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Water-cooling with paralel circuit (simple fluid dynamics?) [edit]

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May 28, 2013 12:05:44 PM

I'm preparing for a new build and I want to use the corsair 650d case, since I'll be doing water cooling and would like to stick with a mid-tower case. I'll be cooling the CPU and graphics.

There's "good" room on top for a 280mm radiator and I wanted to keep front and exhaust fans for memory and chipset cooling.

Can I setup something like:
Reservoir>Pump (A)>Y Splitter (A) inlet>Y Splitter (A) outlet #1>GPU>Y Splitter (B) inlet #1> Radiator> Reservoir
and Pump (A)>Y Splitter (A) inlet>Y Splitter (A) outlet #2>CPU>Y Splitter (B) inlet #2> Radiator> Reservoir

I know how confusing this sounds, all I want (if possible) is to split the loop after the pump, and reunite it before the radiator.

I'm worried that one of the coolant circuits (either the CPU or GPU) has a greater resistance to the passage of fluid than the other and that the coolant all ends up taking the path of least resistance as fluids often tend to (or is that just folk physics?) and leaves me with a scorching processor.

Is this feasible?

Should each circuit have it's pump?
Wouldn't that over-pressurise the radiator or bottleneck the flow of fluid before entering the rad?

[edit] As per your requested here's my idea:
https://docs.google.com/file/d/0B6rkpemdzvWUQWRiZEt1UEp...
May 28, 2013 1:11:22 PM

water will flow down all paths from high pressure to lower pressure sides of the pump. the flow would be greater on the path with least back presure. the more flow the more back presure. when back pressure equals pump pressure, flow stops.

say your 2 loops would each have a back pressure of 1kpa. while your pump feels 0.5kpa, the flow would be equal. if loop 1 was 1kps, and loop 2 was 2kpa. loop 1 would have twice the flow as loop 2, and the pump would feel 0.666kpa

length of tubing, total degrees in bends (one loop will have a min. 360 degrees), and your water blocks will all affect back pressure. you could add valves to increase back pressure and balance the flow. but adding back pressure means you may need a bigger pump to overcome the restriction.

you could do a series loop, or 2 series loops.

your fittings would be the weakest link not the rad or res.
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May 28, 2013 11:41:54 PM

A picture or diagram of your loop setup might help, as I cant figure out the order with that.
Something like this would do.

...............................-> Rad
Pump -> Splitter <...........
...............................-> Rad

Anyway, your understanding of how it will effect flow and resistance is bang on. By running components in parallel you effectively halve the total resistance for the components in there, however if each path offers a different amount of resistance than you will find more water will move through the least resistant path, compromising the cooling of the other path.
My suggestion is too only parallel identical blocks, the prime example would be of GPU blocks.
There is also radiators in parallel, which is useful not to reduce restriction but because a lower flow through them allows more time for the water to be cooled.

Always have pumps in series with each other, having them in parallel offers no performance benefit and if one were to die you lose 80% of your pumping power.
http://martinsliquidlab.org/2011/04/26/pump-setup-serie...

But anyway, if your only using a CPU + GPU loop I don't see any great need to start creating parallels in the loop, your standard D5 pump will be able to power through the restriction and still get you decent flow rates.
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