Pump pulling from CPU does it make a difference?

[voigts]

thanks to the this interesting read, I have a much better understanding of how this flow/head pressure/velocity thing works.

One question I have though not exactly related to the OP's original question, is how does this relate to running two identical rads in series vs. parallel? I've always heard the explanation that two rads in series gives less flow and more pressure drop than 2 rads in parallel. The only test results I've seen in the past seemed to indicate that there really is not a difference running identical rads in series or parallel.

[SNiiPE_DoGG]

With parallel you end up cutting the velocity in half of what it would be in a single rad or two rads in series

[Martinm210]

Yeah, if they are identical, you would see roughly half the flow rate running through each radiator. It's not exactly half though, because you've reduced pressure drop, your system flow rate increase.

You may see 2.0GPM system flow rate in a split parallel, but each radiator would see only 1.0GPM because they are run in split parallel loops.

If you ran both in series, your overall system flow rate would be reduce a bit by the higher pressure drop. That might turn out to be 1.8GPM, but each radiator would get the full 1.8GPM.

If you compare those flow rates to thermal efficiency however, the difference is pretty small.



At a 10C water/air delta the difference with the fans swiftech tested with would be roughly 400 watts parallel vs. 440watts series, or a 10% difference.

So at a 10C delta you could see maybe 1 degree difference or so, not huge, but I'd rather run series myself.

I havn't seen too much testing on this, actually I thought swiftech was going to publish something on their stacking of rads a while back. What ever happened to that swiftech stacked testing??

[voigts]

Thanks for putting numbers on it Martin. I understood about halving the velocity through the rads, but the heat dissipated chart in conjunction with the flow rates being roughly halved makes sense.

[Vapor]

Done with GTZ tests....still waiting on the KL-350, then it'll be ~4-7 days after that for results from the KL-350.

Anyway, here's what I have so far:


4120MHz, 1.46v 920. Test procedure the same as my normal. i7 has 1:1 ambient:CPU temp scaling though, so there's no correction factor used (only difference I suppose).

[Hondacity]

this is really predictable...after one hour the cpu has raised the water temp for both setups at the same temperature...

with good flow the water temp at any point of the loop wouldn't vary...

imagine less than 300ml(total liquid volume) for a normal setup(small res)...with a flow of 8lpm every 2.5xx seconds that 300ml would have gone thru the loop completely...

my assumption is that it would be the same for both setups

Done with GTZ tests....still waiting on the KL-350, then it'll be ~4-7 days after that for results from the KL-350.

Anyway, here's what I have so far:


4120MHz, 1.46v 920. Test procedure the same as my normal. i7 has 1:1 ambient:CPU temp scaling though, so there's no correction factor used (only difference I suppose).

oops i quoted myself

[SNiiPE_DoGG]

all hail fluid dynamics and the laws of physics

[Martinm210]

Done with GTZ tests....still waiting on the KL-350, then it'll be ~4-7 days after that for results from the KL-350.

Anyway, here's what I have so far:


4120MHz, 1.46v 920. Test procedure the same as my normal. i7 has 1:1 ambient:CPU temp scaling though, so there's no correction factor used (only difference I suppose).

Awesome work!! Thanks for testing the flow rate too, that's also confirms the pump and flow rate is not affected either.

So far it appears the suspected "Pressure increase= performance increase" and/or "Pump before the Block" Myth is getting busted!!