9 Replies Latest reply on Jun 5, 2014 6:54 PM by Jared Conway

    External Flow - How to force a flow

    Nuno Moita

      Hi again,

       

      Hope that the question I am asking could help a lot of users too. I am thankfull with the help that could come.

       

      I have modeled a kind of house to simulate the heat transfer from a heat source that will  arrive to the house in pipes. In the pipes there should be an internal fan, but.. instead of that I would like to know if it is possible to force and inlet of a volume rate instead of defining a fan curve. In a simple way:

       

      - Image a straight tube using external flow.

       

      In the midle of this tube is possible to impose a fixed volume flow rate ? My desire is to see the chart of the effect when inflanting and dischaging freely.

      (I want to see the air going from one side of the tube to the other without any lid stoping the fluid to go.)

       

      Best Regards,

       

      Nuno

        • Re: External Flow - How to force a flow
          Jared Conway

          hi

          can you post a picture of what you're talking about

          it is not very easy to visualize

          it sounds like you should just use a volume flow rate

            • Re: External Flow - How to force a flow
              Nuno Moita

              Hi Jared,

               

              Thank you very much for your quick support.

               

              Imagine the following situation, simplified of course of what I have.

               

              Capture.JPG

              In this tube, using external flow simulation using heat condution and radiation, I should have in the position "2", a internal fan, Although, to simplify my model and I do know which volume flow rate I do need. I want to force in "2" a flow simulation and to check how the fluid enters in the section "1" and flow through the tube and how it will be discharged in the section "3". I do have a kind of ballon attached to the section "1" made of glass that is absorbing heat from solar radiation. I want to see in the section "3" not only the chart of velocity and its dispertion but also the temperature.

               

              I hope that this helps to understand what I do need.

               

              Thank you very much.

               

              Regards,

               

              Nuno

                • Re: External Flow - How to force a flow
                  Jared Conway

                  why wouldn't you use an internal fan if that is what is generating the flow? this is the only way to link sections A (left of 2) and B (right of2)

                    • Re: External Flow - How to force a flow
                      Nuno Moita

                      Hi Jared,

                       

                      The reason is because the internal fan needs to define a curve - flow rate vs pressure. And I do want just to set a flow rate not a curve. Beeing the only way.. I will try to figure out if it passes the heat too.

                       

                      Thank you very much!

                       

                      Regards,

                       

                      Nuno

                        • Re: External Flow - How to force a flow
                          Jared Conway

                          what is the physical application at location 2?

                            • Re: External Flow - How to force a flow
                              Nuno Moita

                              It is an internal fan, but I do wanted to force it to have the flow of 300 m^3/h without depend on the pressure and let SW Flow Simulation make iterative calculation.

                               

                              On the real system that I am trying to do, I have a source of heat that flows throught a pipe to an greenhouse so temperature should rise up in the greenhouse . And I did not want to set the internal fan but a flow instead. The heat should flow through the pipe to the greenhouse.

                               

                              best regards,

                               

                              Nuno

                                • Re: External Flow - How to force a flow
                                  Jared Conway

                                  How does the fan flow at that speed and not dependent on the pressure drop?

                                   

                                  Does the fan add the heat or is it just circulating the heat from somewhere?

                                   

                                  Maybe draw the whole system diagram to come up with a better way to do this.

                                   

                                  Why does the flow have to come from the fan face and why does it have to start on the left side and pass trough if you only care about what happens on the right?

                                    • Re: External Flow - How to force a flow
                                      Nuno Moita

                                      The fan should bring air from a compartment that is being heated by the sun to another compartment.

                                       

                                      I do not have detail, right now, about the fan, so , I wanted to impose a volume flow rate to check if, for eg. 300m3/h, was sufficient to deal with my system. If not, another iteration using another volume flow rate. That was my point and to not use lids. Probably, as you did told, just possible with the fan.

                                       

                                      Have tried to put a lid to have a surface, set a boundary condition and on the component control supress that, but did not work (as expected).

                                       

                                      Thank you very much for your help anyway.

                                       

                                      Best regards,

                                       

                                      Nuno

                                        • Re: External Flow - How to force a flow
                                          Jared Conway

                                          remember that the system hsa to have an inlet and outlet

                                           

                                          so in this case if you want to remove the fan, you could put a lid where it should be, on the right hand side, put the flow rate at the temperature you think it is at

                                          on the left hand side, put a volume flow rate out

                                          just make sure on the left and right it has somewhere for the fluid to come in and out respectively with pressure openings