So an update.The manifold:
I found a manifold for my rigs. It is a radiant heating manifold. I was at local plumbing supply house and after explaining what I needed one of the employees found a returned open box manifold. This is a $250+ part but was marked down to $120 due to some damaged. Got them to drop it to $70 with no returns unless not water tight. I will post some images tonight but here is a stock photos. The blue caps at the top are balancing valves and the red tubes at the bottom are flow meters.
One of the balancing valves is jammed, and two of the crimp rings are warped, one of the temp guages doesn't go above 80C. It also has some cosmetic damages and tooling marks. No idea what idiot tried to use this and why the store accepted the return but I got a lot of nice features for very little cost.
Now it is designed for connecting PEX piping and the adapters for each zone are proprietary which makes it a challenge to repurpose. Through trial and error I found that 1/2" ID, 5/8" OD tubing is very close to the nominal dimensions of 1/2" PEX and remains water tight even under pressure using the compression fittings which work with this manifold. I ordered some 7/16" ID tubing which I think will provide an even tighter seal. Another option is changing the fittings on each zone to ones designed for 5/8" PEX which is a good fit for 1/2" ID, 3/4" OD tubing. Since the tubing will be outside the server (connects quick disconnects on front of server to manifold) having a thicker sidewall may be better.
In testing I got 5 loops (no rigs connected) running @ > 1.6 gpm (the max on flow meters). The balancing valves will make is very easy to ensure each rig gets at least 1 gpm to ensure turbulent flow. Honestly despite being damaged this is a total score.The pump and loop:
Hooked the pump up to using some PVC Unions. At this point I am using 3/4" ID tubing (fits tightly over 1" PEX barbs) for the mainline because PEX isn't exactly flexible or easy to work with when testing. Purging air from the system was a challenge. I made a PVC "T" to allow a line for adding coolant and purging air. It only worked marginally. It took hours to purge air from the loops and I don't think I got it all. Went back to Lowes and picked up a 2" PVC T with some 1" threaded adapters. The larger diameter means water will slow down as it enters the T allows the air to separate easier. The heat exchanger:
The good news. It is massive and well built with a ton of surface area both the fins and the internal tubing. The surface area of copper tubing is important because it is how heat is transferred from the water to the fins. You can have a giant heat sink but if it only has a small amount of tubing it isn't going to be very efficient.
To put it into perspective your average 3x120mm water cooling radiator has 1/8" copper tubing usually 4 parallel lines which make one pass.
Surface area of the copper tubing on 2x120mm radiator = 2 * Pi * (1/8) * 14 * 2 * 4 = 88 in^2
This heat exchanger using 8 parallel lines of 3/8" copper tubing and makes 3 round trip passes.
Surface area of copper tubing on this water to air heat exchanger = 2 * Pi * (3/8) * 20 *6 * 8 = 2261 in^2
The bad news. I bought it from an ebay seller and some fins were damaged. I can fix them but I need a "rake". Worse for some reason rather than capping the 1" copper tubes with plastic or rubber plugs they sweated bronze caps (using what looks like two gallons of solder). In the process it looks like they knocked the tubes out of round. I had a nightmare of a time sweating new fittings on. I ended up cutting the caps off and having to bend the tubes back round. It look a lot longer than I had planned. Should have spent a little more because I certainly paid for any discount in manhours.Disclaimer:
I hope these posts have shown that there is nothing "standard" about cooling a rack of servers. Everything requires adjustment and modification as you go. Luckily I own a lot of tools. If I didn't I likely would have had to spent $1000 in tools and supplies (wrenches, channel locks, pipe cutters, soldering torch, mapp gas, tube cutters, pipe dope, thread sealant, etc).What's next:
Will get some photos tonight. Hopefully (work dependent) in the next couple days I can get the time to hook the test rig to the new cooling loop. I have enough waterblocks to test a second 3x5970 rig maybe this weekend. If everything goes good I need to pull the trigger on 20x 5970s waterblocks.