Quote Originally Posted by Nickel020 View Post
Thanks for taking the time to do this Martin! There are awfully few Watercooling reviews on the net

But I don't understand why you plot flow rate against pressure drop and how you even get the data. Or how to make sense of it (well I know that less pressure drop at a given flow rate is better, but what does that mean for actual performance?). Do use a variable voltage on the pump to obtain the different flow rates and then note down the pressure drop? I guess the pressure drop refers to the pressure of the loop without the rad versus the loop with the rad & fittings, right?

Sorry for all the questions, but I can't make any sense of that graph. The way I would test this is hook up the loop with the different barbs which would give me one flow rate and one pressure drop value for each barb. Then I'd check how that affects CPU temperature. But I must be missing something...
I plot flow rate vs. pressure drop because with that equation you can estimate the flow rate for any system. It's sort of the ultimate tool that you can use. I could simply test a whole bunch of actual radiators on a test loop and give you the flow rate that was produced, but that's only good for that one loop. If you figure out the whole curve, I can then use it to estimate flow rates on any system.

I vary the flow rates in my pressure drop testing with household water on a facet and I control flow rates using a standard sink facet valve. I wouldn't recommend that with a bucket flow rate test because if pressure varies during the filling of the bucket, you're flow rate accuracy isn't very good. But in the case of using a flow rate meter, I get instant readings so I can read flow rates and pressure drops at the same time. The other advantages to using household water is that there is not air in the lines, so bleeding of reciculated loop with a pump is not necessary. Also my water pressure in my house is extremely high, so it provides the ability to test clear out to very high pressures and flow rates without running out of pumping power. My first few trys in pressure drop testing witha D5 made that very apparent when I couldn't get results beyond 2 GPM for alot of blocks....not a problem with the household water.

Regardless, I think it would probably be helpfull to at least estimate some flow rate differences between some systems in addition to the curves. This would at least put better scale to the result differences.

The actual flow rate differences between these radiators will be very small because they are all very very low in restriction.