OK, just to review (and maybe I missed something) watercooling in general involves several heat transfers.
1) heat source to block
2) through block to wetted side
3) block to water
4) via water motion to radiator
5) water to wetted side of radiator
6) through radiator walls to fins
7) radiator to air (small amount probably lost via direct radiation)
I don't think we'll see any differences between small and large diameter hosing in 5, 6, or 7. Yes there are "sweet spots" for some rads but I'm ignoring that
I also don't think we'll see a difference here in #1. TIM and clamping pressures seem to be the same.
I'm at work and away from my notes, but as I remember, it doesn't take much water flow to transport, say 100W of heat at, say a 4C heat rise, so I'm not sure that 8mm ID tubing is at a great disadvantage here.
So, what's left is:
2) through block to wetted side:
Again, no reason why a smaller diameter hose system
has to have a thicker baseplate. The Innovatek Rev, rev 4 and the "pyramidal" one do, but is looks as though this alphacool one does not. IMHO the only reason to have a thick baseplate is for thermal damping, but (again very much IMHO) why not just store sudden heat loads in the
water?
...and 3) block to water
So far, Cathar's whitewater and cascade designs appear to do this the best. the greater the water velocity (within reason) the better they transfer heat to water. The larger ID systems seem to all move greater volumes of water than the smaller ID systems (duh!) - and the greater volume gets translated into greater velocity in the water block. BUT I would
guess that there's an optimum velocity, so a block "tuned" for lower flow might indeed perform better at low rates than, say, a whitewater at the same low rates.
I'm curious to see a
real test as well...
Bob
PS: this is not to say that 8mm ID systems might perform better simply with the substitution of larger diameter hosing - unless the blocks are designed so that water velocity really doesn't matter much (like the Rev 3).
PPS: please tell me where I've gotten any of this wrong. I'm trying to
learn about this stuff and getting "slapped down" is actually useful to me