多层桨气-液搅拌反应器内局部特性的数值模拟

采用计算流体力学(CFD)方法,应用Euler双流体模型、标准的k-ε双方程湍流模型及多重参考系法,并与综合考虑了气泡聚并与破碎对气泡尺寸影响的群体平衡模型(PBM)相结合,对多层桨搅拌槽内气-液两相的流场、局部气含率分布、气泡尺寸分布以及局部容积传质系数分布进行了数值模拟。结果表明:在搅拌槽内顶桨与底桨上方靠近壁面处存在气含率和气泡尺寸分布的极大值,与实验结果相吻合;容积传质系数的模拟结果与实验值的相对误差为15%。

Numerical simulation of local characteristics in an aerated stirred tank with multiple impellers

The liquid velocity, local gas holdup distribution, bubble size distribution and local volumetric mass transfer coefficient in a triple-impeller stirred tank have been numerically simulated using computational fluid dynamics (CFD). The Euler-Euler two-flow model, standard κ-εturbulent model and multiple frames of reference (MFR) method were used in the simulations. A population balance model (PBM) model was implemented using the commercial CFD Code. Bubble breakup and coalescence were modeled using isotropic turbulence theory. The local gas holdup distribution, bubble size distribution and local volumetric mass transfer coefficient were predicted by CFD. The simulations showed that two large peaks are present in the void fraction and bubble size profiles,which is in agreement with experiment. The relative error between simulation and experimental values of kLa for the whole vessel is about 15%.