Uniform flux heat transfer in concentric laminar flow of two immiscible liquids

The energy equation was solved exactly for fully developed steady laminar flow in a circular pipe of two immncible Newton liquids with a concentric cylindrical interface between them, assuming invariant physical properties of the liquids, uniform heat flux at the wall and fully developed temperature profiles. It is shown that, even if the viscosity of the annular liquid is orders of magnitude smaller than that of the core liquid, the improvement in heat transfer to the core liquid by infection of the annular liquid cannot exceed a factor of 1 8     

Spectroelectrochemical analysis of ion-transfer and adsorption of the PAMAM dendrimer at a polarized liquid|liquid interface

The interfacial behavior of the fourth generation polyamidoamine (G4 PAMAM) dendrimer at a water|1,2-dichloroethane (DCE) interface was studied by cyclic voltammetry and potential modulated fluorescence (PMF) spectroscopy. Irregular voltammetric responses were observed at positively polarized interfaces. The cyclic voltammogram was strongly dependent on pH and on the concentrations of the G4 PAMAM dendrimer and the organic supporting electrolyte. PMF spectroscopy was successfully used to analyze the interfacial mechanism of the dendrimer by adding an anionic porphyrin derivative as a fluorescent probe. The results of the PMF measurements demonstrated that the G4 PAMAM dendrimer was transferred across the interface, a process that was accompanied by an adsorption step at pH 7. In contrast, under alkaline conditions, the adsorption process did not seem to be involved in the interfacial behavior.     

Kinetic study of atom transfer radical polymerization of methyl methacrylate in ionic liquids

The kinetics of methyl methacrylate (MMA) homopolymerization performed by atom transfer radical polymerization (ATRP) is investigated in detail using ethyl‐2‐bromopropionate (EPN‐Br) as initiator, CuBr as catalyst, and pentamethyldiethylenetriamine (PMDETA) as ligand in ionic liquids (ILs) and acetonitrile. ILs in this research covered two different substitutional imidazolium cations and anions including halogen and halogen‐free ones. The typical cations include 1‐butyl‐3‐methylimidazolium, 1‐ethyl‐3‐methylimidazolium and the typical anions include bromide, tetrafluoroborate. The effects of solvents, temperature, and reaction ingredients ratios on the polymerization kinetics are all investigated in this article and the apparent energy of activation (ΔE) calculated for the ATRP of MMA in 1‐butyl‐3‐methyl‐imidazolium tetrafluoroborate is 6.95 KJ/mol. The number‐average molecular weights (M_n) increase linearly with conversion but are much higher than the theoretical values. It is probably due to the low concentration of deactivator at the early stage of polymerization and the lower bond energy of C‐Br in PMMA‐Br than that in EPN‐Br. Moreover, the catalyst is easily separated from the polymer and the regenerated catalyst is reused for more than three times. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

氨为核树状大分子聚酰胺-胺的制备与破乳性能

采用发散法以氨为核、甲醇为溶剂,交替与丙烯酸甲酯和乙二胺反应,合成了0．5-3．0代的树枝状大分子聚酰胺-胺,采用端基滴定分析对分子的结构进行了表征,并研究了它们对模拟原油乳液的破乳性能。结果表明：它们与以乙二胺为核心的树枝状大分子聚酰胺-胺所表现出来的趋势完全一致。     

Gas–liquid and liquid–liquid mass transfer in microstructured reactors

This article is a comprehensive overview of gas–liquid and liquid–liquid mass transfer in microstructured reactors (MSR). MSR are known to offer high heat and mass transfer rates for two phase systems due to high surface to volume ratio as compared to conventional reactors. The reactions with fast kinetics controlled by mass transfer have been successfully intensified using MSR. The first part of the review deals with the methods of mass transfer characterization. Further, different dimensionless parameters used to analyze mass transfer in MSR are discussed. The literature data with different flow regimes and proposed empirical correlations for both gas–liquid and liquid–liquid systems is also presented. The conventional mass transfer models such as penetration and film theory are analyzed. Finally, the important issues of mass transfer in MSR are summed up.     

The transfer mechanisms and analytical properties of the variable-valency drug cinchonidine across the liquid/liquid interface

The electrochemical transfer of cinchonidine across the liquid/liquid (L/L) interface was investigated by linear current-scanning polarography at the ascending water electrode and chronopotentiometry at the stationary water electrode. The relation between half-wave potential and the pH value of the aqueous phase was established and is in good agreement with the experimental results. Defending on the pH value in the aqueous phase, both singly- and doubly-charged cinchonidine cations can transfer across the L/L interface. This process is controlled simultaneously by diffusion and the rate of re-establishment of the disturbed protonation equilibrium. The effects of the supporting electrolyte, buffer and organic solvent on the polarographic wave were examined, and the transfer characteristics of cinchonidine in the aqueous and organic phases were compared. Direct determinations of cinchonidine in the aqueous phase and organic phase were carried out by linear current-scanning polarography with high selectivity. The linear range for determination is 5 × 10⁻⁵−1 × 10⁻³ mol dm⁻³.     

Theory of the double-layer effect on the rate of charge transfer across an electrolyte/electrolyte interface

Effect of the electric double-layer structure on the rate equations of charge (ion or electron) transfer across an electrolyte/electrolyte solution interface is discussed. The electric double layer is considered as composed of the inner layer sandwiched by two diffuse layers in both side. The charge transfer reaction is considered as taking place between two chemical species at the planes of contact of the inner layer with the two respective diffuse layers. A steady-state ionic transport in the diffuse layers (Levich correction) is assumed. Two ideal processes; inner layer rate-determining process and diffuse layer rate-determining process are addressed.     

Cation transfer across a hydrogel/organic phase: Effect of cation size, hydrophobicity and acid-base properties

The transfers of tetraethylammonium (TEA⁺) and protonated triflupromazine (HTFP⁺) through a hydrogel/liquid interface (g/o) and a liquid/liquid interface (w/o) were compared using cyclic voltammetry. After the two phases were put in contact, the behavior of each molecule was analyzed at different pH values and at different time points. The gel induces hydrophobic and electrostatic interactions with TEA⁺ and HTFP⁺, shifting the peak potentials to more positive values. The diffusion coefficients, D, in both phases (g and w) at different pH values were calculated. In the case of TEA⁺, the D value remains constant in both systems. However, the D value of HTFP⁺ is lower in the gel phase than in the liquid phase.HTFP⁺ is transferred from the aqueous phase to the organic phase via a direct mechanism that involves coupled acid-base and partition processes. At the g/o interface, the coupled chemical reactions of HTFP⁺ were inhibited by the drug/gel interaction. The results demonstrate that the g/o system could be used as a model to study the controlled release of charged drugs.     

Derivation of the explicit equation relating mass-transport-limited-current to voltage at the interface between two immiscible electrolyte solutions (ITIES)

The potential drop between two immiscible electrolyte solutions consists of the sum of that across the double layer and the diffusion barrier layer. A relation between these components has been proposed by Indenbom. We extended his approach to give a relation between the current density and the overall potential drop between the two bulk solutions. The final expression is mathematically similar to the Butler–Volmer equation for classical electrode kinetics.     

Axial mixing and mass transfer investigation in a pulsed packed liquid–liquid extraction column using plug flow and axial dispersion models

In this research work, the volumetric overall mass transfer coefficient based on continuous-phase (K_oca) and axial dispersion coefficients of phases (E_c, E_d) in a pilot Pulsed Packed Liquid Extraction Column (PPLEC) have been studied using plug flow model (PFM) and axial dispersion model (ADM). Experiments have been carried out using standard systems of water/acetone/toluene and water/acetone/n-butyl–acetate. Values of K_oca evaluated by ADM are greater than those of PFM by about 20% indicating that the axial mixing lowers the performance of PPLEC. It was found that the drop-size distribution is the main cause of the axial mixing in PPLEC. Increase in dispersed phase flow rate (Q_d), increases all K_oca, E_d and E_c and the minimum values of both E_d and E_c and the maximum values of K_oca are in pulse intensity ranges of 0.8–1 cm/s. Finally, three empirical correlations are proposed for the prediction of these parameters which are in good agreement with the experimental data.     

Non-equilibrium thermodynamic analysis of coupled heat and moisture transfer across a membrane

Non-equilibrium thermodynamics theory is used to analyze the transmembrane heat and moisture transfer process, which can be observed in a membrane-type total heat exchanger (THX). A theoretical model is developed to simulate the coupled heat and mass transfer across a membrane, total coupling equations and the expressions for the four characteristic parameters including the heat transfer coefficient, molar-driven heat transfer coefficient, thermal-driven mass transfer coefficient, and mass transfer coefficient are derived and provided, with the Onsager’s reciprocal relation being confirmed to verify the rationality of the model. Calculations are conducted to investigate the effects of the membrane property and air state on the coupling transport process. The results show that the four characteristic parameters directly affect the transmembrane heat and mass fluxes: the heat and mass transfer coefficients are both positive, meaning that the temperature difference has a positive contribution to the heat transfer and the humidity ratio difference has a positive contribution to the mass transfer. The molar-driven heat transfer and thermal-driven mass transfer coefficients are both negative, implying that the humidity ratio difference acts to reduce the heat transfer and the temperature difference works to diminish the mass transfer. The mass transfer affects the heat transfer by 1%–2% while the heat transfer influences the mass transfer by 7%–14%. The entropy generation caused by the temperature difference-induced heat transfer is much larger than that by the humidity difference-induced mass transfer.     

Local rates of heat and mass transfer during condensation of non-eutectic vapours of binary immiscible liquids

Heat and mass transfer data are reported for the condensation of vapours of immiscible liquids. Condensation occurred on the outside of 0.0254 m diameter horizontal copper tube. Mixtures of organic vapours in steam have been studied, such mixtures being rich in steam and removed from the eutectic composition.

The condensate flow pattern has been determined experimentally. In systems where the density ratio of the organic to water liquids is less than one, a standing-drop pattern is observed; when the ratio is greater than one, channeling flow is the main feature.

For systems removed from the eutectic composition, diffusional resistance through the vapour phase adjacent to the vapour—liquid interface has a major effect on the transfer rates.     

Liquid-liquid interfacial processes at hydrophobic silica carbon composite electrodes: ion transfer at water-nitrobenzene, water-o-nitrophenyloctylether, and at water-o-nitrophenylphenylether interfaces

Ion transfer processes across liquid-liquid phase boundaries of the type aqueous solution-polar organic solvent supported on a hydrophobic silica carbon composite are studied by cyclic voltammetry and differential pulse voltammetry. The organic phase consists of a redox probe (ferrocene, t-butylferrocene, or decamethylferrocene) dissolved in a polar hydrophobic solvent (nitrobenzene, o-nitrophenyloctylether, or o-nitrophenylphenylether). The organic phase was immobilised in a ceramic carbon material composed of a hydrophobic silicate prepared via a sol-gel process from a methyltrimethoxysilane based sol and carbon particles. When immersed into aqueous electrolyte, ion transfer processes can be monitored as a function of potential. The contributions of solvent, electrolyte, and redox probe to the transition from anion transfer to cation transfer are discussed. Effects due to the presence of a high surface area microporous solid matrix are considered.     

Interpretation of ion transfer reactions across the interface between two immiscible electrolyte solutions by the model of “elastic” inner layer

The model assuming that the elastic force of interfacial tension counteracts introduction of ions into adjacent electrolyte solution is discussed. The main electrochemical properties of ITIES are analyzed on the basis of this model. It is shown that many of experimental results of study of double-layer capacitance, potential drop across the inner layer, kinetics of simple and facilitated ion transfer as well as resolvation energy of hydrophobic ions are in good agreement with predictions drawn from the model. It is concluded that ITIES acquire the property of polarizability although heterogeneous step of simple ion transfer is reversible. The performed theoretical analysis of transfer of ions of supporting electrolytes has offered a simple equation to describe experimental voltammetric curves and to obtain a quantitative criterion of the polarizability.     

Design and synthesis of novel fluorescence sensing perylene diimides based on photoinduced electron transfer

Two novel tetraester- and PAMAM-branched perylene diimides were synthesized and configured as “fluorophore-spacer-receptor” systems based on photoinduced electron transfer. Due to their long alkylester and alkylamine terminal groups the examined compounds were well soluble in organic solvents. Photophysical characteristics of the dyes were investigated in DMF and water/DMF (1:1, v/v) solution. The ability of the synthesized perylene diimides to detect cations was evaluated by the changes in their fluorescence intensity in the presence of metal ions (Zn²⁺, Co²⁺, Cu²⁺, Fe³⁺, Pb²⁺, Hg²⁺, Ag⁺ and Ni²⁺) and protons. The dyes under study displayed “off-on” switching in its fluorescence as a function of pH, which is attributed to disallowing photoinduced electron transfer from the receptor moiety to the fluorophore. PAMAM-branched dye displayed a good pH sensor activity (FE = 6.4), however the pH sensing ability of tetraester was substantially higher (FE = 184). In the presence of Cu²⁺ and Pb²⁺ ions tetraester quenched its fluorescence intensity (FQ = 22 and 12 respectively), while PAMAM-branched dye enhanced its fluorescence intensity with pronounced selectivity to Cu²⁺ and Fe³⁺ (FE = 3.2 and 4.9, respectively). The results obtained indicate the potential of the novel compounds as fluorescent detectors for metal ions with pronounced selectivity towards Cu²⁺, Pb²⁺ and Fe³⁺ ions and highly efficient “off-on” pH switches, especially a tetraester-branched perylene diimide.     

m－DVB和p－DVB原子转移自由基聚合动力学

以氯端基聚苯乙烯为大分子引发剂,氯化亚铜／２,２’－联二吡喧为催化剂,邻二甲苯为溶剂,用气相色谱分别研究了对二乙烯基苯（ｐ－ＤＶＢ）和间二乙烯在苯（ｍ－ＤＶＢ）在１００￣１３０℃的原子转移自由基聚合动力学。结果表明,聚合符合表观一级反应动力学。ｐ－ＤＶＢ在１００,１１０,１２０、１３０℃的聚合速率常数分别为０．０７２,０．１２８,０．３７９,０．５４６ｈ＾－１,ｍ－ＤＶＢ在上述不同温度的聚合速率常     

Transfer coefficients for the liquid–vapor interface of a two-component mixture

We present the excess entropy production for heat and mass transport across an interface of a non-ideal two-component mixture, using as interface variables the excess densities proposed by Gibbs. With the help of these variables we define the interface as an autonomous system in local equilibrium and study its transport properties. The entropy production determines the conjugate fluxes and forces, and equivalent forms are given. The forms contain finite differences of intensive variables into and across the surface as driving forces. These expressions for the fluxes serve as boundary conditions for integration across heterogeneous systems that are far from global equilibrium.The resistivities to heat transfer and the coupling coefficients for heat and mass transfer were determined using non-equilibrium molecular dynamics (NEMD) simulations in a system of Lennard-Jones spline particles of the same diameter and mass, but with potential depths that differ by a factor 0.8. The coupling coefficients for heat and mass transfer are significant. A relation of the coupling coefficients and the partial molar enthalpy of evaporation is verified for each component. As a consequence, it is not sufficient to use for instance Fourier's law for transport of heat across surfaces.Support is presented for a new method to find coefficients from integral relations. The method was verified using one of the NEMD coefficients, and used to calculate contributions to the remaining resistivities. One would expect kinetic theory to predict the resistivities at low vapor densities, but this is found to be correct only for the thermal resistivity. The interfacial heat and mass transfer coefficients are found to differ widely from kinetic theory predictions. Estimates of the resistivities to mass transfer differ by more than an order of magnitude. These results will have a bearing on the dynamic modeling of evaporation/condensation and desorption/adsorption.     

隔离壁精馏塔水平传热设计与研究

通过将隔离壁精馏塔(DWC)的隔板两侧进行水平传热,可以进一步降低DWC的能量消耗。本文以假想的三组分混合物A,B,C为例,在三塔简捷计算初值的基础上,利用Mathematica对DWC进行最终的优化设计,并进行了主塔和副塔间水平传热的研究。结果表明,与未耦合的DWC对比,耦合DWC最大能够节能0.9%,且耦合塔板数与耦合面积能够影响DWC的节能效果。     

重力场对管内液液间传质影响的数值模拟

针对管内液液传质现象,建立速度场、重力场及湍流涡旋影响下的质量传递非稳态数学模型。利用PHOE-NICS 3.6软件数值求解,分析了在不同工况下管内柴油与汽油顺序输送界面处的体积分数分布情况。结果表明,在紊流输送下,密度差影响体积分数分布曲线的位置,管道倾角影响体积分数曲线的斜率,重力场对管内液液间传质总体影响较小;在停输下,较重液体处在势能高处时,则产生自然对流,对传质影响很大,且随时间延长持续下去;对较重液体处在势能较低处时,随时间延长,自然对流传质被抑制,二液体分子扩散起主导作用,且产生明显的分层。因此,依据此研究方法所得结果比试验测定提供了更为丰富的体积分数场分布信息。     

Electrosynthesis in systems of two immiscible liquids and a phase transfer catalyst. VI. The influence of zinc chloride on the chlorination of naphthalene

The influence of zinc chloride on the chlorination of naphthalene by electrolysis in a water-methylene chloride emulsion and using tetrabutylammonium ion as a phase transfer catalyst is described. It is shown that when the aqueous medium contains both NaCl and ZnCl₂ it is the anion ZnCl ₄ ^2– which transfers into the organic phase and it is confirmed that the presence of ZnCl₂ in the electrolyte is, indeed, beneficial. The electrolyses have been carried out in both divided and undivided cells and in both the organic yield of 1-chloronaphthalene can exceed 80% but the former is better from the viewpoint of speed of electrolysis; in the divided cell, the conversion was 85% (cf. typically 60% in the undivided cell) after the passage of 2.3 F mol^–1 of naphthalene. Possible mechanisms for the effect of ZnCl[in2] are discussed.On leave of absence from the Faculty of Technology, University of Banja Luka, Yugoslavia.