Actually, it was carried out lots of validation for this study (based on the change of enthalpy and mass flow rate) and everything seems quite logical. Also, as Oğuzhan mentioned, the change of pressure towards axial direction was calculated by using momentum equation (pressure drop was calculated depending on friction resulted from wall shear and thermal acceleration) and the result can be seen in figure entitled as calculated, so as the change of pressure make sense for this theoretical approach calculated by using the Ansys data (density, velocity, etc.), the change of pressure taken from CFD-post (it is stated "Ansys Results") by using areaAve(related cross-section plane) definition is not logical. Is there any missed point about compressible pressure drop calculation in Fluent? (For example, selection of compressible flow etc.). Thank you for helping.

Your model has an underestimated performance. Something is wrong. For instance, values in boundary conditions.

Dear Oğuzhan Gökkaya

Please try to change the inlet condition to ne "velocity inlet". I hope it would give you a better results.

Have a nice job.

I think there is a problem in convergence of your solution. Either change the mesh or change your convergence monitors.

Thanks