2 Replies Latest reply on Dec 5, 2013 10:48 PM by Jared Conway

    Internal Fan Simulation

    Travis Rowell


      I am having some trouble modeling an internal fan simulation. I am simulating 4 fans running inside of a box. The fans are 38X38X25mm and run at 23CFM no load. The fans are placed in parallel inside the clube close to the front opening. I have an opening at both the front and the back of the cube where I have set the boundary conditions to ambient pressure (14.7psi). Inside of the cube I set up a internal fan condition for each of the 4 fans. I entered the fan profile from the manufacturer spec sheet. I then set a goal at the surfaces of the fan inlets and exists to determine the static pressure at the fan. I used 1 of these static pressure goals for convergence. After running my simulation I am finding that the pressure throughout my cube remains at ambient. All of my static pressure goals also display the ambiet pressure of 14.7psi. I am getting no pressure drop or rise anywhere in my model. This does not seem right to me. It is my belief that the fans should be causing a pressure differential. When I look at the flow of air, I see that the air does flow from the front of the cube to the back of the cube at a rate of 2m/s. Is there anyone out there who might be able to explain to me what is going on? I am unable to upload my model for NDA reasons. 


      Thank you

        • Re: Internal Fan Simulation
          Bill McEachern

          Sounds exactly as it should be. Trying using Pa which have 5 significant figures. You will never see the variations at one decimal in lbf/sq.in. The mass or volume flow rates on the fans might be more enlightening.

          • Re: Internal Fan Simulation
            Jared Conway

            Does the fan create the pressure or does the pressure drive the fan? They are linked! And you can prove it to yourself. Put a fan in a huge enclosure. You will have zero pressure difference and the fan will go at full speed. Now put a plate in front and back close to the fan. Run it, the fan will barely be able to push any flow.


            Both of bills suggestions are good ones.


            I would recommend setting up a non nda assy that you can post. It will help you isolate if your problem is file or setup specific.


            If you're looking for someone to evaluate it, we can help. Email me at jared@hawkridgesys.com