تحليل عددي پارامترهاي هيدروديناميكي موثر در برج هاي جذب بستر چرخان (RPB ) توسط آناليز ديناميك سيالات محاسباتي

چكيده انگليسي :

Numerical Analysis of Hydrodynamic Parameters Affecting Rotating Packed Beds RPB Using Computational Fluid Dynamics Mansureh Hamedi Mansureh Hamedi@gmail com June 19 2011 Department of Chemical Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisor Masoud Haghshenas Fard Haghshenas@cc iut ac irAbstractIn spite of wide range of conventional packed bed columns application in gas liquid separation processes ithas been illustrated that there are significant pressure drop and mass transfer limitations in this columns Themain reason for these limitations could be due to unsuitable phase distribution and limited driving force forphase motion in a conventional packed bed column In recent decades a challenge with promise has comeabout obviation of these limitations in separation industries and that is utilization of Rotating Packed Beds RPB The core of RPB technology is replacing the gravitational field by a high centrifugal field If theacceleration due to gravity could be increased then an intensified driving force would be available for phasemotion in the packed bed Under this situation the tendency of flooding would be reduced So the RPBcould be operated at higher gas and or liquid flow rates owing to lower tendency of flooding Moreover thinfilms and small droplets of liquid may be generated and regeneration of the interface between gas and liquidsides occurs more rapid compared with that in a conventional packed bed and the mass transfer efficiencywould be greatly intensified This increase in gas liquid mass transfer efficiency would decrease RPBphysical size The time required for a process to reach the steady state in a RPB system is comparativelyshort because of the plug flow hydrodynamics and greater mass transfer coefficient In this work CFDsimulation as a useful tool has been used for investigation of hydrodynamics parameters such as pressuredrop gas phase distribution and liquid hold up in the RPB The Ansys Fluent software version 12 has beenused in this work In the first section the gas phase flow through the packed bed has been considered and drypressure drop and gas phase maldistribution factor have been calculated Then in the second part the radialand tangential liquid velocities liquid film thickness liquid hold up and finally the two phase pressure drophave 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 speedand gas flow rate Three different feed designs i e gas inlet pipe with respectively normal 45 degree andtangential inclinations respect to housing body considered to investigate the effect of gas feed design on thepressure drop and distribution of gas flow rate in the RPB The Results showed that for the tangential gasinlet maldistribution of gas flow nearby the packing housing junction is less than other gas feed designs Themaximum values of maldistribution factor for radial and tangential gas velocities within housing section oftangential gas feed design earned 0 64 and 1 65 respectively which were less than other designs The resultsof second step of this thesis illustrated that at a given gas and liquid flow rate the liquid holdup decreaseswith increasing in the rotational speed Also at a given rotational speed increase in liquid flow rate increasesliquid holdup within the RPB It is clear from the results that the wet pressure drop of gas phase especially athigh rotational speeds is lower than dry pressure drop This phenomenon could be due to that the liquid

حامدي، منصوره

تحليل عددي پارامترهاي هيدروديناميكي موثر در برج هاي جذب بستر چرخان (RPB ) توسط آناليز ديناميك سيالات محاسباتي

بستر پرشده چرخان , افت فشار , تجمع مايع , ضريب توزيع نامنظم