So I have recently decided that it is finally time for me to build myself a really nice computer. The last time I built one was about 15 years ago, and things have changed a bit since then....The newest thing that is all the rage is to use a water cooling setup to cool the CPU and GPU, and what ever else you want to cool in the system. (Central Processing Unit, and Graphics Processing Unit for the uninitiated). The reasons for this are obvious enough (much better cooling potential vs fans) and the downsides are equally obvious (water and computers don't play well together). So in the course of doing my homework for what would work best for my computer, I came to the realization that given what I am going to put into the computer, water cooling really does make sense. Researching water cooling systems brought me to the realization that it seems no one in the PC water cooling industry seems to have thought that it might be a good idea to talk to an HVAC engineer, or plumber about how best to design something like this.
The design idea is pretty straight forward. You have a 'waterblock' that sits in close contact with the part needing cooling using thermal paste, water is pumped through the waterblock, to a radiator (essentially the same as any AC coil or car radiator you have seen, basic fin tube design) that exhausts air from the inside of the computer case over the radiator using a fan. Simple hydronic circuit. Most custom water cooling set ups have a fluid reservoir somewhere in the loop as well, and a pump obviously.
What struck me first was the fact that pretty much every single one of the guides I read stated that the best way to do this was to make a single loop. Reservoir to CPU waterblock, to GPU waterblock, to pump, to radiator, back to reservoir. Well first of all, for optimal performance, it struck me that it would be bad to do a series loop like this. Also, since the reservoir has an air space in it, it is acting as the expansion tank as well, and should be pumped away from, especially considering most of these are operating at or near 0 psi (static when cold) with pumps that can actually produce up to 15 or 16 feet of head with max flows (at 0 head I'm assuming) of 5 or 6 GPM! (no joke, these pumps are pretty amazing considering their size of about a 2" cube). The common consensus online seemed to be that a parallel loop sounds good on paper as you will deliver colder water to each component, but because you are splitting the flow it would not work very well and trying to balance flow between components becomes impossible. With series you will always get the full flow through each component.....
Another thing that came up was that it was supposedly very important to install the pump after the CPU/GPU in the loop to ensure that the pump did not add heat to the water before hitting the units to be cooled. Further reading found all the complaints about how their pumps are noisier than they like, and how they are so glad they installed them downstream of the CPU/GPU because it was getting so hot.
Here is where I started laughing....
So to sum up, we have high head, vastly oversized pumps, pumping against a series loop of high resistance components, using 1/4" ID tubing (did I mention that?) pumping towards the PONC, with virtually no NPSH, and its a mystery as to why some of these systems are not performing up to expectations, and pumps are noisy and hot.
I decided to apply my knowledge and build a system that actually works. Unfortunately some of the calculations are going to be educated guesses as the important things to know, such as the Cv of a particular component, or even a real pump curve are things that I cannot even get from the manufacturers of the components yet. Still trying. Most of the pump data I have found gives a maximum head and a flow rate (I assume it is the rate at 0 head, but I have no idea) nothing more. I am hopeful that I can get something more useful, we will see.
My idea is basically use the reservoir as a hydro sep, pump a parallel reverse return loop to the CPU/GPU using generously sized tubing and few fittings, then pump a separate loop on the other side of the reservoir to the radiator. Use the reservoir (water heater tank shaped, smaller obviously) to try and create some level of stratification and keep the coldest water low (radiator to reservoir, and supply to system) and the hottest water high (system return to reservoir, and reservoir to radiator). Should work to my advantage as long as the radiator flow is higher than the system flow. After much digging I found one reservoir that has all the tappings that I need and a short dip tube so that I can have an air gap in the reservoir, and still be able to pump out of the top of it. Thinking about adding a fitting into the system at the top of the reservoir so I can add at least a little bit of static pressure to the system, though I will have to be careful as most components are rated for no more than 14 or maybe 16 psi. Thinking of maybe 3-5 psi static cold, and aim for a top pressure with everything as hot as It can get of about 7-8 psi. Will generously over size the radiator, and leave it completely outside of the computer case using room air to cool instead of using already warmed air from the computer case. The oversized rad allows me to run the fans for it at a low speed even under high load, and thus this thing will be very quiet. Using this approach I can then use the on-board PWM fan/pump control built into the mother board to adjust the flow through the radiator and the flow through the system independently and thus achieve the maximum efficiency, and the best cooling.
Just thought I would share, never thought Hydronics would help me build computers!
I would love other ideas and thoughts too, if anyone cares to comment or has any experience with PC water cooling systems