info you could use on that project.

FlorisNielssen · Post by **FlorisNielssen** » Fri Oct 26, 2007 2:07 am

Hehe, I like the comparison with the houses, CyberDog.

But. About sound path's and such. You don't want a direct path from the noise (from fans) to your ears.
If you're keeping the bottom of the chimney as an intake the fans do not have a direct path to your ears.
It's like with the Antec P150 (to pick an example), the intakefan is behind the 'door'. But the air gets in through the sides of the door, so no direct soundpath from the fan behind the door to your ears.

Back to your design. The soundpath in your chimney from fans to your ears won't go directly to your ears, but firstley to the ceiling or the floor. So I think the sound baffle's won't decrease the noise you hear.

Then, the fans. Why do you put them above the components in your new design? I suppose you don't want them to blow downwards (against natural convection of heat, which is bad, fans have to blow harder), but upwards. So, why not below the HD's? Or in any case below the motherboards? Fans blowing instead of sucking is more efficient for cooling. (In any case on a heatsink..)

Practical thing: are you going to put a door in it? (On the side which you don't show in your pictures I suppose?)

By the way, have you modelled al the cooler parts yourself?

Jeff Cutsinger · Post by **Jeff Cutsinger** » Fri Oct 26, 2007 5:00 am

FlorisNielssen wrote: If you use a TEC you'll have to dissipate mÃ³re heat. Because one side gets cold, but to do so, the other side gets a lot hotter. It's good for getting (extreme) low temperatures on a certain point, for example for overclocking. (Also said in the thread you mentioned.)

This is off-topic, but I had an idea to take advantage of a TEC while minimizing its detriments. You couldn't do it with a chimney, but the result would be chimney-like. The basic idea is that you'd have a case where the intake and exhaust would be long "tunnels" where the beginning of the intake was adjacent to the exhaust (so if you took a chimney and folded the bottom third so the bottom and top were pointing up, it'd be similar). Then at the point where the exhaust and intake were adjacent, you'd put a (or many) TEC with the cold side by the intake and the hot side by the exhaust, with a good heatsink on both sides. Since both the intake and the exhaust would be vertical, this would have the effect of creating a convective current, with extra-cold intake and extra-hot exhaust.

Besides the impracticality of designing such a case (though it could be done, and the long intake and exhausts could be turned into baffles, making for a really quiet case), I'm not sure if it would really help or just end up hurting (the heat generated by the TEC might work its way down despite the contrary air flow, making it worse). Not to mention issues with condensation.

But I do think it's a good idea, and with the right execution, it just might make for a really cool, quiet case.

FlorisNielssen · Post by **FlorisNielssen** » Fri Oct 26, 2007 7:20 am

Jeff Cutsinger wrote:
FlorisNielssen wrote:...
This is off-topic, but I had an idea to take advantage of a TEC while minimizing its detriments. You couldn't do it with a chimney, but the result would be chimney-like. The basic idea is that you'd have a case where the intake and exhaust would be long "tunnels" where the beginning of the intake was adjacent to the exhaust (so if you took a chimney and folded the bottom third so the bottom and top were pointing up, it'd be similar). Then at the point where the exhaust and intake were adjacent, you'd put a (or many) TEC with the cold side by the intake and the hot side by the exhaust, with a good heatsink on both sides. Since both the intake and the exhaust would be vertical, this would have the effect of creating a convective current, with extra-cold intake and extra-hot exhaust.

Besides the impracticality of designing such a case (though it could be done, and the long intake and exhausts could be turned into baffles, making for a really quiet case), I'm not sure if it would really help or just end up hurting (the heat generated by the TEC might work its way down despite the contrary air flow, making it worse). Not to mention issues with condensation.

But I do think it's a good idea, and with the right execution, it just might make for a really cool, quiet case.

Interesting idea, but I think the hot side of the TEC would get a little too hot, thus decreasing it's lifespan. A TEC needs cooling too and just the extra hot exhaust won't do it good I suppose.
That's just the thing with TEC's, like I said, you can cool a single spot with them very well, but the other side of the TEC has to dissipate all of the heat that's taken away from that spot, plus the heat created by the current you send through it. Which is a lot, because of the low efficiency.

ddrueding1 · Post by **ddrueding1** » Fri Oct 26, 2007 7:42 am

Thanks for all the comments. I'd completely forgotten about the floor and ceiling and their potential role WRT noise. Oops.

I put the fans above the components because of 2 things:

1. I wanted the components lower in the tower for easier maintenance
2. I wanted the fans at one extreme or the other of the components so I wouldn't have to route wires around them.

Will it really cool better if they are below? I thought they were just assisting the upwards airflow, and could do that from anywhere in the design.

NyteOwl · Post by **NyteOwl** » Fri Oct 26, 2007 10:10 am

Racks can be quiet; they are used all the time in recording studios.

ddrueding1 · Post by **ddrueding1** » Fri Oct 26, 2007 10:26 am

I've been building quiet computers for a long time. Ok, not that long, maybe 5 years? But I've built around 40 of them for myself, my friends, and some of my clients. Always I've made compromises to achieve quiet; 2.5" drives, low-power GPUs, high operating temperatures, etc. I know how to build a quiet tower, or rack mount, or SFF HTPC; and they are all a lot of work.

My vision with this project is to future-proof silence. I want to be able to take just about any component off the shelf, stick it in here, and not worry about noise or ambient temps anymore. I want this to have enough airflow through the tunnel that putting a passive heatsink on anything will be enough.

To make quiet systems there is always a compromise. In this system I wanted the compromise to be something that doesn't bother me, size.

ddrueding1 · Post by **ddrueding1** » Fri Oct 26, 2007 3:43 pm

FlorisNielssen wrote:By the way, have you modelled al the cooler parts yourself?

Not a chance. I am hopeless when it comes to this stuff. All the bits were pulled from the "3D Warehouse" of other people's contributions.

FlorisNielssen · Post by **FlorisNielssen** » Sat Oct 27, 2007 2:13 am

About the fans sucking or blowing:
I'm confused! Been doing some research, looking in an other thread on the forum here. Basicly, you seem to be right. Blowing or sucking doesn't make a difference.
So, you can mount your fans above your components.
But, on heatsinks, especially tower heatsinks, blowing seems to be better. Somehow.

Next question: how are you going to mount your HD's, because an anti-gravity field like in your model is hard to achieve...

You could build some kind of rack where you can screw them on and hang the whole rack on bungee-cord or something. (If that's not too heavy. If it is, you can try building 3 racks next to each other, seperately soft mounted.) If you don't understand I'll try and make a model of it.

jaganath · Post by **jaganath** » Sat Oct 27, 2007 2:26 am

But, on heatsinks, especially tower heatsinks, blowing seems to be better. Somehow.

the air going into a fan is largely smooth and undisturbed, but the air coming out is swirly and vortex-y (i know that's not a word, but whatever

). this swirly air is good for heat dissipation, as it improves heat transfer. so you may find that having all the fans above the parts to be cooled, the air just flows around the heatsinks and HDD, rather than through and past them. may be better off having half the fans below and half above. although, to shamelessly steal from someone's sig, "in theory, reality and theory are the same. in reality, they aren't."

CyberDog · Post by **CyberDog** » Sat Oct 27, 2007 6:17 am

Why you want to use a passive heatsinks? Why not use towersinks with fans blowing up like chimney fans?

And remember, sound doesn't act like light... Which can be good or bad, depending on situation.

ddrueding1 · Post by **ddrueding1** » Sat Oct 27, 2007 8:12 am

The HDD mount is something I am still working on. What I will probably to is suspend each row separately.

I'll sandwich each row with 2 copper plates, drilled for the purpose, then suspended. The plates would be drilled so that there was ~1" of space between the drives for airflow.

If you think this is too much or too little, let me know.

Each drive weighs 0.79lbs, I suspect the plates will weigh about 1lb each. So if each row holds 6 drives, that totals ~6.75lbs (~3kg).

What material is good for damping this much weight?

Should I have a cross-member above the drives and suspend vertically? Or can I have the suspension material mount to the outside walls of the chimney?

ddrueding1 · Post by **ddrueding1** » Sat Oct 27, 2007 8:16 am

CyberDog wrote:And remember, sound doesn't act like light... Which can be good or bad, depending on situation.

I know it doesn't, but what properties are you thinking of when you say that?

I know sound can be transmitted 2 ways, vibration of the air and causing objects to vibrate. By preventing the outer chassis from vibrating, I hope to stop the second. By not having a direct path out of the chassis and lining the inside with acoustically absorbent panels, I hope to stop the first.

Am I missing something?

CyberDog · Post by **CyberDog** » Sat Oct 27, 2007 9:52 am

Basically your not missing any. But chancing canal diameter suddenly will cause an impedance difference which will cause sound to be dampened. And you can use reflectors also. These are all discussed on books that deal with air canals on building etc. Maybe they are explained better because I cant explain it properly on english cos I studied it in finnish.

Ashex · Post by **Ashex** » Sat Oct 27, 2007 12:02 pm

Add a fan or two at the bottom below everything to create turbulence in the air. This would ensure that the hardware is being cooled properly.
Try and channel the air by directing it through the hardware specifically, you can use plates of some sort to help with this. Allow me to attempt to illustrate

|FAN|||FAN|
|________|
|________|
|________|
|________|
|/_MOBO_\|
|/__HDS__\|

That was probably a complete failure, but it's to direct all the moving air towards the components themselves.

FlorisNielssen · Post by **FlorisNielssen** » Sun Oct 28, 2007 10:19 am

Code: Select all

|FAN||FAN|
|________|
|________|
|________|
|________|
|/_MOBO_\|
|/__HDS_\|

This what you meant?

Ashex · Post by **Ashex** » Sun Oct 28, 2007 10:44 am

FlorisNielssen wrote:
Code: Select all
|FAN||FAN|
|________|
|________|
|________|
|________|
|/_MOBO_\|
|/__HDS_\| 
This what you meant?

Well, yeah, yours just looks nicer

I didn't really put much detail into that though, so you'd have more components below, and a couple fans under it.