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The laminar flow field in a Kenics KM static mixer has been studied using laser induced fluorescence and digital image analysis. Mixing was quantified by measurement of the number average striation thickness, variance of striation widths and interfacial area, for elements of length to diameter (L/D) ratios of 0.8, 1.0, 1.5 with 90° twist per element. From flow visualisations, transitions were observed in the flow where vortices developed above the first and second elements at Reynolds numbers of 43 and 90 for L/D = 0.8 and Reynolds numbers of 55 and 105 for L/D = 1.0. It was found that these vortices did not appreciably enhance mixing based on striation thickness and variance of striation widths measurements after 4 to 5 elements. The influence of viscosity ratio showed a viscosity ratio (dyed stream/bulk stream) of I had faster interfacial area growth and created more uniform mixtures compared to a viscosity ratio of 0.2 for flow rate ratio of 0.2. 相似文献
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介绍了激光诱导荧光测试技术(laser induced fluorescence,LIF)的基本原理,结合时间分辨率和空间分辨率,分析了测试系统所包含的激光器、示踪剂和相机等关键要素的最新进展情况,在此基础上对LIF技术在液体物理混合、混合-反应流等领域的应用进行了综述,并展望了这一先进测试技术的应用前景,提出如何实现激光器与高速相机的有效匹配是制约其同时在高空间分辨率和高时间分辨率下研究混合过程的重要因素,实现测量设备的小型化、高精度、低价格,将直接决定LIF测试技术在实际生产过程开发中的应用。 相似文献
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Han E.H. MeijerMrityunjay K. Singh Patrick D. Anderson 《Progress in Polymer Science》2012,37(10):1333-1349
The performance of industrially relevant static mixers that work via chaotic advection in the Stokes regime for highly viscous fluids, flowing at low Reynolds numbers, like the Kenics, the Ross Low-Pressure Drop (LPD) and Low-Low-Pressure Drop (LLPD), the standard Sulzer SMX, and the recently developed new design series of the SMX, denoted as SMX(n) (n, Np, Nx) = (n, 2n − 1, 3n), is compared using as criteria both energy consumption, measured in terms of the dimensionless pressure drop, and compactness, measured as the dimensionless length. Results are generally according to expectations: open mixers are most energy efficient, giving the lowest pressure drop, but this goes at the cost of length, while the most compact mixers require large pressure gradients to drive the flow. In compactness, the new series SMX(n), like the SMX(n = 3) (3, 5, 9) design, outperform all other devices with at least a factor 2. An interesting result is that in terms of energy efficiency the simple SMX (1, 1, 4, θ = 135°) outperforms the Kenics RL 180°, which was the standard in low pressure drop mixing, and gives results identical to the optimized Kenics RL 140°. This makes the versatile “X”-designs, based on crossing bars, superior in all respects. 相似文献
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A comprehensive study on the liquid mixing with/without instantaneous reactions was conducted using planar laser induced fluorescence (PLIF) technique, where a novel reactive PLIF technique was adopted to quantitatively visualize the dynamic variation of the concentration of fluorescence dye due to signal quenching by a Fenton reaction. The factors (e.g., tracer injection direction, tracer injection position, impeller speed) influencing the reactive and non-reactive mixing processes were investigated, and the mixing performances were characterized by non-reactive mixing times (τ95 and τ99), and reactive mixing time (θ99), respectively. The experimental results from the 2-D measurements of liquid mixing behavior emphasized the significance of the understanding on the spatio-temporal mixing patterns: not only did the tracer injection position affect the mixing performances in the stirred tank, but also the sampling position to monitor the mixing status would lead to a large difference in evaluating the mixing performance. For the stirred tank with fast reactions, the reactive mixing performance had a strong interplay with the non-reactive mixing. 相似文献
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Zhenhao XI Weizhen SUN Ling ZHAO Zhaoyan LIU 《Frontiers of Chemical Engineering in China》2009,3(1):93-96
A new static mixer Cross-over-Disc has been invented to strip off the boundary layer and to make strong radial mixing. The
pressure drop of Cross-over-Disc is 12-26 times as large as that of empty pipe with equivalent diameter and length. The mixing
performance of Cross-over-Disc with 14 elements has been investigated in the viscosity range of 190–250 Pa·s by decoloration
method, and the gray analysis of images shows that mixing inhomogeneity is about 7.5% and 9.4% for the mixing ratio of 5:1
and 10:1, respectively. Furthermore, mixing inhomogeneity for a combination of static mixing elements (four from Cross-over-Disc
and three pairs from Sulzer-type) can be decreased to 2.1%–3.1% within a reasonable range of pressure drop. 相似文献
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Hassan Mahmoodi Kiyanoosh Razzaghi Farhad Shahraki 《American Institute of Chemical Engineers》2020,66(11):e17034
This article addresses design modification to a flat-blade static mixer to enhance mixing performance. The static mixer elements used in this work consist of four blades with curvature made to intensify turbulent-like flow, while reducing the pressure drop. The blades were mounted on a cylindrical housing with 45° rotation relative to the axial direction. The mixer assembly was used in three different arrangements of 8, 10, and 14 elements for a range of Reynolds number between 600 and 7,000. The coefficient of variance (COV) of samples was used to measure the mixing quality. The curved-blade mixer provides considerable improvement in mixing quality compared with the flat-blade mixer and comparable to the SMX mixer. Compared with the flat-blade static mixer, the new design reduces the COV by up to about 50%. This effect is more pronounced when the number of mixing elements increases. Furthermore, the friction factors for the modified mixer, obtained at a wide range of Reynolds number, were apparently smaller than those for the flat-blade, SMX, and SMV mixers. The correlation presented for the friction factor, when all mixer arrangements and aspect ratios were considered, supports the experimental data with ±15% deviation. 相似文献
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Lucian M. Rusnac Octavian Floarea Radu V. Vladea 《Journal of the American Oil Chemists' Society》1992,69(4):384-386
Continuous hydrogenation of industrially refined soybean oil with Harshaw Ni catalyst was achieved in a slurry column equipped
with Sulzer SMV motionless mixers. The influence of the operating parameters (temperature, pressure, catalyst concentration
and gas velocity) was investigated. The presumption that, in this equipment, the liquid-solid mass transfer limits the rate
of the process is in good agreement with the experimental data. 相似文献
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翼片间距和尾距对HEV型静态混合器混合特性的影响 总被引:1,自引:0,他引:1
以变异系数作为评价混合器混合性能的指标,利用实验和数值模拟相结合的方法研究了翼片间距和尾距对HEV型静态混合器混合特性的影响。首先利用实验方法测量了静态混合器出口处示踪流体的体积分数,基于实验结果对数值模拟中的5种湍流模型(standard k-ε、RNG k-ε、realizable k-ε、SST k-ω、standard k-ω)进行对比分析,选出最优计算模型,在此基础上,模拟研究了不同翼片间距在同一基准断面处示踪流体变异系数的变化规律,以及翼片间距在0.8D~2.0D之间时,出口处示踪流体的变异系数随着尾距的变化规律。结果表明:RNG k-ε模型模拟的结果与实验结果最为接近(相对误差为3.37%),即该模型最能真实地反映此混合器的流场特性;HEV型静态混合器混合的均匀程度随着翼片间距的增大呈现先提高再降低的趋势,当翼片间距 ≤1.7D时,随着翼片间距的增大,变异系数迅速降低,当翼片间距 ≥1.7D时,随着翼片间距的增大,变异系数呈上升趋势,翼片间距为1.7D时,CV值最低,混合效果最好;在一定长度范围内,出口处示踪流体的变异系数随着尾距的增加迅速降低,但是尾距增加到一定距离以后,继续增加尾距对混合效果的改善不明显。 相似文献
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A fast liquid mixing process was implemented by the cross-flow impingement of thin liquid sheets in the confined mixing channels with the width of millimeter(s). The species transport between the two liquids was studied by visualizing the 2-D concentration field of Rhodamine dye with the planar laser induced fluorescence (PLIF) technique, on which the intensity of segregation (IOS) and the 95% mixing time (τ95) were calculated to evaluate the mixing quality. Due to the reduced spatial scale of liquid mixing and the high energy dissipation rate of ∼1000 to produced by the strong impingement between the liquid sheets, fast mixing of liquids was achieved at a time scale of milliseconds. The effects of operating conditions and the mixer geometry on the mixing behavior were investigated comprehensively by both experiments and computational fluid dynamics (CFD) simulations. Good agreement of the CFD predictions with the experimental data was obtained by the k-? model with species transport, where dependence of the CFD predictions on the turbulent Schmidt number (i.e. Sct) was discussed in detail. The results show that for this turbulence-induced mixing procedure the momentum ratio and the cross-flow angle between the two liquids play significant roles in the mixing efficiency. The absolute liquid velocity has little effect on the species transport in space, i.e. the mixing distance to reach IOS of 5%. Nevertheless, the mixing time is shortened at higher velocity conditions. The fluctuation of the transient concentration signals shows stronger interaction at the interface between the two liquid sheets. And the local concentration fluctuations can be well described by the β-PDF (probability density function) model. 相似文献
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Mrityunjay K. Singh Tae G. Kang Patrick D. Anderson Han E. H. Meijer Andy N. Hrymak 《American Institute of Chemical Engineers》2009,55(9):2208-2216
Various designs of the so called Low-Pressure Drop (LPD) static mixer are analyzed for their mixing performance using the mapping method. The two types of LPD designs, the RR and RL type, show essentially different mixing patterns. The RL design provides globally chaotic mixing, whereas the RR design always yields unmixed regions separated by KAM boundaries from mixed regions. The crossing angle between the elliptical plates of the LPD is the key design parameter to decide the performance of various designs. Four different crossing angles from 90° to 160° are used for both the RR and RL designs. Mixing performance is computed as a function of the energy to mix, reflected in overall pressure drop for all designs. Optimization using the flux-weighted intensity of segregation versus pressure drop proves the existence of the best mixer with an optimized crossing angle. The optimized angle proves to be indeed the LLPD design used in practice: the RL-120 with θ = 120°, although RL-140 θ = 140° performs as good. Shear thinning shows minor effects on the mixing profiles, and the main optimization conclusions remain unaltered. © 2009 American Institute of Chemical Engineers AIChE J, 2009 相似文献
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The performance of six static mixer (Kenics, Inliner, LPD, Cleveland, SMX and ISG) are compared using 3D numerical simulations in laminar creeping flow regime. Numerical pressure drop results are tested against experimental ones, showing overall a good agreement. Besides pressure drop, four criteria (extensional efficiency, stretching, mean shear rate and intensity of segregation) are chosen to compare the static mixers. It appears that Kenics, Inliner, LPD and Cleveland mixers are rather similar. The ISG mixer seems better than this first group of mixers, but pressure drop is too high compared to other advantages. From our numerical results, SMX appears to be the most efficient of the six compared static mixers. 相似文献
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Paulo E. Laranjeira António A. Martins José Carlos B. Lopes Madalena M. Dias 《American Institute of Chemical Engineers》2009,55(9):2226-2243
NETmix® is a new technology for static mixing based on a network of chambers connected by channels. The NETmix® model is the basis of a flow simulator coupled with chemical reaction used to characterize macro and micromixing in structured porous media. The chambers are modeled as perfectly mixing zones and the channels as plug flow perfect segregation zones. A segregation parameter is introduced as the ratio between the channels volume and the whole network volume. Different kinetics and reactants injection schemes can be implemented. Results show that the number of rows in the flow direction and the segregation parameter control both macro and micromixing, but the degree of micromixing is also controlled by the reactants injection scheme. The NETmix® model enables the systematic study of micromixing and macromixing for different network structures and reaction schemes, enabling the design of network structures to ensure the desired yield and selectivity. © 2009 American Institute of Chemical Engineers AIChE J, 2009 相似文献
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首先概括了静态混合的技术特色;其次,重点综述了近年来旋流静态混合器内脉动压力与速度波动的统计特征、多尺度分形和混沌混合特性等方面的研究进展;实验研究发现Kenics静态混合器各点压力最大波动幅值与进口流量呈二次函数关系,脉动功率谱随着频率的增加呈幂函数关系衰减;轴截面内壁面自由涡和主体区强制涡相互耦合诱导混沌流的产生,同时提高速度与温度梯度的场协同程度。最后,总结了静态混合器内螺旋元件的切割分流、改变流向和径向混合等功能在强化CO2水合物形成过程中的作用。指出将计算流体力学、映射法等方法同LIF、PIV、PFS有机结合可有效地分析静态混合器内多相流动混合机理。 相似文献
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利用平面激光诱导荧光测试技术对多孔错流喷射混合器内液体混合过程进行了研究,考察了操作条件(射流速度比r、混合流股Reynolds数ReM)和混合器的结构参数(射流小孔直径d、孔径管径比d/D、射流小孔个数n)对射流轨迹线的影响。结果表明,混合流股Reynolds数对射流轨迹线影响较小,射流速度比和混合器的结构参数是影响射流轨迹线的主要因素。建立了射流轨迹线的数学模型,并利用实验结果回归了模型参数。模型预测的液体混合过程射流轨迹线与实验结果基本吻合。 相似文献
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Comparative analysis of different static mixers performance by CFD technique: An innovative mixer 总被引:1,自引:0,他引:1
The flow and mixing behavior of two miscible liquids has been studied in an innovative static mixer by using CFD,with Reynolds numbers ranging from 20 to 160. The performance of the new mixer is compared with those of Kenics, SMX, and Komax static mixers. The pressure drop ratio(Z-factor), coefficient of variation(CoV), and extensional efficiency(α) features have been used to evaluate power consumption, distributive mixing, and dispersive mixing performances, respectively, in all mixers. The model is firstly validated based on experimental data measured for the pressure drop ratio and the coefficient of variation. CFD results are consistent with measured data and those obtained by available correlations in the literature. The new mixer shows a superior mixing performance compared to the other mixers. 相似文献