Here's a collection of the most frequently asked cooling related questions we get.
- What does șC/W mean, and why is it of such great importance when talking about coolers?
- What is a TEC?
- Couldn't I just buy a TEC, and use it with my standard cooler?
- What does the Pmax value of a TEC mean?
- What happens if the power dissipation of my CPU exceeds the Pmax value?
- How about cascading TEC's?
- Why do you use copper for you heat sinks instead of aluminum like the rest of the manufacturers?
- Will the CoolWhip Air Slot1 fit on the AMD Athlon line of processors?
- Why do you list all the temperatures in șC, and how do I convert from Celcius to Fahrenheit?
What does șC/W mean, and why is it of such great importance when talking about coolers?
Cooler efficiency is measured in șC/Watt.
This means that the temperature of the heat sink rises above room temperature by
the amount of heat (Watt) you put into the heat sink x șC/Watt. Confused? Well,
let's use an example:
25W (app. the same as a Celeron 500MHz at 100% CPU utilization) put into a cooler with an efficiency of 0,8șC/W, gives a temperature increase of 20șC above the surrounding temperature, and with a case temperature of nearly 30șC (an average, bad ventilated case temperature), that results in a CPU temperature of no less than 50șC!
Now that's just about the average CPU temp. you obtain from an typical CPU cooler, so now we know that the typical cooler has an efficiency of around 0,7 to 0,8 șC/W.
If instead we had used a cooler with an
efficiency of 0,28șC/W, the temperature increase would have been only 6șC, and
the resulting CPU temperature would then be 36șC!
For comparison, our CoolWhip Air Slot1 cooler has an efficiency of 0,28șC/W, and our CoolWhip Liquid 120/x has an efficiency of just 0,04șC/W!!!
What is a TEC?
A TEC (also known as a Peltier) is a small ceramic plate, which works as a heat pump when current is applied to it's wires. Therefore, one side of the TEC get very cold, while the other side gets very hot (if not properly cooled). The downside to TEC's, is that even though they pump heat from one side to the other, they produce a lot of heat themselves. Therefore, you have to pair them with a high-efficiency heat sink or a water cooler, to make sure they won't get overheated.
Couldn't I just buy a TEC, and use it with my standard cooler?
To illustrate the effect of a TEC for
cooling down CPU's, let's take a look at what happens if we take a 59W TEC and
use it with a standard (0,8șC/W) heat sink, to cool our Celeron 500 CPU.
A 59W TEC uses about 50W when running at 12V, and that's about the consumption that's needed to maintain a temperature difference of app. 25ș between the hot and the cold side of the TEC, with the 25W load from the CPU. If we use a smaller (less powerful) TEC on our 25W CPU, the difference temperature decreases, and with a bigger (more powerful) TEC on the CPU, the temperature difference increases.
All in all we are putting 75W (25W from the CPU, and 50W from the TEC) of heat into our cooler. Let's calculate: 75W x 0,8șC/W = 60șC above the case temperature, and with a case temperature of 30șC, the heat sink temperature is up at a steaming 90șC!!! (ouch!) Now, even though we detracts the 25șC (difference temperature over the TEC), we still get a CPU temp. of no less than 65șC! That's even worse than with no TEC at all, so the conclusion must be, not to use a TEC if the cooler isn't powerful enough to handle the extra heat generation.
Let's take the CoolWhip Air Slot1 cooler instead. We still send 75W into the cooler, but the higher efficiency of 0,28șC/W gives a very different result. The heat sink temperature will then be 49șC (30șC + 75W x 0,26șC/W), and the temp. difference over the TEC is still 25șC, so we now get a CPU temp. of only 24șC. IT WORKS!
Now, if we were to improve the case ventilation a bit by adding another fan, we could probably maintain a heat sink temperature of 44șC, and the CPU temp. would now be 19șC!
Ok. But what if we used the CoolWhip Liquid with an efficiency of 0,04șC/W?
The result would then be: 25șC + (50+25) x 0,04șC/W - 25 = 3șC
Impressed? Well, let's see what the result
will be with 2x80W TEC (produces app. 60W of heat each), which gives a temp.
difference of app. 50șC with a 25W CPU.
25șC + (2 x 60W + 25W) x 0,04șC/W - 50șC = -19,2șC
This is the configuration of our most powerful water cooler...
The CoolWhip Liquid 120/160
If the temperature should be -19,2șC, why do you write only -5șC in the description of the CoolWhip Liquid 120/160?
The formula lacks some parameters like the thermal resistance in the cool plate,
the loss between the different layers of the setup, the energy transport through
the insulation around the CPU and cool plate...
If you calculate app. 25-30% performance loss, you are probably closer to the truth.
So the calculations for the CoolWhip Liquid 120/160 will then be:
25șC + (2 x 60W + 25W) x 0,04șC/W - (50șC - 25%) = -6,7șC
This result is also pretty consistent with the actual temperature readings we have performed on the coolers, so use the 25-30% performance loss, as a rule of thumb.
What does the Pmax value of a TEC mean?
Unlike what many people think, the Pmax value is not an indication of the max. electrical power consumed by the Peltier, however it is the max. heat power dissipation it can transport through the element while still maintaining a temperature difference of 0șC across the element.
What happens if the power dissipation of my CPU exceeds the Pmax value?
Well then you get a thermal run-away condition, causing the temperature to constantly rise and rise, at a speed determined by the amount of excessive power. Therefore, be sure that you know what you are doing, and test your setup with thermometer monitoring to insure that you have reached a stable temperature.
How about cascading TEC's?
The same story as above. Make sure never to load the last stage with more than its Pmax value, and remember to include both the power of the CPU and the first stage TEC power consumption when you calculate the configuration of the second stage. Typically it is a much better idea to cool from both sides with a much smaller Peltier from the rear where ever possible. The CoolWhip series also offers rear water Coolers for that purpose.
Why do you use copper for you heat sinks instead of aluminum like the rest of the manufacturers?
The reason we chose copper for the base plates in our CoolWhip Air series, and for the cooling head in our
CoolWhip Liquid series, is that copper is a much better heat conductor (nearly
twice as good) as aluminum, and therefore a much better material for
heat away from your CPU.
We also use copper for the cool plates in our TEC based coolers for the same reason.
Aluminum has it advantages though. It provides better radiation abilities than copper, and that's the reason we make the complex folded thin fins on our coolers in aluminum.
Will the CoolWhip Air Slot1 fit on the AMD Athlon line of processors?
Unfortunately our current heat sinks does NOT come with
the holes needed for Athlon mounting.
If you're a bit of a handyman, you can easily make the holes yourself.
Our next batch of heat sinks from the plant, will be predrilled for Athlon mounting, so if you are uncomfortable with drilling the holes yourself you will have to wait a few weeks.
Why do you list all the temperatures in șC, and how do I convert from Celsius to Fahrenheit?
Since CoolWhip resides in Denmark, and most foreign countries also use Celsius for measuring temperatures, we have chosen to list all temperature in Celsius.
The calculations for converting Celsius to Fahrenheit is a bit complicated, so we have provided you with a small conversion program below you can use instead.
More to come...