I am trying to study heat transfer on this model. Air is flowing inside the device while it will get heated up by flue gas flowing outside the tubes. Now for the flue gas region, I want to create a domain in the pipe section only and excluding the top diffuser and bottom box. I tried doing so by enclosure by I am unable to locate the end coordinates of the pipe section so that I can give the same dimensions to my enclosure.
Can anyone suggest me how to proceed with that?