Hi Stuart, mass flow rate is an integral parameter so it needs a face of some sort to be read off. Based on your description it seems like you've got to that point. But what it sounds like you will want to do is use component control to disable that component before you run your simulation so that it doesn't affect your analysis. Flow will pass right through it but you'll be able to use the volume to measure things within it or you can use the face to read things like mass flow or volume flow rate.
The trick is though, this has to happen before you run the analysis. If you add it after the fact, it isn't part of the mesh and flow simulation can't read things off of it. There are a few enhancement requests along this line in the SWX kb but that's how it is right now.
If the analysis takes a long time to run, your closest bet would be to create a cut plot of velocity, map out manually some areas within the channel..etc that you'r interested in, find an average velocity in that area and then convert to volume flow rate and then do the same for density to get density. it won't be exact but can work in a pinch if you forgot to add the componet for reading before you run the analysis.
side note, one of the things we teach in our mentoring service is to set these up as goals. that way the value is locked in and easy to export by just looking at your goal plot.
Thanks for the info, I figured it was along those lines but just couldn't get the simulation to work when adding in a part with a face where I needed the readings, I thought I had disabled it in component control already but It's worth double checking. And yes, the simulation does take a little time (Currently at 3+ hours) and I need to run several variations and gather the same readings from all of them.
I already have the inlet and outlet as mass flow goals so I know what the system does, I just needed readings in specific areas within the model, sounds like i need to add in a few more parts...