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Thread: Radiator Fan Setup

  1. #1
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    Radiator Fan Setup

    Right now I'm planning out my water cooling setup and I've decided on running two loops with my G0 Q6600 on the first and 8800GTX on the second. Both loops will have MCR320s as radiators. I want to get a pretty nice overclock on my processor, around 3.6-4 GHz and a good overclock on my GTX. The procesor temperatures are most important, and the GTX's temperature should should be reasonable but doesn't have to be too extreme. I want to have the benefits of two loops but without having six fans blowing right next to me. I will be using Yate Loon Medium fans and was wondering if it would be possible to just use three fans in a setup like this:



    I was wondering if there would be a big performance hit to either the processor or graphics card and if the setup would work like this. Thanks in advance.

  2. #2
    Xtreme Enthusiast leo_bsb's Avatar
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    your second rad will receive hot air from the first rad, so your loss will be the cooling capacity of the first rad. If the rad can take 5 degrees from the hot water than your second rad will step up from that temperature.
    If your second loop is colder than the first loop it will make everything worst.

  3. #3
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    You would be much better off with six quiet fans.
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    Xtreme Enthusiast Brian MP5T's Avatar
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    Agreed, That is called "Heat Soaking"


    It is not desirable. You are simply moving the heat from one loop to the next.
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    You'll also have to use two less-than-optimal L-shaped barbs for the second radiator, which will kill flow. Not so good an idea. It'll be different if you are going overboard with two radiators per loop, but that uses Y-junctions and is a whole different story.
    Last edited by IanY; 09-25-2007 at 05:04 PM.

  6. #6
    Xtreme Enthusiast Brian MP5T's Avatar
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    So what did you decide?

    did you modify the plan?
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  7. #7
    Xtreme Addict Serpentarius's Avatar
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    will this setup bring better temps if the warm water travel to the hotter rad and to the cooler rad later .. in series?

    given the hotter rad took much of the heat away, the cooler rad will have lesser watts to handle, and if cool air is driven in the cooler rad, maybe it's better?

  8. #8
    Xtreme Enthusiast Brian MP5T's Avatar
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    This is a poor design no matter what way it goes...

    Basically, any design that moves heat from one part to another is never going to be as good as one that moves the heat totally away.
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  9. #9
    XIP - can sit on his hair Marci's Avatar
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    Search for "Radiator Stacking"...

    Radiator stacking simply reduces the efficiency of every radiator after the first as you're using warmer air...

    Because at the sorts of air pressures that most PC cooling fans can provide, coupled with the fin density of the heat exchangers being used, a single radiator will typically achieve between 90-98% thermal transfer efficiency for the amount of air-flow that a single fan is capable of pushing through the singular radiator.

    If you double up the radiators, one after the other, the second radiator is receiving air that is within 10% of the temperature of the coolant already. Worse, the second radiator will in turn double the air-flow resistance, effectively cutting the air-flow through the radiators by around 30%. So the 10% of possible fluid-air heat transfer capacity that the first radiator didn't achieve that you're counting on the second radiator to scavenge, gets totally overwhelmed by the fact that there's now 30% less air going through to pick up the heat.

    i.e. you'd see ~20% higher water temps as a result.

    Now if your fan is SO powerful that the first radiator's thermal transfer efficiency is low enough that adding the air resistance of the second radiator is minor in comparison to the amount of heat transfer that the second radiator is capable of scavenging, then that's where it'd work.

    In my experience, this isn't going to happen for PC sized 12cm radiators until you start using >200CFM singular fans, or alternately double up some 100cfm fans in a push-pull arrangement, and even then, it's going to be borderline better than the single radiator with the single fan.

    If you're going to use two radiators, they need to both be pulling their own clean air source for best effect.
    Source: http://forums.overclockers.com.au/sh...1&postcount=12

    Hmmm, I suppose I should've explained it better.

    Air has a finite thermal capacity per volume. It happens to be around 1250J/m³.K (round figure).

    i.e. it takes around 1250 Joules to raise 1m³ of air by 1°C.

    So if the fan is moving 1.5m³/min of air through the radiator, then the air-flow has an inherent thermal capacity of around 31.25W/C, or a C/W of 0.032. i.e. the radiator CANNOT perform any better than the inherent thermal capacity of the air. Even if the radiator was 100% efficient, the C/W will never be lower than 0.032C/W.

    Now if the radiator is 90% efficient at this air-flow speed, this means that the radiator will have a C/W of 0.032/0.9 =~ 0.036. i.e. the equilibrium point will be such that the water warm up by 0.036°C per Watt of heat input (from CPU + GPU + pump + whatever else is being water-cooled).

    If we now add on a second radiator, and this increases the air-flow resistance such that the air-flow through the two radiators is now 1.1m³/min, then the inherent thermal capacity of the air is now 22.9W/C, or a C/W of around 0.044.

    i.e. even if we achieved a 100% thermal transfer efficiency of heat from the fluid into the air using the two radiators, at best we will achieve a C/W of 0.044, or about 20% worse than the 0.036 of the single radiator.

    Now as air-flow goes up, radiator's thermal transfer efficiency goes down. There is eventually a cross-over point where adding a second radiator in air-flow series to the first radiator does help, but for PC water-cooling radiators, that doesn't occur until you start stacking extremely noisy fans, or using obscenely noisy single fans (Delta FFB/TFB, etc).
    Source: http://forums.overclockers.com.au/sh...2&postcount=16 (later in same thread)

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