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Originally Posted by Cathar
While we're also discussing pressure drops and their impact on flow rates (/me cheers as this is really what all this stuff is about), we also need to consider that radiators are not static with respect to varying flow rates too.
Throw in a super restrictive block and peg the flow rates back by 20-30%, and if you're already operating just below the 1gpm mark, this will make a significant difference in the performance of heater-core style radiators:
http://thermal-management-testing.com/Thermo12.gif
Ideally we don't want to be falling much below 0.70gpm/2.5LPM if we can help it, even for a weak pump like an Eheim 1046. |
The graph you put here isn't an evidence of your argument : the constant in the test is the coolant/air differential, so when you put more water into the radiator, you put more heat, so it is evident that radiator dissipated more heat. It doesn't mean than the radiator has a better efficiency with more flow !
We need same graph but with a constant power as a CPU will put the same power in water in a high or a flow rate. So the coolant/air differential will increase when flow decrease...
And the EHEIM1048 and 1046 are used for low flow since they are quiet and resistant, but their PQ curve aren't really good for high pressure. Try the same test with the Laing DDC and D4 (maybe results will be the same, but I dont think EHEIM are representative of good pumps for high drop pressure)
EDIT: sorry if this point was already discussed, I realize I havent read half of the topic yet !
EDIT2 : IMO, most users mix "low flow" with "µchannel". In commercial blocks which use "µchannel", the pressure drop is very high so the "low flow" is a direct effect. But it's not the "low flow" which is efficient but the "µchannel". As you all know, same block will always be more efficient with higher flow (without dealing with the pump and his power). If you look at the tests of roscal's blocks (named "proto") you can see an example of a real "µchannel" (0.3 mm) whith a PQ curve very different of all other µchannel blocks (
http://www.cooling-masters.com/image...pdc_blocs1.png )
To my mind, the good way is in this direction : µchannel to increase the exchange surface and decrease the layer (in a 0.3mm channel, the layer can't be more than 0.15 mm
) but without adding restriction like the nexxos or 1a blocks with "stupid" way for water.