Understanding & Mastering Water Cooling

[strawroot]

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Link : Understanding & Mastering Water Cooling

[neverthar]

Originally Posted by Olle P

You're totally correct, but draw the wrong conclusion.
We're discussing pressure loss in a closed loop. Therefore it's the grand total system restriction that's the only factor (apart from the pump) that decide the flow rate.

It principally doesn't matter whether a piece of tube is positioned before or after the block. The difference it makes is what absolute pressure the water has in the block, it makes no difference to the pressure loss in the block nor does it influence the flow rate. (A reduced pressure loss before the block is countered by an increased pressure loss after the block.)

/Olle

You therefore do not seem to understand that water blocks are also very dependant on head pressure as more restrictive block design would require greater head pressure to overcome resistance in flow. Reduced water flow in the block would mean there would be saturation in heat in the water which would not be beneficial at all. Which is why Delta charts exist. Otherwise explain this chart borrowed from Swiftech. This is the same chart people use to do comparative analysis of pressure drops versus thermal resistance

http://www.swiftnets.com/assets/imag...;20vs%20FR.GIF
Disclaimer:this is an example chart, not verifiable independantly

[Chai]

Originally Posted by neverthar

You therefore do not seem to understand that water blocks are also very dependant on head pressure as more restrictive block design would require greater head pressure to overcome resistance in flow. Reduced water flow in the block would mean there would be saturation in heat in the water which would not be beneficial at all. Which is why Delta charts exist. Otherwise explain this chart borrowed from Swiftech. This is the same chart people use to do comparative analysis of pressure drops versus thermal resistance

http://www.swiftnets.com/assets/imag...;20vs%20FR.GIF
Disclaimer:this is an example chart, not verifiable independantly

I think you don't get what he meant.

The flow rate at the intake and the output of the pump will always be the same, as long as the tubes are in serial, and the total length of the tube in the loop is the same. The pressure drop in the loop is equalised.

This is the same myth as same people claimed, slower flow rate in the radiator improves cooling, which is not true. The water spend the same amount of time in the radiator regardless of the flow rate, and in fact, higher flow rate = better performance.

[Olle P]

Originally Posted by Chai

The flow rate at the intake and the output of the pump will always be the same, ... The pressure drop in the loop is equalised.

Exactly! It doesn't matter where the restriction is added as long as it's somewhere in the entire loop.

Originally Posted by Chai

The water spend the same amount of time in the radiator regardless of the flow rate, ...

That's a new one (myth, that is) to me...

The fact is that what happens with higher flow is that the water spend less time in the blocks as well as in the radiator.
That results in a lesser temperature difference between the "hot" and "cool" water.
Heat transfer is always improved exponentially with the temperature gradient, which means that in the radiator (as well as the cooling block) it's the water that just enter that provide the most heat transfer, and the longer it "hang around", the less heat is transferred (because the water temperature is closer to that of the surroundings).
By increasing the water flow you make the water about to leave the component almost as good in heat transfer as the one just entering (because it has virtually the same temperature), thereby improving the cooling efficiency.

Cheers
Olle

[Olle P]

Comments on part 3 of the article:

1. Page 13 is missing! (Replaced by page 11.)

2. Page 11, cleaning radiator and blocks.
- You tell us to use vinegar for cleaning, but don't say why. Why use vinegar?
- Given that vinegar is used, then there's no reason to not use (filtered) tap water for the initial rinses, since the acid will remove any remaining mineral stains.
- Why have the block's base soak in vinegar before polishing and cleaning with alcohol? The alcohol should suffice for cleaning.

3. Page 11, vinegar in the coolant.
What should be prevented by a proper selection of coolant is:
- Chemically altered tubes. (They might be dissolved or swollen.)
- Growth of algae, fungus or bacteria.
- Galvanic corrosion.
- Short circuits in the event of a leakage.

Vinegar will;
- have no to little impact on the tubing, if the material is properly chosen.
- help prevent the growth of life in the system.
- work as an electrolyte that promote galvanic corrosion. Can be countered by making sure that all metal parts in contact with the liquid are of the same material, preferably exactly the same alloy composition!
- work as an electrolyte that promote short circuits in the event of a leakage.

4. Page 12. Checking for leaks.
One common supplemental test is to simply assemble and run the cooling system outside the computer before letting it close to any sensitive components.
That will disclose any faulty components with a minimum of fuzz.
It does not get rid of the need for testing after installation though, as the installation itself may have produced leaks in the tube fittings.

5. Page 12. Temperatures.

You can all but disregard the useless numbers it reports to you.

Not quite true.
The measurements may (and most often do) have a lousy accuracy, but they also have a fairly good precision!
This means that as long as you use the same BIOS and software for measuring the temperature the different results are fully comparable to each other when it comes to show differences in temperature.

/Olle

[Chai]

Those myth are constantly brought up by noobs. hehe. "Myth: Water must slow down to fully absorb heat"

http://www.overclockers.com/articles1088/

Well, not completely related to the current discussion. But the thing is, no matter how long or short the tube from the pump to the waterblock, as long as the total length of the loop remains the same, there shouldn't be any major temperature difference (same amount of flow rate and pressure across the loop, and same amount of heat generated by the pump will reach the waterblock), unless there're other factors like altering the waterblock mount (which is highly possible even though you didn't physically remount, because changing the tubing alone will definitely move the waterblock in some ways). Even the most professional water cooling gurus cannot guarantee the same optimum mount everytime they mount the waterblock, which is why they have to remount and retest several times to ensure consistency when testing waterblocks, which I'm sure you are fully aware of.

Although I have some differences with Olle P, but I fully agree with him on this.

[neverthar]

Originally Posted by Chai

I think you don't get what he meant.

The flow rate at the intake and the output of the pump will always be the same, as long as the tubes are in serial, and the total length of the tube in the loop is the same. The pressure drop in the loop is equalised.

This is the same myth as same people claimed, slower flow rate in the radiator improves cooling, which is not true. The water spend the same amount of time in the radiator regardless of the flow rate, and in fact, higher flow rate = better performance.

I get pretty damn well what he means but he's deviating very far from original point of argument which is about pump to block head pressure. This is despite the fact it is generally understood that pump pressure at head is vital for many impingement based designs

Originally Posted by Olle P

Comments on part 3 of the article:

1. Page 13 is missing! (Replaced by page 11.)

2. Page 11, cleaning radiator and blocks.
- You tell us to use vinegar for cleaning, but don't say why. Why use vinegar?
- Given that vinegar is used, then there's no reason to not use (filtered) tap water for the initial rinses, since the acid will remove any remaining mineral stains.
- Why have the block's base soak in vinegar before polishing and cleaning with alcohol? The alcohol should suffice for cleaning.

3. Page 11, vinegar in the coolant.
What should be prevented by a proper selection of coolant is:
- Chemically altered tubes. (They might be dissolved or swollen.)
- Growth of algae, fungus or bacteria.
- Galvanic corrosion.
- Short circuits in the event of a leakage.

Vinegar will;
- have no to little impact on the tubing, if the material is properly chosen.
- help prevent the growth of life in the system.
- work as an electrolyte that promote galvanic corrosion. Can be countered by making sure that all metal parts in contact with the liquid are of the same material, preferably exactly the same alloy composition!
- work as an electrolyte that promote short circuits in the event of a leakage.

4. Page 12. Checking for leaks.
One common supplemental test is to simply assemble and run the cooling system outside the computer before letting it close to any sensitive components.
That will disclose any faulty components with a minimum of fuzz.
It does not get rid of the need for testing after installation though, as the installation itself may have produced leaks in the tube fittings.

5. Page 12. Temperatures.Not quite true.
The measurements may (and most often do) have a lousy accuracy, but they also have a fairly good precision!
This means that as long as you use the same BIOS and software for measuring the temperature the different results are fully comparable to each other when it comes to show differences in temperature.

/Olle

Vinegar is used as it is a light acid which is enough to dissolve the residue materials/chemicals which were there during fabrication.

Rinsing with filtered tap water is to get rid of the vinegar itself unless you think leaving the residue of vinegar inside is very good for you.

The base as in the inner base of the waterblock to remove any residue of milling coolants whatsoever left as residue, Unless you have a better idea of getting rid of residue in the channels.

while I agree with Olle on the pros of using vinegar but it was never said to be for long term use. Only for the initial cycle to make sure everything comes out. And it is always assumed never to be mixed in terms of materials as regardless with or without any promoter of ion carriers, such a setup would promote oxidisation (May need to consider editing the article for further fine tuning)

For testing, why the added hassle of testing outside the CPU? If the CPU is fully disconnected, shorting would not occur. Only a damned fool would plug in the AC plug while testing the watercooling components. Besides that, it is better due to the reason you stated, faulty tubing clamping detection.

As for the temp measurement, for daily usage maybe it would be ok to use the motherboard monitors but for ndetermination as to exact reduction in temps, it's always better to use proper thermal probes to measure. Older systems tend to have thermal diodes which would be affected by many factors like airflow around CPU socket and such.

And as for waterblock, I've explained what needs to be explained as I stress again it is a tip for weaker water pumps (Very weak I might add). If you cannot accept such a principle, then so be it. I will not argue or elaborate on any further armchair discussion anymore as I feel this useless and unhelpful for others as it has gone beyond the point of a newbie's understanding which defeats the purpose of the article, which is to help newbies. If anyone of you can propose or write a much better article which would be understandable by 90% of the readers out there, I sincerely welcome and support the idea. I have done the best that I can with whatever limitations that I faced. Whether my efforts are appereciated or not, I do not care. I am only just trying to help and I do not ask for anything in return.

Any request for assistance or advice in PM I will gladly entertain but I take my leave from this thread.

[PsYkHoTiK]

o_0

Apart from vinegar, I use ketchup too...

[wiLL*lianG]

Page 14 "Up Next" missing... is it part 4 continue page?

BTW, any other can replace vinegar?

[Olle P]

Originally Posted by neverthar

... This is despite the fact it is generally understood that pump pressure at head is vital for many impingement based designs...

That type of blocks provide a huge restriction on the flow, thus creating a relatively large pressure drop that increase with the flow rate.
In order to work properly they still need a sufficient flow, which require a sufficiently powerful pump to overcome the pressure drop.
But there's no difference in efficiency between a set-up with a block inlet pressure of 50 psi and outlet pressure 45 psi, and one with an inlet pressure of 10 psi and outlet 5 psi.

Originally Posted by neverthar

Rinsing with filtered tap water is to get rid of the vinegar itself ...

That's not what I (nor you) suggested.
In the article you write:
1. Rinse with deionised water.
2. Rinse with vinegar.
3. Rinse with deionised water again.

My suggestion is to not use deionised, but regular, water before the vinegar.

Originally Posted by neverthar

The base as in the inner base of the waterblock ...

That is a bit unclear by reading the article, especially since you stress that it shouldn't touch the bowl. The inside just won't touch the bowl anyway.
Assuming that the reader use a full metal water block, why not just drench the whole thing in vinegar? No reason to leave machining residue in the upper half of the block, is it?

Originally Posted by neverthar

while I agree with Olle on the pros of using vinegar but it was never said to be for long term use.

It's most definitely not said to be for short term use. Therefore long term use is assumed.

Originally Posted by neverthar

And it is always assumed never to be mixed in terms of materials ...

Mixed materials is the norm, don't you know?
- Block bases of "pure" copper.
- Barbs made of brass, stainless steel or some plated material.
- Radiators made of copper but with soldering material exposed.

Originally Posted by neverthar

For testing, why the added hassle of testing outside the CPU?

Mix-up of terminology here? The CPU is a pretty small component, I can't see how anybody could fit a water cooling system in there...
With push-lock fittings on the barbs testing outside the computer case is a quick and simple way to make an initial check for leakages that save you lots of work if there is a major leak.

Originally Posted by neverthar

... but for ndetermination as to exact reduction in temps, it's always better to use proper thermal probes to measure.

As you point out yourself in the article; the probes in use are "proper", it's just the firmware that isn't properly calibrated.
If you measure the "before" temperature a couple of times with all settings (CPU work load, room temperature, relative humidity, air pressure, etc.) equal, you'll end up with an average that's somewhere within 10 degrees of the correct temperature because of the crappy accuracy due to poor calibration.
That's useless if you are to compare that to a measurement from any other computer!
Now to the interesting part: We're not going to compare it to another computer, but the very same!
Enter observation #2: Thanks to the proper hardware used for the measurements, the temperature readings done are all within a very narrow interval, like +-0.1 degrees of the average, a trademark of good precision.
Using the same tools for a series of "after" temperature readings will provide reliable numbers for the difference, since these new readings will deviate from the true value exactly as much as the previous readings did.

/Olle