Hondacity's HeatKillers GTX285 in Triple Sli (simple test)

heres one i did in July last year

http://lh5.ggpht.com/_5JXSu5Gfgo4/SI...0/DSC03021.JPG

temps on GPU 2 were higher than the others until i figured out that the sli fittings needed spacers, the threads were too long and there was only a gap of a few mm between them

Quote:

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Originally Posted by KaptCrunch

let me give you 25 elbows to see if Inertia doesn't hurt flow #'s,

in a full paralle loop yes pressure matters but with mixed its not a issue

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wow 25!!! 90 elbows?

i only have 10 :)

http://i24.photobucket.com/albums/c5...5/P1020470.jpg

What I am thinking is happening in the GPU blocks with parallel flow is completely different then what the blocks were designed to do. The GPU blocks were designed to have flow go through them but with parallel I don't think there is actual flow as we normally see it but is happening in a different way. It's too bad we do not have some sort of visual pinwheels on two sides near the ports on the GPU blocks to confirm this but what I think is happening is that the water is being exchanged at the ports of the blocks and are not really circulating in the block itself as much as it is just exchanging slowly off of the lip of the ports. When you stop to think about it and the results show it too is the temps are consistent through the 3 blocks. The flow is going the path of least resistance down the tubes but is scrapping off fluid along the way and is exchanging that way. So the water in the blocks is kinda sitting there exchanging a little at a time slowly but enough not to overheat the water and I think there is even some protection there as the water heats up and expands into the running water in the ports. I don't know....Just ramblings on my part and may mean nothing.

Quote:

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Originally Posted by KaptCrunch

let me give you 25 elbows to see if Inertia doesn't hurt flow #'s,

in a full paralle loop yes pressure matters but with mixed its not a issue

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Sorry I should have been more specific, inertia has little to do with how water travels through branches in a parallel water cooling system. Because while traveling through the tubing the flow of the water is pretty much laminar, and in laminar flow situations according to the Navier-Stokes equation the fluid inertia factor can, for all intents and purposes, be considered zero and canceled out. In fact, inertia is very important in watercooling because it is fluid inertia that creates turbulent flow (the kind inside waterblocks that is so good at removing heat).

In determining which branch to travel through in a parallel loop it is pressure that is the largest deciding factor. When the water reaches the first waterblock it has two paths it can take. It can continue on to the last 2 waterblocks, or it can go through the first waterblock. There is less pressure to continue on to the other two blocks because they are in parallel and provide less restriction, so most of the water (about 2/3) will continue on to the final two blocks whereas the other third will travel to the first block. Then when it reaches the junction of the second waterblock it can continue on to the third or go through the second. The pressure from the third is roughly the same as the second, so the remaining water splits about equally between the two. The end result is about 1/3 of the flow moving through each block.

Quote:

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Originally Posted by Sadasius

What I am thinking is happening in the GPU blocks with parallel flow is completely different then what the blocks were designed to do. The GPU blocks were designed to have flow go through them but with parallel I don't think there is actual flow as we normally see it but is happening in a different way. It's too bad we do not have some sort of visual pinwheels on two sides near the ports on the GPU blocks to confirm this but what I think is happening is that the water is being exchanged at the ports of the blocks and are not really circulating in the block itself as much as it is just exchanging slowly off of the lip of the ports. When you stop to think about it and the results show it too is the temps are consistent through the 3 blocks. The flow is going the path of least resistance down the tubes but is scrapping off fluid along the way and is exchanging that way. So the water in the blocks is kinda sitting there exchanging a little at a time slowly but enough not to overheat the water and I think there is even some protection there as the water heats up and expands into the running water in the ports. I don't know....Just ramblings on my part and may mean nothing.

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This is WAAAAAY off. Of course water is traveling through the waterblocks, it has nowhere else to go.

Yeah I was way off because I was thinking of a different setup and not the actual one he was running. Must have been in a daze or something. Really bored here at work!

well, I didn't forget about the parallel tests. :D

was monkeying around this weekend while CPU block tests were running (yes, I am delaying the Radiator data). Here is what I came up with to put numbers to the pressure debate.

http://skinneelabs.com/images/sl_sli-tester.jpg

tube lengths are cut as precise as possible with extra tubing I had lying about, the tube lengths are perfectly sized so I can swap in the manometer T's. Valves are so I can vary the amount of restriction to see the pressure differential fluctuate. We'll see about getting this on the pump tester soon. :D

dude you forgot the flow meters! lol :D

awesome setup :D

Quote:

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Originally Posted by Hondacity

dude you forgot the flow meters! lol :D

awesome setup :D

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This, the entire debate has been about equal flow to all the branches.

Awesome skinnee! I'm looking forward to your tests, as always!

I vote parellel
Also how exactly do flow meters determine flow without restricting it?
Id imagine that all flow meters restrict the flow in some way right?
Or is that restriction a constant and factored in.