Three-dimensional Simulation Of Gas-liquid Two Phase Flow Around Particle Using Computetional Fluid Dynamics

The trickle-bed reactor(TBR)represents an important class of multiphase reactors which is widely used in the petroleum,chemical industries and wastewater treatment process,in which gas and liquid reactants flow concurrently downwards across packed solid catalyst beds.The characteristics of hydrodynamics in the trickle-bed reactor is complex and hydrodynamics have effect on the performance of reactor.Researching from the particle scale,we can carefully observe the fluid flow characteristics on the surface of the catalyst particle and the interaction among the gas-liquid-solid phase,which is essential for understanding the concept of flow mal-distribution.Therefore,in this study,the CFD-VOF method was employed to investigate the gas-liquid two-phase flow around a spherical particle and the effects of gas velocity,liquid velocity,liquid-solid contact angle,surface tension coefficient and liquid viscosity,which provide reliable information for the trickle bed.By observing the whole process of vortex generation,developing and elapse and the effect of liquid flow pattern,we found that the liquid spread fast on particle surface with the increasing of gas and liquid velocities.The breakage extent of the liquid film is mainly affected by the gas velocity rather than liquid velocity.The vortex radius increases with the increment of both gas and liquid velocities.The higher liquid-solid friction caused by increasing liquid viscosity may led to slower liquid spreading on particle surface and decrement of vortex radius.With the increment of the surface tension,liquid film may be broken earlier and the flow pattern tends to annulus films.Although liquid solid contact angle has less effect on vortex,it significantly affects the distribution of liquid flow on the particle surface.Parametric studies were conducted to investigate the changes of drag coefficient and liquid holdup at different conditions,the results can be concluded that the drag coefficient increases with the increment of gas and liquid velocities.The residence time of gas and liquid on the particle surface become shorter with increasing the gas velocity,and the time of drag coefficient reached steady decrease which the liquid fluid spread more symmetrical on the particle surface.Maximum of liquid holdup increase withthe increment of the liquid velocity.Moreover,with increasing the viscosity of the liquid,the drag coefficient is reduced and the residence time of fluid on the particle surface extend.