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Unequal resistance in parallel loop - problem?

post #1 of 4
Thread Starter 
I'm in the process of installing my dual 7970s in my water loop, and I wanted to connect them in parallel instead of serial, but they will have (at least slightly) different amounts of resistance. They both have different blocks - the bottom card has the original EK 7970 block, which can have the inlet on the side of the block that faces the top of the case



The top card has the newer design CSQ block from EK, and thanks to it's stupid and frustrating design, it only has an inlet facing the bottom of the case. Attaching the Link System piece will change the inlet 90 degrees to face the side of the case, but you then need to add another adapter to the already-in-place adapter to change the inlet another 90 degrees to finally face the top of the case just like the other card. This is what it looks like with both adapters attached:



So basically, when a loop splits into a parallel section, water will follow the path of least resistance, correct? When the water comes down to the first block, some of it will need to make a 90 degree turn in towards the motherboard, then another 90 degree turn back upwards, and then yet another 90 degree turn towards the motherboard again. 270 degrees just to get into the GPU block itself. There will be another 270 degrees to travel through when the water exits the block and goes back into the tubing.

When the water comes down to the 2nd block, it only needs to take one 90 degree turn towards the motherboard to enter the block, and then again only one 90 degree turn to leave the block and re-enter the tubing.

I feel this inequality in resistance will cause the top block to have much less flow than the lower block and potentially a bigger difference in temperatures than I would have running serial. What do you suggest? Would there be less temperature difference between the GPUs in a serial loop than in a parallel loop with unequal resistance like this one?
post #2 of 4
I have owned both block types. The added turns the water makes does not increases resistance to any great degree. The water flow design inside the blocks is what determines how restrictive it is, and they are very similar so I doubt there would be much difference in flow to each block.

Trying it is the only way you will know for sure.
Kusanagi
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Kusanagi
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post #3 of 4
Both water blocks are almost identical in terms of hydraulic pressure drop so parallel flow shouldn't be a problem at all.

I agree with you it's frustrating to connect two blocks of completely different design, I am sorry for that.
    
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post #4 of 4
Thread Starter 
Quote:
Originally Posted by EK_tiborrr View Post

Both water blocks are almost identical in terms of hydraulic pressure drop so parallel flow shouldn't be a problem at all.

I agree with you it's frustrating to connect two blocks of completely different design, I am sorry for that.

Well I know the blocks themselves are almost identical, it's just that the water must turn 270 degrees to enter the first block and only 90 degrees to enter the second block. I really do like the look and style of the CSQ block, I just REALLY dislike the fact that the inlet only faces the bottom of the case instead of giving us the option like the old design.

Anyway, I'll try it and see how it goes. If temps are too different between the GPUs, I guess I could always get a Y splitter and just curl the tubing 180 degrees into the inlet, and let the outlet come straight out...
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