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  #31 (permalink)  
Old September 18, 2009, 12:18 AM
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Originally Posted by Jackquelegs View Post
Enaberif already clarified about the tubing. I'm explaining the non linear relationship of drag versus velocity, as a counter to your horse theory. Where as the horse's time in a certain section of the track translates into the volume of water that passes a given section of the loop.

I'm emphasizing the importance of the difference in velocity. While the horse may spend the same time in the straights. A higher velocity will yield an exponentially higher drag force (quadratic form IIRC), therefore, it's not the time it spends in a certain point that really matters, rather, the work/energy that the action releases.
So what you're saying is essentially that pumps have a pressure curve? The faster the liquid flows the more resistance because of the non linear relationship between drag and velocity.

Crystal clear now. Thanks.

I guess the only thing I don't understand now is what this has to do with the cooling abililty of the rad...
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  #32 (permalink)  
Old September 18, 2009, 12:18 AM
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  #33 (permalink)  
Old September 18, 2009, 12:33 AM
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That doesn't seem like a very supportive way to help me figure out this concept.

It's not like I have the benefit of courses & such that will help me understand it, so all I've done here is ask you nicely to lend me some of your experience.

I think that was entirely uncalled for.
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Old September 18, 2009, 06:03 AM
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Old September 18, 2009, 06:10 AM
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Originally Posted by Squeetard View Post
I should've said better flow does not ALWAYS equal better cooling. There are a lot of factors.
I still stand by this. And I have an example that proves it. Peeps shouls get a variable speed pump and try it themselves. Perhaps my 'time in contact with the heat' was off, but what about time spent in the radiator? The longer your coolant spends in the rad the closer to ambient it gets.
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Old September 18, 2009, 08:00 AM
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I still stand by this. And I have an example that proves it. Peeps shouls get a variable speed pump and try it themselves. Perhaps my 'time in contact with the heat' was off, but what about time spent in the radiator? The longer your coolant spends in the rad the closer to ambient it gets.
That's the same sort of scenario, though. You're suggesting that the conduction of heat improves if two items stay in contact for a longer period of time, whether it's from the block->water, or water->radiator.

You have to be very careful when you try to isolate portions of the water like that in a closed loop circuit, and you have to be careful to distinguish between 'temperature' and 'wattage'. Yes, a given portion of the water will reach a lower temperature if flow is lower, BUT the overall heat dissipated (in watts) by the system will be less. Ultimately, in a closed loop system, the latter is the more important item.

To look at it one way, thermal conduction is directly dependent on the temperature difference between the two objects. So in a water-cooling loop, as soon as the water comes in contact with the radiator, heat transfers (via conduction) from the water to the radiator, cooling the water and raising the temperature of the radiator. This means that the temperature difference between the two shrinks, which slows down the rate of any further heat transfer.

In order to keep the heat transfer going at full speed, the best option is to keep getting rid of the cooler water, and replace it with warmer water. And if you can do that faster (i.e. higher flow rate), you'll maximize the temperature difference between the water and radiator.

This is only one part of it, of course. Turbulence is a whole other ball game, but there are very few instances in computer water loop where more turbulence is bad. Other situations (such as automotive cooling loops, perhaps), could go either way.
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Old September 18, 2009, 09:15 AM
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Originally Posted by MpG View Post
In order to keep the heat transfer going at full speed, the best option is to keep getting rid of the warmer water, and replace it with cooler water. And if you can do that faster (i.e. higher flow rate), you'll maximize the temperature difference between the water and radiator.

This is only one part of it, of course. Turbulence is a whole other ball game, but there are very few instances in computer water loop where more turbulence is bad. Other situations (such as automotive cooling loops, perhaps), could go either way.
Fixed

I couldn't have said it better MpG.

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  #38 (permalink)  
Old September 18, 2009, 09:25 AM
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Originally Posted by MpG View Post
That's the same sort of scenario, though. You're suggesting that the conduction of heat improves if two items stay in contact for a longer period of time, whether it's from the block->water, or water->radiator.

You have to be very careful when you try to isolate portions of the water like that in a closed loop circuit, and you have to be careful to distinguish between 'temperature' and 'wattage'. Yes, a given portion of the water will reach a lower temperature if flow is lower, BUT the overall heat dissipated (in watts) by the system will be less. Ultimately, in a closed loop system, the latter is the more important item.

To look at it one way, thermal conduction is directly dependent on the temperature difference between the two objects. So in a water-cooling loop, as soon as the water comes in contact with the radiator, heat transfers (via conduction) from the water to the radiator, cooling the water and raising the temperature of the radiator. This means that the temperature difference between the two shrinks, which slows down the rate of any further heat transfer.

In order to keep the heat transfer going at full speed, the best option is to keep getting rid of the cooler water, and replace it with warmer water. And if you can do that faster (i.e. higher flow rate), you'll maximize the temperature difference between the water and radiator.

This is only one part of it, of course. Turbulence is a whole other ball game, but there are very few instances in computer water loop where more turbulence is bad. Other situations (such as automotive cooling loops, perhaps), could go either way.
this.

Higher flow is *always* better for our purposes in closed loop water cooling UNLESS you're throwing so much pump power at the problem that you end up with enough heat dump to offset the improved cooling performance you're getting from the higher flow.

The principles at work in a CPU block are not really different from a radiator, so you will actually see BETTER performance from a radiator that has higher flow, not worse (this does not apply to an open loop) where the water would not get cycled back to the radiator again.

For a micro example of this try putting your arm in front of a fan on low and high settings. For the sake of this experiment we can treat your room basically like a closed loop since you won't heat it significantly in a couple of seconds.

By the "more time to take away heat" line of thinking, the low fan setting should cool your arm better because the air has more time to pick up heat from your arm, but it doesn't. More flow = a larger differential in temperatures and more turbulence (more contact between individual molecules in the fluid medium with the solid you're trying to cool). That means you get better cooling with the higher fan setting.
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  #39 (permalink)  
Old September 18, 2009, 01:26 PM
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Fixed

I couldn't have said it better MpG.


Edit: No, wait a minute, I was talking about water-> radiator, in which case the water is the warmer of the two, and cools down over time.
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Old September 18, 2009, 02:48 PM
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lost everyone yet ha ha
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