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1.
Extensive experimental results on the free fall of a range of non-spherical particles such as square bars, cylinders, spheres and crushed rock chips in Newtonian, inelastic, viscoelastic and Boger fluids are presented. It is demonstrated that the use of a volume equivalent sphere diameter in addition to a shape factor provides an adequate approximation for the non-sphericity of particles used in this study. The applicability of two rheological models, namely, the power-law and the Carreau viscosity model has been examined in representing the drag coefficient results. Appropriate predictive expressions of the drag coefficient as a function of the particle Reynolds number and the Deborah number, encompassing wide ranges of rheological and kinematic conditions, are presented. 相似文献
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Sabine Tran-Cong 《Powder Technology》2004,139(1):21-32
The steady-state free-fall conditions of isolated groups of ordered packed spheres moving through Newtonian fluids have been studied experimentally. Measurements of the drag coefficients are reported in this paper for six different geometrical shapes, including isometric, axisymmetric, orthotropic, plane and elongated conglomerates of spheres. From these measurements, a new and accurate empirical correlation for the drag coefficient, CD, of variously shaped particles has been developed. This correlation has been formulated in terms of the Reynolds number based on the particle nominal diameter, Re, the ratio of the surface-equivalent-sphere to the nominal diameters, dA/dn, and the particle circularity, c. The predictions have been tested against both the experimental data for CD collected in this study and the ones reported in previous works for cubes, rectangular parallelepipeds, tetrahedrons, cylinders and other shapes. A good agreement has been observed for the variously shaped agglomerates of spheres as well as for the regularly shape particles, over the ranges 0.15<Re<1500, 0.80<dA/dn<1.50 and 0.4<c<1.0. 相似文献
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Solid particles of cylindrical shape play a significant role in many separations processes. Explicit equations for the drag coefficient and the terminal velocity of free-falling cylindrical particles have been developed in this work. The developed equations are based on available experimental data for falling cylindrical particles in all flow regimes. The aspect ratio (i.e., length-over-diameter ratio) has been used to account for the particle shape. Comparisons with correlations proposed by other researchers using different parameters to account for the geometry are presented. Good agreement is found for small aspect ratios, and increasing differences appear when the aspect ratio increases. The aspect ratio of cylindrical particles satisfactorily accounts for the geometrical influence on fluid flow of settling particles. 相似文献
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A simple correlation formula for the standard drag coefficient (i.e. a single stationary particle in a uniform flow) of arbitrary shaped particles is established using a large number of experimental data from the literature and a comprehensive numerical study [A. Hölzer, M. Sommerfeld, IUTAM Symposium on Computational Approaches to Multiphase Flow, Springer, 2006]. This new correlation formula accounts for the particle orientation over the entire range of Reynolds numbers up to the critical Reynolds number. Such a correlation may be easily used in the frame of Lagrangian computations where also the particle orientation along the trajectory is computed. 相似文献
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Extensive measurements of pressure drop in fixed beds, minimum fluidization velocity and expansion characteristics for beds of non-spherical particles are reported in the following ranges of conditions: 10-3 ≤ Re ≤ 20; 0.66 ≤ n ≤ 1 and 0.41 ≤ ? ≤ 0.75. Based on an analysis of these results, it is illustrated that the existing frameworks originally developed for Newtonian fluid flow through beds of spherical particles are also satisfactory for power law fluid flow through beds of non-spherical particles, provided a volume equivalent diameter modified by a sphericity factor and a modified Reynolds number are used instead of their usual definitions. 相似文献
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Comparison of formulas for drag coefficient and settling velocity of spherical particles 总被引:1,自引:0,他引:1
Nian-Sheng Cheng 《Powder Technology》2009,189(3):395-1451
Two formulas are proposed for explicitly evaluating drag coefficient and settling velocity of spherical particles, respectively, in the entire subcritical region. Comparisons with fourteen previously-developed formulas show that the present study gives the best representation of a complete set of historical data reported in the literature for Reynolds numbers up to 2 × 105. 相似文献
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Zhongliang Lu Kai Miao Weijun Zhu Yi Chen Yuanlin Xia Dichen Li 《Journal of the European Ceramic Society》2018,38(2):671-678
A new approach for the preparation of suspensions with a high solid loading and low viscosity by using irregular particles was proposed. These suspensions were prepared for the fabrication of multiscale ceramic components by gelcasting. Based on the Funk-Dinger function and fractal theory, the closest packing theory was applied to optimize the volume fractions of different particles. The maximum solid loading of slurries prepared for gelcasting was 62 vol%, and the viscosity at a shear rate of 100 s?1 was only 0.29 Pa s. By as-prepared suspensions, a decimeter-scale ceramic part with submillimeter features was fabricated successfully by gelcasting, which verify the feasibility of the proposed method. 相似文献
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G. I. Kelbaliyev 《Theoretical Foundations of Chemical Engineering》2011,45(3):248-266
This article, which is largely a review, deals with the drag force and drag coefficient for rigid spherical and deformable
particles in ordinary and non-Newtonian fluids. The most important theoretical formulas for small Reynolds numbers of Re ≪
1 and semiempirical formulas for the drag coefficient in a wide Re range up to 106 are presented. The deformation of drops and bubbles and its effect on the drag coefficient are considered. 相似文献
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The Use of Drag Reduction Agent and a Detergent for Drag Reduction in Circulatory Vertical Pipe Flow
B. A. Jubran Y. H. Zurigat M. S. Al-Shukri H. H. Al-Busaidi 《Polymer-Plastics Technology and Engineering》2013,52(4):533-538
This paper describes the results of an experimental study of drag reduction in a circulatory vertical pipe system for both upward and downward flows using a drag reduction agent, corrosion inhibitor, and a cheap detergent (washing-up liquid) with various concentrations for different flow rates. It was found that the corrosion inhibitor did not produce any drag reduction effect for both upward and downward flows while the drag reduction agent was effective for both flows; whereas, the detergent was effective only for upward flow. A comparison of the effectiveness of the drag reduction agent against the detergent showed that the effectiveness of the drag reduction agent is much higher than that of the detergent. The effect of liquid detergent is only noticeable if a large concentration is used. A 1000-ppm of detergent produces the same results as 25 ppm of drag reduction agent, which undermined the lower cost of the detergent. Over the range of Reynolds numbers tested the maximum drag reduction for upward flow is 35% while for the downward flow is 42%. 相似文献
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Effects of the confining wall or blockage on the heat transfer phenomena of spheroid particles were numerically investigated. The heated spheroid particles were maintained at constant temperature and allowed to sediment in cylindrical tubes filled with Newtonian liquids. In this flow configuration, the heat transfer took place from the heated spheroid particles to the surrounding Newtonian liquid. The governing conservation equations of the mass, momentum, and energy together with appropriate boundary conditions were numerically solved using commercial software based on computational fluid dynamics. A simple correlation for the average Nusselt number of the confined spheroid particles was developed which can be applied in new applications. 相似文献
14.
抽油机及其拖动系统节能综述 总被引:1,自引:0,他引:1
目前,油田在用的游梁式抽油机效率低、耗能高,在一定程度上加重了企业生产成本,节能降耗问题越来越受到关注。通过分析抽油机系统效率的影响因素、抽油机负荷以及电机的工作原理,得出抽油机低效率、高耗能的原因(也是抽油机拖动系统的高耗能原因),并总结了节能型抽油机、节能驱动设备和节能减速器三类节能方法,介绍了现有抽油机拖动系统的节能措施。 相似文献
15.
Roberta K. Rodrigues Lucas A. S. Silva Gabriel G. Vargas Bruno V. Loureiro 《Journal of surfactants and detergents》2020,23(1):21-40
This study describes the effects of wormlike micelles formed by the commercial surfactants tallowalkylamidopropyl dimethylamine oxide (Aromox APA-TW) and oleyl methyl bis(2-hydroxyethyl) ammonium chloride (Ethoquad O/12) as drag reducers. Ethoquad O/12 is immune to degradation by heat and microorganisms. Conversely, Aromox APA-TW is biodegradable in the environment, and its susceptibility to heat-induced degradation was previously assessed. This work considers the effects of temperature, salt, and time on the drag-reduction capacity (in different Reynolds number) of wormlike micelles of these two surfactants. Wormlike micelles formed by Aromox APA-TW are able to reduce drag at higher temperatures compared to wormlike micelles formed by Ethoquad O/12. However, Aromox APA-TW can degrade after being heated to 80 °C and also after storage of the wormlike micelle solutions. Ethoquad O/12 does not undergo degradation after being heated or stored. These surfactants have the potential to be used as additives in industrial operations, as the wormlike micelles formed are able to reduce drag in systems with long pumping distances or recirculation, even in solutions with high salt concentrations (brine) and high temperatures. 相似文献
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The very wide varieties of geometries of irregular particles makes it difficult to study their motion also propose a simple and general equation to estimate their drag coefficient (CD). The goal of this research is to (1) experimentally validate the general CD correlation previously proposed by the authors of this article as a simple tool to estimate the CD of spherical to highly irregular particles over a wide ranges of Re from 0.001 to 300,000, and (2) examine and expand the reference model particles proposed by the authors to represent a wide range of irregular shapes (60 non-flat and 36 flat). A comparison between the CD experimentally measured using reference model particles over a range of Re from 9 to 2481 and the CD estimated using general CD correlation, also comparing with CD correlations by others, demonstrated the accuracy and simplicity of the proposed general CD correlation. 相似文献
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使用3-溴丙烯和N,N-二甲基十八烷基叔胺合成水溶性阳离子疏水单体N,N-二甲基十八烷基烯丙基溴化铵(DOAB),仅使用水作为溶剂,合成了含有高摩尔分数疏水单体的部分水解聚丙烯酰胺型降阻剂,以核磁氢谱和元素分析得到降阻剂的结构为P(AM0.877-AA0.113-DOAB0.01);激光光散射法测得降阻剂摩尔质量为1.22×10~7 g/mol;黏度法测得临界缔合浓度(CAC)为2.8 g/L。测试了不同质量浓度下降阻剂稀溶液(即滑溜水)在不同流速下的摩阻,以清水为空白组计算降阻率,当降阻剂质量浓度为1.3 g/L时,降阻率最高可达72%;在盐水中,滑溜水降阻率下降,通过提高降阻剂质量浓度的方式可以提升降阻率,盐水中的降阻剂质量浓度为2 g/L时,降阻率最高达70.06%。由SEM得知,降阻剂在水中形成的网状结构是聚合物具有降阻性的直接原因。 相似文献
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以乙烯基三乙氧基硅烷 无水乙醚溶液处理玻璃管道内壁 ,降低流体水与管壁间的粘附功 ,研究了低粘附功内壁管道的内流减阻性能。结果表明 ,在管壁与液体间的粘附功小于液体的内聚功条件下 ,当雷诺数大于临界雷诺数时 ,低粘附功内壁管道呈现明显的内流减阻效果 ,临界雷诺数的值与一定的临界壁面剪力值或层流底层临界厚度值相对应 ;在减阻区内 ,减阻率随雷诺数的增加及管道内径的减小而增大 ,阻力系数的无因次关联式可表示为λ=f (Re ,X) ,其中X为无因次数群 [W / (du2 ρ) ]。 相似文献