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柱式萃取设备内液-液两相流体动力学及其稳定性的研究
鲍晓军
Subtype博士
Thesis Advisor陈家镛
1990-06-30
Degree Grantor中国科学院研究生院
Abstract本文以往复振动筛板萃取柱为对象,从理论和实验两个方面研究了萃取柱内液-液两相逆流流动的流体动力学。本文将分散体系中液滴群的运动视为单液滴在由连续相介质和周围其它液滴所组成的“新”流体-拟流体中的运动,通过引入拟流体的虚拟密度考虑了液滴间连续相流体的速度分布对液滴所受曳力的影响,对液滴在分散体系中受到的浮力采用拟流体的平均密度进行了修正,根据前人关于两相悬浮体的表现粘度的研究结果定义了拟流体的表现粘度,提出了描述分散体系中液滴群运动的拟流体模型。以轴向扩散模型为基础,综合考虑了两相的相对运动、反混以及液滴的分散现象的作用,建立了往复振动筛板萃取柱内分散相液滴的群体平衡方程。该模型区别了液滴的前混、湍流扩散及液滴的破碎和凝聚对分散相轴和混合的影响,反映了柱内两相流动的非均匀性。本文偿试运用了不可逆过程热力学,从系统的稳定性分析着手,根据最小熵增率原理提出了往复振动筛板萃取柱内液-液两相逆流流动的稳定性条件,对质量不守恒的原因进行了初步的探讨。
Other AbstractIn present work, an interactive mathematical model for the dispersed liquid-liquid countercurrent two phase flow in column-type extractors was proposed. A pseudo-fluid model for the dispersed two phase flow of drops was developed by assuming a simple similarity between the motion of a single drop in infinite continuous medium and that of a drop moving in a suspension defined as pseudo-fluid composed f continuous medium and all the other droplets present. The expressions of buoyancy force, drag force and drag coefficient for a drop in dispersion were formulated in terms of the pseudo-density, mean density and apparent viscosity of the pseudo-fluid, taking into account of the effects of both velocity profile of the continuous medium in interstices of the drops and the presence of other drops. The equations of motion of a multi-droplet system in a form identical with those of a single drop system can be derived from the pseudo-fluid model and thus simplifies the description of the characteristics of dispersed two phase flow. On the basis of the traditional diffusion model, a population balance equation for dispersed phase drops was established. This equation could take into account such as relative effect of the forward mixing, turbulent diffusion and droplet mixing processes of breakage and coalescence on the hydrodynamic behavior of column extractors. In view of the material unbalance of the flow of dispersed phase through the column encountered in simulation, a non-equilibrium thermodynamic approach was attempted to investigate the stability of the countercurrent two phase flow in the column and thus to analyze the problem of the unbalance. Based on the assumption of a linear system, an expression for entropy production due to various irreversible processes occurred inside the reciprocating plate extraction column was deduced. The modelling of the two phase flow in a column was thus subject to the constraint of minimization of rate of entropy production and also to the constraint of hydrodynamics.
Pages123
Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/6810
Collection研究所(批量导入)
Recommended Citation
GB/T 7714
鲍晓军. 柱式萃取设备内液-液两相流体动力学及其稳定性的研究[D]. 中国科学院研究生院,1990.
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