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1.
This paper addresses an experimental investigation in the hydrodynamic behavior of a new type of cap trays called Conical Cap tray (ConCap tray). The hydrodynamics of the tray was investigated in a commercial scale air–water column with an internal diameter of 1.2 m. The experimental liquid loads were 29.9, 44.4, 60 and 74.4 (m3/h)/m of weir length and gas flow in terms of Fs in the range of 0.2–1.5 m/s (kg/m3)0.5. The dry pressure drop, total pressure drop, weeping and entrainment for the ConCap tray and a valve tray were measured and compared. Correlations for pressure drop, weeping and entrainment of the ConCap tray were provided using regression analysis method. Standard deviations of correlations, R2, are quoted. The ConCap tray was compared with a bubble cap tray using correlations. The pressure drop of the ConCap tray was less than the bubble cap and close to the valve tray. The weeping rate of the ConCap tray was less than the valve tray. Its entrainment is more than the valve tray and less than the bubble cap tray. Good turndown ratio is important characteristic of the ConCap tray which is achieved without having too much pressure drop. 相似文献
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Taleb Zarei Rahbar Rahimi Mortaza Zivdar 《Korean Journal of Chemical Engineering》2009,26(5):1213-1219
The flow pattern and hydraulics of a Mini V-Grid valve (MVG) tray is predicted by using computational fluid dynamics simulation.
A 3-D CFD model in the Eulerian framework was used. The simulation results for MVG tray are compared with that of sieve tray.
The sieve tray geometry and operating conditions are based on the Solari and Bell’s sieve tray [1]. The MVG tray differs from
that of Solari and Bell’s sieve tray solely by the difference in design of available openings for the flow of gas. The simulation
results show that the clear liquid height and the pressure drop of MVG tray are lower than that of sieve tray whereas the
liquid velocity is higher and contacts of phases are good. The simulation results of sieve tray are in agreement with the
experimental data of Solari and Bell [1]. 相似文献
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Asghar Alizadehdakhel Masoud Rahimi Ammar Abdulaziz Alsairafi 《Korean Journal of Chemical Engineering》2009,26(2):475-484
This paper reports experimental and computational fluid dynamics (CFD) modeling studies on the performance of three modified
valves operating in a valve tray column. The original and modified valves including vnotched, warped and double-valve are
tested experimentally. The experimental rig was a Perspex column having a single valve equipped with a fluctuating plate to
measure the quality of gas distribution by using laser sensors. Two-stage nested designs were employed to show the repeatability
and consistency of the measurements. In the CFD modeling, the volume of fluid (VOF) method was used to model the gas-liquid
two-phase flow inside the column. A good agreement was observed between experimental data and the CFD predictions. The results
showed that the double-valve layout provides a better gas distribution, smaller bubbles with greater interface area and lower
pressure drop in comparison with the original and the two other modified valves. 相似文献
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《Chemical engineering science》2001,56(21-22):6385-6391
Two-phase flow through reactor internals have been experimentally and numerically studied. Experiments have been carried out with a setup running under ambient pressure for two configurations. The first configuration consists of a mixing box orifice inlet through which liquid flows as a film sheared by a gas flow. The liquid height at orifice inlet is documented over a wide range of liquid and gas flowrates. The second configuration consists of the two-phase flow through a downcomer of a distributing tray. Two and three dimensional computational fluid dynamic (CFD) simulations using the volume of fluid approach have been used to compute both flows for similar flow conditions as used in the experiments. It is shown that the agreement between experiments and calculations is very good. Based on this good agreement, it is finally discussed how CFD can be used to achieve better design rules for gas liquid reactor internals via simulations carried out for industrial process conditions. 相似文献
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以一种文丘里型气液分布器为对象,在直径为28 cm的冷模装置中考察了其流体力学性能。气、液流量分别在5~25 m3·h-1、0.2~0.6 m3·h-1范围内,使用激光粒度仪测量了液滴Sauter平均粒径(D32),并测定了其分布均匀性和抗塔板倾斜性能。结果表明:文丘里结构加强了气液混合,与泡罩型分布器相比,此分布器具有更好的液滴破碎性能;气速增大会使出口液体从伞状流变为喷射流,但仍能在直径约为出口直径10倍的区域内均匀分布;在气、液相负荷分别为10~20 m3·h-1、0.4~0.6 m3·h-1时,液位在进液口和进气口之间,此时分布器具有优异的抗塔板倾斜性能。采用计算流体力学软件模拟了分布器内部气液流动过程,得到了相含率和速度矢量图,所得结果有利于分布器的分析与改进。 相似文献
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Sieve trays are widely used in fractionating devices like tray distillation towers existing in separation and purification industries. The weeping phenomenon that has a critical effect on the efficiency of tray towers was studied by a numerical model and some experiments. The experiments were carried out in a pilot scale column with the diameter of 1.22 m that includes two test trays and two chimney trays. Weeping rates and some hydraulic parameters were measured in sieve trays with the hole area of 7.04%. Furthermore, the total weeping rate and weeping rate in inlet and outlet halves of the test tray were determined. It was also used an Eulerian–Eulerian computational fluid dynamics (CFD) method for the present study. The model was able to predict the dry tray pressure drop, total pressure drop, clear liquid height, froth height, and weeping rate simultaneously. Furthermore, the obtained CFD results were in a good agreement with the experimental data in terms of pressure drop and the model properly predicted several hydraulic parameters like the liquid weeping behavior along the tray. 相似文献
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The effect of inclination angle of a packed bed on its corresponding gas–liquid flow segregation and liquid saturation spatial distribution was measured in co‐current descending gas–liquid flows for varying inclinations and fluid velocities, and simulated using a two‐phase Eulerian computational fluid dynamics framework (CFD) adapted from trickle‐bed vertical configuration and based on the porous media concept. The model predictions were validated with our own experimental data obtained using electrical capacitance tomography. This preliminary attempt to forecast the hydrodynamics in inclined packed bed geometries recommends for the formulation of appropriate drag force closures which should be integrated in the CFD model for improved quantitative estimation. 相似文献
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采用计算流体力学方法对直径为2 600 mm的工业规模双溢流立体传质塔板板上气液二相流动进行了模拟研究。计算了不同工况下收缩流和扩张流2种流型的液相流场分布,得到了双溢流塔板收缩流和扩张流2种流型的板上气液二相流场分布规律。通过将清液层高度的CFD结果和经验公式的计算结果进行对比,验证了所建模型的正确性。模拟计算结果表明:边降液管收缩流板面液相流动较均匀,近似于均匀的收缩流,不存在回流区;中降液管扩张流板面液相流动不均匀,靠近塔板中心流速较快,塔板弓形区存在着回流现象;板孔处的帽罩区液层较其他地方小,液相体积分数较其他地方低,扩张流受气相的影响较收缩流大。 相似文献
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Adnan Almuttahar 《Chemical engineering science》2008,63(6):1696-1709
A computational fluid dynamics (CFD) model was developed to simulate the hydrodynamics of gas-solid flow in a circulating fluidized bed (CFB) riser at various fluidization conditions using the Eulerian-Granular multiphase model. The model was evaluated comprehensively by comparing its predictions with experimental results reported for a CFB riser operating at various solid mass fluxes and superficial gas velocities. The model was capable of predicting the main features of the complex gas-solids flow, including the cluster formation of the solid phase along the walls, for different operating conditions. The model also predicted the coexistence of up-flow in the lower regions and downward flow in the upper regions at the wall of the riser for high gas velocity and solid mass flux, as reported in the literature. The predicted solid volume fraction and axial particle velocity were in good agreement with the experimental data within the high density fast fluidization regime. However, the model showed some discrepancy in predicting the gas-solid flow behavior in the riser operating in dense suspension up-flow and low density fast fluidization regimes. 相似文献
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A Eulerian-Eulerian model incorporating the kinetic theory of granular flow is adopted to describe the gas-solid two-phase flows in a multizone circulating propylene polymerization reactor. Corresponding simulations are carried out in a commercial computational fluid dynamics (CFD) code Fluent. First, the model is validated by comparing simulation results with the experimental data. Entire fields in the reactor composed of a riser and a downer are also obtained numerically. Furthermore, the model is used to distinguish the flow behaviors in the riser and the downer. The effects of riser-outlet configuration and operation gas velocity on the flow behaviors in the reactor are also investigated numerically. The simulated results show that the flow behaviors in the riser of MZCR are different from those in the downer of MZCR. In addition, the simulation results also show that both the exit configuration of the riser and the operation gas velocity can significantly affect the flow behaviors in the MZCR. 相似文献
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Hydrodynamics of inclined packed beds under flow modulation ‐ CFD simulation and experimental validation 下载免费PDF全文
Amir Motamed Dashliborun Mohsen Hamidipour Faïçal Larachi 《American Institute of Chemical Engineers》2017,63(9):4161-4176
A three‐dimensional unsteady‐state Eulerian multi‐fluid CFD model was developed to simulate the hydrodynamic behavior of inclined gas‐liquid cocurrent downflow packed beds under ON‐OFF liquid, ON‐OFF gas, and gas/liquid alternating cyclic operations. Validation of the CFD simulation results was performed with experimental data provided by electrical capacitance tomography imaging. Incorporation in the Eulerian multifluid CFD model of capillary pressure and mechanical dispersion force was essential to accurately capture the transient spatial heterogeneities arising in tilted packed beds under different cyclic modulation strategies. The applied CFD model was able to satisfactorily predict the values of liquid holdup and pressure drop as well as the morphological characteristics of the traveling waves inside the bed for the examined flow modulations. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4161–4176, 2017 相似文献
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Microscale studies, which can provide basic information for meso‐ and macroscale studies, are essential for the realization of flow characteristics of a packed bed. In the present study, the effects of gas velocity, liquid velocity, liquid‐solid contact angle, and liquid viscosity on the flow behavior were parametrically investigated for gas‐liquid two‐phase flow around a spherical particle, using computational fluid dynamics (CFD) methodology in combination with the volume‐of‐fluid (VOF) model. The VOF model was first validated and proved to be in good agreement with the experimental data. The simulation results show that the film thickness decreases with increasing gas velocity. This trend is more obvious with increasing operating pressure. With increasing liquid velocity, the film thickness tends to be uniform on the particle surface. The flow regime can change from film flow to transition flow to bubble flow with increasing contact angle. In addition, only at relatively high values does the liquid viscosity affect the residence time of the liquid on the particle surface. 相似文献
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Cholthicha Amornsirirat Benjapon Chalermsinsuwan Lursuang Mekasut Prapan Kuchonthara Pornpote Piumsomboon 《Korean Journal of Chemical Engineering》2011,28(3):686-696
A circulating fluidized bed (CFB) is widely applied in many industries because it has high efficiency. To develop and improve
the process, an understanding of the hydrodynamics inside the CFB is very important. Computational fluid dynamics (CFD) represents
a powerful tool for helping to understand the phenomena involved in the process. In this study, a CFD model was developed
to represent a cold model of the laboratory scale CFB which was designed to study the hydrodynamics of a CFB using commercial
CFD software. The Eulerian approach with kinetic theory of granular flow was used for simulating the hydrodynamics inside
the system. After proper tuning of relevant parameters, the pressure profile along the equipment from the simulation was well
agreed with that from the experiment. The simulation result expresses the hydrodynamic parameters of the slug flow such as
solid volume fraction, gas and solid velocities and granular temperature in the riser. 相似文献
18.
A three-dimensional computational fluid dynamics (CFD) model for gas flow through a serrated valve tray was presented. The flow field, as well as the dry-pressure drop of the valve under the full-opening condition was simulated based on the proposed model by using FLUENT 6.0 software. Compared with the values of dry-pressure dro.p in different turbulent models, the.simulated.results using RNG κ-ε model are in reasonable agreement with experimental data, indicating that RNG κ-ε model is suitable in simulating gas flow through the serrated valve tray. Then the CFD model combining RNG κ-ε model was used to study the three-dimensional gas flow through the considered serrated valve tray. The simulated results showed that various eddies existed on the serrated valve tray, and both the eddy and the non-eddy areas were nearly equal. The existence of addendum can decrease the eddy area caused by gas passing through the lateral outlet slots. The size of eddies can be reduced by optimizing the distance between valves. 相似文献
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介绍一种新型穿流塔板--正交波纹板。以欧拉-欧拉两相流模型为基础,建立了正交波纹板上气液两相流场的三维数学模型。CFD模型中主要考虑了气液两相间的曳力作用,相间动量传递源相采用Krishna计算方法。以清液层高度为指标,对CFD模型的可靠性进行了验证。在不同气液负荷下,对正交波纹板的压降、板上液相速度分布及塔内气液分布状况等流体力学性能进行了研究,并与淋降筛板进行对比,结果表明正交波纹板具有更高的操作弹性和更好的操作稳定性。 相似文献
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规整填料塔内两相流动的三维计算流体力学建模(英文) 总被引:1,自引:0,他引:1
Characterizing the complex two-phase hydrodynamics in structured packed columns requires a power- ful modeling tool. The traditional two-dimensional model exhibits limitations when one attempts to model the de- tailed two-phase flow inside the columns. The present paper presents a three-dimensional computational fluid dy- namics (CFD) model to simulate the two-phase flow in a representative unit of the column. The unit consists of an CFD calculations on column packed with Flexipak 1Y were implemented within the volume of fluid (VOF) mathe- matical framework. The CFD model was validated by comparing the calculated thickness of liquid film with the available experimental data. Special attention was given to quantitative analysis of the effects of gravity on the hy- drodynamics. Fluctuations in the liquid mass flow rate and the calculated pressure drop loss were found to be quali- tatively in agreement with the experimental observations. 相似文献