Modeling Temperature Fields in Glass Articles in Annealing

Methods for the calculation of temperature fields in flat and cylindrical glass articles are considered. The advantages of numerical methods compared to analytical methods for the calculation of temperature fields in complex shapes of articles and heat-exchange processes are demonstrated.     

Thermodynamic Analysis of Combustion Products at High Temperature and Pressure

An algorithm of calculation of equilibrium composition of complex chemically reacting systems at high pressure and temperature is described. The algorithm, which was used for the development of a computer code, may be applied for examination of various classes of thermodynamic systems, but its principal area of applicability is analysis of combustion products. Two real gas equations of state(virial with three coefficients and equation of state, proposed by V.I. Nedostup) are incorporated into the code. Results of test calculations presented demonstrates the capabilities of the program and confirms the reliability of the data obtained.     

Semi-automatic generation of film compensation tables

An algorithm for the refinement of film compensation tables in digital film recorders has been incorporated as part of a user-oriented computer program. The program allows quick table calculations with minimum technical knowledge over a wide variety of desired results for color-transparency-film types. We are able to develop adequate tables within three trials under most circumstances.     

Mathematical simulation of the thermal stability of magnesium oxide

A simulation of the behavior of nonporous single-crystal magnesium oxide under conditions of heat loading that approach the operating conditions of casting ladles in ferrous metallurgy is performed by means of mathematical methods. Both numerical and analytic methods are used for the calculations. The temperature and mechanical stress fields and such breakdown parameters of materials as the moment of appearance of cracks, the thermal stability criterion (breakdown temperature drop of surface of material), etc. were determined as a result of the calculations. Results of calculations are presented and an analysis of the application of mathematical methods to the simulation of different heat treatment regimes of a material is performed.     

Estimation of dehumidifying performance of solid polymer electrolytic dehumidifier for practical application

A two-layer model for a solid polymer electrolytic (SPE) dehumidifier is applied to a system in which the chamber to be dehumidified has some leakage area. By introducing this area, the attainable humidity in the chamber, which is the steady-state humidity to be attained after a long-time dehumidification, can be defined. Experimental results of dehumidification by an SPE dehumidifier are compared to the calculations based on the two-layer model for the SPE dehumidifier, which was presented in our previous paper. Equations for the two-layer model are simplified by making use of assumptions for the current characteristics and a constant environmental condition, and it is reduced to equations including a differential equation on the time variation of the humidity in the chamber. The differential equation to describe the attainable humidity in the chamber and time constant for the dehumidification is obtained. The current flowing in the dehumidifier under steady state conditions is also given as a function of the humidities in the spaces facing the anode and the cathode. A diagram to estimate the attainable humidity and the time required for dehumidification from the dehumidifying area and leakage area is also given.     

Einsatz von programmierbaren Taschenrechnern für verfahrenstechnische Berechnungen

Using of programmable pocket-calculators for process engineering calculations . Part of a chemical engineer's daily work are repeated calculations to illustrate special relations. Suitable for this purpose are programmable pocket computers, which allow easy and quick programming by the user. This contribution gives brief instructions for creation of short and more complex programs in addition to those found in the user's manual. Independently of calculator type and nature of the problem, the single steps required to get a complete program are described. Using a special example from chemical engineering, the optimal pathway from the algorithm to the program listing is shown for two calculator types.     

Processing and Characterization of Thin Films of the Two-Layer Superconducting Phase in the Bi─Sr─Ca─Cu─O System: Evidence for Solid Solution

Thin films in the Bi─Sr─Ca─Cu─O system have been synthesized from liquid ethylhexanoate precursors by spin pyrolysis. An extensive solid-solution range was found for the two-Cu-layer phase through the study of c -axis-oriented, single-phase thin films fabricated on single-crystal, (100)-oriented, MgO substrates. All two-layer compositions were excess in Bi and deficient in Sr + Ca relative to the ideal 2212 composition and showed an overall cation deficiency. The solidus temperature and c lattice parameter were found to vary systematically with composition. Sharp superconductive transitions were obtained in the case of a number of different compositions with T _c varying between 72 and 84 K. Evidence for significant compositional heterogeneities within single-phase two-layer thin films was found and the implications for superconductivity are discussed. Compositions within the solid-solution range gave single-phase, c -axis-oriented films over a wide temperature range extending from 730°C to an upper, solidus (or peritectic) temperature (780° to 840°C) which is dependent on the initial starting composition. A model has been developed that describes the formation of the two-layer phase from a fugitive liquid.     

用VOF方法数值计算液滴燃烧

引 言 液体燃料通过喷射进入内燃机的汽缸或喷气发动机的透平中燃烧产生热能.近年来能源危机加剧及减排CO2以保护环境意识提高,促使研究者们采用新的技术提高化石燃料的燃烧效率,其中对单个液滴燃烧物理过程的深刻了解是改进喷射燃烧为特征的内燃机械能量利用效率的基本.对液滴燃烧过程的数值及实验研究已经有几十年.最早的研究者有Godsave[1]、Spalding[2]等,他们基于常物性、球对称及类稳态假设,对液滴在静止空气中的燃烧过程建立了基本数学描述,并得到了著名的"d2定律",即液滴直径平方随时间线性减小,用公式表示为dd2/dt=k,k为燃烧速率常数.     

Mathematical modeling of the dynamics of slagging and thermochemical destruction of carbon composite thermal protective materials in a high-temperature two-phase flow

A new complex physicomathematical model, a numerical algorithm, and a computational program are developed for the calculation of the dynamics of slagging and thermochemical destruction of carbon composite thermal protective materials of multilayer walls in a subsonic high-temperature two-phase flow with inertial precipitation of polydisperse liquid particles of metal oxides in cycles of heating and cooling (aftereffect). The results of a numerical study of the thermal and chemical effects of inertially precipitated liquid aluminum oxide particles on the heating and ablation parameters of a typical thermally reactive pressed carbon composite in one cycle of heating and cooling of a two-layer wall of the channel in a power plant are given. Institute of Applied Mathematics and Mechanics, Tomsk 634050. Translated from Fizika Goreniya i Vzryva, Vol. 33, No. 4, pp. 91–102, July–August, 1997.     

Yttrium Silicate Coatings on Chemical Vapor Deposition-SiC-Precoated C/C–SiC: Thermodynamic Assessment and High-Temperature Investigation

Yttrium silicates are promising materials for improved oxidation and erosion protection for carbon fiber-reinforced composites. A two-layer coating system of low-pressure plasma-sprayed yttrium silicate on chemical vapor deposition-SiC-precoated C/C–SiC was tested under atmospheric re-entry conditions simulated within a plasma wind tunnel test facility. The thermal expansion behavior of Y₂SiO₅ and Y₂Si₂O₇ was investigated. The chemical compatibility with and without increasing oxygen partial pressure at the interface of the two-layer system was calculated by the CALPHAD method. The calculations were compared with experimental results. Furthermore, a thermodynamic explanation is presented to understand and predict the observed coating failure mechanism, identified as blister formation.     

Analysis of non-explosive bubble growth within a superheated liquid droplet suspended in an immiscible liquid

Bubble growth within a volatile droplet (liquid 1) at its superheat limit suspended in an immiscible nonvolatile field liquid (liquid 2) is analysed by solving the coupled energy and momentum equations for the temperature fields in liquids 1 and 2. A numerical solution is presented for a two-phase droplet modelled as a vapour bubble growing from the centre of liquid 1. It is shown that when the properties of liquids 1 and 2 are appreciably different, the bubble growth rate can experience a significant increase or decrease when the thermal boundary layer extends into liquid 2. The present calculations are also compared with available data and the agreement is reasonable.     

A Zone-type Model for a Building Fire and Its Sensitivity Analysis

Based on the CFAST model, this paper describes a two-layer zone model developed to predict the environment in a multi-compartment structure subjected to a fire. The predictive equations, fire sub-processes and algorithm are concisely described. In order to validate the model and program a series of experimental data obtained from Cooper's work at NIST were selected for comparison with numerical results, and the comparison is fundamentally favourable. This paper presents an example of this comparison, including the results simulated by the CFAST zone model (Version 1.6). It is shown from the comparison that this model predicts better results than that of the CFAST for these cases, and convection heat transfer may be underestimated in the two models. It is also shown that C.W. Gear's stiffly stable method is feasible in numerically integrating the governing equation set. Additionally, this model is applied to conduct a parameter sensitivity analysis for a two-room fire, and some informative results are given and discussed.     

Simulation of temperature fields in a narrow tubular adsorber by thermal lattice Boltzmann methods

Significant temperature gradients may exist in packed bed adsorbers due to the exothermic heat of adsorption. In this study we investigate temperature fields in a narrow tubular packed bed adsorber having tube to particle size ratio <10. Theoretical calculations are carried out using lattice Boltzmann methods (LBM) to simulate three-dimensional concentration and temperature profiles in macro- as well as micro-pores of the adsorption bed. Model simulation results show non-uniform temperature gradients across the tube's cross-section. Zones of significantly high temperature are observed within macro-voids. Temperature gradient is found to be primarily dependent on the amount of heat released, internal BET surface area, and hydrodynamic conditions prevailing in the adsorber. Agreement between the model results and the experimental data obtained with the aid of the tomography technique for a tubular adsorber is observed to be reasonable. The study is important from the point of view of a realistic design of packed bed adsorbers.     

An analysis of the temperature field in the refractory feeder of a horizontal continuous billet casting machine

Conclusions A mathematical model of the process of formation of the front of solidification of the billet skin in the refractory feeder of a horizontal continuous casting machine taking into consideration possible changes in the geometric and thermophysical parameters of the refractory has been developed.An algorithm and a program have been set up making it possible to calculate the temperature field in the refractory feeder taking into consideration the front of solidification of the billet skin. Using the program developed the temperature field was calculated for a graphite-containing refractory in teeming of 45 steel. The calculations made agree with experimental results on wear of the refractory.The data obtained makes it possible to explain the wear of the refractory in the zone of contact with the mold and also to optimize the configuration of the working portion of the horizontal continuous casting machine refractory feeder.Translated from Ogneupory, No. 6, pp. 36–40, June, 1988.     

Computational algorithm to predict peak profiles in preparative high-performance chromatography

The computational algorithm and the Prep-LEAR program have been performed on the basis of the LEA model of chromatography. This program intends for calculation of peak profiles in non-linear high-performance chromatography and uses unsimplified adsorption isotherm equations. The computational algorithm and program have been tested by applying these to experimental data of thymine adsorption under conditions of reversed-phase high-performance liquid chromatography. The results of numerical calculations for different sample size introduced agree satisfactorily with experimental data and show the characteristic properties of high-performance chromatography. The usefulness of the Prep-LEAR program was confirmed by predicting peak profiles in preparative adsorption Chromatographic processes.     

水质自动分析仪智能控制器软件开发中的若干问题

在水质自动分析仪软件的开发中，采用软件解决采样部分与8031单片机之间的配合协调问题；在强弱电均存在的情况下，用软件避免噪声干扰。同时改进了常用的开方迭代算法，减少了迭代次数。     

Parametric and nonparametric model based control of a packed distillation column

Parametric and nonparametric model based control systems were applied to control the overhead temperature of a packed distillation column separating methanol–water mixture. Experimental and theoretical studies have been done to observe the efficiency and performance of both control systems. Generalized predictive control (GPC) system based on a parametric model has been tried to keep the overhead temperature at the desired set point. First, a parametric model which is controlled auto regressive integrated moving average (CARIMA) was developed and then the parameters of this model were identified by applying pseudo random binary sequence (PRBS) and using Bierman algorithm. After that this model was used to design the GPC system. Tuning parameters of the GPC system have been calculated using the simulation program of the packed distillation column. Using the predicted parameters, experimental and theoretical GPC systems were found very effective in controlling the overhead temperature. Dynamic matrix control (DMC) system based on a nonparametric model has been used to track the overhead temperature of the packed distillation column. For this purpose, a nonparametric model known as the dynamic matrix was determined using the reaction curve method. A step change in heat input to the reboiler was applied to the manipulated variable and the temperature of the overhead product was observed. After that, the dynamic matrix was used to design the DMC system. Several calculations have been done to define the DMC control parameters. The best values of the tuning parameter were used to realize the DMC system for controlling the overhead temperature experimentally and theoretically. In the presence of some disturbances, the DMC system gives oscillation and offset in experimental studies.     

Choice of the supercell with the optimum atomic configuration in simulation of disordered solid solutions

Different methods currently employed for choosing and analyzing model configurations of binary systems with isomorphous substitution in the sublattice were considered. A new more efficient algorithm was proposed for determining the most disordered atomic configuration of an arbitrary composition for a cell with any size. The algorithm was implemented in the form of a computer program which makes it possible to approach the most optimum topology of the arrangement of solid solution components over atomic positions. The program was tested using a number of binary systems and can be recommended for ab initio calculations and simulation with semiempirical methods. Moreover, this approach can be used to decompose complex experimental spectra of isomorphous mixtures which are difficult to interpret without recourse to model concepts regarding the local structure of multicomponent systems.     

Stratified two-phase flog of molten polymers in circular dies

A theoretical study has been carried out on the steady, axisymmetric two-phase flow of molten polymers in circular dies. For both fluids, the shear rate dependence of the viscosity is described by a power law and the temperature dependence by an exponential function. Taking into account viscous dissipation, a numerical program has been developed to predict the radial position of the interface between the two fluids, the developing temperature and velocity fields, the shear rates, the shear stresses, the pressure drop as well as the field of shear deformation and the residence time distribution for different thermal boundary conditions. The numerical program is applied to the flow of a high-viscous polymer melt, (high density polyethylene), surrounded by a small annulus of less viscous polymer ni lt, (low density polyethylene). Computed results are shown graphically.     

我国电气设计规范与国际电工标准的差距--从都江堰拉法基水泥厂电气设计的经验和教训说起

在工程设计中,遵循IEC标准、电气设备编码规定、电气设计规范是十分重要的。在都江堰拉法基水泥厂的设计过程中,我们发现国内现有电气设计规范主要存在以下几点问题:仅有文字表述条款,缺乏图例表示;一些规范条文缺少以人为本的精神;个别条文规定模糊,难以执行;个别条文规定相互矛盾或未相互照应。另外,水泥厂电气室布置设计缺少详尽的规定;电气计算与国际要求存在差距。