8 Replies Latest reply on Apr 8, 2013 3:16 PM by Shane Atienza

    when modeling fans, does the surface area of the body have to match the fan?

    Shane Atienza

      I have a box or a lid that i chose the back face to be the fan, in an electronics enclosure, internal study. does this part have to match the size of the fan? for example the fan is a 1.5x15." square, if i draw the dummy fan block as a 1x1" square, is it going to matter for simulation?

       

      what about multiple fans? if i chose one inlet fan and click on a couple different bodies, does it treat each of these as one fan or does it disprese the flow of one fan across all three bodies?

        • Re: when modeling fans, does the surface area of the body have to match the fan?
          Jared Conway

          fan shape/size should be close to what they are in "the real" world.

           

          they should be circular and if you're using an axial fan, they should have the hub and external dimensions the same as the definition in the engineering database. use a splitline on your square box to get a circular profile for your fan.

           

          each fan should be defined as separate entities. that goes for other boundary conditions as well even if the software allows you to do it. One thing that trips up customers often is that they choose multiple components and apply a certain heat wattage. they expect it to be heat input x number of components when the software interprets it as a distributed heat based on volume.

            • Re: when modeling fans, does the surface area of the body have to match the fan?
              Shane Atienza

              Hi Jared,

               

              I was not aware of the split line feature, that's really useful. I wonder how much the area of the represented fan affects the performance? i had a scenario where i wanted to try a bigger fan quickly to see what would happen, but in order to change the actual area of my pre existing lid that i used as the face for the fan, i would have had to re work several components dimensions.

               

              I suppose i can do a simulation and see how much the area affects fan's performance.

               

              as far as each fan being defined as sperate entities, is this true with all versions of sw? i have 2013, it lets me chose multiple faces and i was under the impression that those were then modeled as seperate fans.

               

              For the heat sources, in the solidworks flow training book there are examples showing multiple heat sources being chosen under one heat source instance. It seems like here if you apply 2 watts to the resistors in this example, its going to treat each of those as 2 watts, not both equal to 2 watts. Is this what you are referring to?

               

              I think i am just going to start doing seperate instances for every fan and component, to be on the safe side. I am working with components now in a box with fans, that are 90 watt components, i have two of them and have them both under the same heat source.

               

              solidworks flow sim book.jpg

              • Re: when modeling fans, does the surface area of the body have to match the fan?
                Shane Atienza

                Hi Jared,

                 

                you are right about the fans! i re ran the sim, and did each fan seperately, and got way more ideal results. i had three fans, and basically it was like using one fan the way i did it before.

                 

                but now for the heat source. im running that now, hoping you are wrong because i dont want anymore heat in this thing :-P my fans were 1/3rd the power, the results are ideal now but im not sure if they will be with twice the heat.(I have two major heat components).

                 

                what about when you do flow trajectories, and you click multiple faces? does this work or do you have to look at one fan at a time?

                 


                I will make a small example of the fans and post it when i get a chance.

                 

                 

                edit:

                 

                i re ran the sim, and it seems like making the heat sources seperate does act completely different. The way the training book shows this is either wrong or misleading...