Influence of transverse rotating magnetic field on enhancement of solid dissolution process

The main objective of this work is to study the effect of transverse rotating magnetic field (TRMF) on the enhancement of solid dissolution process in the novel type reactor (TRMFR). The application of magnetically driven fluidization (MDF with homogeneous and heterogeneous systems) on mass transfer process is presented. A study of the effect of ferromagnetic particles content on solid–liquid mass transfer has been made. The experimental investigations are provided for the explanation of the influence on the dissolution process of a solid body to surrounding its dilute solution in a novel type reactor with the ferromagnetic particles suspended. The mass transfer coefficient is calculated from a kinetic equation and correlated in the relationship including standard and magnetic dimensionless numbers. The overall enhancements due to TRMF and MDF were compared. Unique correlating relations were obtained to generalize the experimental database. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Study of effect of temperature gradient on solid dissolution process under action of transverse rotating magnetic field

The study of effect of the transverse rotating magnetic field on the dissolution process of rock‐salt sample is the main purpose of this work. Moreover, the experimental study of the influence of the temperature gradient between the surface of sample and the solvent temperature on this process is presented in this article. The results of investigations are worked out by means of the novel type dimensionless equations including standard and magnetic numbers. The obtained results are compared with the data given in the previous literature. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Magnetic-field assisted mixing of liquids using magnetic nanoparticles

Size and magnetic properties of magnetic nanoparticles (MNPs) in fluids allow special remote control of fluid flow using appropriate externally applied magnetic fields, especially when submicronic mixing is critical, inter alia, for catalytic reactions, separation and drug delivery. This work explores MNPs as nanoscale devices to control mixing at microscale by submitting the system of interest to a rotating magnetic field (RMF). Magnetic nanoparticles are harnessed by RMF and converted into nanostirrers thereby generating MNP-pinned localized agitation in the liquid phase. Using this technique, self-diffusion coefficient of water in a static diffusion cell was intensified up to 200 folds. Also, axial dispersion of capillary Poiseuille flows under RMF underwent a reduction prompted by MNP-mediated intensification of lateral mixing relative to that in absence of magnetic field. Finally a multiphase flow case concerned gas–liquid mass transfer from oxygen Taylor bubbles to the liquid in capillaries where dilute MNP solutions led to measurable enhancement of k_La under RMF.     

磁电复合场下正极钒离子的跨膜传质

探究了全钒液流电池在外加磁场、电场、磁电复合场下正极电解液中的钒离子在Nafion117膜上的跨膜传质过程,以及在磁电复合场下硫酸浓度和电解液添加剂对传质过程的影响。根据达西定律拟合得出相应的扩散传质系数。实验结果表明正向电场会加剧钒离子渗透,且当电场强度达到30 V·m^-1时渗透情况严重可达到无电场时的2.53倍。非匀强磁场的加入可明显降低钒离子的跨膜渗透性。且当外加磁场和电场复合场时,磁场对降低钒离子跨膜渗透的作用更加显著。实验还得出在不同的外加复合场中较高浓度硫酸有利于降低钒离子的跨膜渗透。此外丙三醇、木质素磺酸钠正极电解液添加剂的加入也降低了VO₂⁺的跨膜渗透性。     

磁性埃洛石复合材料的制备及其对亚甲基蓝吸附性能研究

利用简单的化学共沉淀法成功合成了磁性埃洛石复合材料,并用静态批示法对其吸附亚甲基蓝的行为进行研究。采用红外光谱仪( FT-IR)、透射电子显微镜( TEM)、X射线衍射仪( XRD)和振动样品磁强计( VSM)对磁性埃洛石进行表征,考察了埃洛石/FeCl3·6H2 O质量比、吸附剂投入量、亚甲基蓝初始浓度、溶液初始pH值和吸附时间等因素对亚甲基蓝在磁性埃洛石上吸附的影响,并进行了吸附动力学研究。结果表明：Fe3 O4纳米粒子成功地复合到埃洛石的表面;溶液初始pH值对磁性埃洛石吸附亚甲基蓝的影响较大;磁性埃洛石复合材料对亚甲基蓝的吸附行为符合准二级动力学模型。     

The Effect of Rotating Magnetic Field on Susceptibility Profile of Methicillin-Resistant Staphylococcus aureus Strains Exposed to Activity of Different Groups of Antibiotics

Methicillin-resistant strains of Staphylococcus aureus (MRSA) have become a global issue for healthcare systems due to their resistance to most β-lactam antibiotics, frequently accompanied by resistance to other classes of antibiotics. In this work, we analyzed the impact of combined use of rotating magnetic field (RMF) with various classes of antibiotics (β-lactams, glycopeptides, macrolides, lincosamides, aminoglycosides, tetracyclines, and fluoroquinolones) against nine S. aureus strains (eight methicillin-resistant and one methicillin-sensitive). The results indicated that the application of RMF combined with antibiotics interfering with cell walls (particularly with the β-lactam antibiotics) translate into favorable changes in staphylococcal growth inhibition zones or in minimal inhibitory concentration values compared to the control settings, which were unexposed to RMF. As an example, the MIC value of cefoxitin was reduced in all MRSA strains by up to 42 times. Apart from the β-lactams, the reduced MIC values were also found for erythromycin, clindamycin, and tetracycline (three strains), ciprofloxacin (one strain), gentamicin (six strains), and teicoplanin (seven strains). The results obtained with the use of in vitro biofilm model confirm that the disturbances caused by RMF in the bacterial cell walls increase the effectiveness of the antibiotics towards MRSA. Because the clinical demand for new therapeutic options effective against MRSA is undisputable, the outcomes and conclusions drawn from the present study may be considered an important road into the application of magnetic fields to fight infections caused by methicillin-resistant staphylococci.     

Modulation of Cellular Response to Different Parameters of the Rotating Magnetic Field (RMF)—An In Vitro Wound Healing Study

Since the effect of MFs (magnetic fields) on various biological systems has been studied, different results have been obtained from an insignificant effect of weak MFs on the disruption of the circadian clock system. On the other hand, magnetic fields, electromagnetic fields, or electric fields are used in medicine. The presented study was conducted to determine whether a low-frequency RMF (rotating magnetic field) with different field parameters could evoke the cellular response in vitro and is possible to modulate the cellular response. The cellular metabolic activity, ROS and Ca²⁺ concentration levels, wound healing assay, and gene expression analyses were conducted to evaluate the effect of RMF. It was shown that different values of magnetic induction (B) and frequency (f) of RMF evoke a different response of cells, e.g., increase in the general metabolic activity may be associated with the increasing of ROS levels. The lower intracellular Ca²⁺ concentration (for 50 Hz) evoked the inability of cells to wound closure. It can be stated that the subtle balance in the ROS level is crucial in the wound for the effective healing process, and it is possible to modulate the cellular response to the RMF in the context of an in vitro wound healing.     

A Reynolds mass flux model for gas separation process simulation:I. Modeling and validation

Separation process undertaken in packed columns often displays anisotropic turbulent mass diffusion. The aniso-tropic turbulent mass diffusion can be characterized rigorously by using the Reynolds mass flux (RMF) model. With the RMF model, the concentration and temperature as well as the velocity distributions can be simulated numerical y. The modeled Reynolds mass flux equation is adopted to close the turbulent mass transfer equation, while the modeled Reynolds heat flux and Reynolds stress equations are used to close the turbulent heat and mo-mentum transfer equations, so that the Boussinesq postulate and the isotropic assumption are abandoned. To val-idate the presented RMF model, simulation is carried out for CO2 absorption into aqueous NaOH solutions in a packed column (0.1 m id, packed with 12.7 mm Berl saddles up to a height of 6.55 m). The simulated results are compared with the experimental data and satisfactory agreement is found both in concentration and temper-ature distributions. The sequel Part II extends the model application to the simulation of an unsteady state ad-sorption process in a packed column.     

磁场对正丁醇-水物系汽液平衡的影响

为探讨磁场对二元共沸物系汽液平衡的影响,在不同磁感应强度的磁场中,研究了正丁醇-水物系的汽液平衡.结果表明,外加磁场对正丁醇-水物系的汽液平衡有一定的影响,总体上呈正效应,即外加磁场有利于该物系的精馏过程.采用NRTL模型对正丁醇-水物系的汽液平衡数据进行了拟合,得到了不同磁感应强度下的NRTL模型参数,并进行了热力学一致性检验,验证了试验数据的可靠性.     

Enhancing liquid micromixing using low‐frequency rotating nanoparticles

Magnetic nanofluid actuation by rotating magnetic fields was proposed as a high‐performance tool for liquid mixing with enhanced micromixing features. A comparative study was conducted to evaluate the mixing index in T‐type mixers of magnetic and nonmagnetic fluids subject to static (SMF), oscillating (OMF), and rotating (RMF) magnetic fields. RMF excitation unveiled superior mixing indices with strong dependences to magnetic field frequency and content of magnetic nanoparticles. The impact of magnetic field types on micromixing was further examined at low and moderate Re numbers using the Villermaux–Dushman reaction and IEM micromixing model. The IEM‐inferred micromixing times were remarkably shorter by nearly four orders of magnitude in comparison with OMF and SMF excitations, and without magnetic field. The proposed mixing strategy is foreseen to complement innovative microfluidic devices with valuable mixing tools and methods for the diagnosis of the coupling between transport and intrinsic kinetics. © 2016 American Institute of Chemical Engineers AIChE J, 63: 337–346, 2017     

磁场调控磁性纳米流体流动和传热研究进展

磁性纳米流体在实现能量高效和可控传递领域极具发展潜力。本文综述了磁场作用下磁性纳米流体对流换热及沸腾换热的最新进展,主要包括强制对流换热、混合对流换热、自然对流换热、池沸腾换热及管内沸腾换热等方面的实验研究,分析了磁场类型、强度、梯度、频率、方向及磁铁位置等对磁性纳米流体流动和热传输特性的影响,指出可通过改变外加磁场来实现对磁性纳米流体流动和传热的控制,并探讨了磁性纳米流体流-磁耦合作用下的传热机理以及目前所面临的挑战。在此基础上,提出了未来磁场调控磁性纳米流体对流换热和沸腾换热的主要发展方向：制备稳定的磁性纳米流体,建立系统有效的流动和传热理论模型,并从微介观尺度诠释热-流-磁耦合协同换热机理。     

交变外磁场对硫酸钙垢溶解行为的影响及其机理

为阐明交变外磁场对硫酸钙垢溶解行为的影响规律,采用离子浓度、电导率和红外光谱等手段检测硫酸钙垢溶解液的性质,并利用X射线衍射（XRD）和检测硫酸钙垢溶解量等方法对硫酸钙垢进行表征和分析。结果表明,交变外磁场对硫酸钙垢的溶解有明显的促进作用。与无磁场作用的硫酸钙垢溶解液相比,交变外磁场作用60 min后硫酸钙垢溶解液的硫酸根质量浓度由2.41 g/L增大至3.52 g/L,电导率由5.85 mS/cm增大至7.24 mS/cm,硫酸钙垢的溶解量增加了40%。外加交变磁场可以促进硫酸钙垢溶解的原因是,外加交变磁场可以使蒸馏水中亲水性羟基的比例增加,促进水分子与硫酸钙垢的分子亲合力。此外,交变外磁场的作用还导致硫酸钙垢的结晶度减小、主晶面的面间距增大,最终有利于垢与水的接触和溶解。此研究可为利用交变外磁场调控硫酸钙垢的溶解行为提供理论依据。     

Rotating Magnetic Field Increases β-Lactam Antibiotic Susceptibility of Methicillin-Resistant Staphylococcus aureus Strains

Methicillin-resistant strains of Staphylococcus aureus (MRSA) have developed resistance to most β-lactam antibiotics and have become a global health issue. In this work, we analyzed the impact of a rotating magnetic field (RMF) of well-defined and strictly controlled characteristics coupled with β-lactam antibiotics against a total of 28 methicillin-resistant and sensitive S. aureus strains. The results indicate that the application of RMF combined with β-lactam antibiotics correlated with favorable changes in growth inhibition zones or in minimal inhibitory concentrations of the antibiotics compared to controls unexposed to RMF. Fluorescence microscopy indicated a drop in the relative number of cells with intact cell walls after exposure to RMF. These findings were additionally supported by the use of SEM and TEM microscopy, which revealed morphological alterations of RMF-exposed cells manifested by change of shape, drop in cell wall density and cytoplasm condensation. The obtained results indicate that the originally limited impact of β-lactam antibiotics in MRSA is boosted by the disturbances caused by RMF in the bacterial cell walls. Taking into account the high clinical need for new therapeutic options, effective against MRSA, the data presented in this study have high developmental potential and could serve as a basis for new treatment options for MRSA infections.     

气相第2组分对水溶解CO2过程界面对流影响的LIF观测

采用激光诱导荧光（LIF）观测方法考察了在气相中分别添加乙醇和二氯甲烷分别对CO₂在水中溶解过程界面对流的影响,得到了液相中CO₂浓度分布及其演化的观测结果,通过物料衡算得到了相应条件下的液相传质系数。CO₂溶解过程会出现由密度梯度引起的Rayleigh对流。实验结果表明,当添加的乙醇含量小于8.47 mg·L^-1时,Rayleigh对流会被增强,进而促进了CO₂的溶解;随着气相中乙醇含量的增大,Rayleigh对流反而被抑制;气相添加二氯甲烷会显著增强Rayleigh对流,提高了CO₂的传质速率,随着气相二氯甲烷含量的增大,CO₂在水中溶解过程的液相传质系数呈现先加强后恒定的趋势。     

Mixing energy investigations in a liquid vessel that is mixed by using a rotating magnetic field

The purpose of the present report is, first, to develop the basic equations and similarity criteria governing the mixing system with the magnetic particles under the effect of a rotating magnetic field (RMF); second, to carry out the experimental investigations dealt with the power consumption and mixing time under the action of RMF. Dimensionless correlations are proposed to predict power consumption and the mixing time in the analyzed mixing system. The study relates to the mixing energy defined as the product of the power input and the mixing time in a tested experimental set-up. The data obtained for mixing efficiency was correlated in terms of the modified Reynolds number which can be used for predictions of mixing process in systems with the magnetic particles. The magnetic particle may be treated as a miniaturized mixer and it may offer a unique alternative approach to mixing. The satisfactory comparison indicates that the mixing process under the action RMF has the significantly higher of the energy consumption than the classical agitators.     

磁场作用下垂直管外氨水降膜吸收的模型研究

在氨气吸收过程中增加了宏观磁场力，考虑了吸收过程中降膜溶液膜厚的变化、膜厚方向的对流以及氨水溶液物性的变化，建立了磁场条件下垂直管外氨水降膜吸收数学模型。在磁感应强度0－3T范围内，对数学模型进行数值求解，得到温度、浓度、速度分布等参数。结果显示磁场对于氨水降膜吸收过程有一定的增强作用。     

第三组分对气液传质影响的研究

The influence of the third component on gas-liquid mass transfer was studied by use of laser holographic interferometry. Four surfactants were added respectively and experimental results show that the mlcroamount of surfactants can change obviously the concentration near the interface on bubble mass transfer process, which indicated that the third component has a significant effect on the bubble mass transfer process.     

固体溶质溶解过程自然对流非稳态数值模拟

利用多物理场耦合分析软件Comsol Multiphysic 3.5及其动网格技术,结合传质学相关理论对固体溶质溶解过程进行了直接数值模拟.考虑了溶解过程中液相部分的自然对流,溶解引起的其表面形态的变化由溶解质量与相界面处的浓度梯度的关系建立的方程描述.研究结果表明:文中方法可以很好地捕捉由于溶解引起的界面运动和变形的...     

传质控制下宽分布石膏颗粒群溶解特性

烟气CO₂直接与工业固废磷石膏矿化反应生成碳酸钙与硫酸铵的控速步骤是磷石膏的溶解。在传质控制下,准确表达溶解特性是矿化反应器设计的理论依据。采用种群平衡模型预测传质控制下粒径宽分布石膏颗粒群溶解特性,采用矩积分法和特征线法对模型进行数值求解并与传统的平均粒径模型表达进行对比。结果显示：种群平衡模型反映了粒径分布对溶解速率的影响,计算得到溶解过程中总容积传质系数的变化,与实验结果吻合良好,证实了种群平衡模型预测的可靠性。与之相比,平均粒径模型预测溶解速率值比实验值偏大,由此解释了工业反应器中物料实际停留时间大于模型计算值的原因。     

Investigation of the effect of magnetic field on mass transfer parameters of CO2 absorption using Fe3O4‐water nanofluid

In this study, the enhancement of physical absorption of carbon dioxide by Fe₃O₄‐water nanofluid under the influence of AC and DC magnetic fields was investigated. Furthermore, a gas‐liquid mass transfer model for single bubble systems was applied to predict mass transfer parameters. The coated Fe₃O₄ nanoparticles were prepared using co‐percipitation method. The results from characterization indicated that the nanoparticles surfaces were covered with hydroxyl groups and nanoparticles diameter were 10–13 nm. The findings showed that the mass transfer rate and solubility of carbon dioxide in magnetic nanofluid increased with an increase in the magnetic field strength. Results indicated that the enhancement of carbon dioxide solubility and average molar flux gas into liquid phase, particularly in the case of AC magnetic field. Moreover, results demonstrated that mass diffusivity of CO₂ in nanofluid and renewal surface factor increased when the intensity of the field increased and consequently diffusion layer thickness decreased. © 2016 American Institute of Chemical Engineers AIChE J, 63: 2176–2186, 2017