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Table of Content
25 October 1995, Volume 46 Issue 5
    化工学报
    PHASE EQUILIBRIA FOR CHAIN MOLECULE SYSTEMS FROM MONTE CARLO SIMULATIONS
    Van Qiliang, Jiang Jianwen. Liu Honglai and Hu Ying(Department of Chemistry, East China University of Science and Technology, Shanghai 200237)
    1995, 46(5):  517-523. 
    Abstract ( 537 )   PDF (331KB) ( 120 )  
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    Monte Carlo simulations of phase equilibria for lattice polymer systems with chain length r=1,2,4,8 are carried out in the canonical ensemble. All chain molecules are introduced into the cell regularly upon initiation, followed by being perturbed through the repta-tion, end - rotate, crank - shaft and L - flip motions. A cavity biased Widom test particle method was proposed and adopted in calculating the residual chemical potentials at various temperatures and densities. The chemical potential, pressure and compressibility factor of systems are then calculated from the residual chemical potentials through classical thermodynamics. Phase equilibrium coexistence curves are obtained according to the phase equilibrium criteria. Results are compared with those calculated from Flory - Huggins theory, Freeds theory, and Hu et als work. The comparison shows that Hu et als work gives the best prediction, while Flory -Huggins theory shows large discrepancy. Freeds theory also gives satisfactory results, but a little poorer than Hu et als work.
    MOLECULAR THERMODYNAMIC MODEL FOR TEMPERATURE-SENSITIVE HYDROGELS
    Lu Danian and Hu Ying(Depart!tent of Chemistry, East China University of Science and Technology, Shanghai, 200253)
    1995, 46(5):  524-531. 
    Abstract ( 656 )   PDF (388KB) ( 101 )  
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    Possibility of non -Gaussian short chains and interlooping chains formed in gel-network, and their influence on swelling characteristics of gels are discussed on the basis of Florys physical -entanglement model. A new molecular thermodynamic theory for non -ionic gels basec on a lattic - fluid model and an elastic model is introduced in which the elastic contribution by the non -Gaussian short chains and interlooping chains is included. The theory can be used to describe various phase behaviors for temperature -sensitive gels. Satisfactory results art obtaind in the correlation of practical swelling equilibria.
    EFFECTS OF SURFACE VISCOSITIES ON COALESCENCE BETWEEN TWO SMALL BUBBLES
    Li Dongming and Jia Shaoyi(Department of Chemical Engineering,Tianjin University,Tianjin 300072)
    1995, 46(5):  532-538. 
    Abstract ( 711 )   PDF (281KB) ( 278 )  
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    When two small bubbles approach each other, a dimpled thin film is formed between them. A model is developed for the dynamics of the thinning film with tangential mobile interfaces,in which the London -van der Waals forces are recognized. The model predicts the coalescence time, which is the time required for the thinning and rupture of the liquid film, given only the radii of the two bubbles and the required physical properties of the bulk fluid and interface. A more general expression for coalescence time is derived. It indicates that the surface viscosities play an important role in determining the surface mobility. The predicted result is in good agreement with previous experimental results.
    BUBBLE SIZE DISTRIBUTION IN BUBBLE COLUMNS
    Luo Mean(Department of Chemical Engineering, Xiungtan University ,Xiangtan 411105)Hallvard F. Svendsen(Department of Chemical Engineering Norwegian Institute of Iechnology , Norway)
    1995, 46(5):  539-544. 
    Abstract ( 687 )   PDF (279KB) ( 109 )  
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    Based on the coalescence and break - up rates of bubbles, this paper proposes a population balance model for describing the bubble size distribution in bubble columns. Changes of bubble size distribution in the axial direction can be obtained by simulation from this model. The simulated results for an air - water system is in good agreement with the measurement.
    A MATHEMATICAL MODEL OF STRONGLY SWIRLING GAS-PARTICLE TURBULENT FLOW AND PULVERIZED COAL COMBUSTION AND ITS APPLICATION TO VORTEX COMBUSTOR (Ⅰ)MODEL
    Zhang Jian(Department of Engineering Mechanics, Tsinghua University, Beijing 100084)S. Nieh(Department of Mechanical Engineering, The Catholic University of America, Washington, U.S.A.)
    1995, 46(5):  545-551. 
    Abstract ( 544 )   PDF (332KB) ( 99 )  
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    A two - dimensional mathematical model of strongly swirling gas - partical turbulent flow and pulverized coal combustion was developed and formulated in this paper in conjunction with the development of a novel coal-fired vortex combustor and its cold flow measurements and combustion tests. The present model forms the basis for numerical simulation of multiphase flow, heat transfer, and combustion in the vortex combustor.
    A MATHEMATICAL MODEL OF STRONGLY SWIRLING GAS-PARTICLE TURBULENT FLOW AND PULVERIZED COAL COMBUSTION AND ITS APPLICATION TO VORTEX COMBUSTOR (Ⅱ)APPLICATION
    /hang Jian(Department of Engineering Mechanics,Tsinghua University, Beijing 100084)S. NiehDepartment of Mechanical Engineering,The Catholic University of America ,Washington ,U.S.A )
    1995, 46(5):  552-556. 
    Abstract ( 550 )   PDF (289KB) ( 134 )  
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    The two -dimensional mathematical model of strongly swirling gas - partical turbulent flow and pulverized coal combustion developed and formulated in paper (Ⅰ) was applied to the systematic numerical simulations of isothermal gas flow,gaseous combustion,and pulverized coal combustion in the novel coalfired vortex combustor. General agreement was achieved between the calculated results and the cold flow and combustion test data. The simulation results delineate the detailed properties and characteristics of flow, heat transfer, and combustion in the vortex combustor.
    MECHANISM OF MICRO-TIP ELECTROCHEMICAL ETCHING AND TIP RADIUS CONTROL TECHNIQUE
    Hu Xiaotang, Guo Yu, Liu Anwei and Ji Guijun(Department oj Precision Instrument Engineering ,Tianjin University,Tianjin 300072)
    1995, 46(5):  557-561. 
    Abstract ( 631 )   PDF (227KB) ( 187 )  
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    The microtip is the key part with which Scanning Probe Microscopy is used to measure and machine on the scale of atom. It is also oxidation damageable in a short time. So it is very important to develop a convenient and efficient fabricating technique for the microtip.In this paper, a theoretical model according to which the microtip takes shape is proposed on the basis of the electrochemical etching proess. The formation of the tip is ascribed to electrochemical etching and drawing force. When the stress on the tungsten filament is greater than its limiting stress,the tungsten filament breaks off and the tip is formed. At this moment,the electrolytic current is decreased suddenly. Thereby the electrolytic current is cut off automatically just at the moment when the tip is formed. In addition,by delaying the "cut of" time,the radius of the tip can be controlled. A related tip radius control technique is developed.
    STRUCTURAL KINETIC MODEL OF PYROLYSIS PROCESS OF PARAFFINS AND ITS SIMULATION
    Ni Li jun, Zhang Liguo,Ni Jinfang and Yuan Weikang(UNILAB Reaction Centre,East China University of Science and Technology,Shanghai 200237)
    1995, 46(5):  562-570. 
    Abstract ( 580 )   PDF (386KB) ( 118 )  
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    The kinetic parameters of main elementary reactions for pyrolysis of paraffins are predicted according lo the dependence of structure -reactivity proposed by the authors. The pyrolysis for a mixture of ethane-propane based on different reaction networks are simulated and compared with pilot data. Thus a reaction network which can describe the process properly and really and has a smaller reaction number is proposed in this paper. Gear method is used to solve the structural kinetic model of C4 paraffin pyrolysis. The predicted product distributions based on the model agree well with pilot data published in the literature.
    ADSORPTION CHARACTERISTICS OF ACTIVATED CARBON FIBER IN A BATCH TANK
    Xiu Gouhua.Li Ping and Jin Ge(Department of Chemical Engineering, Shenyang Institute of Chemical Technology, Shenyang 110021)
    1995, 46(5):  571-578. 
    Abstract ( 709 )   PDF (301KB) ( 147 )  
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    In order to study the adsorption characteristics of activated carbon fiber, a new analytic solution for batch adsorption with a linear isothermal is obtained. Experiments were carried out for the adsorption of chloroform on activated carbon fiber in a batch tank. With the adsorption equilibrium constant determined from a separate experiment, the particle -fluid mass transfer coefficient and the effective diffusivity were evaluated by the error map for the analytic solution.
    A SIMPLIFIED DRYING MODEL OF HEAT AND MASS TRANSFER
    Wang Zhaohui(Department of Power Engineering,Southeast University,Nanjing 210018)Tu Jie(Institute of Thermal Energy ,Tianjin University,Tianjin 300072)
    1995, 46(5):  579-585. 
    Abstract ( 640 )   PDF (272KB) ( 259 )  
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    The convective drying of banana pieces is investigated experimentally and theoretically. The experimental results show that for all tests Rebinder number is much less than 1 at any time except for the rising rate period. Based on the fact, a simplified drying model of heat and mass transfer is deduced from volume average theory. The model is satisfactory for the drying of porous media with high initial moisture content. The capillary action zone, vapor diffusion zone and transition zone are described in one diffusion equation and a theoretical expression of the effective diffusivity is obtained which takes into account the transfer mechanisms of capillary action and vapor diffusion. The model is solved numerically and the calculation procedure proves to be very simple. It is found that predicted values are in good agreement with the experimental data.
    RuO_2-SnO_2 ELECTRODE XPS STUDIES AND ACID-BASE PROPERTIES OF OXIDE SURFACE
    Chen Yanxi.Xia Xiaoxia.Chen Yanying and Han Zuoqing(Department of Applied Chemistry,Tianjin University Tianjin 300072)
    1995, 46(5):  586-592. 
    Abstract ( 558 )   PDF (314KB) ( 138 )  
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    A RuO2 -SnO2 mixed metal oxides electrode was investigated. The results showed that it has a good activity and selectivity for C12 evolution electrocatalysis in NaCl solution. By means of XPS the surface composition of electrode was studied. It was found that Ru content and adsorbed chlorine of DSA (Ru -Sn) was higher than DSA (Ru -Ti). Potentiometric titration was used to characterize the acid - base properties of the surface of mixed electrodes. PZC and APZC obtained suggested that DSA (Ru -Sn) surface has stronger acidity and more specific adsorption of Cl . The electrocataysis behavior of mixed metal oxides electrode is in a close relationship with surface composition and properties.
    KINETIC MODELS OF CONTROLLED RELEASE FOR MONOLITHIC MATRIX SYSTEM
    Xu Tongwen and |Wang Shaoting(Department of Chemical Engineering,Tianjin University ,Tianjin 300072)
    1995, 46(5):  593-600. 
    Abstract ( 529 )   PDF (293KB) ( 103 )  
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    This paper deals with controlled release of drug based on the principle of chemical engineering. The comprehensive kinetic models for monolithic matrix are derived and the internal diffusional process is discussed. The models are tested by the polyCethylene -vinyl al-cohol)/5 - Fluorouracilum(EVAL/5 -FU)matrix system. The results show that the models, which can theoretically support the hypotheses of Higuchis model, agree well with experimental data.
    INVESTIGATION OF HEAT TRANSFER AND FLOW RESISTANCE ON TWISTED TUBE HEAT EXCHANGER
    Si Qin and Xia Qing(Chemical EngineeringDepartment Tianjin UniversityTianjin 300072)Liang Longhu(Luoyang PetroleumChemical EngineeringCompany ,Luoyang 471003)Li Dingxu(Lanzhou CHangzheng Machine Factory, Lanzhou 730050)
    1995, 46(5):  601-608. 
    Abstract ( 611 )   PDF (356KB) ( 243 )  
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    Twisted tubes with different structural parameters (Froude number) were investigated at 1000
    DETERMINATION OF VAPOR HEAT CAPACITIES OF ACETONE - CHLOROFORM,BENZENE-CARBON TETRACHLORIDE AND BENZENE -ETHANOL BINARY SYSTEMS
    Yu Qingsen Fang Wenjiin Zong Hanxing and Lin Ruisen(Department oj Chemistry,Zhejiang University ,Hangzhou 310027)
    1995, 46(5):  609-614. 
    Abstract ( 754 )   PDF (277KB) ( 167 )  
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    The vapor heat capacities as a function of temperature at 101. 3kPa of three binary systems, acetone-chloroform, benzene - carbon tetrachloride and benzene-ethanol, were measured in a multicomponent vapor flow calorimeter constructed in this laboratory. The results show that the vapor heat capacities of acetone - chloroform are positive and those of benzene -ethanol are negative as compared with the linear additive values while the non-ideality of benzene - carbon tetrachloride system is very small. The effect of intermolecular forces on the vapor heat capacity was discussed.
    MOLECULAR THERMODYNAMIC MODEL OF POLYELECTROLYTE SOLUTIONS
    Feng Zhe(Department of Material Engineering,Shanghai Institute of Building Material ^Shanghai 200433)Liu Honglai and Hu Ying(Department of chemistry, East China University of Science and Technology,Shanghai 200237)
    1995, 46(5):  615-620. 
    Abstract ( 650 )   PDF (255KB) ( 110 )  
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    The method of numerical solution of Poisson - Boltzmann equation for polyelec-trolyte solutions containing simple salt presented by Vink is used to calculate the distribution of electric potential around the polyion in cylindrical cell model. Combining with the thermodynamics of polyelectrolyte solution, the activity coefficients of counterion, coion and polyion are obtained from those electric potential data. The osmotic coefficients of solvent are also obtained. These numerical data are correlated with general function of parameter of electric charge density ε parameter of polyelectrolyte concentration X and the ratio of concentrations of simple salt and polyelectrolyte f. The mean activity coefficients of simple salt calculated by this work for systems of NaPP - NaCl, NaPP - NaBr and Napp - Nal are agreement with the experimental data, better than that predicted by Mannings model.
    APPLICATION OF HOT-FILM ANEMOMETER TO MEASUREMENT OF LOCAL GAS HOLDUP IN VAPOR-LIQUID TWO PHASE FLOW ON SIEVE TRAY
    Xu Songlin.Liu Fustian,Xu Hongqin,Huang Jie and Yu Guocong (K. T. Yu)(Chemical Engineering Research Center,Tianjin University,Tianjin 300072)
    1995, 46(5):  621-624. 
    Abstract ( 532 )   PDF (179KB) ( 192 )  
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    Local gas-holdup in vapor - liquid two phase flow was measured by constant temperature anemometer (CTA) on a sieve tray with a micro-computer for data acquisition. Local gas holdup were obtained at different points and different liquid heights on the tray under various liquid and gas flow rates.
    ALTERNATING CURRENT HIGH VOLTAGE ELECTRIC DEMULSIFIER IN MEMBRANE SEPARATION PROCESSES
    Zhu Xian{Department of Chemistry,Shanghai University , Jia Ding,Shanghai 201800)Jiang Chusheng(Research Institute of Science andTechnology,Ministry of ChemicalIndustry, Beijing 100029)Lu Qionghua Li pansheng(.Department of Chemical Engineering,East China
    1995, 46(5):  625-630. 
    Abstract ( 633 )   PDF (212KB) ( 143 )  
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    The demulsification conditions and the design methods of alternating current high voltage electric demulsifier applied to emulsion liquid membranes have been, studied. The design methods of alternating current high voltage eletric demulsifier based on plate capacitor equivalent model have also been set up. The experimental results of batch and continuous electric demulsifier show that the electric demulsifier designed by this method can satisfy the process conditions.
    INFERENTIAL CONTROL OF A FIXED BED REACTOR USING RBF NETWORK
    Wang Huazhong and Hua XiangmingResearch Institute of Audomatic Control,East China University of Science and Technology ,Shanghai 200237
    1995, 46(5):  631-634. 
    Abstract ( 566 )   PDF (205KB) ( 142 )  
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    In this paper, a new inlereiitial control strategy based on RBF network for a non adiabalie tubular fixed -bed reactor is presented. An on-line self learning inferential estimator based on RHF network is developed, and then a predictive control system with output of the estim nor as feedback variable is designed. It is shown via simulation, where a phthalic anhydride reactor is taken as a research plant, thai the estimator has the performance of on line self - learning ability and good accuracy. Moreover, the performance of the control system is satisfactory.
    SOLIDS FLOW CHARACTERISTICS IN SPOUT - FLUIDIZED BED WITH DRAFT TUBE
    Li Baoxia and Zhang Jiyu(Institute of Coal Chemistry ,Acadumic Sinica ,Taiyuan 030001)
    1995, 46(5):  635-640. 
    Abstract ( 642 )   PDF (283KB) ( 142 )  
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    A 200mm×50mm×1450min two -dimensional spout -fluidized bed with a central draft tube was used to study the effect of geometry and operating parameters as well as phys ical properties of material on solids circulation rate. Four different solids and draft tube sizes were used in this study. With increasing gas feed rate, the gap between the draft tube inlet and conical distributor (R), the distance between the nozzle and the draft tube inlet (L1) , the draft tube area, and the solid circulation rate will be increased. The draft tube height has no effect on solids circulation rate. A quantitative correlation, derived from the concept of the gravity flow of particles through the gap (R) and consisting of geometric, operating, as well as material parameter, was proposed for predicting the solids circulation rate of this type of bed.