Mass Transfer from Ensembles of Newtonian Fluid Spheres at Moderate Reynolds and Peclet Numbers
Mass Transfer from Ensembles of Newtonian Fluid Spheres at Moderate Reynolds and Peclet Numbers
复制标题
中等雷诺数和佩克莱特数下牛顿流体球系团的质量传递
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
V. Eswaran
中科院分区：
文献类型：
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作者：
N. Kishore;R. Chhabra;V. Eswaran
摘要 在这项工作中，对中等雷诺数和佩克莱特数下从单一尺寸球形牛顿液滴（不含表面活性剂）到牛顿连续相的传质速率进行了数值研究。一个简单的球形细胞模型（所谓的自由表面细胞模型）已用于解释液滴间的流体动力学相互作用。已获得大量数值结果来阐明雷诺数 (Reo)、内部与外部流体粘度之比 (k)、分散相体积分数 (ɛ) 和施密特数 (Sc) 对局部和平均舍伍德数 (Sh) 在条件范围内的影响：1 ≤ Reo ≤ 200， 0.2 ≤ ɛ ≤ 0.6、 0.1 ≤ k≤ 50 和 1 ≤ Sc ≤ 10 000。据观察，对于所有分散相浓度值，对于小佩克莱特数 (Pe) 值，粘度比对局部和平均舍伍德数的影响不太显着。随着粘度比值的增加，所有液滴浓度和雷诺数值的平均舍伍德数都会降低。基于目前的数值结果，提出了一种简单的预测相关性，可用于估计新应用中液-液系统中的相间传质速率。然而，这里还需要补充一点，在较高浓度下，流体球会显着相互作用、变形和合并。本研究忽略了所有这些影响。因此，目前的结果仅对稀至中等浓度的分散相有效。
Abstract In this work, the rate of mass transfer from an ensemble of mono-size spherical Newtonian droplets (free from surfactants) to a Newtonian continuous phase has been numerically studied at moderate Reynolds and Peclet numbers. A simple spherical cell model (so-called free surface cell model) has been used to account for inter-drop hydrodynamic interactions. Extensive numerical results have been obtained to elucidate the effects of the Reynolds number (Reo), the ratio of internal to external fluid viscosity (k), the volume fraction of the dispersed phase (ɛ) and the Schmidt number (Sc) on the local and average Sherwood number (Sh) over the ranges of conditions: 1 ≤ Reo ≤ 200, 0.2 ≤ ɛ ≤ 0.6, 0.1 ≤ k≤ 50 and 1 ≤ Sc ≤ 10 000. It has been observed that the effects of viscosity ratio on the local and average Sherwood number is less significant for small values of the Peclet number (Pe) for all values of dispersed phase concentration. As the value of the viscosity ratio increases, the average Sherwood number decreases for all values of the droplet concentration and the Reynolds number. Based on the present numerical results, a simple predictive correlation is proposed which can be used to estimate the rate of inter-phase mass transfer in a liquid–liquid system in a new application. However, it is also appropriate to add here that at higher concentrations, fluid spheres interact significantly, deform and coalesce. All these effects are neglected in this study. Therefore, the present results are valid only for dilute to moderate concentration of the dispersed phase.