For radiator testing, the best way to conduct the tests is to apply a heat load, just like your CPU, GPU(s) and other components you can put a block on and add to your loop. In order to supply the heat load for testing, I use modified aquarium heaters. Aquarium heaters are available in a variety of different wattages, lucky for us wattage is exactly what we are looking for in heat dissipation results. However, the tricky part with aquarium heaters is circumventing the safety mechanism that shuts off the heater when the set temperature is reached. Modifying the aquarium heater allows for a constant heat load to be applied to the loop rather than heating the water to a given temperature and shutting off.
Measurements and calculations, what exactly are we going for here? One of the best means to determine the capabilities of a radiator is C/W, Martin turned me on to this in one of his early tests. Ultimately, C/W is a calculation of Water Out temperature minus the Air Temperature being pulled or pushed through the radiator divided by the heat load (wattage). This calculation gives you the delta in degrees of the radiator leaving water for each watt of heat applied to the radiator. Confused yet? An easier way to think of C/W is the temperature of the water over ambient temperature for each watt of heat in your loop. Now that we have this equation and results, we can specify a set delta and figure out what heat load the radiator can dissipate at that specified delta. In short, this helps answer the question, can this radiator handle a CPU and GPU and get me decent temps. A bit more on C/W, this time in relation to Fan RPM. On several charts later in the test report you will see Fan RPM charted with C/W. This is to show the effect on radiator performance in using different speed fans, some radiators perform very well using low speed/CFM fans and get better the more cfm you push/pull through the radiator. Where some radiators perform sub-par with low speed/cfm fans and require high speed/CFM fans to effectively dissipate heat from your loop. Yes this has a lot to do with how the radiator was design, but I feel it is an important piece of data to show as a misconception I had early on in the start of my liquid cooling addiction was low speed/CFM fans could not be used on radiators optimized for high speed/CFM fans. I was quickly shown how wrong my thinking was.
Besides the typical Fan RPM, air temps and water temp measurements you will see Air Capacity Used listed in the data table.
Test Note: Maintaining a constant wattage for each test is nearly impossible even with a AC Transformer (Variac). You will see slight wattage variations amongst the test results.
A total of 6 tests per round were completed with a total of 2 rounds (1 set wattage per round), each one of the tests used a different Fan RPM to represent different fan scenarios. This gives a best coverage of uses of the radiator out in the wild, not everyone will want to use the same fans or run their fans at a specific RPM, so I tried to cover 6 different RPM settings. Each test consisted of a 30 minute warm-up period with the heat load applied to the loop and a 60 minute logged test run. The heat load was applied by adding the modified aquarium heater in a custom built half-gallon reservoir. Below is list of all of the tools
One major change from the initial Radiator tests to now is the move from Water Out only for calculating Delta and C/W. We used to just use water outlet averaged temperature in the calculation, but now we are using the loop water average in the calculation. This change was brought on by a brave fact finding mission by Martinm210. I have mixed feelings about the use of loop average versus water out, but this method does result in more accurate C/W. All radiator tests have been updated to use the water average calculations.
Strap in, time to view the thermals results…