intensified driving force would be available for phase motion in the packed bed. Under this situation, the tendency of flooding would be reduced. So, the RPB could be operated at higher gas and/or liquid flow rates owing to lower tendency of flooding. Moreover, thin films and small droplets of liquid may be generated and regeneration of the interface between gas and liquid sides occurs more rapid compared with that in a conventional packed bed, and the mass transfer efficiency would be greatly intensified. This increase in gas-liquid mass transfer efficiency would decrease RPB physical size. The time required for a process to reach the steady state in a RPB system is comparatively short because of the plug flow hydrodynamics and greater mass transfer coefficient. In this work, CFD simulation as a useful tool has been used for investigation of hydrodynamics parameters such as pressure drop, gas phase distribution and liquid hold up in the RPB. The Ansys- Fluent software version 12 has been used in this work. In the first section, the gas phase flow through the packed bed has been considered and dry pressure drop and gas phase maldistribution factor have been calculated. Then in the second part, the radial and tangential liquid velocities, liquid film thickness, liquid hold up, and finally the two phase pressure drop have been predicted using the momentum integral model and the CFD predictions in the first section. Simulation results showed that RPB total pressure drop in dry bed increases with increase in rotational speed and gas flow rate. Three different feed designs, i.e. gas inlet pipe with respectively normal, 45 degree and tangential inclinations respect to housing body, considered to investigate the effect of gas feed design on the pressure drop and distribution of gas flow rate in the RPB. The Results showed that for the tangential gas inlet, maldistribution of gas flow nearby the packing-housing junction is less than other gas feed designs. The maximum values of maldistribution factor for radial and tangential gas velocities within housing section of tangential gas feed design, earned 0.64 and 1.65 respectively, which were less than other designs. The results of second step of this thesis illustrated that at a given gas and liquid flow rate, the liquid holdup decreases with increasing in the rotational speed. Also, at a given rotational speed, increase in liquid flow rate increases liquid holdup within the RPB. It is clear from the results that the wet pressure drop of gas phase, especially at high rotational speeds, is lower than dry pressure drop. This phenomenon could be due to that the liquid phase, at high rotational speeds, as a lubricant, simplifies the gas flow motion within the rotating packed bed. Furthermore, presence of liquid phase within the bed shortens in the gas flow path length.