1 Reply Latest reply on Sep 11, 2015 3:44 PM by Amit Katz

    Multiple Fans in Electronics Box causes Unrealistic Results

    Austin Lines

      I have an electronics box where I have five external inlet fans blowing into the box at different angles (internal study). I've found that when I run the study, one or two fans overpower all the other fans, causing them not to function because the "mass flow out of fan curve's range". Also, the pressure produced in the box gets up to 19 psi with a small, 53.4mm diameter NMB DC axial fan. The opening to environmental pressure is very large, so this does not seem realistic. I've checked all the fan curves and made sure the units and numbers are correct.

       

      Also, I've cloned the study and replaced all the fan inputs to volume flow rate inputs to match where I would expect the fans to be on their curves. The results from this study seem very realistic and the pressure rise in the box is less than .01 psi.

       

      Please let me know if you've run into this before and let me know what you did to fix it.

       

      Thanks.

        • Re: Multiple Fans in Electronics Box causes Unrealistic Results
          Amit Katz

          Austin,

          Maybe you should check your fan curves just one more time, because when I look at them I see this:

           

          Capture.PNG

           

          And this is waaaaaaay off the manufacturer's specs (which I looked up thanks to your highly detailed Engineering Database notes.) I changed the fan curves in the model (and I changed the fan lids to simple discs, you don't need to model the core), and the results look better. I got about 80 CFM per fan from the top three, and almost no flow from the bottom two. This makes sense to me because those fans are extremely weak, they stall out at 73 Pa of pressure which is almost nothing, I don't think those are the right fans for the job.