Flow of a FENE Fluid in Packed Beds or Porous Media

An analysis describing viscoelastic flow of a FENE fluid in packed beds or porous media is presented based on the capillary hybrid model of the flow. A close similarity is revealed between the functional relationship of the reduced elongational viscosity to and that relating the reduced mean elongational viscosity λ_H ? to the Deborah number which is utilized in the flow expressions. The agreement obtained between the predicted and experimentally determined evaluations of the resistance factor, including the effects of variation of polymer concentration, molecular weight and solvent quality was found to be satisfactory. Onset Reynolds numbers for enhanced flow resistance are also predicted successfully.     

基于离散相模型的旋转填充床内的流场分析

利用CFD软件Fluent初步模拟了旋转填充床(Rotating Packed Bed,RPB)内的流体流动.计算中气相采用RNGk-ε湍流模型,液相采用拉格朗日离散相模型(DPM).通过一定简化后建立了旋转填充床二维模型,考察了液体颗粒在填充床内的速度分布,以及转速对液体颗粒速度的影响.结果显示液滴速度随转速的增加而增加,转速对液滴径向速度的影响不大.此外还针对转速、气体进口速度对干床压降的影响做了一定的研究,发现压降随转速的增加而增加,但其影响没有气体进口速度对压降的影响明显.填料的内缘处存在剧烈的端效应,模拟结果表明,端效应区的湍动强度明显大于其他区域.     

填充床中空隙率分布的研究综述

综述了充床中空隙率径向分布的几种主要测量技术和数学模型,概括了空隙率分布的一般规律,为试验研究和工程设计工作提供重要依据。     

Effect of Superimposed Pulsating Flow on Liquid‐Solid Mass Transfer in Fixed Beds

The liquid‐solid mass transfer behaviour of a fixed bed of cylinders has been studied using the dissolution of copper in acidified dichromate solution under pulsating flow conditions. The bed diameter was 100 mm. The depth of the working section was 95 mm and the length and diameter of the cylinders were 19.1 mm. Variables studied were steady flow superficial liquid velocity, and oscillation amplitude and frequency. Data have been correlated as the Sherwood number in terms of Schmidt number and the cylinder Reynolds numbers for steady and oscillatory flow. The form of the correlation permits comparison with literature data for the limiting cases where either of these Reynolds numbers is zero.     

Towards the Development of Advanced Packing Design for Distillation in Rotating Packed Beds

The growing demand for flexible and compact separation technologies has promoted the application of high‐gravity technology, like rotating packed beds (RPBs). Mass transfer characterization and packing design play an important role in the development of this technology. This article provides a systematic approach towards the evaluation of packing and the development of advanced packing design for distillation in RPBs. For the latter, an additive manufacturing approach is used to develop a new Zickzack packing for RPBs. The new packing provides better mass transfer at reduced pressure drop compared to available conventional packings, while being competitive in terms of mass transfer with the industrially applied rotating zigzag bed at significantly reduced pressure drop.     

滴流床中流体分布的研究现状及展望

回顾了滴流床流体分布研究的历史和技术进步,分析了测量液体分布大尺度和小尺度均匀性的方法,讨论了改善流体分布均匀性的措施,指出了滴流床操作特性的非线性与小尺度不均匀性的关系,最后对值得深入的工作提出了建议。     

Analysis of Flow Patterns in High‐Gravity Equipment Using Gamma‐Ray Computed Tomography

The capacity of today's gas‐liquid contacting equipment such as tray or packed columns is limited by the gravitational‐driven liquid flow. Intensified equipment applying centrifugal force offers great potential for enhancing the mass transfer and for reducing equipment size. Yet, detailed knowledge about the liquid flow inside rotating packings is scarce due to limited accessibility with conventional measurement systems. In this study, a gamma‐ray computed tomography is employed to quantify the liquid hold‐up and its distribution in the moving packing.     

基于三维XCT对碳化引起水泥砂浆内部缺陷改变的测试和分析

为了揭示碳化反应对水泥砂浆内部缺陷分布的影响规律,采用三维XCT(X-ray computed tomography)对碳化前后的水泥砂浆的三维内部缺陷体积分数和缺陷尺度分布进行了定量分析.通过XCT的配套软件VG Studio MAX 2.0对水泥砂浆内部缺陷的投影进行三维重构.并通过配套的三维缺陷分析模块软件从三维...     

新型内构件填充床反应器数值模拟-I.气相流场和停留时间分布

针对含新型内构件的复杂填充床内部结构，建立了包含颗粒填充床、气体通道、气体挡板的几何模型下气液两相流动的数学模型，采用计算流体力学(CFD)技术首先对气流在复杂结构下的流动分配、流型和停留时间分布进行了详细的模拟，并考察了操作参数和结构设计对流场和停留时间分布的影响. 通过压降实验数据在宏观尺度上验证了CFD模拟的正确性. 详细的内部流场展示了气体在颗粒床和气体通道内的曲折流动行为，增加了气体的平均停留时间；停留时间分布预测表明气相流动没有短路发生，平均停留时间与表观气速成反比. 内构件结构参数对气体流场和停留时间分布产生重要的影响.     

电容层析成像技术在线测量气固流化床空隙率的研究

基于电容层析成像技术，提出了一种在线测量气固流化床空隙率的新方法。建立了相应的12电极电容层析成像气固流化床空隙率测量系统，可同时实现气固 流化床空隙率分布的在线显示和整体空隙率测量。选择加权反投影算法进行图像重建以保证空隙率分布显示的实时性和有效性。采用Tikhonov正则化原理和ART算法相结合的组合型新图像重建算法来实现整体空隙率的测量。Tikhonov正则化原理用于克服图像重建过程中的不适定问题，ART算法用于提高最终重建图像的质量。研究表明以上提出的空隙率测量新方法是有效的。空隙率分布在线测量的速度可达25幅／秒以上，整体空隙率测量的最大误差可小于5％。     

固体输送中聚合物形态的层析测量与分析

基于聚合物自由体积理论和应力应变关系，提出了对固体输送中聚合物形态进行计算机层析图像测量和形态特性撮与分析的新方法，实验表明，该方法不仅能对处于密闭空间的挤出聚合物形态进行动态、在线、非破坏性地测量，而且可以推导出固体输送中聚合物的形态与其性能之间的关系。     

The Soret and Dufour Effects in Non-thermal Equilibrium Packed Beds with Forced Convection and Endothermic Reactions

To study the influence of the Soret and Dufour effects on the reactive characteristics of a porous packed bed with endothermic reactions and forced convection, a two-dimensional mathematical model cons...     

喷动流化床气相旋流流场的数值模拟及试验

基于Fluent软件,采用标准k-ε双方程模型对喷动流化床内气相旋流流场进行了数值模拟,获得了有利于造粒和包衣操作的流动结构,并通过试验测量验证了预测结果的可靠性.该研究为喷动流化床的设计和结构优化提供了有价值的参考.     

基于分相流模型的气液两相流流量测量

从伯努利方程出发,基于分相流模型,推导出气液两相流流过文丘里管的流量公式.在分析了两相流通过节流装置的实际流动情况后,作者认为气液两相滑移比是影响流量公式误差的一个重要因素.在理论与实验研究的基础上,作者提出了气液两相流流过文丘里管的滑移比经验关联式.利用作者提出的滑移比经验关联式和分相流模型的流量公式测量两相流流量,体积流量误差的均方根小于5.1%,表明该方法适用流过文丘里管的两相流流量测量,尤其对于两相流动激烈的两相相互作用区域,流量误差满足测量的要求.     

基于ANSYS的气/液两相流电容相关流速测量仿真研究

以气/液两相流互相关测量系统为研究对象,采用MATLAB建模仿真方法,研究由电容传感嚣构成的基于离散相浓度的电容互相关流速测量机理.并针对电容传感器的"软场"特性,利用ANSYS软件分析电容传感器与离散相浓度的关系,采用Monte-Carlo方法建立气/液两相流流动模型,研究"凝固流动图型"、"非凝固流动图型"以及速度...     

电阻层析成像技术测量两相流气相流量

提出利用双截面电阻层析成像(ERT)系统,并采用相关方法进行两相流气相流量的测量。介绍像素相关与基于边界电压特征值相关两种相关方法,并进行单气泡模拟实验。实验结果表明用这两种相关方法进行两相流的气相流量测量是可行的。     

Evaluation of Hepatic Tissue Blood Flow Using Xenon Computed Tomography with Fibrosis Progression in Nonalcoholic Fatty Liver Disease: Comparison with Chronic Hepatitis C

Aims

The present study evaluated the utility of xenon computed tomography (Xe-CT) as a noninvasive diagnostic procedure for the measurement of hepatic tissue blood flow (TBF) in patients with nonalcoholic fatty liver disease (NAFLD) or chronic hepatitis C (CH-C).

Methods

Xe-CT was performed in 93 patients with NAFLD and in 109 patients with CH-C. Subjects were classified into one of three groups, based on fibrosis stage: group 1, no bridging fibrosis; group 2, bridging fibrosis; and group 3, liver cirrhosis. Correlations between hepatic TBFs in each fibrosis stage were examined.

Results

In group 1, portal venous TBF (PVTBF), hepatic arterial (HATBF), and total hepatic TBF (THTBF) were significantly lower in patients with in nonalcoholic steatohepatitis (NASH) than in those with CH-C (p < 0.001, p < 0.05, p < 0.001, respectively). In group 2, PVTBF and THTBF were significantly lower in patients with in NASH than in those with CH-C (p < 0.001, p < 0.05, respectively). In group 3, hepatic TBFs were not significantly different when comparing patients with NASH and those with CH-C.

Conclusions

PVTBF decreased due to fat infiltration. Therefore, hemodynamic changes occur relatively earlier in NAFLD than in CH-C. Patients with NASH should be monitored carefully for portal hypertensive complications in the early fibrosis stage.     

基于电容层析成像和模糊模式识别的油气两相流流型辨识新方法的研究

基于电容层析成像和模糊模式识别技术别提出了一种油气两相流流型辨识的新方法。建立了12电极电容层析成像流型自动识别系统，该系统利用Tikhonov正则化原理并结合SIRT(Simultaneous Reconstruction Techniques)算法进行图像重建。Tikhonov正则化原理用于克服图像重建过程中的不适定问题，SIRT算法用于提高最终重建图像的质量。根据流型的随机和模糊特性，提出了一种根据管截面重建图像进行流型辨识的模糊流型判别方法。研究结果表明，提出的流型辨识新方法是有效的。对于层状流、核心流、环状流、均相流等流型，流型辨识的准确率高于95％，辨识一个流型所用的时间小于0.3秒。对于塞状流，流型辨识的准确率高于90％。     

填料塔膜流模型用于最小润湿速率研究

根据液体在填料表面膜状流动的特点 ,建立了填料塔的膜流模型 ,并将该模型用于填料塔最小润湿速率的研究。结果表明 ,填料塔的最小润湿速率与填料大小无关 ,而与堆积方式有关。文中提供的最小润湿速率算式可以作为确定填料塔喷淋密度的依据