[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]