Water Cooling, the TRUTH behind the Mystery

[gilgamesh]

This gude was originaly posted on my website, by myself. So for you water coolers our there, here are some truths' to dispell the myths that have built up

I hope you like this folks, Runn3r we could use this in a water cooling FAQ also???

Myths exposed.

Myth:The order of components can effectively change the performance of the loop

Quote
False: Changing the Order of the loop only makes a 0.5 degree differnce There is only one difference, and that is the position of the pump in the loop, be it before or after the CPU. Assuming the pump dumps about 50 watts of heat into the water and the flow rate is 1 gallon/minute (gpm - very reasonable assumptions):

Water has a thermal capacity of 4186J/Kg-C at 22ºC and a density of about 1g/mL

With a flow rate of 1 gpm, that's ~3.75 liters/minute (lpm).

3.75 lpm / 60 seconds= 0.0625 liters or kilograms through the waterblocks per second.

4186 * 0.0625 = 261.625 W/C

So that's 1ºC warmer for every 261 watts; but only 50 watts of heat are present, so:

50 / 261.625 = 0.19ºC

Ergo there is a 0.19ºC difference in water temperature between the inlet and outlet of the pump. This does not mean the water is only 0.19ºC warmer than air - that is an entirely different calculation.

And that's with 50 watts. If you're running a smaller pump, such as the D4, you're looking at about 15 watts.

So, do what allows for the simplest tubing runs - tubing length/kinking will have a greater impact on temps.

source (www.overclockers.com accessed 31/10/08)

Myth: Aluminum absorbs/dissipates heat faster than copper

False: The thermal capcity of copper (ergo density) is higher than aluminium

Myth: Using Anti-Freeze Kills prevents alqea buildup in your system


Only partly true: Anti Freeze is used to reduce the SURFACE tension of the water to prevent bubbles in addition to help prevent corrosion by the use of dissimilar metals used in a loop!

Myth: On-board temperature sensors are accurate.

FALSE: No motherboards onboard sensors are totally accurate: some can be as much as 13c out.

If a block is shiney its flat!

FALSE. Shiny-ness is NOT condusive to flatness! Being shiny means that it is smooth NOT flat! There is a differnce!

Myth: A QUAD pass Rad performs better than a dual pass rad:

False: This depends on the design, as the tubes where the water flows will be closer together, ergo less air passing through the fins!

Myth: You can use white-wine vinegar to flush out a radiator

False: This statement used to be true however, with the new water-based flux on designs such as thermochill radiators, this is no longer needed. Simple repeated flushes with hot tap water is enough. So long as the FINAL RINSE is completed by using distilled water!

THe purpose of vinegar was to strip off a layer of impurties that had built up inside the radiator. Users where then finding that even after repeated flushing using distilled water that they where having problems with tube discolouration performance loss, tube rot etc.

The best way to counteract the negative effects of vinegar was to flush the acidic solution by neutralising the acid in the vinegar with the use of baking powder (or bio-carbonate of soda).

Experiment:
Pour a spoon full of baking powder into a bowl full of vinegar: The resulting bubbles are carbon dioxide, this shows that the baking powder is neutralising the acidity in the vinegar, thus the reaction. So the best way to flush out the vinegar was to create a solution with baking powder. This was then left for an hour, after which repeated flushing with distilled water was the final step.

With modern radiators vinegar is no longer needed, a simple HOT water flush then a final rinse with distilled water is the most efficient way of producing the desired results.

Q: A Push-Pull configeration is always the best solution

A: NO not at all, around 80 percent of water cooling  enviroments, this solution is not needed. Thermochill radiators are built for lower CFM fans, ergo they have 11 Fins per Inch, the same is applied with XSPC radiators, however the old blackice GX series have 25 Fins per Inch, this is when the push-pull configeration will come in handy! As this means the more fins per inch the higher the fans CFM needs to be , to push the air through the fins!
Recently Blackice have produced the SR1 range which has the same FPI as thermochill! So in almost all circumstances a push-pull solution would make around 1-2c difference at the most!

you can find the original guide on my site at:

http://www.overclockerstech.com/forums/showthread.php?t=40

gilgamesh

[jonj678]

We are about to fall out. I shall address your points in order.

1/ Pump before or after the cpu block is irrelevant to performance.Source. Reservoir/T line before pump makes filling the loop easier as pumps do not like being run dry.

2/ Heat capacity of the metal, or conductivity of the metal, is not related to the rate at which heat can be removed from the surface. You want to look for coefficient of emissivity of aluminium vs copper, and at the coefficient associated with convective heat transfer. I can't be bothered to look up either. Incidentally if aluminium has a lower specific heat capacity it will absorb heat faster, as it'll increase in temperature faster and it's temperature gradient that drives conduction. So not only have you quoted the wrong constant, you've got the conclusion backwards.

3/ Algae doesn't grow well in antifreeze solution. Ethylene glycol is added to inhibit electrochemical corrosion, I'm unsure of the mechanism but it will be independent from surface tension. I'm not convinced dilute antifreeze is more resistant to cavitation than water, might check this. Cavitation is only related to the pump though, not to corrosion.

4/ On board temperature sensors are pretty rubbish, but you've picked 13 centigrade as a worst case scenario out of the air. You should not quote arbitrary figures to disguise ignorance. It's OK that you don't know how unreliable the sensors are, I don't know either.

5/ Shiny is indeed unrelated to flat. The issue generally comes up in lapping.

6/ Unsure on this one. I agree that there is a lot more to a radiator than how many passes the water makes through it. I imagine each have their place. Air deflected around the greater number of tubes won't matter much, if at all. For that matter there's no reason to think a quad pass radiator uses more tubes than a dual pass one.

7/ Of course you can still use vinegar. It's useful if the radiator is full of dye residue, or if the previous owner used tap water. The purpose to flushing with vinegar is to remove the flux from the soldering process, the reason it is no longer needed is that water soluble flux is now used. Recommending flushing with a base afterwards is ridiculous, flushing with water is quite effective enough at reducing the H+ conc to negligible levels, and your approach would just make the water corrosive in a different way were your initial assumption correct.

8/ Push pull will always outperform push only or pull only. Shrouds are generally a better first step. The trick is in matching fan pressure to the radiator, or in using powerful fans which you spin slower and slower until performance becomes too poor. Radiator thickness is as relevant as fins per inch, and even low fpi radiators benefit from a second fan. You personally may well feel that single fan's are the best solution, but this doesn't make you right.

I'm not going to bother going to your site, as you don't know what you're talking about. I vote against stickying this thread.

[gilgamesh]

Im afraid it is yourself whom has no idea on what you are talking about.

I wont go listing my experience and quals (im above that)

YOur arrogance is simply astounding

I had a word with Cathar about this (I presume you know who he is>?)
http://www.overclockers.com/forums/showthread.php?t=387122&page=2

Regarding shinyness

Incidently Thermochill do not recommend using white-wine vinegar anymore speak to rob at wcuk in addition speak to the OLD owner of thermochill steve verity, www.over-clock.co.uk (incidently it was myself whom tested and evaluated the prototype 140.3 TC rad-of which I still have)

I do not have time to address all your points, however your completely incorrect and your arrogance simply astounds me!

Anyone reading this thread I think we should take a vote on weather this becomes a sticky

I have pointed catchar and others towards this thread

[jonj678]

I welcome any information which I do not have. As such if Cathar wishes to turn up here and correct me, he is more than welcome to do so. I will of course cross check anything he says in the literature before accepting it as correct, but I am always ready to learn more.

You have not replied to anything I have said, nor pointed at a link which contradicts me, and have instead chosen to insult me and namedrop. It's not generally a good idea to use "whom" when the grammatical quality of the rest of the post is lacking either.


I'm going to rewrite the aluminium vs copper point as it was not very clearly phrased in my initial reply.
 
Heat capacity of the metal, or conductivity of the metal, is not directly related to the rate at which heat can be removed from the surface. You want to look for coefficient of emissivity of aluminium vs copper, and at the coefficient associated with convective heat transfer.
Heat capacity of aluminium is 900 J/kgK, of copper is 400 J/kgK. For some reason you state that copper has greater heat capacity than aluminium.

The rate at which heat enters the block is dependent on temperature gradient and interface resistance.  Likewise the rate at which heat leaves the block. Thermal conductivity will affect the temperature gradient across the block, as will distance between source and sink, in the obvious way. Heat capacity affects how quickly the temperature gradient is established after a change in surface temperature, nothing else. It is independent from the interface resistance coefficient which determine at what rate it can absorb heat. 

[scjet]

 This was a great chemical analysis, but to me, just like the water/antifreeze in my rad (car, or otherwise), it WILL eventually evaporate...?
This is why I don't really trust water-cooling in the long run, atleast not yet,-it would have to be a perfect-hermeticrally sealed unit otherwise.

 So, I'll take heatpipes and a big-assed tower fan anyday - I can clean it mechanically, and "seeing is believing !"