A New Way of Testing Fan Airflow

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PRELIMINARY RESULTS

To verify that the new airflow test box could produce useful results, we tested a handful of fans that have already been measured the previous way. The results are summarized in the table below. You'll notice the airflow is reported in LFM (Linear Feet per Minute) instead of the usual CFM (Cubic Feet per Minute) unit we've used in the past. The reason for this will come later.

Airflow Measurements Compared: LFM of 120mm Fans
Fan
Method
12V
9V
7V
5V
Arctic Fan 12L
old
350
270
200
120
new
390
300
230
140
Antec TriCool
old
770
610
470
320
new
810
650
530
370
Nexus 120
old
480
360
270
160
new
470
370
300
210
Noctua NS-S12-1200
old
650
530
430
310
new
590
480
390
280
Scythe S-Flex SFF21E
old
550
390
280
140
new
600
430
310
170
SilenX IXP-74-11
old
580
470
420
330
new
510
420
360
270

The exceptional fans, the ones that produced suspect measurements before, now produced results more in line with our expectations. The results for the Noctua and SilenX fans — both of which previously measured unaccountably high — dropped down closer to what we would expect. And the results for the reverse-direction Arctic Fan 12L rose slightly, though it still seemed to blow less air at a given speed than the more conventional fans we tested. The Antec Tricool and Scythe fans also measured higher. The Nexus measurements were closest to each other, but the new method showed greater airflow at low speed.

The graphs of the data may be easier to understand. The two sets of measurements for each fan is in similar colors to make them easier to see and to compare. Note how most of them run parallel to each other.

All in all we were quite pleased with the result. This airflow measurement method seemed to produce more reliable results, and it also simplified testing. We could now dial in a specific voltage with any fan, and quickly obtain an airflow measurement consistent within 10~20 LFM. Quick, consistent results were very difficult to obtain with our old manual technique.

We also tested a few 92mm and 80mm fans to see how they were affected. Here, we found bigger differences between the old measurements and the new ones. The measured airflow of virtually every fan we tested dropped substantially.

Airflow Measurements Compared: LFM of 80mm & 92mm Fans
Fan
Method
12V
9V
7V
5V
Nexus 92
old
490
390
300
190
new
410
320
250
150
Fander FX92-W
old
810
640
480
340
new
580
460
360
250
Nexus 80
old
550
370
250
120
new
390
280
180
100
Scythe SA0825FDB12SL
old
630
440
300
140
new
420
310
200
100
Arctic Fan 3
old
320
260
170
90
new
410
320
260
160

The graph below illustrates it more dramatically. This time, the pair of curves for each fan is the same color. Note how much wider the gap is between the two lines for most of the fans, compared to the 120mm fans above. The greater difference at 12V is more marked as well.



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