Modeling and calculation of the temperature fields in two-layer articles

A mathematical model and algorithm for calculation of the temperature fields for two-layer articles are developed. Using the new algorithm a program is created and numerical calculations of the temperature fields that develop in a two-layer article (nonswirl nozzle) in the course of preparation of the pony ladle of a continuous-casting machine for service and in its operating regime are performed. With the use of the program and computer software (in light of experimental results) it becomes possible to perform calculations and predict the sintering mode of ceramic refractory materials as well as optimize the temperature and time heat-treatment diagrams of one-and two-layer articles.     

煤灰流动性研究方法进展

随着煤转化工业对转化率和生产效率要求的进一步提高,煤的热转化过程更趋向于在高温高压转化器中进行。在高温高压的液态排渣燃烧炉和气化炉中,煤中矿物质完全熔融成熔渣形式再排出。对于采用液态排渣和水冷壁的气流床气化炉,要求煤灰熔融温度低于操作温度,熔渣黏度范围为2.5~25.0 Pa·s,且在操作温度范围内黏度随温度的波动较小,因此气化过程中煤灰的熔融性和黏温特性是影响熔渣流动的关键因素。笔者论述了传统灰熔融评价方法的发展过程,各国标准方法的原理都是通过被压实样品在升温过程中的形变来判断得出熔融温度,但仅靠熔融温度无法提供实现现代大型气化过程精细化控制所需信息,而对煤灰熔融过程的全阶段测试有助于更准确地指导实际生产。对比各国研究者对熔融过程的定性和定量研究表明,熔融温度中的变形温度并非煤灰开始熔融的温度,针对煤灰沉积、烧结等问题,熔融全过程测试提供的开始收缩温度和热力学计算预测的液相最初形成温度有助于更准确地预测煤灰可能产生沉积或烧结的温度。黏温特性的测试目前仍依靠高温旋转黏度测试法,该法耗时较长且流程繁琐,因此研究者更趋向于用更简便和省时的方法实现对适用样品的黏温特性的快速筛选。除了试验方法,模拟计算方法在煤灰流动性研究中的应用越来越普遍,通过热力学计算和分子模拟方法,能够获得试验难以测得的矿物质组成及熔体的微观结构变化,且分子模拟中非平衡分子动力学方法可更准确模拟复杂流体的剪切稀化过程,从而获得更接近试验值的黏度计算结果。采用非平衡方法提高了计算结果的准确度,但也增加了计算的复杂程度及所耗费的机时,且目前煤灰体系的计算模型选择不多,因此采用分子模拟方法应综合考虑体系的复杂度与计算结果的准确性。随着熔融过程研究的进一步深入和模拟计算方法的普遍应用,试验结果呈现的宏观性质变化机理将更易于通过微观结构变化来阐明,反过来也将有助于优化现有的模拟计算方法和参数。     

一种扁管管翅式换热器的高效数值设计方法

传统的数值模拟方法计算量大,计算时间长,很难满足现代工业发展的需求。以扁管管翅式换热器为例,采用适体坐标与最佳正交分解（POD）相结合的方法构建了低阶模型,在等热流边界条件下对扁管管翅式换热器中流动与传热过程进行计算,并将POD计算结果与有限体积法（FVM）计算结果进行了对比。结果表明：POD方法能准确地捕捉到不同数量参数变化情况下的温度场及速度场信息。对于3变量工况重构速度场及温度场的相对偏差平均值的最大值分别为1.90%、0.308%。采用POD方法在保证计算精度的前提下将FVM计算速度最大能提高3093.4倍。研究对于提高扁管管翅式换热器数值设计效率、拓展POD方法的工程应用领域有一定的理论参考价值。     

Self-ignition and special features of flow in a planar vortex chamber

Regular self-ignition of hydrogen and kerosene was registered upon their mixing with oxygen-enriched air in a straight-flow vortex, chamber of planar-radial geometry. These fuel components were injected into the chamber from tanks with room temperature and pressure 4–10 MPa. The velocity, pressure, and temperature fields in the chamber were studied using experimental methods and numerical modeling on the basis of full Navier-Stokes equations. The measurment and calculation showed that a region of elevated temperatures appears in an unsteady vortex flow. The calculation was performed for Reynolds number up to 5·10³ and revealed an increase in temperature with increase in Reynolds number. Nevertheless, both the calculated and measured temperatures were lower than the known self-ignition temperatures. The nature of the ignition, observed remains unclear. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 6, pp. 26–41, November–December 1999.     

Nonisothermal method for calculating the mold equipment of an apparatus for compacting the hot products of self-propagating high-temperature synthesis

The existing methods for calculating molding equipment are discussed. Their common disadvantage lies in the fact that they do not reflect the unsteady-state state and the gradient nature of heat exchange during self-propagating high-temperature synthesis (SHS) inside a mold. The results of the application of mathematical modeling in the study of the temperature fields that appear in mold equipment during SHS compaction are described. It is recommended that the thermal method be used for calculating the mold equipment, and a theoretical rationale is given to justify the application of this method. The paper cites examples of calculating the wall thickness of the mold by the standard and proposed methods. It is shown that a nonisothermal calculation allows for a significant decrease in the wall thickness and, accordingly, the mass of the mold.     

石蜡在管外凝固过程的理论和实验分析

对使用水作为传热流体的蛇形管式换热器中,进口水温对石蜡在管外凝固过程的影响进行了研究。建立了水温沿流向变化,石蜡温度沿径向变化的传热模型。使用控制容积法及焓法建立了求解水和石蜡耦合温度场的数值方程,这两个温度场的计算结果与实验结果能很好吻合。冷却水进口温度不同,靠近铜管已凝固石蜡中的温度场存在显著差别,离铜管较远石蜡中的温度几乎不受进口水温影响,石蜡的无量纲温度场在离相界面较远处具有相似分布的特点。相界面移动具有先快后慢,然后再变快的特征。研究可为保证蛇形管外石蜡凝固速率选择恰当的进口水温提供计算方法。     

基于ANSYS的LNG管道保冷结构分析

介绍了LNG管道保冷结构以及保冷层厚度的计算方法,应用有限元分析软件对LNG低温长输管道进行了稳态热力分析。在计算管道截面温度场时,采用保冷层材料导热系数随温度变化和平均导热系数两种方法进行模拟。研究结果表明温度分布基本相同,而热流密度值不同。     

Development of convection in near-wall granular bed during nonstationary heating

Based on the developed and realized optical method of the polarization of temperature fields, the results of experiments on the visualization of temperature fields and the development of convective flows during the nonstationary conductive heating of the cell wall involving a layer of pebble beds placed in liquid are presented. Upon variations in the heat physical properties of liquid and particles (pebbles) of the granular bed, as well as the value of the supplied heat flow, the mechanism of the pebble-bed effect on the time and character of the formation of free convection close to the wall heated from below has been studied. The calculation model of the process has been suggested.     

超高相对分子质量聚乙烯纤维的改性及其应用

超高相对分子质量聚乙烯（UHMWPE）纤维以其优异的性能而成为一种重要的高科技纤维品种,但由于本身的结构特点,使得其存在一定的性能缺陷而限制了应用范围。通过等离子体处理法、氧化法等各种物理和化学的方法对UHMWPE纤维表面进行改性处理,可不同程度改善其耐热、界面、抗蠕变等弱性。详细介绍了该纤维的改性方法及其在绳索类、防护用品以及其他方面的应用。     

Calculation of Temperatures in Microwave-Heated Two-Dimensional Ceramic Bodies

Tempertures are calculated in a ceramic material exposed to microwaves. The method entails calculation of electromagnetic fields by integral formulation and subsequent solution of the heat conduction equation for temperature in a ceramic piece. The solution of the equation is numerical and the parameters used are estimates for properties of SiC. The results include a case where the complex dielectric constant is varied with temperature The computed results demonstrate that SiC can be heated to high temperatures (1000-1500 K) and that both the temperature and the temperature gradient can be controlled by varying the power density of the micro waves and the external cooling. The results also exhibit high sensitivity of temperatures to the dimensions of the material and the orientation in which microwaves impinge on the ceramic body.     

蒸汽加热模具及模具变温辅助控制装置的研制

对高光无痕注射成型工艺的成型装置和辅助控制系统进行了研究和开发,介绍了蒸汽加热注射成型工艺原理。通过辅助系统来控制蒸汽加热模具的型腔温度,特殊的水道设计使模具型腔的温度能够迅速升至熔体的热变形温度以上,进而获得高光表面制品。同时指出了蒸汽加热模具在模具材料的选择、测温点的分布等方面的设计思想,阐述了辅助控制装置的组成部分及控制原理。结果表明,蒸汽加热模具可加工高表面光洁度、无熔接痕、无流痕的塑料制品,可免除后续喷涂工艺,降低了生产成本,成型周期由120 s 缩短到43 s。     

A Brief Review of Carbazole-Based Photorefractive Liquid Crystalline Materials

Liquid crystals are commonplace in technological devices, such as watch and computer displays and temperature and pressure monitors. Such materials are central to our technological lifestyles. Classically, liquid crystalline materials are based on a structural motif which could be classed as rod-like (e.g. biphenyl derivatives) and in more recent times as disc-like (e.g. triphenylene derivatives). The rod-like materials are very attractive in terms of their chemical stability and their response to electric fields, both of which are a prerequisite for display devices, whereas disc-like materials show promise as one-dimensional conducting materials. Increasing scientific and technological requirements mean that new materials are continually sought to surpass the liquid crystalline materials which are presently known. Carbazole derivatives are well-known interesting natural products. Several methods have been developed and reported in the literature for the synthesis of carbazole derivatives. There are several review articles published on the photorefractive properties of carbazole-based materials. Chemical modification of the carbazole moiety to create a new class of discotic, calamitic and banana-shaped liquid crystalline materials, which will have novel and enhanced photorefractive properties over the amorphous carbazole derivatives, will be discussed in this mini review.     

边界单元法在聚合物加工研究中的应用

将边界单元法引入聚合物加工过程粘性流场的数值计算中，并与其它数值计算方法进行了比较。结果表明边界单元具有计算量少，计算精度高等优点，便于推广应用，以挤出机排气段熔体输送流场求解为例，说明了边界单元法的实际应用。     

超细碳酸钙碳化塔换热系统设计计算

本文介绍了生产超细碳酸钙的主要技术指标控制碳化温度的问题，着重介绍了碳化塔换热系统的设计计算，并推荐了几种换热方案。     

Production of heat-insulating diatomite articles by a plastic method of molding

The basic technological parameters of the process of molding by means of extrusion of diatomic articles at OOO Diatomitovye Kombinat are determined, in particular, the composition of the charge, methods of preparation of the charge, and the molding and heat processing regimes. It is shown that addition of chalk to the charge increases the working temperature to 1200°C and improves the physico-chemical indicators of the properties of the resulting articles.     

Mathematical Model of Hydrodynamics of a Glass-Melting Tank

The importance of studying the hydrodynamics of the glass-melting tank is substantiated. The main equations of a numerical model of the tank hydrodynamics are given. The calculation results of temperature fields and streamlines are given for a glass-melting furnace with an output of 300 tons per day. The adequacy of the calculation results as applied to real furnace operating conditions is demonstrated. The developed model of hydrodynamics of the melting tank can be used in solving applied problems of designing glass-melting furnaces.__________Translated from Steklo i Keramika, No. 1, pp. 3 – 8, January, 2005.     

On the information and methods for computing phase equilibria and thermodynamic properties

The Helmholtz free energy or an equation of state relating temperature, pressure, volume and composition plays a key role in the calculation of phase equilibria and thermodynamic properties. Such information is usually available for vapor, partially available for liquids, and rarely available for solids. Depending on the information available, different methods are used for properties calculation. In this study, various methods were systematically presented and their relations with available information were comprehensively discussed.     

Effect of swirl and confinement on the flow and temperature fields in an inductively coupled r.f. plasma

A mathematical model was used for the calculation of the flow and temperature fields in the fire-ball of an inductively coupled plasma (ICP) under confined and free discharge conditions taking into account gravity and swirl in the sheath gas. Computations were made for an argon plasma at atmospheric pressure operating at a power level of 3kW and a frequnecy of 3 MHz. Natural convection has a negligible effect on the flow and temperature fields under confined discharge conditions, but a significant effect, for the free plasma discharge. The back flow in the discharge was substantially reduced in the presence of swirl for swirl velocities over the range 0-70 m/s. With a moderate increase in swirl, the conduction heat flux to the wall decreased but increased with the further increase in swirl.