… and airflow
To write that we have something mapped out to the last detail is perhaps too bold, but after proper preparation, few pieces of hardware are as easy to evaluate as fans. Of course, this had to be preceded by long preparations, developing a methodology, but you already know the story. What you don’t know yet is the first fruit, or rather the results of Akasa, SilentiumPC, SilverStone, Xigmatek or more exotic Reeven fans.
… and airflow
With airflow measurements, we can well explain why the test tunnel is shaped the way it is. It doesn’t consist of two parts just so that the “exhaust” can be conveniently clogged for pressure measurements. The anemometer (i.e. the wind speed measuring instrument) is held together by two parts, two formations, through the flanges.
The front part, at the beginning of which the fan is mounted, becomes steadily narrower and from about two thirds of the way through the cross-section is smaller than that of a 120 mm fan. The reason for this is that the cross-section of the anemometer is always smaller than that of the fans tested. The taper towards the anemometer fan is as smooth as could be chosen and the tunnel walls are smooth. This has minimized the occurrence of unnatural turbulence.
The difference between the cross section at the intake (fan under test) and at the constriction point (anemometer) also means a difference in dynamic pressure, the principles of the Venturi effect apply here. In order to avoid distortion at this level and to ensure that the fan airflow is not different from what it actually is, the Bernoulli equation must be applied to the measured values (for maximum accuracy, the calculation also takes into account the internal cross-sectional area of the anemometer, i.e. its inactive part ). After all this, it is again possible to confront our results with the paper parameters.
We use an Extech AN300 anemometer with a large 100 mm fan for the measurements. Its big advantage over other anemometers is that it is made for bidirectional sensing. This allows tests at different fan orientations. However, the “pull” position is more suitable or accurate for measurements, even though it may not seem so at first glance, but we’ll explain.
Here, we get to the second part of the tunnel, the part behind the anemometer. It is part of the whole device, mainly to allow a laminar flow of air to arrive at the rotor of the anemometer. Otherwise, uncontrolled side whirls would be reflected in the results, which are inconsistent with accurate measurements. Therefore, we will test the flow in the pull position. If anyone would like us to elaborate more on this topic, we can elaborate further at any time in the discussion below the article. Ask away. 🙂
In connection with the anemometer, we will return a little more to the noise measurements and to the setting of modes according to fixed noise levels. It may have occurred to you as you were reading that the anemometer fan is also a source of sound that needs to be filtered out when testing fans. For this reason, we insert a belay pad between the frame and the anemometer fan before each measurement and mode setting according to the fixed noise level.
- Contents
- Cooler Master MasterFan SF120M in detail
- The basis of the methodology, the wind tunnel
- Mounting and vibration measurement
- Initial warm-up and speed recording
- Base 7 equal noise levels…
- .. and sound color (frequency characteristic)
- Static pressure measurement…
- … and airflow
- Everything changes with obstacles
- How we measure power draw and motor power
- Measuring the intensity (and power draw) of lighting
- Results: Speed
- Results: Airlow w/o obstacles
- Results: Airflow through a nylon filter
- Results: Airflow through a plastic filter
- Results: Airflow through a hexagonal grille
- Results: Airflow through a thinner radiator
- Results: Airflow through a thicker radiator
- Results: Static pressure w/o obstacles
- Results: Static pressure through a nylon filter
- Results: Static pressure through a plastic filter
- Results: Static pressure through a hexagonal grille
- Results: Static pressure through a thinner radiator
- Results: Static pressure through a thicker radiator
- Results: Static pressure, efficiency by orientation
- Reality vs. specifications
- Results: Frequency response of sound w/o obstacles
- Results: Frequency response of sound with a dust filter
- Results: Frequency response of sound with a hexagonal grille
- Results: Frequency response of sound with a radiator
- Results: Vibration, in total (3D vector length)
- Results: Vibration, X-axis
- Results: Vibration, Y-axis
- Results: Vibration, Z-axis
- Results: Power draw (and motor power)
- Results: Cooling performance per watt, airflow
- Results: Cooling performance per watt, static pressure
- Airflow per euro
- Static pressure per euro
- Results: Lighting – LED luminance and power draw
- Results: LED to motor power draw ratio
- Evaluation
It looks like the frequency response charts do not show.
Thanks for the heads up, it’s now corrected.
In some of the older articles in English, imperfect processing techniques combined with a lack of focus resulted in incorrect paths to the spectrograms being left in the source code. If you should come across something like that again, the original language version (there are graphs with EN descriptions anyway, you can get to it by clicking the flag in the upper right corner of the page) is always correct. Alternatively, the spectrograms of the individual fans can be accessed by entering the URL according to the format “name-of-the-fan-g***”, where the *** a number from the interval 233 to 244. Of course, this is only a temporary solution until we fix it (after you reporting it). But otherwise it must always work without such complications. 🙂
Thanks, I will keep it in mind if I encounter such an issue in the future and report it so that everyone can have it fixed.
I wanted to see the frequencies because of Noctua NF-A12x25 which has a highly disturbing peak right before 400 Hz. The frequency response of SF120M looks so much better at “33dB” in comparison. That’s why it would be great to have at least 1 sound sample per fan at 33dB, to judge the noise according to personal preference.
This is true, but the reason for this is that the SF120M has an overall “dropped” aerodynamic noise spectrum in this mode due to the higher tonal peaks of the motor and bearings. This is also why it achieves a lower airflow. If the test modes were aligned for equal airflow (i.e., the SF120M would have higher RPM), I expect that the NF-A12x25 might not be noisier even at 380 Hz.