backpressure issue
 

HI,there!
I got a case which is to calculate the back pressure of an exhaust system, and it's perfectly converged ,but i was a little bit confused when it comes to post processing as the followings:
In the surface integrals of the report:
area-weighted average
total pressure Pa
inlet 52716.32
outlet 1773.2864
net 24235.805
problem is the net doesn't equal inlet minus outlet.why?

Because "net" means the area-weighted average of both faces and not its difference.

cheers