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Too big a pump

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Senior Member
Mar 1, 2001
Sacramento, CA.
I was just looking at some pumps and got to thinking, In a car, if the water gets pumped through the radiator too fast, the water doesn't get a chance to get cooled off enough. That same thinking should apply to computer watercooling setups. If your pump pumps the water too fast through your system the same thing can occur. I wonder what the gph limit for effectiveness is? My little 4 pass radiator would probably get overrun pretty easily.
This was tested a while ago, but I cannot remember the link. What was done was, a valve and a flow meter were put on the output line of the pump. They then tested the pump with different flow rates untill they found the best for that system. I remember them saying that it will be sifferent for each system and the only way to tell is to try.

I currently use a 210 GPH with my setup running through APX 8 ft of tubing(including the radiator) and the flow is severly impacted. I am probably only getting like 1/3 or 1/4 the rated flow. But it keeps the 80w peltier cool enough to keep my Cele 633 @ 1107 at -23c under full load.
I have an Aquastealth II system but I have no idea what the pump is or how much it pumps. It doesn't seem very strong but then my radiator aint that big either. It seems to be keepin my 85 watt pelt cool enough though. I'm not gettin sub zero temps but then I didnt want temps that low anyway (condensation worries) I'm runnin about 17c full load on my chip with a case temp of 30c.
i'd think that a normal 180-250 gph rated pump is not pushing water fast enough to create a problem here, when you get to the 400-500 range it might be a different story
There was a discussion about this a while back on the old OC.com forums. In the end they pretty much proved that the water can't go through the radiator too fast. If the water is flowing just as fast through the water-block then it's not picking up as much heat per unit of water, but it's still picking up the same amount of heat, if not more... so even though any given amount of water will not lose the same amount of heat in a radiator it is traveling faster through, there isn't as much heat per unit to lose in the first place (I'm not an expert on this, it's just what I remember).

What I do know is that I saw someone test a TBird peltier setup with different pumps from 150Gph up to 700Gph. 150 was way too low (water became heat-saturate in the block) and was about useless. At no point, however, did a pump do worse than a slower one. The 700 was the best, but just barely bette than the 500 (there wasn't enough heat to justify that much water flow).

Basicly , if you CAN have water going too fast in a computer then the pump you would need to do so would not be of practical use due to noise and line pressure. As far as the original issue, I'm not saying you're wrong, but I know some physics professors that would disagree with you. There are a lot of variables that could account for something like that, but we won't really know without a decent testing method.

I tried a 540 gallon 1/25 hp pump and with the computer shut off the water temperature would climb to about 7 degrees above room #3/8" lines and about 2.5 litres coolant, as unrestrictive as I could make it. Every one is different but I think you can definitely have too much flow