2 Replies Latest reply on Dec 21, 2011 2:46 PM by david shinn

    Changing flow trajectory units

    david shinn

      I am trying to model an adapter roof curb for HVAC systems that usually are presented with spec sheets in USA units (more specifically CFM). However, when a flow trajectory plot is generated only SI units are available. Is it possible to change this to CFM? I know you can add a parameter from the engineering database, but it seems that only pre-defined or user defined will work which requires a formula for the specific variable.

       

      Also, is the flow simulation advanced enough to account for basic fluid situations and equations?  As in my case, I have a confined structure with an inlet and outlet duct however there are many possible situations that could introduce transition walls from inlet to outlet. I guess my question is, can I simply define an equation goal for the pressure drop as P1-P2?

       

      thanks

        • Re: Changing flow trajectory units
          Rich Bayless

          Hello,

           

          From the top menu bar, select 'Flow Simulation', 'Units', then select 'Load', and 'FPS'.  This will change your project's units system from SI to FPS.  Then you can select CFM.

           

          I'm not sure what you are asking in your second paragraph.  If you are talking about setting a boundary condition for a lid that is connected to atmospheric pressure, then Flow will calculate whether the flow is exiting the lid or entering from the lid.  Post a simplified model and then ask again.

           

          Rich.

            • Re: Changing flow trajectory units
              david shinn

              thanks for the advice on changing the units. i see that the units change but when i try to add a parameter i dont see flow rate in the table that pops up as shown in one of my attachments. I actually tried making my own parameter in the engineering database by using x and y coordinates as an area and the velocity, but it was giving me a negative CFM at the inlet.

               

              also why is it that the outlet volume flow rate negative? I tried to account for the negative in my equation goal by adding the inlet and outlet volume flow rates to get a change in volume flow rate (which is my overall goal to determine), but they still add the two volume flow rates no matter. Its not that big of a deal because i still can determine to difference between the two, it would just be nice if it was presented by flow works.

               

              The last part of my original post, can be viewed in the other attachments. One is showing a flow simulation from inlet to outlet, so my question is do i need to do any other flow analysis at the points of contact where the flow is diverted to the outlet? The other word documents show a a nasty transition. The first pic shows an steep transition and the second is a top view where the inlet air flows all around the middle section and is sucked up at the outlet opening. so the same question is applied to this situation in terms of extra analysis.

               

               

              thanks