| The mixing of Multiphase flow was frequently encountered in industry ofpetrochemical, pharmacy and fermentation. It was very important tounderstand the characteristics of the flow in stirred tank for the optimization ofthe reactor and operating parameters. There were many researches on thesingle flow in the stirred tank, and the studies on the multiphase flow weredeveloped later. The multiphase flow in stirred tank mainly includedsolid-liquid, gas-liquid, liquid-liquid and gas-liquid-solid flow. The flow instirred tank was usually turbulent and there were many methods to measurethe flow field, such as hot film anemometer, laser Doppler anemometer andparticle image velocimetry (PIV). PIV can obtain the instantaneous velocitiesof many points in the flow field at a time without interference, so it wassuperiority in the measurement of flow field.The study mainly concentrated on the microcosmic flow field ingas-liquid and gas-liquid-solid flow, discussed the distribution of velocity,turbulent kinetic energy and turbulent kinetic energy dissipation rate andinvestigated the influence of gas holdup and particle concentration on thevelocity and turbulence flow field in the solid-liquid and gas-liquid-solid flow,respectively. The experiment employed PIV to measure the flow field ingas-liquid and gas-liquid-solid flow in a square tank and the measurement plane was2mm away from the wall. The flow fields of single phase andgas-liquid flow at7different gas volume rates were obtained and the largestgas volume was160L/h corresponding to the gas holdup equal to5.78%. Theflow fields in solid-liquid and gas-liquid-solid flow at two different gas holdup1.42%and3.73%were obtained and the largest particle concentration ingas-liquid-solid phase with1.42%gas holdup was1.6%and it was1.0%forthe3.73%gas holdup three-phase system.The results show that the liquid velocity and turbulent kinetic energybecame larger and the liquid turbulent dissipation rate first increased and thendecreased with increase of gas holdup. The particle had larger influence onsolid-liquid two-phase flow and three-phase flow with1.42%gas holdup andhad smaller influence on the three-phase flow with3.73%gas holdup. In themulti-phase flow, the velocity of continued phase was greatly influenced bythe concentration of dispersed phase, and was rarely influenced by its density.The density of dispersed phase had mild influence on the turbulent kineticenergy, but the influence was greater than that on the velocity. The turbulentdissipation rate was not only greatly influenced by concentration of dispersedphase but also greatly influenced by the density of dispersed phase. |
PDF Full Text Request