气升式环流反应器数值模拟研究进展

气升式环流反应器是一种结构简单,传质、传热效率高的多相反应器,反应器性能受物性参数和结构参数的影响,由于两相和三相流的复杂性,使得其在工业化设计放大和应用过程中存在困难。论述了气升式环流反应器内相间作用力类别和计算模型,对应用于气升式环流反应器模拟计算的简化模型、两相流模型和k-ε湍流模型进行总结,在分析现阶段气液两相流理论的基础上,明确反应器内不同流动形态下相间作用力、气泡的分散机理、气泡对湍流的影响、流动模拟模型的选取标准,能有效提高气升式环流反应器模拟的准确性及模型的普适性,为反应器的设计放大及传质模拟计算提供更加可靠的理论依据。     

气升式内环流反应器流场及传质特性数值模拟

采用双流体模型和气液二相流体动力学理论建立了气升式环流反应器流体流动的数学模型,在此模型的基础上利用溶质渗透理论和各向同性湍流理论建立了局部液相体积传质系数数学模型。采用计算流体软件F luent对气升式环流反应器内气液二相流动状况进行模拟,模拟结果较好地解释了气升式环流反应器内的流动行为及传质特性。模拟计算值与文献实验值的吻合说明了模型的可行性。     

气升-射流式多段环流反应器的流体力学和传质特性

气升式环流反应器在气液或气液固三相反应以及分离过程应用广泛,为提高气液分布和传质性能,在气升式多段环流反应器的第2段引入射流,开发一种气升-射流式多段环流反应器.在160 L的实验装置中,以水-空气体系,研究了气升-射流式多段环流反应器的流体力学和传质特性.射流可减小上升气泡的弦长,提高总体气含率,改善下降段气液分布,...     

固体颗粒对三相气升式环流反应器流动特性的影响

将液相视为连续相,气相和固相视为分散相,同时考虑各相之间的相互作用,结合气液固三相流体的动力学理论,建立气液固三相环流反应器三流体湍流流动的Eulerian模型.采用计算模拟软件Fluent对三相环流反应器的流动状况进行模拟,考察表观气速、固含率、颗粒大小对反应器的气含率以及液体流动速度的影响.模拟结果较好地解释了气升式环流反应器内的三相流体行为,模型与实验结果较好地吻合,表明了模型的可行性.     

新型气升式环流反应器流场数值模拟

利用CFD软件ANSYS 14.0及欧拉-欧拉多相流模型,模拟了一种采用微孔曝气器的新型气升式环流反应器的气液两相流动,得到反应器内气含率和循环液速等参数的详细分布。模拟结果表明：新型气升式环流反应器的平均气含率与气量成正比关系;气量为2.5 m3/h时具有更高的循环液速。     

新型气液双升式动物细胞培养反应器的初步研究

为克服目前动物细胞反应器中存在的不足，本文研究设计了一种新型动物细胞反应器一气液双升式反应器．该反应器具有气升式反应器的所有优点，同时在结构上使气泡和流体自然流动与分离，并使气泡与细胞不直接接触，从而消除了气泡凝聚破裂细胞造成的机械损伤．根据悬浮气泡在流体中的受力平衡原理，提出了通过测定气泡大小来确定液体流速的新方法，用于研究气液双升式反应器的循环流速与表观气速、气体分布器孔径及介质的关系，并确定了培养动物细胞时的通气率和循环流速，该方法简单、有效．用动态法测定了气液双升式反应器的氧传递系数及其…     

气升式环流反应器的实验及数值模拟研究进展

介绍了气升式环流反应器的概况,综述了气升式环流反应器实验及流体数值模拟研究的进展,包括实验方法的不断改进及模型的选取,并提出了今后研究工作的主攻方向.     

CFD在气升式环流反应器结构优化上的应用

利用CFD软件ANSYS 14.0及欧拉-欧拉多相流模型,模拟不同高径比、环隙比下气升式环流反应器的气液两相流动,得到反应器内循环液速和气含率等参数的详细分布。对比模拟结果表明,高径比为7,环隙比1时,反应器具有最优流化状态。CFD在气升式环流反应器的结构优化具有明显的指导意义。     

分布器结构对环流反应器气含率分布的影响

采用κ-ε二方程模型和欧拉多相流模型,对一种单筒单级气升式气液环流反应器内的湍流气液两相流进行了全尺寸的数值模拟研究,考察了采用3种不同气体分布器时反应器内气含率和流速分布的细节.模拟结果表明不同结构的分布器对总体气含率和内筒中的两相速度分布有很大影响,因而对气含率分布和气液两相接触效果有较大影响,从而对反应过程产生影响.单环分布器产生的气液两相接触效果较差,对于反应过程很不利.对于大直径的环流反应器推荐使用多环分布器.计算所得的整体气含率与实测的整体气含率进行了对比,吻合较好.     

大型气升环流反应器加置内件时氧传递规律的研究

研究了用结构简单而实用性强的筛板及折皱丝网组件作为内件,来促进大型气升环流反应器中气泡的分散,改善气液两相的混合,从而强化氧传递过程.文中分析了筛板开孔直径与开孔率对氧传递系数的影响,比较了两种内件效果,讨论了最佳结构尺寸.针对高径比大的气升环流系统提出了测定K_La值的平推流动态模型.模型计算结果与实测数据吻合较好.     

CFD simulation of hydrodynamics and mass transfer in an internal airlift loop reactor using a steady two-fluid model

Steady state simulation of the hydrodynamics and mass transfer in bubbly flow in an axisymmetric internal airlift loop reactor (IALR) with the special treatment of interphase decoupling and outlet boundary conditions is performed, which is based on a Favre averaging two-fluid model for multiphase flow. Different models of mass transfer coefficient are compared and validated with the literature data. A model for describing the mass transfer for a wide range of superficial gas velocity is chosen and the predicted mass transfer coefficient agrees well with the experimental data in the literature. The numerical procedure can be used as a tool for the design and scale-up of IALRs.     

Sensitivity Study on Modeling an Internal Airlift Loop Reactor Using a Steady 2D Two‐Fluid Model

The sensitivity study of bubbly flow in an internal airlift loop reactor is presented using a steady Reynolds averaging two‐fluid model. Comparative evaluation of different drag formulations, drag coefficient correlations, turbulence effect on the drag coefficient, outlet slip velocity, and bubble size is performed and the respective influence to the simulation results is highlighted. It is found that a complicated drag formulation may not result in reliable predictions. All the drag coefficient correlations underpredict the gas holdup if the influence of turbulence on the drag coefficient is not well incorporated. Fortunately, the global hydrodynamics is not sensitive to the outflow slip velocity for a wide range, so a steady two‐fluid model can be used to simulate the bubbly flow when the flow field is fully developed. The correct estimation of bubble size with properly selected correlations play an important role in successful simulation of gas‐liquid bubbly flow in airlift loop reactors.     

Hydrodynamic Modelling of Internal Loop Airlift Reactor Applying Drift‐Flux Model in Bubbly Flow Regime

A new model for the liquid circulation rates in airlift reactor (ALR) is presented. The model is based on the energy balance for the flow loop (riser, turn riser‐downcomer, downcomer, and turn downcomer‐riser) coupled with a drift flux theory of two‐phase flow gas‐liquid system, considering a bubbly flow regime. The predicted values of the liquid circulation rates by the developed model are compared with experimental results performed in a 22 dm³ internal loop airlift reactor and with the results obtained in the literatures. The proposed model predicted the experimental results very well. Slip velocity relationship based on the drift flux model was proposed; including the gas holdup, bubble size and the liquid physical properties. The predicted slip velocity was similar to that obtained from the literature. The study revealed that appropriate arrangements of internal bioreactor parts can positively influence the liquid circulation velocity at the same energy consumption. The proposed models are useful in the design; scale up and characterization of the internal loop airlift reactors, and provides a direct method of predicting hydrodynamic behaviour in gas‐liquid airlift reactors.     

3‐D Simulations of an Internal Airlift Loop Reactor using a Steady Two‐Fluid Model

Three‐dimensional (3‐D) simulations of an internal airlift loop reactor in a cylindrical reference frame are presented, which are based on a two‐fluid model with a revised k‐? turbulence model for two‐phase bubbly flow. A steady state formulation is used with the purpose of time saving for cases with superficial gas velocity values as high as 0.12 m/s. Special 3‐D treatment of the boundary conditions at the axis is undertaken to allow asymmetric gas‐liquid flow. The simulation results are compared to the experimental data on average gas holdup, average liquid velocity in the riser and the downcomer, and good agreement is observed. The turbulent dispersion in the present two‐fluid model has a strong effect on the gas holdup distribution and wall‐peaking behavior is predicted. The CFD code developed has the potential to be applied as a tool for scaling up loop reactors.     

LOCAL LIQUID SIDE MASS TRANSFER MODEL IN AIRLIFT LOOP REACTOR AND SELF-ASPIRATED REVERSED FLOW JET LOOP REACTOR

Combining Higbie's penetration theory and Kolmogoroff's theory of isotropic turbulence, a small-scale isotropic mass transfer model for the local liquid side mass transfer coefficients in a gas-liquid two-phase airlift loop reactor and a self-aspirated reversed flow jet loop reactor has been developed. Good agreement with the experimental data suggests a general applicability of the proposed model in these reactors.     

绝热层流泡状流运动的双流体模型

绝热层流泡状流是泡状流研究中的一个基础范例 .目前描述绝热层流泡状流常采用的双流体模型由于相间作用考虑欠缺而适用性差 .本文结合理论和实验研究结果导出了描述壁面“排斥”作用的表达式 ,并建立了一个封闭的双流体模型 .模型预测值和实验值的比较表明 ,由于相间作用的合理考虑 ,扩大了该模型的适用范围     

CFD simulation of the hydrodynamics in an internal air-lift reactor with two different configurations

Computational fluid dynamics (CFD) was used to investigate the hydrodynamic parameters of two internal airlift bioreactors with different configurations. Both had a riser diameter of 0.1 m. The model was used to predict the effect of the reactor geometry on the reactor hydrodynamics. Water was utilized as the continuous phase and air in the form of bubbles was applied as the dispersed phase. A two-phase flow model provided by the bubbly flow application mode was employed in this project. In the liquid phase, the turbulence can be described using the k-? model. Simulated gas holdup and liquid circulation velocity results were compared with experimental data. The predictions of the simulation are in good agreement with the experimental data.     

用CFD研究气升式内环流生物反应器下降管中的流体力学性质

在对气升式内环流生物反应器内部流动分析基础上,全面考虑反应器下降管中气泡的并聚破碎、气液两相间相互作用和滑移等, 建立了能描述反应器下降管中复杂流动的CFD数学模型. 运用CFX-4.4对模型方程进行求解, 通过求解得到了包括气液两相速度场、局部气含率分布等详尽信息,并就液相流动速度与相应条件下的PIV测试结果进行了比较,主体流动速度的偏差在20%以下,且两者总的变化趋势一致.该模型能较好地预测反应器下降管内的复杂流场.     

气升式环流反应器内传质行为的分析与测量

1 INTRODUCTION Airlift loop reactors have emerged as one of the most promising devices in chemical, biochemical and environmental engineering operations. Its main ad-vantages over conventional reactors include excellent contact among different phases, ease of removal or replenishment of particles, and high heat and mass transfer rates[1]. High gas-liquid contacting area and favorable flow pattern are the attractive features of this type of three-phase contactors. Typical processes that ca…     

层流泡状流的近似解析解

当前描述泡状流的双流体模型无法求得解析解,只能通过数值计算的方法进行模拟.本文则针对最基本的泡状流（垂直圆管内稳态层流泡状流）,通过对其双流体模型进行积分,得到比较直观的揭示层流泡状流流场成因的近似解析表达式.并用数值积分的方法迭代求解该表达式,所得到的数值结果与实验数据吻合很好.虽然该表达式是积分形式的,仅能算是近似的解析解,但它揭示了影响泡状流流场的因素,在理论上向前迈进了一步.