RADIAL FLOW HOLLOW FIBERREVERSE OSMOSIS: EXPERIMENTS AND THEORY

The performance of a hollow fiber reverse osmosis system is studied both theoretically and experimentally. Experiments were carried out for applied pressure ranging from 200 to 400 psig, feed rates varying from 75 to 380 cc/sec and for feed concentrations up to 34,000 ppm of sodium chloride.

A mathematical model is proposed to predict productivity, ?, and product concentration, θ_p. The model involves solving membrane transport equations simultaneously with the hydrodynamic equations. The solubility-diffusion-imperfection, or pore diffusion model, is used to describe solute and solvent transport across the membrane. The axial gradients of shell side concentration, neglected in previous investigations, are taken into account. The differential equations are solved numerically by the 4th Order Runge-Kutta method.

Predicted values of ? and θ_p agree within 8% and 17% respectively, with experimental data over the entire range of operating conditions. However, membrane transport coefficients were found to be concentration dependent.

An approximate analysis shows that the concentration polarization is negligible in present day hollow fiber systems.     

荷电中空纤维复合膜及其正渗透性能研究

以聚丙烯中空纤维微滤膜为底膜、羧甲基纤维素钠为功能材料、氯化铁为交联剂,采用溶液涂覆-交联工艺制备了表面荷电的中空纤维复合膜,将该中空纤维复合膜用于正渗透(FO)过程,研究了汲取液盐含量、原料液流速等对FO通量的影响。结果表明,制备的荷电中空纤维复合膜可用于FO过程,以蒸馏水为原料液、Na2SO4水溶液为汲取液,采用PRO模式进行FO试验,当原料液与汲取液体积流量均为15 mL/min、汲取液浓度为0.5 mol/L时,FO水通量为12.3 L/(m2.h),盐通量与水通量的比为1.42 g/L。     

低压醋酸纤维素中空纤维反渗透膜及组件研制

本文报导了以二醋酸纤维素(CA)为原料,通过溶液干湿法多孔纺丝制膜技术生产低压中空纤维反渗透膜及组件的研究成果。研制的TF-100型(4″)RO 组件在以自来水为进水,操作压力1MPa,水回收率50%条件下测试;脱盐率为93%,产水量为200 L/h(25℃)。组件可用于自来水和低度含盐水的脱盐。     

EVALUATION OF SURFACE FORCE-PORE FLOW AND MODIFIED SURFACE FORCE-PORE FLOW MODELS FOR REVERSE OSMOSIS TRANSPORT

The surface force-pore flow (SF-PF) model of reverse osmosis transport and the extended and modified form (the MD-SF-PF model) have been employed to predict the performance of four aromatic polyamide (FilmTec, FT30)reverse osmosis membranes. The evaluation is based on a comparison of model predictions with experimental data. Dilute sodium chloride-water solution experimental data were used to estimate model parameters. The models are then used to predict flux and separation at various operating pressures and concentrations. Membrane performance (i.e., separation and permeate flux) can be well predicted by the MD-SF-PF model while the SF-PF model predicts the performance for the sodium chloride system less satisfactorily.     

正渗透膜净水试验研究

研究了正渗透(FO)过程中水通量和驱动溶质扩散规律,并以奎宁和腐殖酸作为模型有机物,研究FO膜对有机物的截留性能。结果表明,FO水通量与驱动液含量正相关,但由于内部浓差极化的影响并不呈正比例;温度越高所产生的水通量也越大,在温度11～36℃时水通量从4 L/(m2.h)上升至10 L/(m.h)。驱动溶质的反扩散量随运行时间的延长线性增加,由于唐南效应Na+的反扩散量大于2价阳离子。FO膜对奎宁和腐殖酸均有较好的截留效果。     

移动床径向反应器中流体力学行为的研究

比较了直径500mm移动床径向反应器中向心Z型、向心Π型、离心Z型、离心Π型4种气体流动类型.实验表明,离心Π型流动时,气体轴向分布不均匀度小于5%,为最佳气体流动类型.文中还得到了描述主流道中静压分布的动量交换系数K值.     

径向流固定床反应器的流动特性研究及结构参数的合理选择

径向流固定床反应器的操作状态和反应效果在很大程度上取决于反应器内穿越催化剂床层径向气流沿反应器轴向分布的均匀程度，亦即床层内催化剂负荷的均布程度。本文对此类反应器内的流动特性进行了研究，对立了描述反应器内流动规律的基本运动方程。研究结果表明，径向气流的轴向分布情况与反应器的流动结构型式、反应器内分流流道与合流流道截面积的比值、催化剂床层的阻力系数以及反应器的高径比等参数有关。并提出了如何合理选择反     

RTM二维径向流动模型的理论概况及研究

综述了牛顿流体在放置了各向同性和各向异性预制件的RTM平板模具中二维径向恒流和恒压渗流的流动模型.对各个模型的可测量物理量之间的关系通过求解其解析解进行了必要的拓展补充推导和研究分析,对传统的二维解析方程进行了拓展和改进,提供了在不透明模具中测定渗透率的方法.即在恒流条件下利用压力传感器和恒流泵测定预制件的二维渗透率;或者在恒压条件下利用数字流量计和压力表测得二维渗透率.这些解析解的关系式也可用于实验预估模具中的压力分布及充模时间等.     

A REVIEW OF THEORY AND EXPERIMENTS ON DIFFUSION FROM SUBMICROSCOPIC PARTICLES

Diffusion-controlled evaporation or growth of submicroscopic particles is considered theoretically and experimentally. The conditions for which Fick's law apply are elucidated for Knudsen aerosols, and Fick's law together with the Chapman-Enskog molecular theory of gases are applied to determine diffusivities and Lennard-Jones intermolecular force parameters from experimental data on single submicron aerosol evaporation. The experimental method involving light scattering from a single droplet suspended in an electric field is reviewed, and the results for diffusion-controlled and noncontinuum evaporation are presented. For Knudsen numbers greater than 0.05, where diffusion theory does not apply, evaporation rate data are compared with available theoretical and semi-theoretical equations. A recently published solution of the stationary Boltzmann equation, modified to include the collision integral, is shown to be in excellent agreement with our experimental data for dibutyl sebacate evaporating into nitrogen.     

A REVIEW OF THEORY AND EXPERIMENTS ON DIFFUSION FROM SUBMICROSCOPIC PARTICLES

Diffusion-controlled evaporation or growth of submicroscopic particles is considered theoretically and experimentally. The conditions for which Fick's law apply are elucidated for Knudsen aerosols, and Fick's law together with the Chapman-Enskog molecular theory of gases are applied to determine diffusivities and Lennard-Jones intermolecular force parameters from experimental data on single submicron aerosol evaporation. The experimental method involving light scattering from a single droplet suspended in an electric field is reviewed, and the results for diffusion-controlled and noncontinuum evaporation are presented. For Knudsen numbers greater than 0.05, where diffusion theory does not apply, evaporation rate data are compared with available theoretical and semi-theoretical equations. A recently published solution of the stationary Boltzmann equation, modified to include the collision integral, is shown to be in excellent agreement with our experimental data for dibutyl sebacate evaporating into nitrogen.     

RADIAL FLOW CHROMATOGRAPHY IN COMPRESSED PANCAKE-SHAPED BEDS

High compression of sorbent powders promotes flow uniformity and reduces interstitial porosity. These features were exploited in a radial flow configuration to show that good peak resolution was possible for applications to analytical chromatography. An exact analytical solution was uncovered to predict the transient response of an elementary pulse of solute in a flowing inert gas. Experiments on the system methane on alumina are compared quite favorably with theory, showing that the key dissipative force for band broadening is radial diffusion     

OBSERVABLE MULTIPLICITY FEATURES OF INHOMOGENEOUS SOLUTIONS MEASURED BY THE THERMOCHEMIC METHOD: THEORY AND EXPERIMENTS

The thermochemic method, where the catalyst temperature is manipulated by Joule-heating, may falsify the underlying kinetics by inducing inhomogeneous solutions. This work analyzes the multiplicity and stability of these states in a wire with uniform activity with or without gaps in heat conduction. Measurements of integral properties may indicate the existence of inhomogeneities either by the existence of characteristic multiplicity patterns and bifurcation maps or by unique quantitative features

These tests are employed to show that the two intermediate branches, out of four observed in ammonia oxidation, are inhomogeneous solutions induced by lack of communication. The measured bifurcation set, separating the domains of existence of the four states, is mapped in the three dimensional space of reactants concentrations and temperature.     

OBSERVABLE MULTIPLICITY FEATURES OF INHOMOGENEOUS SOLUTIONS MEASURED BY THE THERMOCHEMIC METHOD: THEORY AND EXPERIMENTS

The thermochemic method, where the catalyst temperature is manipulated by Joule-heating, may falsify the underlying kinetics by inducing inhomogeneous solutions. This work analyzes the multiplicity and stability of these states in a wire with uniform activity with or without gaps in heat conduction. Measurements of integral properties may indicate the existence of inhomogeneities either by the existence of characteristic multiplicity patterns and bifurcation maps or by unique quantitative features

These tests are employed to show that the two intermediate branches, out of four observed in ammonia oxidation, are inhomogeneous solutions induced by lack of communication. The measured bifurcation set, separating the domains of existence of the four states, is mapped in the three dimensional space of reactants concentrations and temperature.     

传热系数对中空纤维周向和径向温度梯度分布的影响

由侧吹风引起的传热系数 (h)对纤维的传热影响较大 ,尤其是不对称冷却吹风将引起纤维截面温度分布的不对称性。文中利用计算机纺丝模拟 ,详细讨论了中空纤维在强吹风条件下 ,h随纺程在截面上的变化及其对温度截面梯度的影响。对强吹风中空纤维的纺丝模拟的传热系数进行了修正     

气固流化床中气泡流运动特征和空隙率径向分布

The flow behavior of the bubble in gas/solid fluidized bed is studied in multi-scales.A hypotheses of taking dispersed bubble as the continuous medium and the hydromechanics expression based on volume flux are proposed.The mathematical model of radial porosity distribution in the dense zone is developed.The radial distribution of the porosity is parabolic in nature according to the theoretical calculation and the calculated data is consistent with experimental data satisfactorily.     

气固流化床中气泡流运动特征和空隙率径向分布

引言流态化技术在工业领域应用越来越广,但由于流态化行为复杂,许多内在规律还有待于进一步揭示．气固流化床中最基本的特征是颗粒聚集的乳化相与气体聚集的气泡相共存,它的复杂性就在于它的不均匀性和多态性．气固流化床中的不均匀性是由空隙率分布来描述的,然而空隙率的分布目前还未能从理论上得到定量的描述．气固流化床内的空隙率分布与气泡的运动密切相关,因此对床层空隙率的了解最终决定于对流化床气泡运动的研究．在此作者采用流体力学的方法从宏尺度和宇尺度范围来探讨气固流化床内气泡的运动规律,建立相应的多尺度、连续介质…     

检验反渗装置流率参数的方程式

本文根据反渗透过程的物科平衡的原理，推导一组以可测的浓度和流率为自变量的多段设计的ＲＯ装置流率参数的一般方程式，借此，可用来检验或调整设计的ＲＯ装置的流率参数，使之符合设计的操作要求，本文还对这些方程式的应用作了概述。     

移动床径向反应器中气体离心流动对颗粒移动状况的影响

对于催化剂不断失活但可再生的工业过程,广泛采用移动床径向反应器在较低的系统压降下进行连续操作.此时存在由贴壁和空腔现象所决定的径向气体流量的上限值.本文分析了有径向离心气体流动时颗粒层中的应力分布,应用散料力学理论建立了计算床中初始形成空腔时无因次床层总压降的理论模型,模型预测值与实验值符合很好.同时测定了不同条件下空腔界面的形状.