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Dual Pumps - How?

post #1 of 8
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So, I started out with CPU cooling only and now I've got 2 GPUs in the loop. I was thinking about doing 2 loops, one for CPU and one for GPU.

Then I read an article that said 2 pumps in series (1 big loop) was actually better than 2 seperate loops.

If I did decide to do two in series, could I go one pump right into the next? If/when I do this, I will get a dual bay/pump res and going one into the next is the easiest way.

I still might go seperate loops though, because cooling the CPU is more important to me than the GPUs.

BTW, I have a 3x120, a 2x120 and a 1x120 reservoir. Any suggestions on this?
    
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post #2 of 8
I don't know if one or two loops would be better, but if you go with one loop the pumps should be in a series (res > pump > pump > cpu, gpu etc).
post #3 of 8
You don't need two pumps or two loops.

And just because this is somewhat relevant: Maximum PC DM2010.
post #4 of 8
Two ways:

1. Pump > pump in series plumbed with fittings and tubing.

2. Dual pump top, something like this

To be honest though if you have something like a MCP355 of 35x you don't need two pumps; one will be enough. So long as you are over 1GPM there are no real performance increases to be had by adding more pumps.

As for the dual vs single loops, I take it the article you read was the one by the one by Gabe @ Swiftech. That doesn't really show much to be honest, if you put enough rad into a single loop then you can get the same performance as two smaller dual loops.

If you put the CPU first that will knock a few °C off your CPU temps, probably in the region of 1-3°C if your two 590's are running flat out.

I would stick with single loop and single pump for now, you can always upgrade later if you want to.

Edit:

I have no idea where I got the GTX590's from. You can have them if you want!

If you are at or above 1GPM, the temperature difference of the water going through both GPUs running flat out, even OC'd, will be more like 1-2°C, no more.
Edited by GingerJohn - 4/21/11 at 11:42am
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post #5 of 8
I think you'd may even decrease performance adding another pump. ~ You'll be adding another 18W of energy to the loop for little gains elsewhere.

If you add it in series, you wont increase your flow by much, because pumps in series double your pressure.

Pumps in parallel will double your flow but at the same head, so you only really need 2 pumps if you have a huge amount of stuff in your loop.
    
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post #6 of 8
You shouldn't be running into any flow restrictions by cooling a CPU and dual GPU so a second pump shouldn't be needed. Also, you've got PLENTY of rad for what you're doing.
post #7 of 8
Quote:
Originally Posted by Crabid View Post
I think you'd may even decrease performance adding another pump. ~ You'll be adding another 18W of energy to the loop for little gains elsewhere.
Very possible.

Quote:
Originally Posted by Crabid View Post
If you add it in series, you wont increase your flow by much, because pumps in series double your pressure.
Pumps in parallel will double your flow but at the same head, so you only really need 2 pumps if you have a huge amount of stuff in your loop.
Not quite. You are right that series will increase max pressure with the similar flow, and parallel will increase flow with the similar head. But this is only true at terminal conditions; complete restriction or no restriction.

In a WC loop, restriction increases with flow rate; the more water you try to force through the components the more resistance they will provide. Pressure is what pushes through restriction, therefore if you increase the pressure you will increase the flow rate. This can be shown on a sample PQ curve:



Therefore, unless you have a really un-restrictive loop, you want to put pumps in series to increase flow rates.
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post #8 of 8
Quote:
Originally Posted by GingerJohn View Post
Very possible.



Not quite. You are right that series will increase max pressure with the similar flow, and parallel will increase flow with the similar head. But this is only true at terminal conditions; complete restriction or no restriction.

In a WC loop, restriction increases with flow rate; the more water you try to force through the components the more resistance they will provide. Pressure is what pushes through restriction, therefore if you increase the pressure you will increase the flow rate. This can be shown on a sample PQ curve:



Therefore, unless you have a really un-restrictive loop, you want to put pumps in series to increase flow rates.
I know

But unless you're struggling due to restrictions in the loop already, increasing the head wont have much of an effect.


Not to mention, additional flowrate doesn't make much difference in temps anyway with current waterblocks, unless your pump isn't man enough.
    
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