4 Replies Latest reply on Jun 17, 2015 2:46 PM by David Yu

    Fan modeling

    David Yu

      I am modeling the effect of 3 HVLS fans on air flows (air velocity, temperature) in a plant facility and I encounter the following questions:

       

      1. When I changed the customized fan specifications and reran the project, the result did not change. I added heat sources to some of the components in the facility but that does not seem to change the result either. But when I change the area of the disks used to represent the fans and then rerun the test, the result change. Would someone help me understand why is that?

       

      2. When I look at the temperature cut plot, the temperature is absolutely uniform. That shouldn't be the case but I don't know where I am doing it wrong.

       

      Thanks for your guys help!

        • Re: Fan modeling
          Shivani Patel

          Can you run the simulation using one of the standard fan curves instead of customized ones? See if you get a temp distribution and velocity and so on. This way we can eliminate any other potential errors. As for the fan curves, what is the pressure drop across the fan? What is the pressure/volume flow rate on the inlet face? What is the corresponding point on the fan curve? It might help if you could attach a couple screen shots of your custom fan data.

           

          I've seen that temperature problem before, and it was because I input the fan curve wrong. The initial point in the calculation is likely for atmospheric pressure, and if you don't have a reasonable datapoint for that pressure, the calculation never gets going. Or watch how the inlet/outlet pressure changes during the first couple steps of the calculation and compare that with the fan curve, you may notice something.

           

          1. It sounds to me like your custom fan has a outer diameter parameter that you've put in. So when you're changing that number in the model, it's scaling the mass/volume flow rate appropriately.

            • Re: Fan modeling
              David Yu

              Hi Shivani thanks for your reply! I have been having problems with the fan curves. The HVLS (High Volume Low Speed) fans that I am trying to simulate are huge (12 ft diameter for my case). I was told by the manufacture of the fans that they don't have fan curves for those huge fans because there is not a standard way of testing fan (standard testing procedure only valid for fans up to diameter of 8 ft diameter?)

               

              The attached pictures are what I put in for the fan that I am using. This is probably where it starts to go wrong.

               

              fan 1.JPGfan 2.JPG

              Do you know if any of the existing fan curves in the database will match the fan profile that I am looking for?

              Thanks for your help!

                • Re: Fan modeling
                  Shivani Patel

                  Okay, your lack of fan curve is definitely the problem. I believe all the fan curves in Flow are for smaller fans. Is there a way for you to find pressure drop when volume flow rate is zero? You could create a linear curve.

                   

                  If you don't find technical specs for a similar fan via Google or the manufacturer... you could try running an analysis with a rotating region (long calculation time) to find another datapoint for volume flow rate vs pressure drop. There is also a way to have inlet flow be swirling. Perhaps this runs faster and you could find another datapoint that way.

                    • Re: Fan modeling
                      David Yu

                      Okay. So I suppressed my fan and added a boundary condition swirl to the inlet of the disk (which represents the fan) and a static pressure boundary condition to the outlet of the fan. Does that sound right? How do I get the data point that you mentioned about though? Thanks!