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Old 12-15-09, 09:46 AM   #4
Wants Old Title Back
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Conumdrum's Avatar 

Join Date: Sep 2007
Location: Las Vegas

Something for the Flowrate sticky. The old one has tons of great info, some applies, some is way out and does not apply to our needs. This will kinda sum it up.

Flow rate is important to the effective operation of a CPU block. Modern blocks need 1 to 1.5 GPM of flow rate to effectly remove heat. Below 1 GPM you can impact the CPU temps. Above 1.5 GPM the benefits can drop off and flatten out on curves. Look inside any modern block. And if you can find some of the simulations posted how the water acts in the block they can show it, I have seen them in the past.

Fluid needs to be at high enough flow to get very turbulent inside the block. This causes more molecules to contact the warmer copper surfaces, thus collecting more heat to be dissipated in the rad.

We want linear flow in the hoses, but not in the blocks. You reduce flow and you can severly impact the cooling capability of the CPU block. Smooth flow in the hoses, the intake to the pump, generally anywhere helps except in the blocks.

Slowing the flow thinking the water will be there longer and cool more in the rad also reduces flow in the blocks. So as it enters the block it's cool. When it exits it's warmer than it could be, because it's flowing slower. So besides the impingment problems metioned above, you can cause more problems.

Lastly, we are dealing with a closed loop. Lets set the flow rate at 2 GPM. For easy demonstration purposes this will cause a water molecule to make a loop every 5 seconds, and stay in the rad for 1 second. So, every minute the molecule will be in the rad for 12 seconds.

Lets reduce the flow to 1 GPM. Every 10 seconds. 2 seconds. The molecule will still be in the rad for 12 seconds. Reducing flow rate does not keep the water in the rad for any longer...........................

In summary, the purchase of a good pump and not getting crazy with two many blocks and 90 degree fittings your flow rate will be just fine. All modern rads and recommended pumps are just fine even with two GPU blocks and a CPU block. Add in a full set of Mosfet blocks etc and you might be hurting your flow rate. How do you know? Your temps are poor is a good indication. It can be tested with a 10 gallon bucket. Fill use the 10 gallons as your res. Bleed the loop. Then put the pump out hose into the sink and turn it on. How long does it take the 10 gallons to get to 2 gallons? There is your systems flow rate.

All of this can be supported by tests at Martins and Skinnees and other info on the web.

I want my old title back.
Old beast is torn down.
Will update later.

900 watt (1500VA) UPS
27" ASUS VG 3D/Nvidia V2 3D glasses and 24" Acer H243H

Last edited by Conumdrum; 12-26-09 at 10:35 AM.
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