Yes, I picked 1.5 rather arbitrarily, in gpm flow rates, in 0.5 increments, for the sake of round numbers, but see below for more
If I was going to be picky, I'd say 1.7 gpm: that where the flow speed in 3/8" tubing still falls under 5 fps, but the drop at that point (over three feet length) is still 11 inches.
The original figure I found was 8 fps, and that was a recomendation as the upper limit, for PVC tubing (source:
http://www.ppfahome.org/pdf/pvcpipewaterspec.pdf ). Also: "A flow speed of 5 fps is the guideline for 1 inch ID and higher.". Then, "uncle" Dave reminded me that "This guideline works fine for industrial pumps, but would cause most aquarium style pumps to struggle. Low speed is the weak pump's friend. Save the high speed for where it is needed, and that isn't in the tubing.", and having run the numbers, I've found that 5 fps makes for a pretty good guideline, considering the pressure drops involved.
Otherwise, I'll still stick to my original figure of 1.5 gpm. As most of us know, 1.0 gpm is "typical" of an average loop (ref: the OC article). Any one of us who puts more care in component selection (Johnson pump aside...
) will easily achieve 1.5 gpm and that, IMO, dictates the use of 1/2" ID tubing. Plus, as I've said before, 1/2" fittings are much easier to find locally, so it's really a natural choice.
I agree with pHaestus though: at 3 gpm, the cost of the system becomes unreasonable (aka unjustifiable), but then water cooling itself isn't cost justifiable, unless one can put a price on "peace and quiet".
Back to the evolution of this topic...
Yes, a thicker baseplate gives you more "buffering", for those heat spikes. I particularly enjoyed reading Cathar's figures, on OCAU. Cascade's response time is, relatively, frighteningly low, but should still allow for a thermal protection to kick in. It's still much better than direct die cooling...
. It's a trade-off: reduce the baseplate thickness, and depend more on the pump to remain operational, not to cook the CPU.
Has anyone messed with Intel's thermal throttling, to see what temps they can hit?