WATER SIMULATION OF SODIUM REACTORS

The thermal hydraulic simulation of a large sodium reactor by a scaled water model is examined. The Richardson Number, friction coefficient and the Peclet Number can be closely matched with the water system at full power and the similarity is retained for buoyancy driven flows. The simulation of thermal-hydraulic conditions in a reactor vessel provided by a scaled water experiment is better than that by a scaled sodium test. The results from a correctly scaled water test can be tentatively extrapolated to a full size sodium system.     

Numerical simulation of motion of rigid spherical particles in a rotating tumbler with an inner wavelike surface

The present work is a numerical simulation of motion of rigid spherical particles within a 2-D tumbler with an inner wavelike surface. The rotation of the tumbler is simulated as a traveling sine wave around a circle. The discrete element method (DEM, a hard sphere approach) is used. The particle-wall interactions are taken into account in a changed numerical approach of hard sphere model. The effects of two basic factors of the rotating velocity (phase velocity) and the wave numbers are separately investigated. A simple but useful method for cluster identification is provided and used. The energy-based analysis of particle clusters and the motion pattern study indicate the existence of a pulsed variation in the kinetic energy of the clusters at low wave numbers and a cyclic bulk motion of the clusters at high wave numbers. The necessary conditions for the pulsed variation of motion of particle clusters at low wave number are analyzed and a mode for industrial application, e.g. coal grinding process in power plant, is demonstrated.     

Determination of the Metastable Zone Width by a Simple Optical Probe

The metastable zone width (MSZW) defines an operating boundary for a crystallization process; thus, it is important to determine the MSZW for a given crystallization process. The application of a simple optical probe consisting of a line laser source, a light‐dependent resistor, and a simple processing circuit in the determination of the MSZW of an anti‐solvent crystallization process is presented. The optical probe detects the point of nucleation as a sharp change in output voltage upon the onset of nucleation. The isothermal crystallization of glycine from a glycine/water solution using ethanol as anti‐solvent was used here to assess the performance of the proposed measurement system. The effects of various operating parameters on the MSZW of glycine were also investigated. The kinetic parameters of nucleation were estimated from the data obtained.     

Statistical description of the uniaxial creep behavior of polypropylene foam

The basis of a statistical method for the analysis of creep data is described. The method consists of response surface fitting to a Taylor series expansion of a function about a point. The method is capable of treating multiaxial stress data and includes other variables, such as temperature, without undue mathematical complications. In addition, the statistical approach can account for such things as experimental error and sample variation. The uniaxial compressive creep-recovery behavior of a newly developed polypropylene foam was measured under loads of 140–705 g./cm.² and temperatures of 23–74°C. The foam has a nominal density of 0.07 g./cc. and a mean molecular weight between crosslinks of 10,000. The creep behavior is described by a Taylor series expansion through the second order of a function of applied load, test temperature, foam density, and log time.     

Foam generation in a rotor—stator mixer: schaumerzeugung in einem rotor—stator mischer

The foaming process of an aqueous liquid system with surface active agents and thickeners in a rotor-stator mixer has been studied.The foaming capacity of a rotor—stator mixer may be represented by a so-called mixing characteristic. The foamabilities of several liquid systems have been measured as a function of the mixer geometry and the rotational speed.The hydrodynamics in a rotor-stator mixer is characterized by a Newton—Reynolds relationship. The mechanism of foaming and the dependence of several mixing parameters are different for the turbulent and laminar flow regions. The mixing process is evaluated in both regimes. In the transition region from turbulent to laminar the foaming is very poor in comparison with that in the turbulent and laminar flow regimes.     

Mathematical Support for the CAD Technological Subsystem of a Glass-Melting Furnace

The advisability of constructing a CAD system for glass-melting furnaces is demonstrated. The main principles of the mathematical support for the CAD technological subsystem are formulated. The principles of constructing a mathematical model of the thermal performance of a furnace are described. The main equations providing for a combined solution of the exterior and the interior problems of heat and mass exchange taking into account the specifics of the physiochemical aspects of the glass-melting process are given.     

Break-up of a drop in a stirred tank

The drop break-up mechanism was studied in a stirred tank containing two immiscible liquids. The daughter drops formed by break-up of a single drop of known size were recorded photographically. From the experiments at constant agitator speed the following results were obtained. There is a critical drop size under which drops do not break up under given conditions. The break-up frequency increases approximately linearly with increase in drop volume. The number of daughter drops, v, is a random variable with a mean v > 2 which increases with the volume of the mother drop. The relative volume of a daughter drop has a β-distribution.     

Continuous flow systems with stochastic transfer functions—II solution by the associated Kolmogorov equation

The moments of the response of a stirred tank with randomly perturbed holding time to a tracer impulse is determined. Two models for the holding-time perturbation are used. The first produces a Gaussian probability density and the second a gamma probability density. The second is more realistic because it does not allow negative values for the holding time. The method of partial moments is used.     

Experimental and theoretical investigation of the inflation of variable thickness parisons

In today's blow molding of complex parts, an optimal resin distribution is critical to a successful operation. These goals are mostly attained through a technique known as parison programming. The process involves varying the die gap during extrusion and therefore results in a parison having a variable thickness along its length. The subsequent inflation of a variable thickness parison is a complex phenomenon involving the interaction of many process variables. The final thickness distribution and inflation patterns were obtained for various programmed parisons. Constant, one step, two step, and sinusoidal thickness parisons were studied. The inflation patterns were monitored by employing a transparent mold in conjunction with a video camera. The experimental data indicated the presence of an oscillatory inflation pattern for some of the variable thickness parisons. The experimental final part thickness distribution for these cases was highly nonlinear. Theoretical predictions of the final thickness distribution were also obtained for some of the cases. The simulation is based on the inflation of a Mooney-Rivlin hyperelastic material. A wide range of deformation is accounted for by introducing an evolutionary Mooney constant, dependent on the level of deformation.     

Bubble sizes produced by shear and turbulence in a bubble column

Measurements of bubble sizes for co-current upward air-water flow in a recirculating loop bubble column are described. The bubble sizes were determined with a two electrode conductivity detector. The effectiveness of two different designs of baffle in reducing the bubble size is assessed. The first type of baffle was a perforated plate placed across the air-water flow, which broke the bubbles by the shear flow and turbulence it caused. The measurements with this type of baffle are consistent with a recently developed theory of bubble break-up in shear flow. The second type of baffle consisted of a series of wire arrays placed across the flow. These broke the bubbles by a cutting action. The rate of bubble coalescence downstream of this baffle was determined, over a range of gas hold-up.     

Numerical Evaluation of Toughening by Crack-Face Grain Interlocking in Self-Reinforced Ceramics

Crack bridging associated with the pull-out process of interlocking grains in self-reinforced ceramic materials is studied through a micromechanical simulation. The pullout of a single inclined grain is modeled via the numerical solution of a general contact problem. The bridging-force versus crack-opening-distance curve indicates a nonlinear, springlike response for the pullout of interlocking grains. The sliding friction along the debonded interface, induced by highly localized contact stresses, dominates the total bridging force. The bridging force increases with grain inclination until eventual bridge failure. The pullout of misaligned grains mainly affects short-crack toughening, with a rising R -curve, whereas aligned grains contribute to long-crack toughening. The residual stresses of the thermal expansion anisotropy play a minor role in the pull-out process of grain interlocking and the resultant toughening. The proposed mechanism is operative in both single-phase and composite ceramics in which pullout of elongated grains/reinforcements occurs.     

等温热压印法制备超疏水薄膜

以刷涂有疏水性SiO2微球的筛网作为模具,通过等温热压印的方法,在聚乙烯（PE）塑铝复合薄膜上制备出超疏水表面。对压印压力、筛网目数、SiO2微球直径等参数对制品表面微结构形貌和疏水性能的影响进行了研究。结果表明,该方法可以在PE塑铝复合薄膜表面构筑出具有良好疏水效果的二级复合微结构;在压力作用下,SiO2微球会与PE基体共混形成复合体系,使得SiO2微球与基体的连接更加稳定;增加热压印压力可以增大微米级结构的深度,但是过大的压力会导致SiO2微球被PE覆盖,合理的压印压力应在8~12 MPa之间;减小SiO2微球的粒径可以进一步提高接触角数值;制品对水的接触角达到150°,滚动角低至1°,达到了超疏水的标准。     

Détermination de constantes cinétiques du craquage catalytique par la modélisation du test de microactivité (MAT)

The microactivity test (MAT) for cracking catalyst test works with an approximately plug flow isothermal reactor. The yields at the outlet of such a reactor is numerically computed in the case of lumped kinetic with large molecular expansion and rapid catalyst deactivation expressed versus poison concentration. The poison (coke in cracking reaction) is considered as a product formed by several reaction routes. The results are applied to catalytic cracking kinetic with a four lump model (feedstock, gasoline, gas, coke). The comparison between experimental and computed yields, permits the adjustment of kinetic constants with a set of experimental results obtained from a laboratory scale reactor derived from the MAT. The simulation of concentration profile in the reactor permits a better understanding of the reaction courses.     

Polymer track membranes as a trap support for reagent in fiber optic sensors

The article presents a new idea of the application of polymer track membranes (PTM) for immobilization of a reagent in fiber optic chemical sensors. PTM was made of a poly(ethylene terephthalate) foil (10 μm in thickness, pores of 0.2 μm in diameter). The usefulness of membranes additionally covered by poly(vinyl chloride) was tested in a fiber optic redox titrator. The titrator utilized N,N′-diphenylbenzidine as a reagent which changes its absorbance in dependence on the redox potential. The measuring system is based on a lightemitting diode and a silicon photodiode connected to a bifurcated fiber optic bundle. The gain is in price and availability of the membrane. © 1996 John Wiley & Sons, Inc.     

气固流化床固体浓度分布的冷模研究

在内径0.284 m、高6.0 m的气固流化床冷模装置中进行了气固流化实验,采用PC6 D型颗粒浓度测试仪检测固体浓度. 分别采用枝条型(开孔率a=5‰和2.5‰)和环形(a=5‰)气体分布器,以直径154~180 mm、密度2550 kg/m3的砂子为颗粒,在静床高H0=0.6~1.5 m、表观气速u=0.3~0.6 m/s的情况下,考察了时均固体浓度1-e在空间的分布. 结果表明,增加u使密相区的1-e减小,分布器形状对1-e影响不大. 采用较低a的分布器时1-e的变化较大,且其值均较低. H0=0.6 m, 轴向位置H=0.4 m, u=0.3 m/s, 径向位置r=0~0.142 m时,1-e由0.410上升到0.494;H0=0.6 m, H=0.4~0.95 m, u=0.3 m/s, r=0时,1-e从0.410减小到0;H0=1.5 m, H=0.4~1.3 m, u=0.3 m/s, r=0时,1-e从0.397先下降到0.372,再上升到0.424,最后下降到0.328.     

Bonding performance after aging of fusion bonded hybrid joints

The investigations of this article are showing the bonding performance after aging of hybrid fusion bonds in combination with a laser pre-treatment. The investigated materials are a galvanized steel (HX340 LAD Z100MB) and two glass fiber reinforced Polyamide 6 materials. In order to achieve a structural strength of the fusion bond a laser pre-treatment is used. The investigation is focusing on the changes from the laser pre-treatment to the galvanized surface by analyzing the steel surface with a scanning electron microscope, energy disperse X-ray spectroscopy, micro sections and surface roughness measurements. The composition of the applied thermoplastic materials is not in the focus of the article which is why different manufacturers for the fiber reinforced thermoplastic material have been chosen. The aging of the samples is done by a climate change (PV1200) and a salt spray (PV1210) test in order to evaluate different aging mechanisms. Furthermore the investigation is providing a crucial finding by showing the impact of a batch change on the achievable lap-shear strength by comparing two batches from the same manufacturer. The results of the laser surface pre-treatment show that the zinc coating of the steel adherend is reduced significantly and does not provide a closed coating. The climate change test after 100 cycles showed no decrease of lap-shear strength compared to the reference when the highest investigated pre-treatment intensity is applied to the surface. The salt spray test showed a corrosion of the pre-treated area for laser pre-treatment settings which generate a low amount of oxygen on the surface. The pre-treatment settings generating a more oxidized surface (medium and high intensity) showed only a minor influence on the achievable lap-shear strength after 90 cycles.     

Gel-tape casting as a novel method for the production of flexible fine-grained alumina sheets

The paper reports on the development of a new aqueous gel-tape casting method for processing nanosized powders into thin fine-grained sheets with a high relative density after sintering. The method was based on casting a low-viscosity slurry into a tape, using the doctor-blade method and gelling the slurry after the casting. The gelled tape was removed from the tape carrier without any solvent evaporation and the drying of the gelled tape was performed later in a climate box under controlled temperature and humidity. The epoxy-based ceramic slurry could be prepared with a solid loading of 42 vol.%. Ceramic sheets with flat and smooth surfaces were prepared in a thickness range from 0.08 to 0.4 mm after sintering. The sintered sheets reached a relative density of 99.4%, with an average grain size of about 1.1 μm. The strength and flexibility of alumina sheets were investigated and discussed.     

模外装饰自动换膜机构设计

基于模外装饰工艺原理,对模外装饰自动换膜机构进行了详细设计,其中包含抚平轮和夹紧轮部分、机构固定部分、机架部分和裁刀部分。抚平轮和夹紧轮部分由抚平轮、夹紧轮、轴承、轴承套和摇杆等组成;机构固定部分由电机、压块、压块杆、轴承盖和摇杆等组成,机架部分由滚动导轨副、底板、滚珠丝杆副、步进电机、滚筒支架等组成;裁刀部分由侧板、导向杆、滑块和驱动电机组成。该套模外装饰自动换膜机构能够满足设计要求和实际需要。