Industrial Noise & Vibration Centre

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VFD drive cooling system noise control - quieter, more efficient

VFD fan noise CFD model

Variable Frequency (VFD) drive cooling fan noise is often the major source from these systems. Reducing this element of the noise is a non-trivial project given the space limitations and the fact that cooling efficiency must not be affected.

Reviewing the noise attenuation options for their product range led a major VFD drive manufacturer to approach us to help them to design noise attenuation modifications for the cooling system based on our aerodynamic technology. They could then use the technology across the entire product range.

The whole project was carried out remotely via internet, saving time, money and carbon.

How to reduce VFD drive noise - the cooling fan

VFD fan modification noise reduction signatures

The low-noise product design process is outlined below.

  • Provide a detailed set of baseline measurements and procedures
  • Create a Computation Fluid Dynamics (CFD) model of the fan
  • Design the aerodynamic modifications
  • Test the results and copy the design across the product range

VFD noise reduction - the result...

VFD cooling fan noise reduction cfd model

Our final low-cost design modifications cut the annoying fan tone by 99.5% (23dB) and the overall noise by 50% whilst simultaneously increasing the airflow by 3%, ready to be copied across the entire product range.

The key to the successful noise attenuation was to combine aerodynamic expertise with CFD modeling in order to optimise fan efficiency whilst, at the same time, eliminating the annoying fan blade pass tone.

The top figure shows the velocity output from the CFD model for the standard fan. 3 iterations of design and simple testing resulted in modifications to alter the flow through the fan as illustrated in the second picture that reduced the blade pass tone by 23dB in parallel with increased airflow.

VFD cooling fan noise reduction low noise cfd model

Fan noise reduction in product design

This approach is ideally suited to improve the noise profiles of products that include fans. Our aerodynamic fan noise control technology often makes it possible to cut noise at little or no increased product cost and with increased fan efficiency - neither of which applies to conventional silencers. Our current record holder is a dust control fan noise reduction project: 17dB tonal noise attenuation with over 20% improved performance...