Data center noise from axial cooling fans was the source of complaints from the local community. The cause of the noise complaints was a series of low-frequency blade pass tones at around 80Hz and harmonics that traveled a substantial distance from the site.
Conventional silencing was not a practical option as the silencers would either have to be very long (at least 2 wavelengths at 80Hz which is around 8m in length - and installed at a height...) or, a shorter but still very large silencer, with very high backpressure that would have compromised cooling and increased running costs.
Our alternative approach was to work with their engineers and use Computational Fluid Dynamics (CFD) modeling to develop a set of aerodynamic modifications that would not only reduce the tonal noise but, at the same time, improve fan efficiency. The results were spectacular...
97.5% fan noise reduction and up to 22.7% reduced power consumption
- 16dB reduction in the blade pass tone (97.5%)
- 18.2% to 22.7% reduction in fan power consumption at the same duty point (lower speed - see noise signature plot)
- delta p air pressure generated by the fan increased by x2.2 to x2.9 compared with an unmodified fan
This project demonstrates just how effective this aerodynamic approach to data center fan noise reduction can be. Conventionally, fan silencing almost always means significantly reduced system efficiency. In cases like this, the aerodynamic modifications would be worth implementing for the efficiency gains alone, even if there was no noise problem.
Self-financing noise control is no longer an oxymoron...
