采用CFD模拟装备标准透平桨或45°-斜向上桨搅拌反应器内部流体力学特性

The hydrodynamic characteristics generated by the standard Rushton or 45°-upward pitched- blade-turbine (PBT) impellers in a baffled reactor are numerically simulated for different off-bottom clearances (C = 1/3Hand 1/2H) and agitator speeds (100, 150, 200, 250 and 300r.min-1) by using FLUENT code (Version 5.4). Theresults are compared with the experimental and simulated data in the published papers and good agreement isobserved. The shapes of the profile of mean velocities seem independent to the speed of agitators under theexperimental conditions (100-300 r.min-1).     

Dissolution Kinetics of Magnesitic-Dolomite and Magnesite-Chrome Refractories in Secondary Steelmaking Slags

Dissolution kinetics of magnesitic-dolomite and magnesite-chrome refractories in secondary steelmaking slags was studied by means of the rotating cylinder method under forced convection. Materials investigated include four magnesitic-dolomite samples(MgO content 40% to 93%)and two magnesite-chrome samples (co-clinkered and semi-rebonded).Synthetic slags simulative of VOD and AOD slags with varying basicity (0.6-2.68) are used.The experiments are carried out in Ar atmosphere at different temperatures (1 600 ℃-1 750 ℃) and revolution speeds (200 r·min-1to 500 r·min-1).The microstructure of specimens (before and after slag tests) are studied by optical microscopy, SEM and EPMA. Based on our experimental results the mechanism and kinetics of the dissolution process are discussed.     

纯磷脂单分子膜压缩过程中磷脂分子的构象和取向(英文)

On the basis of energy conservation law and surface pressure isotherm, the conformation energy changes of dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylglycerol (DPPG) in pure phospholipid monolayer at the air/water interface during compression are derived. The optimized conformations of phospholipids at absolute freedom state are simulated by Gaussian 98 software. Based on following assumptions: (1)the conformation energy change is mainly caused by the rotation of one special bond; (2)the atoms of glycerol near the water surface are active; (3)the rotation is motivated by hydrogen-bond action; (4)the rotation of bond is inertial, one simplified track of conformational change is suggested and the conformations of DPPC and DPPG at different states are determined by the plots of conformation energy change vs. dihedral angle. The thickness of the simulated phospholipid monolayer is consistent with published experimental result. According to molecular areas at different states, the molecular orientations in the compressing process are also developed.     

Experimental and Numerical Investigations of Single Drop Mass Transfer in Solvent Extraction Systems with Resistance in Both Phases

Numerical simulation of transient mass transfer to a single drop controlled by the internal resistance or by the resistance in both phases was mathematically formulated and simulated in a boundary-fitted orthogonal coordinate system. The simulated results on the transient mass transfer dominated by the internal resistance are in good agreement with the Newman and Kronig-Brink models for drops with low Reynolds number. When the drop Reynolds number is up to 200, the mass transfer coefficient from numerical simulation is very low as compared with the Handlos-Baron model. The cases with mass transfer resistance residing in both the continuous and drop phases were simulated successfully and compared with the experimental data in three extraction systems recommended by European Confederation of Chemical Engineering (EFCE). For single drops with Re < 200, the numerically predicted values of the extraction fraction and overall mass transfer coefficient are in reasonable coincidence with the experimental data. I     

影响纳米碳酸钙制备过程的因素分析

Cubic shaped CaCO3 particles with mean size of 30-40 nm were prepared by intermittent carbonation process without any additives. It was found that the flow rate of CO2 has no distinct influence on the particle size in the range of 30-120ml·min-1 under conditions of 13℃ and stirring rate of 680r·min-1. A further increase of flow rate makes the particles larger. When CO2 flow rate is 70ml·min-1, a high agitation rate is in favor of the reduction of the crystal size in the range of 70-680 r·min-1. When flow rate is 120 ml·min-1, the particles prepared at agitation rates of 680r·min-1 and 280r·min-1 have similar sizes, while products prepared at 90r·min-1 have larger size.     

Kinetic Model of Biomass Pyrolysis Based on Three-component Independent Parallel First-order Reactions

The pyrolysis behavior of two kinds of typical biomass (pine wood and cotton stalk) was studied in nitrogen atmosphere at various heating rates by thermogravimetric analysis (TGA). The pyrolysis process can be divided into three stages: evolution of moisture (<200℃), devolatilization (200~400℃) and carbonization (>400℃). The comparison of DTG curves of two biomass materials show that the higher the hemicellulose content of biomass, the more evident the shoulder peak of DTG curve. The weight loss process of two materials was simulated by the kinetic model assuming cellulose, hemicellulose and lignin pyrolyzing independently and in parallel, obeying first-order reactions. The pyrolysis kinetic parameters corresponding to the three components were estimated by the nonlinear least square algorithm. The results show that their fitting curves are in good agreement with the experimental data. Their activation energy values for pine wood and cotton stalk are in the range of 188~215, 90~102, 29~49 and 187~214, 95~101, 30~38 kJ/mol, respectively. The corresponding pre-exponential factors are in the range of 1.8′1015~2.0′1016, 1.6′107~7.1′108, 9.3′101~1.5′103 and 1.2′1015~6.7′1017, 1.2′108~1.4′109, 1.4′102~4.6′102 min-1, respectively. In addition, the activation energy of cellulose and lignin increased and their contributions to volatile tended to fall, whereas the activation energy of hemicellulose decreased and its contribution to volatile tended to rise with increasing of heating rate.     

The Numerical Analysis of the Gas-Liquid Absorption Process Accompanied by Rayleigh Convection

Flow and concentration fields of liquid phase in a gas-liquid contacting system are simulated to show the Rayleigh convection by utilizing the finite-element method. The Schlieren images in CO2-ethanol system provided direct visual verification of the present simulation, and the simulated results were well consistent with the experimental observation. The influence of the Rayleigh convection on mass transfer is analyzed qualitatively and quantitatively based on the simulated and the experimental results.     

伴有Rayleigh对流的气液吸收过程数值模拟

Flow and concentration fields of liquid phase in a gas-liquid contacting system are simulated to show the Rayleigh convection by utilizing the finite-element method. The Schlieren images in C02-ethanol system provided direct visual verification of the present simulation, and the simulated results were well consistent with the experimental observation. The influence of the Rayleigh convection on mass transfer is analyzed qualitatively and quantitatively based on the simulated and the experimental results.     

太阳能空气加热器管道中填充三角形小翅片扰流器的湍流传热的实验研究(英文)

The paper presents an experimental study on the heat transfer and flow friction characteristics in a solar air heater channel fitted with delta-winglet type vortex generators(DWs).The experiments are conducted by varying the airflow rate for Reynolds number in the range of 5000 to 24000 in the test section with a uniform heat-flux applied on the upper channel wall.Firstly,the DW pairs are mounted only at the entrance of the lower wall of the test channel(called DW-E)to create multiple vortex flows at the entry.The effect of two transverse pitches(RP Pt/H 1 and 2)at three attack angles(α30°,45°and 60°)of the DW-E with its relative height,b/H 0.5(half height of channel)is examined.Secondly,the 30°DWs with three different relative heights(b/H 0.3,0.4 and0.5)are placed on the upper wall only(absorber plate,called DW-A)of the test channel.The experimental result reveals that in the first case,the 60°DW-E at RP1 provides the highest heat transfer and friction factor while the30°DW-E at RP1 performs overall better than the others.In the second case,the 30°DW-A at b/H 0.5 yields the highest heat transfer and friction factor but the best thermal performance is found at b/H 0.4.     

萃取体系滴内和两相阻力控制的单液滴传质实验和数值模拟研究

Numerical simulation of transient mass transfer to a single drop controlled by the internal resistance or by the resistance in both phases was mathematically formulated and simulated in a boundary-fitted orthogonal coordinate system. The simulated results on the transient mass transfer dominated by the internal resistance are in good agreement with the Newman and Kronig-Brink models for drops with low Reynolds number. When the drop Reynolds number is up to 200, the mass transfer coefficient from numerical simulation is very low as compared with the Handlos-Baron model. The cases with mass transfer resistance residing in both the continuous and drop phases were simulated successfully and compared with the experimental data in three extraction systems recommended by European Confederation of Chemical Engineering (EFCE). For single drops with Re ＜ 200, the numerically predicted values of the extraction fraction and overall mass transfer coefficient are in reasonable coincidence with the experimental data. It is concluded that the numerical simulation can be resorted in some cases of solvent extraction for conducting numerical experiments and parametric study. Nevertheless, for better resolution as higher Reynolds number drops are simulated, more sophisticated techniques should be developed and incorporated to deal with the large deformation and transient shape oscillation as well as possible Marangoni effect.     

Determination of free and conjugated triclosan in blood by electron capture gas liquid chromatography

Unconjugated triclosan in blood can be determined by extraction with hexane, followed by its conversion to an acetyl derivative and analysis by electron capture gas liquid chromatography. The conjugated triclosan can be analyzed by an identical procedure, after the complexes have been hydrolyzed with hydrochloric acid. The method was validated by recovery studies using spiking and radioactive techniques and can be used for the determination of triclosan in blood in the concentration range of 1 ppb (ng/ml) to 100 ppm (μg/ml). The precision and accuracy of the method are discussed, and examples of its application are presented. Triclosan is the generic name of 2′,4,4′-trichloro-2-hydroxy-diphenyl ether, and is produced by CIBA-GEIGY Corporation under the tradename IRGASAN DP-300. Presented at the AOCS Spring Meeting, Mexico City, April 1974.     

苯为前驱体的稠环芳烃的自由基反应机理的量子化学研究

The free-radical growth mechanisms for the formation of polycyclic arenes (PCAs) were constructed based on the block unit of benzene, and were calculated by the quantum chemistry PM3 method. Two kinds of reaction paths are proposed and discussed. The calculation results show that the formation of PCAs is only controlled by the elimination of H atom from benzene, and the corresponding activation energy is 307.60 kJ&#8226;mol－1. H2 is only the ef-fluent gas in our proposed reaction mechanism, and the calculation results are in accord with the experimental facts.     

界面传质中Rayleigh对流的格子Boltzmann模拟和实验验证(英文)

Concentration gradient induced Rayleigh convection can influence effectively interfacial mass transfer processes, but the convection phenomena are known as mesoscopic and complex. In order to investigate this phe-nomenon, a two-equation Lattice Boltzmann Method (LBM) is proposed to simulate the velocity and the concentra-tion distributions of Rayleigh convection generated in the CO2 absorption into ethanol liquid. The simulated results on velocity distributions are experimentally verified by PIV (particle image velocimetry technique) measurements. In order to simplify the analysis, the convection in the simulation as well as in the experiment, the Rayleigh convec-tion was manipulated into a single down flow pattern. The simulated results show that the concentration contours agree qualitatively with the schlieren images in the literature. The experimental and simulated results show that the Rayleigh convection under investigation is dominated by the flow in the downward direction and impels exchange of the liquid between the interfacial vicinity and the liquid bulk promoting the renewal of interfacial liquid, and hence enhances mass transfer. The comparison between the simulated and experimental results demonstrated that the proposed LBM is a promising alternative for simulating mass transfer induced Rayleigh convection.     

Molecular dynamics simulation of small gas molecule permeation through CAU-1 membrane

CAU-1 is one of aluminum-based amine-functionalized Metal–Organic Frameworks(MOFs). Gas permeation and separation behaviors through CAU-1 membrane were simulated by the dual-control plane nonequilibrium molecular dynamics(DCP-NEMD) method. The thickness of membrane was 3.55 nm.Gases CO_2, N_2, CH_4, H_2, He, Kr and Xe were chosen for the calculation in both single component and binary mixtures. The permeation process was calculated in grand canonical(l VT) ensemble with periodic boundary conditions(PBC) in x-and y-directions at different temperatures. The calculated permeance of H_2, CH_4, N_2, CO_2 and Kr decreased with increasing temperature in both single and binary system, while that of Xe with kinetic molecule of 0.41 nm increased with increasing temperature. It shows Xe permeation is governed by activated diffusion. The simulated separation factors of CO_2/N_2 and CO_2/CH_4 of 4.2 and 1.3 respectively were lower than the experimental ones when only considering van der Waals interaction. Further consideration of electrostatic potential leads to improved calculation CO_2/N_2 and CO_2/CH_4 separation factor of 23.0 and 12.9 respectively that were consistent with the experimental ones of 26.2 and 14.8. It suggests the necessity of considering the Coulomb interactions between CO_2 and NH_2-on the pore wall of CAU-1 for permeation of CO_2. For H_2/N_2 and H_2/CH_4 the ideal selectivities also keep consistent with our experimental results. Interestingly, the simulated separation factor for noble Kr/Xe reaches infinite, predicting that CAU-1 membrane possesses potential separation properties for radioactive Kr/Xe.     

描述CO2的柔性模型

A fully flexible potential model for carbon dioxide has been developed to predict the vapor-liquid coexistence properties using the NVT-Gibbs ensemble Monte Carlo technique (GEMC). The average absolute deviation between our simulation and the literature experimental data for saturated liquid and vapor densities is 0.3% and 2.0%, respectively. Compared with the experimental data, our calculated results of critical properties (7.39 MPa, 304.04 K, and 0.4679 g&#61655;cm－3) are acceptable and are better than those from the rescaling the potential parameters of elementary physical model (EPM2). The agreement of our simulated densities of supercritical carbon dioxide with the experimental data is acceptable in a wide range of pressure and temperature. The radial distribution function es-timated at the supercritical conditions suggests that the carbon dioxide is a nonlinear molecule with the C O bond length of 0.117 nm and the O C O bond angle of 176.4°, which are consistent with Car-Parrinello molecular- dynamics (CPMD), whereas the EPM2 model shows large deviation at supercritical state. The predicted self-diffusion coefficients are in agreement with the experiments.     

Kinetics of Liquid-Phase Hydrogenation of Benzene in a Metai Hydride Slurry System Formed by MlNi_5 and Benzene

The kinetics of liquid-phase hydrogenation of benzene in misch metai nickel-five (MINi5) and benzene slurry system was studied by investigating the influences of the reaction temperature, pressure, alloy concentration and stirring speed on the mass transfer-reaction processes inside the slurry. The results show that the whole process is controlled by the reaction at the surface of the catalyst. The mass transfer resistance at gas-liquid interface and that from the bulk liquid phase to the surface of the catalyst particles are negligible. The apparent reaction rate is zero order for benzene concentration and first order for hydrogen concentration in the liquid phase. The kinetic modei obtained fits the experimental data very well. The apparent activation energy of the hydrogen absorption reaction of MINi5-C6H6 slurry system is 42.16kJ·mol-1.     

A Reynolds mass flux model for gas separation process simulation:II. Application to adsorption on activated carbon in a packed column☆

Simulations of adsorption process using the Reynolds mass flux model described in Part I of these serial articles are presented. The object of the simulation is the methylene chloride adsorption in a packed column (0.041 m id, packed with spherical activated carbon up to a length of 0.2 m). With the Reynolds mass flux model, breakthrough/regeneration curves, concentration and temperature as well as the velocity distributions can be obtained. The simulated results are compared with the experimental data reported in the literature and satisfactory agreement is found both in breakthrough/regeneration curves and temperature curves. Moreover, the anisotropic turbulent mass diffusion is characterized and discussed.     

EXPERIMENTAL RESEARCHES OF NATURAL GAS HYDRATE IN POROUS SEDIMENTS——A REVIEW

A brief presentations on experimental research of natural gas hydrate (NGH) in porous sediments in the past several years are given. The contents are divided into three sections. (1) phase equilibria, (2) formation/dissociation kinetics, (3) amount estimate. The main works by some researchers are summarized. The prospect and significance of the research are expected at the end of this paper.     

硬木中流体移动的双尺度多孔机理的依据（I）用多色X光束测定榉木浸润中湿含量的演变

An experimental device able to determine the moisture content of wood using X-ray attenuation is used to study the imbibition of beech samples (Fagus silvatica). The apparatus includes an X-ray generator, a protective tube, coUimating plates and a 50 mm detector. Detected particles can be categorised by energy (accuracy of the order of 20%) or by position (accuracy 100μm). The independent choice of both the energy spectrum (through the voltage) and the counting rate (through the current intensity) makes the installation very flexible. However,a rigorous treatment is necessary to deal with the attenuation of a polychromatic spectrum. The appropriate calculations are presented and validated with homogeneous samples made of wood and water. In addition, some results are presented with samples heterogeneous in density and moisture content. Finally, the experimental device is used to study the evolution of moisture content during saturation experiments, for which the moisture migration is mainly due to capillary forces. The geometrical configuration was so arranged that the transfer can be studied in two directions simultaneously.