Mass Flow Rate Conservation Problem
Hello,
I simulate the flow of CO2 in a cylinder. After about 500 iterations, using Reports/Fluxes menu, I've got the good value of MassFlow rate (specified with massflowinlet BC) i.e. 0.10 kg/s but I've got 0.10 kg/s at the outlet (defined as outflow BC) ! How can I solve this problem ? Thanks. Philippe. 
Re: Mass Flow Rate Conservation Problem
Maybe I don't understand the problem: you have a cylindrical pipe and 0.10 kg/s of C02 entering it. FLUENT tells you that 0.10 kg/s enter the tube and 0.10 kg/s exit it. Right?
FLUENT considers negative all flows which exit the domain and positive all fluxes entering it. So the value you have at the outlet seems good. Hi. 
Re: Mass Flow Rate Conservation Problem
Hi,
I think you understand my probleme: I have a negative mass flow rate on the surface which is the outlet of the whole 3D domain. thank you. 
Re: Mass Flow Rate Conservation Problem
Ok. As I've already told you, negative values of the mass flow rate at the outlet are not a problem.
Good work Hi 
Re: Mass Flow Rate Conservation Problem
Hi I also have some negative values of static pressure at the outlet surface ?! I would like to be sure that the flow is computed in a good way.
Thanks. philippe. 
Re: Mass Flow Rate Conservation Problem
Does FLUENT tells you that you have inverted flow on some cell at the outlet?

Re: Mass Flow Rate Conservation Problem
yes It tells that there is some reversed flows on 20/30 faces on the outlet surface. All the residuals are constant.
mass residuals less than 1.e03 velocity residual : 1.e03 energy (thermal model): a little more than 1e03 
Re: Mass Flow Rate Conservation Problem
Try to do more iterations. If residuals of energy is over 1e6, your solution is not considered as a converged one by FLUENT.
Check all boundary conditions. If you can, try to replace the Outflow boundary condition with a Pressure outlet (you need to know gauge pressure at the outlet). Read the manual about Outflow BC use for more info. 
Re: Mass Flow Rate Conservation Problem
thank you !!

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