Project: custom 19in rack passive cooling system

[JinTu]

Hi folks,

I figured that I would share my project with you all in the hope that you get a little enjoyment out of it the way I have.

My primary mining system had to be relocated to a common area at home at the end of last year due to a visitor (read MIL) that has been staying with us since that time following the birth of a child. Normally the fan noise from the GPUs when running full-throttle wouldn't be a concern, but the silly things scream like a banshee which had become detrimental to the WAF for my bitcoin mining, so something had to be done. In the mean time I have had to reduce the fan speed (and correspondingly the hash rate) of my system during daylight hours, and can only run at full throttle in the middle of the night.

To that end, my project has the following design goals:

• Ability to dissipate >900W of heat load
• Near silent when running
• Appealing visual design (remembering the WAF)
• Modular and serviceable
• Minimum external components
• Reasonable cost (funded by mining)
• Flexible design that will allow cooling of next generation mining hardware in addition to the current GPUs

All this in mind, I started looking into water cooling as some folks have had a measure of success increasing efficiency when mining after doing so. Most of the systems I had seen all used active cooling that use one or more fans to pass air through a radiator and remove heat from the cooling liquid. This would work fine if noise isn't a concern, but in my case I had to find another way. As my research progressed, I ran discovered passive cooling. It has the same heat dissipation benefit of active cooling, but needs a larger surface area to allow convection and ambient airflow to dissipate the same heat load. Fortunately my mining rigs are located in a 19in rack with adequate airflow and space to accommodate a larger surface area radiator array.

I discovered the Alphacool Cape Cora series passive radiator modules which met my design goals and began a design based on them. The initial design required keeping at least two rows of the radiators relatively close to the side of the rack, and the original solid aluminum sides of the rack had to be changed out with something that required some air to pass through to allow effective cooling. Also, the radiator modules would be rather heavy once assembled and filled with cooling liquid, so mounts were needed that could accommodate the weight and maintain rigidity. I went through a few designs over the intervening months, but ultimately settled on Design G (the staggered array design below):

High resolution version here.

Since the plan is to use copper heat exchangers and brass fittings in the cooling loop, the aluminum Cape Cora modules posed a problem wrt galvanic corrosion. To that end, I will be electrically insulating the radiator modules and using a corrosion inhibitor in the cooling fluid.

Since there a multiple pumps and sensors, I settled on the Aquaero 5 XT from Aquacomputer to manage everything. At present only Windows drivers are being released by Aquacomputer, so I might need to spend some time updating the Aquaero 4 Linux port someone did a few years ago.

Free time has been hard to come by, so actual construction has been slow. I have uploaded pictures of the progress so far, and will add more as things progress.

Have fun!

[Photon939]

It's a neat idea, here are some things to keep in mind:

Those passive radiators are cool and do work, but they're quite expensive and you will need many to dissipate 900W. For about $100-150 you can buy a brand new car radiator that is designed to handle many kilowatts of heat. Slap a big low RPM fan or two on there and it will be dead silent. Make up a nice box for it and nobody will notice it. This will also take up less space than a giant passive radiator.

If you use copper water blocks with those aluminum radiators, you will need to run a mix of coolant that includes a corrosion inhibitor to prevent galvanic corrosion.

[JinTu]

The first set of parts arrived in March.

Unfortunately one of the T-connectors for the radiator modules was damaged in shipping (from Aquatuning in Germany)


Fortunately they sent me a replacement less than a week later.

The aluminum bar stock prior to cutting



The perf aluminum side panels prior to cutting



The perf side panels after cutting shown next to the rack


The first set of mounts after cutting

[JinTu]

It's a neat idea, here are some things to keep in mind:

Those passive radiators are cool and do work, but they're quite expensive and you will need many to dissipate 900W. For about $100-150 you can buy a brand new car radiator that is designed to handle many kilowatts of heat. Slap a big low RPM fan or two on there and it will be dead silent. Make up a nice box for it and nobody will notice it. This will also take up less space than a giant passive radiator.

If you use copper water blocks with those aluminum radiators, you will need to run a mix of coolant that includes a corrosion inhibitor to prevent galvanic corrosion.

Thanks for the input. Yea, the aluminum radiators are definitely a source of concern wrt galvanic corrosion, so I had to use nylon screws and nylon shoulder washers to electrically insulate the modules from the rack. I'll still use a corrosion inhibitor, but should be pretty well covered in this regard.

The Cape Cora modules dissipate 22.5W/ea, so I need at least 40 (the current design has 42 for symmetry)

[JinTu]

In April the first set of pump parts from Koolance arrived


The reservoir and primary pump after assembly


Measuring the clearance


The final set of Cape Cora modules arrives. This makes 42 modules in total!

[JinTu]

May 2012: assembling the radiator segments of the center module

Segments assembled with T-connectors removed


One of the ends


Showing the length of all 14 segments


All the segments assembled with the T-connectors attached

[JinTu]

June 2012: cutting the rail spacers and drilling the mounts

Checking the fit


Drilling the mounts

[JinTu]

July and August 2012: Drilling and mounting the rails

Drilling the rails


The Aquaero 5 XT has finally arrived! It was back-ordered for three months from Germany. This will serve as the controller for all the pumps and sensors.


Expanding the holes on the rails


Tapping the holes on the mounts


The bottom rail attached to the mount


Top view of the bottom rail and mount


The top and bottom rails and mounts assembled. Less that 0.5mm difference between the two! Not bad for doing everything with hand tools...


Initial assembly of the middle segment and rails with the nylon screws

[jojo69]

It's a neat idea, here are some things to keep in mind:

Those passive radiators are cool and do work, but they're quite expensive and you will need many to dissipate 900W. For about $100-150 you can buy a brand new car radiator that is designed to handle many kilowatts of heat. Slap a big low RPM fan or two on there and it will be dead silent. Make up a nice box for it and nobody will notice it. This will also take up less space than a giant passive radiator.

If you use copper water blocks with those aluminum radiators, you will need to run a mix of coolant that includes a corrosion inhibitor to prevent galvanic corrosion.

all this

you should peruse [H]ardOCP, people have this stuff nailed down pretty good for uber gaming/folding rigs

[JinTu]

September 2012: mounting the rails

Today I trimmed the nylon screws and attached both rails to the center module



Closeup showing nylon spacer


The hardware for mounting the remaining two module segments is on order, but won't arrive for another two weeks.

[JinTu]

you should peruse [H]ardOCP, people have this stuff nailed down pretty good for uber gaming/folding rigs

Lots of good info and designs in the [H]ardOCP forums.

Thanks for the tip!

[Nemesis]

It's a neat idea, here are some things to keep in mind:

Those passive radiators are cool and do work, but they're quite expensive and you will need many to dissipate 900W. For about $100-150 you can buy a brand new car radiator that is designed to handle many kilowatts of heat. Slap a big low RPM fan or two on there and it will be dead silent. Make up a nice box for it and nobody will notice it. This will also take up less space than a giant passive radiator.

If you use copper water blocks with those aluminum radiators, you will need to run a mix of coolant that includes a corrosion inhibitor to prevent galvanic corrosion.

all this

you should peruse [H]ardOCP, people have this stuff nailed down pretty good for uber gaming/folding rigs

lol Hard are kiddo compared to XSystem

Hard = highschool puter modders
Xsystem = Professional in the industry with modding hobby.


Let the OP do his project, stupid to tell ppl dont get a nice SL but mod a Mustang.

[jojo69]

I was not dissing on the OP's project at all, just pointing him at a resource.  Dissimilar metals in a loop are a real concern, or I guess XSystem has overcome electrolysis 

[Nemesis]

I was not dissing on the OP's project at all, just pointing him at a resource.  Dissimilar metals in a loop are a real concern, or I guess XSystem has overcome electrolysis 

What if he use Brass blocks? Dont be a retard and saying "dissimilar metals"... There is a technical term for what you're preferring to.

I'm sure the OP is smart enough to use addictive. Dont assume...

[jojo69]

I was not dissing on the OP's project at all, just pointing him at a resource. Dissimilar metals in a loop are a real concern, or I guess XSystem has overcome electrolysis  

What if he use Brass blocks? Dont be a retard and saying "dissimilar metals"... There is a technical term for what you're preferring to.

I'm sure the OP is smart enough to use addictive. Dont assume...

Uuuuum, try wiki Galvanic corrosion and report back the first two words under "overview"

"preferring to", "use addictive"??

ignore button engaged

[JinTu]

Since folks have expressed concern about galvanic corrosion, here is how I plan to address this for the upper and lower radiator modules. Each module segment will be attached with two screws to both the upper and lower mounts. Since nylon screws likely couldn't take the torque of being moved around a lot, I chose to use stainless steel screws with nylon shoulder washers which will be countersunk into the bottom of the mounts. The radiator-facing side of the mount (right side in the diagram) will have a nylon washer between the mount and the radiator. Here is an exploded view:

[JinTu]

The screws and nylon shoulder washers for the upper and lower modules arrived early, so I was able to drill the pilot holes on the lower mount, and make a jig for drilling the module segments.

[Cablez]

Since folks have expressed concern about galvanic corrosion, here is how I plan to address this for the upper and lower radiator modules. SNIP

I don't think everyone is on the same page about the corrosion issue.  Here is a good primer with pictures: http://martinsliquidlab.org/2012/01/24/corrosion-explored/

The corrosion happens within the water loop due to mixed metals and degrades the blocks, pump and rads. Using additives will assist in keeping this to a minimum but will not stop it completely.

The best approach is to design the loop without mixed metals if you can.

[JinTu]

Since folks have expressed concern about galvanic corrosion, here is how I plan to address this for the upper and lower radiator modules. SNIP

I don't think everyone is on the same page about the corrosion issue.  Here is a good primer with pictures: http://martinsliquidlab.org/2012/01/24/corrosion-explored/

The corrosion happens within the water loop due to mixed metals and degrades the blocks, pump and rads. Using additives will assist in keeping this to a minimum but will not stop it completely.

The best approach is to design the loop without mixed metals if you can.

Yep, lots of good info on martinsliquidlab. His review of the Aquaero 5 is what convinced me to use one in this project. I just wish he was still updating the site

In a typical PC water cooling case, the components are electrically connected to the PC case and therefor to each other satisfying the second requirement for galvanic corrosion to occur

2. These metals must be in electrical contact

For this project, the only components of the loop that I will not be able to electrically isolate are the (GPU) water blocks themselves (which must be tied to the case ground). This will require some planning as new blocks/components are added in the future so not to create a problem, but for now things should be covered. I'll be sure to do electrical continuity tests once all the mounts/modules are assembled to ensure there isn't an inadvertent short between a radiator segment and a mount or rail somewhere.

[JinTu]

Another load of parts, tools and supplies arrived just before Amazon tax day. After some deliberation, I decided on a 150W Pico PSU to power the pumps, Aquaero 5 XT and Poweradjust 2s. Also shown are the PSU bypass plug (allows the PSU to run w/o being attached to a motherboard), an illuminated toggle switch, heat gun some heat shrink tubing and the last of the mounting hardware.


After the last batch of nylon washers arrived I was able to finish off the rails for the middle radiator module. It is shown here next to the rack for scale.



I also drilled the countersink holes for the nylon shoulder washers for the first of the mounts today.