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Unread 01-10-2004, 09:41 PM   #16
Gooserider
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Join Date: Jun 2003
Location: North Billerica, MA, USA
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Quote:
Skulemate:
[Quote: Originally Posted by Gooserider ... 3. In a series system, the flow will be NO MORE than what is allowed by the most restrictive block. 4. In a parallel system the flow will be the sum of what can flow through each block, (up to the input flow)
These points are perhaps a bit misleading. The resistance from blocks, fittings etc. is cumulative, so even though you may have a very restrictive CPU block, that GPU block will contribute to the system resistance, and will alter flow rate. In a parallel setup the flow rate will balance itself across the multiple paths such that the pressure drop along every path is equal. And again, the resistance of each path is cumulative, meaning that if there is both a northbridge and GPU block on a line, both will contribute to the resistance.[/quote]
Technically you are right, however I have found that they are good working approximations. In a series system, the most restrictive block will dominate, with only minor effects from the less restrictive blocks.

In my own setup, either of my CPU blocks would flow just over 3 GPM by itself, I got 3GPM with them in series, or almost no additional pressure drop from the second block. When I put them in parallel, I got 2.5GPM through each block, or 5GPM total for the two.

Quote:
fhorst:
As I said... If your CPU block is restrictive, and your GPU/NB is not.... what will that do to the flow (and pressure gradient) in the CPU block? You are right about "pressure gradient" (I guess, I'm not native speaking English) For mee its all the same. The force that you need tho push the water through the tubes, rad and waterblocks If you split the hose, thsi force will be split also. This force is needed to create a good jet. A better jet will give better temps
Note that I do NOT reccomend splitting flows prior to the CPU block in most cases. I think it is usually best if all the flow goes through the CPU block(s) first, THEN split the flow to the other blocks which don't need as much cooling. This maximizes the flow through the entire system, and the pressure drop across the CPU block.

The ONLY time I reccomend splitting the flow before the CPU block is if the blocks on the other branches are so restrictive that having them in series reduces the flow through the CPU block significantly (which can be found by the bucket test)

If, when you split the flow after the CPU block, there is a great difference in the flow through the parallel branches, and the low flow branch is not cooling adequately I would reccomend re-arranging the branches to get a more even flow, and / or putting a restriction in the high flow branch in order to force more into the low flow branch. If all the branches are cooling adequately, then don't do anything that would reduce the total flow.

Perhaps I need to add another guide:

8. The ultimate objective should be to maximize the flow through the CPU block(s), and have good flow through the GPU block, with adequate flow through the remainder. Remember that except for possibly the GPU, the other blocks don't have to get rid of that much heat, so any flow at all is probably enough.

Gooserider
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Designing system, will have Tyan S2468UGN Dual Athlon MOBO, SCSI HDDS, other goodies. Will run LINUX only. Want to have silent running, minimal fans, and water cooled. Probably not OC'c
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