Koolance's "how to test a radiator" demonstration...

[Marci]

http://www.koolance.com/technical/my...b_results.html
http://www.koolance.com/technical/my...radiators.html



Currently under scrutinisation yonder: http://www.xtremesystems.org/forums/...d.php?t=148286

The flaws are obvious... relevancy to the pc watercooling community? Less than 1%...

[ibmkg]

I cannot say much but what I will point out (again) is that for brass/copper rad you need better cooling. Say raising temperature beyond 100C (considering automobiles), one would end up discovering that Cu-Brass rad is just not good enough. These rads tend to absorb heat effectively but cannot get rid of it as effective enough (assuming using low CFM fan @ high temps). The result would be that rad would tend to get hotter and hotter.

Al on the other hand (even though may not absorb heat as effective as Cu-brass), the very property results it to be better performing at extreme temperatures @ low CFMs.
The reason being that they require less effective cooling methods (as there is not much heat to be removed due to the fact that they do not absorb much from fluid). Ultimately Al rad outperforms Cu-Brass rad and hence end up in automobiles.

If one can prove anyone wrong, they should experiment on varying temperatures with varying CFMs.

[HammerSandwich]

I think you're all wet. Copper's superior conductivity helps, just as in waterblocks, because it allows a smaller temperature delta between the hot and cold sides.

Originally Posted by ibmkg

...(as there is not much heat to be removed due to the fact that they do not absorb much from fluid).

The amount of heat is dictated by the PC's components. If I change my copper HC to an AL rad, would the CPU & GPU burn fewer watts?

[bigben2k]

http://www.cooling-masters.com/news-...adiateurs.html

Rosco checked it out: the water temp is 85 deg C, and airflow is ~330 cfm. Air temp was about 25 deg C. This isn't going to apply to water cooling, but it's great if you're testing a heater core for a car (which, incidentally, is what the third party tester normally tests...).

In short, all the claims are BOGUS and uneducated. Koolance would do well to get with someone who knows what they're doing (and I'd happily volunteer, for a fee), but I suspect that the results would dissapoint their PR department, and that any conscionable effort would be burried (I don't know, but they're not doing well right now).

[bigben2k]

(also posted at xtremesystems)

All this talk, and so little information...

I think everyone understands that the results are skewed. The problem, as I see it, is that the average Joe could infer that, if the performance at one set of parameters shows one product as being superior, then it must retain its superiority under "slightly" different parameters.

Which we know is false, but only a rare few understand why.

I've done a fair amount of work in water block design (theory) and have been following radiator design, because a lot of the principles are very much the same (just in a different order).

So here's my attempt at an explanation, and hopefully this can be complemented by our other "rare few" members:

First, what we start with:
Testing air flow: 330 cfm
Testing coolant flow: 5 lpm, 10 lpm
Testing air temp: 25 C
Testing water temp: 85 C

Then, what would be ideal:
Desired air flow: 80 cfm
Desired coolant flow: 5 lpm
Desired air temp: 25 C
Desired water temp: 30 C

In short, a quarter of the airflow, and a much lower water temperature.

So first, we break down the radiator function into two components, then focus on the elements that make a difference, for the purposes of identifying the testing flaw.

1) Heat transfer from the coolant, to the radiator.
2) Heat transfer from the radiator, into the airflow.

In 1 and 2, I'll define the variables as:
a) flow rate
b) flow geometry
c) flow turbulence
d) temperature
e) surface area
f) surface area effectiveness

I believe that the core of the flaw in the tests reside in item f, so I'll expand: while it's always desirable in a heatsink to have large and plentiful fins, it does not mean that infinitely long fins add any significant cooling, as the variable I've dubbed "surface area effectiveness" depends on d: temperature, or more specifically, how the temperature differs, between the mass of the fin, and the air flow. In other words, you're not going to transfer a lot of heat from a mass (fin) to the air, when the temperature is just about the same.

To make this clear, I'll exagerate: if you were running a heatsink on a CPU, it would dissipate just about as much heat, as it would if the fins were insanely long, like 1 meter/3 feet (fan aside). Why? Because *most* of the heat will still be dissipated at the bottom of the fins, regardless of how long they actually are, unless of course, the original heatsink is poorly designed, with fins that are too short.

The fins on a heatsink, correspond to the fins in a radiator. In a compact design, like the Black Ice and Thermochill units, the "fin length" is just right for the intended purpose. The Koolance is actually larger than it needs to be, for water cooling (but that's ok, because longer fins won't have much impact, other than ending up with a larger radiator than needed).

Now we put the same water cooling rads through a testing sequence, where the coolant temperature is too high, and what do we have? A huge difference. Why? As I mentionned above, a heatsink is considered poorly designed when the fins are too short. When you test a water cooling radiator under automotive conditions, you end up with the same "poorly designed" heatsink: the Thermochill and Black Ice unit's fins (and fin effectiveness) are too short, and are overwhelmed, as any poor designed heatsink would be.

The "correct" conclusion from Koolance's testing is:
-The Black Ice and Thermochill radiators make poor automotive heatercores.

And that's why Koolance's contracted testing is irrelevant.


[note: the above is really over-simplified, but should help the average Joe understand clearly enough]

[ibmkg]

I cannot agree more. Al should remain with automobile that operates at higher temperatures. What PC water-cooling requires is an exceptionally sensitive cooling rig. A slight change in degree and an action taken in accordance.

I understand that tests might be rigged. The only way anyone can satisfy me is to perform extensive, variable, idealistic and practical tests.

BTW... I know this is out of the topic question but I have noticed something strange with LGA775 HSF.

I have a 3.0GHz Intel HT. It was running at exceptionally high temperature. I noticed that this HSF had a Cu base extending all the way to fan (its sort of an inch of Cu rod between the Al fins). Al fins were bonded to it.

I had a leftover same spec LGA775 HSF (which comes with newer CPU) except that it was pure Al (including base). I swapped the HSF and noticed 5-10C difference (idle-load).

My question: Intel never conducted a test on HSF or what? Mixing of metals, great.

[Spot]

After all the reading, I simply felt that the W/C scene is so much alive again.

[bigben2k]

Mixing metals is ok, in a dry environment. Actually, a lot of the newer HSF combine copper and Alu, which is ok. The only water contacting them, is ambient humidity, but your pc will have found the bottom of the recycle pile before any significant corrosion hits it.

[BGP Spook]

Originally Posted by Spot

After all the reading, I simply felt that the W/C scene is so much alive again.

Unfortunately, that is only because of the predominance of ignorance.

I have just about given up on explaining to the world how this stuff works.

[bobkoure]

Originally Posted by ibmkg

I understand that tests might be rigged. The only way anyone can satisfy me is to perform extensive, variable, idealistic and practical tests..

The issue is not that the tests are rigged, but that they are testing using automotive conditions (to generalize: very hot coolant, very cold air, very strong water pump (and high flow) and very strong blower (high pressure and high airflow).
PC cooling is the obverse of all these situations (generalizing again: not very hot coolant, not very cold air, not very strong pump, fairly weak axial fan (low-medium airflow, low pressure))
So... about all you can apply from these certified tests is, well, it didn't leak.

As a side issue, it wouldn't surprise me if koolance is right about all-aluminum radiators. However, it is their sales material and I can't help but wonder if the higher thermal resistance of copper-brass-copper is offset by better conductivity water->copper and along the copper fins themselves (so creating a larger effective heat transfer area).
IMHO, this is exactly the kind of thing that might work one way under automotive conditions and another way under PC cooling conditions.

[Cathar]

Originally Posted by bobkoure

IMHO, this is exactly the kind of thing that might work one way under automotive conditions and another way under PC cooling conditions.

You've pretty much hit the nail on the head here.

The brass tube -> solder join -> copper fin, interface becomes more of an issue at very high air-flow speeds, such as those experienced in vehicles travelling at 60-80mph. At PC cooling air-speeds, where the low speed of the air-flow is by far the predominant factor in the thermal performance of the radiator, the impact of the tub->fin interaction is immensely reduced. Given common characteristics and materials used, in typical PC fan power applications, I calculated that at worst it accounts around 1% of the total thermal resistance of the radiator. Using 200cfm fans, maybe around 3%. As fan speed/air-flow increases, the problem gets bigger. For PC's, >100cfm 12cm fans are pretty much intolerable.

As for Koolance's marketing. After factoring in all of their stated test parameters, it turns out that for various data points in their results, for that to occur, the average radiator discharge air-temperature would need to be 15-20C hotter than the water intake temperature. Further, none of their liquid pressure drops at 5lpm even remotely co-incide with values independently established by testers. We're talking 10x liquid pressure drops to what has been established. Air-flow pressure drops are also dramatically different to what would be expected. It's as if there are major systemic errors in their testbed that somehow are variable from test to test. The more cynical person would go so far as to suggest that the either the competitor testbeds were deliberately sabotaged, or the Koolance radiator specific tests were run with a MUCH higher air-flow than stated.

[bobkoure]

Originally Posted by Cathar

...the average radiator discharge air-temperature would need to be 15-20C hotter than the water intake temperature...

So they've somehow repealed the second law? Time to hook it up to a cold fusion reactor and power the planet