I am modelling a steady state case of flow through a tube (containing baffles) with one inlet and one outlet.At inlet and outlet, I have given pressure B.C.S. I am not getting the required flow rate(kg/sec.)Pressure drop corresponding to the flow rate have been calculated by empirical correlations and standard methods.Any way model is not giving any error on check. What may be the possible causes.???

There could be modelling (especially turbulence) and discretization errors (coarse mesh) on the CFD side. But, on the other hand, be careful of putting too much trust in "empirical correlations" and "standard methods". Do you know for sure that these have the level of accuracy which you ascribe to them?

Just go the other way. Define the mass flux and look for the pressure do you get.

Does your empirical correleations take into consideration the possible bends / curvs, flow seperation, swirl, wall roughness, ... and many more physical effects?

Especially flow seperation is a problem, which is extremly affected by the turbulence model, and on the flow velocity (definition of RE-number).