Hi Forum,

I have done some initial tests to establish inlet conditions for a CFD analysis. The objective is to predict electronic and optics cooling. However when I perform velocity measurements at the outlet of the fan house, about 1/4 of fan outlet area have 'negative velocities' - which appears to be a constant recirculation. My question to the forum is (if anybody have worked with radial blowers for similar applications), does this kind of behaviour arise from a bad design or is this to be expected of any radial blower fan.

I am willing to disclose the measurements and give further details, if anyone wants to discuss this further.

My guess would be that if you are at 'design' flow then there is room for improvement in the housing. Otherwise, I would expect it to be somewhat typical depending on the geometry, etc. Areas of interest definitely being the wheel, cutoff, and the housing...

Hi Erich,

Thanks for your quick response. I am running the fan at the design point, so I will try to get some samples from other manufacturer to compare the measurements and pick the best solution.

Your comments are really appreciated.

I think it is standard for radial fans that there exist a region with reversed flow. I once had to look at the flow distribution in a duct system where the flow was from a radial fan. In the data from the fan there was a sketch of the flow distribution out of the fan where a recirculation zone was clearly seen. I did try to get some measurement, but either they were not available or I could not get them. But I was told that they would expect 1/3 or the section to be reversed flow and in the region with maximum velocity, would the peak velocity be around 2*mean. Have you looked into the housing is there niót an obstruction in the region with reversed flow? I do not know if this helps, but your results sounds familiar