Testing Methodology

Although the testing of a cooler appears to be a simple task, that could not be much further from the truth. Proper thermal testing cannot be performed with a cooler mounted on a single chip, for multiple reasons. Some of these reasons include the instability of the thermal load and the inability to fully control and or monitor it, as well as the inaccuracy of the chip-integrated sensors. It is also impossible to compare results taken on different chips, let alone entirely different systems, which is a great problem when testing computer coolers, as the hardware changes every several months. Finally, testing a cooler on a typical system prevents the tester from assessing the most vital characteristic of a cooler, its absolute thermal resistance.

The absolute thermal resistance defines the absolute performance of a heatsink by indicating the temperature rise per unit of power, in our case in degrees Celsius per Watt (°C/W). In layman's terms, if the thermal resistance of a heatsink is known, the user can assess the highest possible temperature rise of a chip over ambient by simply multiplying the maximum thermal design power (TDP) rating of the chip with it. Extracting the absolute thermal resistance of a cooler however is no simple task, as the load has to be perfectly even, steady and variable, as the thermal resistance also varies depending on the magnitude of the thermal load. Therefore, even if it would be possible to assess the thermal resistance of a cooler while it is mounted on a working chip, it would not suffice, as a large change of the thermal load can yield much different results.

Appropriate thermal testing requires the creation of a proper testing station and the use of laboratory-grade equipment. Therefore, we created a thermal testing platform with a fully controllable thermal energy source that may be used to test any kind of cooler, regardless of its design and or compatibility. The thermal cartridge inside the core of our testing station can have its power adjusted between 60 W and 340 W, in 2 W increments (and it never throttles). Furthermore, monitoring and logging of the testing process via software minimizes the possibility of human errors during testing. A multifunction data acquisition module (DAQ) is responsible for the automatic or the manual control of the testing equipment, the acquisition of the ambient and the in-core temperatures via PT100 sensors, the logging of the test results and the mathematical extraction of performance figures.

Finally, as noise measurements are a bit tricky, their measurement is being performed manually. Fans can have significant variations in speed from their rated values, thus their actual speed during the thermal testing is being recorded via a laser tachometer. The fans (and pumps, when applicable) are being powered via an adjustable, fanless desktop DC power supply and noise measurements are being taken 1 meter away from the cooler, in a straight line ahead from its fan engine. At this point we should also note that the Decibel scale is logarithmic, which means that roughly every 3 dB(A) the sound pressure doubles. Therefore, the difference of sound pressure between 30 dB(A) and 60 dB(A) is not "twice as much" but nearly a thousand times greater. The table below should help you cross-reference our test results with real-life situations.

The noise floor of our recording equipment is 30.2-30.4 dB(A), which represents a medium-sized room without any active noise sources. All of our acoustic testing takes place during night hours, minimizing the possibility of external disruptions.

<35dB(A) Virtually inaudible
35-38dB(A) Very quiet (whisper-slight humming)
38-40dB(A) Quiet (relatively comfortable - humming)
40-44dB(A) Normal (humming noise, above comfortable for a large % of users)
44-47dB(A)* Loud* (strong aerodynamic noise)
47-50dB(A) Very loud (strong whining noise)
50-54dB(A) Extremely loud (painfully distracting for the vast majority of users)
>54dB(A) Intolerable for home/office use, special applications only.

*noise levels above this are not suggested for daily use

The Corsair H150i Elite Capellix Liquid Cooler & iCUE Software Testing Results
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  • 29a - Friday, October 16, 2020 - link

    It has to do with the price of copper vs aluminum. Reply
  • Slash3 - Friday, October 16, 2020 - link

    Alphacool and Be Quiet offer full copper block/rad AIOs. Reply
  • Quantumz0d - Thursday, October 15, 2020 - link

    I think GN's test shows AiOs being somewhat superior. But as for the Air cooling vs AiO, I will always choose Air coolers. Noctua is top quality and the best part is you get a superb looking beast machine, vs the RGB vomit and cabling issues, and the most important aspect being the lifetime. AiOs always no matter what the coolant will be losing it's efficiency overtime also the particulates in the mixture. Any small leak in any time = death of the data + hard cash. No risks no half measures, only full measures = Air cooling.

    My build for a long term plan of a PC (usually they can last more than 10 years), will be Noctua Chromax black and red, with no RGB G.Skill B-Die, maybe the mobo / GPU gets a little lighting to make it look even intense of the coloring to match the Chromax.
    Reply
  • StevoLincolnite - Thursday, October 15, 2020 - link

    My current PC is 11 years old and uses a Corsair Hydro AIO water cooler.
    No issues.
    Reply
  • TelstarTOS - Thursday, October 15, 2020 - link

    The usual strategy, performance at price of high noise. Reply
  • Manch - Thursday, October 15, 2020 - link

    Short of making the radiator bigger, would adding a reservoir help cooling at this point? Reply
  • Everett F Sargent - Thursday, October 15, 2020 - link

    Yes, of course. As long as the reservoir is big enough. Ideally you want the coolant to return to its initial ambient temperature. The major problem with all liquid cooling solutions is an inherent inability to return the coolant back to its original ambient temperature. All you have to do is try to touch the radiator or use an IR digital thermometer.

    The equation is as simple as Q=VA (Q is the flow rate in liters per second) and the coolant volume or total amount of coolant in the loop, VC = liters, so that VC/Q = seconds or mean residence time, the bigger that number the better chance you have of returning the coolant to its original ambient temperature. The goal is to maintain the maximum delta temperature between the coolant and the CPU. Hot (to the touch or via IR thermometry) radiators defeat the entire exercise (or some fraction thereof) to begin with in the 1st place.
    Reply
  • Tomatotech - Friday, October 16, 2020 - link

    You are correct in that coolant volume is a factor, however heat flow rate from the radiator is also a large factor. For the same size radiator, factors affecting heat flow would be: thermal conductivity of the radiator, exposed surface area of the radiator, airflow across the radiator. If any of these are very high then cooling* will be effective even with tiny coolant volume.

    *Reduction of increase in temperature above internal working temperature of CPU. Over time, all radiator systems, even maximally efficient ones, will reach a temperature of at least the internal temperature of the CPU.
    Reply
  • Everett F Sargent - Friday, October 16, 2020 - link

    Yes there are many factors, but I think my basic claim still holds true. Keeping the coolant temperature low is a must, or preferred, all other things being equal. But I think I will do a little more on quantifying those calculations with my new build. Reply
  • Everett F Sargent - Thursday, October 15, 2020 - link

    Go bigger or go home ...
    https://www.performance-pcs.com/water-cooling/aio-...
    Currently out of stock as I got the last one.
    Reply

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