Mean Residence Time (MRT) was determined numerically for the pilot packed bed reactor filled with the ceramic raschig rings. Three well-defined patterns and one randomly packed bed were studied, where a tube-toparticle ratio (N) was around 7. A case study of Dry Methane Reforming (DMR) was investigated at 600 °C, 1 atm. Reactant feeding rates were varied in the range of 0.985 to 2.957 L/min. The MRTs of four difference packing pattern, namely, vertical-staggered (pattern 1), chessboard-staggered (pattern 2), reciprocal-staggered (pattern 3), and randomly packed bed were conducted using finite-element based Computational Fluid Dynamics (CFD). The results were shown in terms of E(t) function where a higher value of the E(t) function means greater deviation from the ideal plug flow. Results showed that chessboard-staggered pattern had the lowest E(t) values compared with all patterns and all feeding rates. To deeply representative results for the system configurations, the discussion on nonideal behaviors of each structured packing can be made systematically in this work.