Pro/Forums - View Single Post - Thoughts on water pressure & flow rate...

Cathar · 04-21-2003, 08:22 PM

Well, after playing around with quite a few different pumps, my view on "where the line is", can be defined in a number of ways.

If we're talking specific pumps, then a 60Hz MD-15R is about where it's at, or a 50Hz MD-20RZ for those of us living in 50Hz countries.

I honestly cannot say that you will see anything that amounts to improved cooling performance with anything specced higher than these pumps. Both pumps will give you 2gpm+ for pretty much any waterblock (including the White Water).

Beyond pumps like these pump heat becomes the "enemy" for radiator based setups. Even for evaporative cooling tower setups the heat of the pump is still a major factor in causing increasingly diminutive returns.

BillA's test data is excellent, albeit slightly misleading for flow rates in real-world setups, but this is not his fault. His test setup ensures that a supply of a constant water temperature entering the block. ie. the variable of pump heat vs pump power has been removed from the equation, and the resultant affect that this would have on the radiator causing the water to get warmer than Bill's tests would indicate.

The relationship is rather complex, and it matches off pumping power vs block performance vs radiator performance. It's a triangular relationship with some cross-dependent values (ie. block and radiator performance are both affected by flow rate), flow rate and pump heat affects radiator performance, which in turn affects the waterblock performance. When we dig deeper at the differences as we change these variable, we find that we're talking about ~0.5C changes until we get extreme. ie. there seems to be a fairly broad plateau of basically the same performance given a wide variety of pumping power.

A dirty rule of thumb is that I have yet to see any pump that draws more than 40W of power give anything but worse results.

ie. the "ideal" watercooling pump is anything that will give you:

1) > 3lpm flow rates in your setup
2) > 1.5m/5' of pumping pressure head
3) < 40W of motor power draw
4) the highest flow rates given the restrictions placed by 2/3 above.

Note that there will always be edge cases where this won't hold, but in general I stand by the above recommendations.

04-21-2003, 08:22 PM	#144
Cathar Thermophile Join Date: Sep 2002 Location: Melbourne, Australia Posts: 2,538	Well, after playing around with quite a few different pumps, my view on "where the line is", can be defined in a number of ways. If we're talking specific pumps, then a 60Hz MD-15R is about where it's at, or a 50Hz MD-20RZ for those of us living in 50Hz countries. I honestly cannot say that you will see anything that amounts to improved cooling performance with anything specced higher than these pumps. Both pumps will give you 2gpm+ for pretty much any waterblock (including the White Water). Beyond pumps like these pump heat becomes the "enemy" for radiator based setups. Even for evaporative cooling tower setups the heat of the pump is still a major factor in causing increasingly diminutive returns. BillA's test data is excellent, albeit slightly misleading for flow rates in real-world setups, but this is not his fault. His test setup ensures that a supply of a constant water temperature entering the block. ie. the variable of pump heat vs pump power has been removed from the equation, and the resultant affect that this would have on the radiator causing the water to get warmer than Bill's tests would indicate. The relationship is rather complex, and it matches off pumping power vs block performance vs radiator performance. It's a triangular relationship with some cross-dependent values (ie. block and radiator performance are both affected by flow rate), flow rate and pump heat affects radiator performance, which in turn affects the waterblock performance. When we dig deeper at the differences as we change these variable, we find that we're talking about ~0.5C changes until we get extreme. ie. there seems to be a fairly broad plateau of basically the same performance given a wide variety of pumping power. A dirty rule of thumb is that I have yet to see any pump that draws more than 40W of power give anything but worse results. ie. the "ideal" watercooling pump is anything that will give you: 1) > 3lpm flow rates in your setup 2) > 1.5m/5' of pumping pressure head 3) < 40W of motor power draw 4) the highest flow rates given the restrictions placed by 2/3 above. Note that there will always be edge cases where this won't hold, but in general I stand by the above recommendations.