热模拟法研究消除应力裂纹

采用模拟焊接热影响区粗晶区应力释放的试验方法，研究ＣＦ６２钢在焊后热处理过程中的消除应力裂纹敏感性及其形成机理．结果表明：ＣＦ６２钢焊接热影响区粗晶区具有消除应力裂纹敏感性，并随焊后热处理加热温度的升高而增大．消除应力裂纹敏感性取决于焊后热处理过程中材料所承受的塑性变形量和其进行塑性变形、蠕变变形的能力．粗大晶粒和高残余拉伸应力的存在是产生消除应力裂纹的必要条件．

智能变压器绕组热点温升的在线监测

分析了智能变压器绕组热点温升监测的意义,对热模拟法、直接测量法和计算法进行介绍及对比,分析了三种方法的优劣,提出了在智能变压器热点温度监测的发展趋势。

镍钛对结构钢焊接热影响区组织和性能的影响

本文通过加入微量铌或铌、钛结构钢的焊接热模拟试验,研究了铌、钛使焊接热影响区晶粒和组织细化,从而提高冲击韧度的机理,并揭示出铌、钛在钢中的作用虽然相似,但是由于TiN的熔点比Nb(CN)高,因此在钛含量适中的情况下,铌、钛同时加入其钢的冲击韧度要比单独加铌的更好。

变压器绕组温度计异常的原因及改进建议

介绍了9F燃机发电机主变压器的绕组温度计异常现象的分析和处理及绕组温度测量的热模拟法和改进建议。

变压器绕组温度计的跨线整定规则改进

主要介绍了变压器绕组温度常用的三种在线测量方法;热模拟法绕组温度计的原理;本单位主变压器绕组温度计的一起异常的现象、分析、处理过程;及绕组温度计的跨线的整定规则等改进建议。

变压器绕组温度计的原理及其应用

变压器的使用寿命取决于它的绕组温度。绕组温度对绝缘材料的温度和老化起着决定性的作用,故在大、中型变压器上都配备了绕组温度监测装置,介绍了变压器绕组温度计工作原理。监测装置须可靠,若变压器超出允许温度或监测装置不准确时,会影响变压器的正常运行,论述了使用绕组温度计应注意的事项。

焊缝粒状贝氏体组织的相变过程

采用热模拟方法,研究了焊接冷却过程中 15MnVN 钢焊缝中粒状贝氏体的相变过程。结果表明,焊缝粒状贝氏体的相变过程可以划分为铁素达形核、铁素体纵向长大、铁素体横向长大、铁素体交叉分割奥氏体和残余奥氏体岛收缩五个阶段。

遮阳有效性分析方法研究

在绿色建筑中遮阳技术得到广泛应用,设计有效的遮阳需要对遮阳有效性进行准确分析,但目前尚未有对遮阳有效性评价指标、分析方法的系统介绍。通过对常用评价指标、分析方法的比较,及对工程项目的调研,给出适用于绿色建筑领域的遮阳有效性分析方法——表面得热模拟法,并采用该方法进行了案例分析。

特高压站主变绕组测温装置异常分析

分析某特高压站主变绕组测温装置异常情况,介绍变压器绕组测温装置原理、电流匹配器整定计算,检查发现主变绕组测温装置异常由电流匹配器分流电阻整定错误所致。

变压器绕组温度计隐患分析及改进设想

变压器是电力系统的重要组成部分之一,它的安全稳定运行是电网安全可靠的必备条件。而变压器的使用寿命取决于其各部件绝缘能力是否满足相关要求,其中绕组绝缘能力就是关键一项。绕组温度超过其绝缘耐受强度将会加速绝缘老化,影响变压器正常工作,缩短变压器使用寿命,因而测量、监控变压器绕组温度显得尤为重要。

Synthesis of Large-scale Multistream Heat Exchanger Networks Based on Stream Pseudo Temperature

Effective temperature level of stream, namely stream pseudo temperature, is determined by its actual temperature and heat transfer temperature difference contribution value. Heat transfer temperature difference con-tribution value of a stream depends on its heat transfer film coefficient, cost per unit heat transfer area, actual tem-perature, and so on. In the determination of the suitable heat transfer temperature difference contribution values of the stream, the total annual cost of multistream heat exchanger network (MSHEN) is regarded as an objective func-tion, and genetic/simulated annealing algorithm (GA/SA) is adopted for optimizing the heat transfer temperature difference contribution values of the stream. The stream pseudo temperatures are subsequently obtained. On the ba-sis of stream pseudo temperature, optimized MSHEN can be attained by the temperature-enthalpy (T-H) diagram method. This approach is characterized with fewer decision variables and higher feasibility of solutions. The calcu-lation efficiency of GA/SA can be remarkably enhanced by this approach and more probability is shown in search-ing the global optimum solution. Hence this approach is presented for solving industrial-sized MSHEN which is difficult to deal by traditional algorithm. Moreover, in the optimization of stream heat transfer temperature differ-ence contribution values, the effects of the stream temperature, the heat transfer film coefficient, and the construc-tion material of heat exchangers are considered, therefore this approach can be used to optimize and design heat exchanger network (HEN) with unequal heat transfer film coefficients and different of construction materials. The performance of the proposed approach has been demonstrated with three examples and the obtained solutions are compared with those available in literatures. The results show that the large-scale MSHEN synthesis problems can be solved to obtain good solutions with the modest computational effort.

Thermal conductivity of dielectric nanowires with different cross-section shapes

Non-equilibrium molecular dynamics simulations have been performed to investigate the effect of the cross-section shape on the thermal conductivity of argon nanowires. Some typical cross-section shapes, such as triangle, square, pentagon, hexagon and circle, axe carefully explored. The simulation results show that with the same cross-sectional area of the regular polygons, tim thermal conductivities decrease with the reduction of the sides of the polygons, and the thermal conductivity of the circular nanowire is larger than those of the other polygonal ones. Phonon gas kinetic theory is used to analyse the phonon transport in nanowires, and the concept of equivalent diameter is proposed to illustrate the characteristic dimension of the none-circulax cross-section.

Deformation simulation of low-temperature high-speed extrusion for 6063 Al alloy

The hot compression test of 6063 Al alloy was performed on a Gleeble-1500 thermo-simulation machine, and the forming of 6063 rod cxtrudate in low-temperature high-speed extrusion was simulated with extrusion ratio of 25 on the platform of DEFORM 2D successfully. From the compression experimental results, the flow stress model of this Al alloy is obtained which could be the constitutive equation in the simulation of low-temperature high-speed extrusion process. From the numerical simulation results, there is a higher strain concentration at the entrance of the die and the exit temperature reaches up to 522 ℃ in low-temperature high-speed extrusion, which approaches to the quenching temperature of the 6063 Al alloy. The results show that the low-temperature high-speed extrusion method as a promsing one can reduce energy consumption effectively.

Simulated Annealing Approach to the Optimal Synthesis of Distillation Column with Intermediate Heat Exchangers

This article presents a simulated annealing-based approach to the optimal synthesis of distillation column considering intermediate heat exchangers arrangements. T-he number of intermediate condensers and/or intermediate reboilers, the placement locations, the.operating pressure of column, and the heat duties of intermediate heat exchangers are treated as optimization variables. A novel coding procedure making use of an integer number series is proposed to represent and manipulate the structure of system and a stage-to-stage method is used for column design and cost calculation. With the representation procedure, the synthesis problem is formulated as a mixed integer nonlinear programming （MINLP） problem, which can then be solved with an improved simulated annealing algorithm. Two examples are illustrated to show the effectiveness of the suggested approach.

A Method for Improving Simulation of PNA Teleconnection Interannual Variation in a Climate Model

The climate modeling community has been challenged to develop a method for improving the simulation of the Pacific-North America （PNA） teleconnection pattern in climate models. The accuracy of PNA teleconnection simulation is significantly improved by considering mesoscale convection contributions to sea surface fluxes. The variation in the PNA over the past 22 years was simulated by the Grid Atmospheric Model of lAP LASG version 1.0 （GAMIL1.0）, which was guided by observational SST from January 1979 to December 2000. Results show that heating in the tropical central-eastern Pacific is simulated more realistically, and sea surface latent heat flux and precipitation anomalies are more similar to the reanalysis data when mesoscale enhancement is considered during the parameterization scheme of sea surface turbulent fluxes in GAMIL1.0. Realistic heating in the tropical central-eastern Pacific in turn significantly improves the simulation of interannual variation and spatial patterns of PNA.

Numerical and experimental evaluation on methods for parameter identification of thermal response tests

Several parameter identification methods of thermal response test were evaluated through numerical and experimental study.A three-dimensional finite-volume numerical model was established under the assumption that the soil thermal conductivity had been known in the simulation of thermal response test.The thermal response curve was firstly obtained through numerical calculation.Then,the accuracy of the numerical model was verified with measured data obtained through a thermal response test.Based on the numerical and experimental thermal response curves,the thermal conductivity of the soil was calculated by different parameter identification methods.The calculated results were compared with the assumed value and then the accuracy of these methods was evaluated.Furthermore,the effects of test time,variable data quality,borehole radius,initial ground temperature,and heat injection rate were analyzed.The results show that the method based on cylinder-source model has a low precision and the identified thermal conductivity decreases with an increase in borehole radius.For parameter estimation,the measuring accuracy of the initial temperature of the deep ground soil has greater effect on identified thermal conductivity.

Numerical Simulation of Thermal Discharge Based on FVM Method

A two-dimensional numerical model is proposed to simulate the thermal discharge from a power plant in Jiangsu Province. The equations in the model consist of two-dimensional non-steady shallow water equations and thermal waste transport equations. Finite volume method （FVM） is used to discretize the shallow water equations, and flux difference splitting （FDS） scheme is applied. The calculated area with the same temperature increment shows the effect of thermal discharge on sea water. A comparison between simulated results and the experimental data shows good agreement. It indicates that this method can give high precision in the heat transfer simulation in coastal areas.

Numerical modeling dynamic process of multi-feed microwave heating of industrial solution media

The exothermic efficiency of microwave heating an electrolyte/water solution is remarkably high due to the dielectric heating by orientation polarization of water and resistance heating by the Joule process occurred simultaneously compared with pure water.A three-dimensional finite element numerical model of multi-feed microwave heating industrial liquids continuously flowing in a meter-scale circular tube is presented.The temperature field inside the applicator tube in the cavity is solved by COMSOL Multiphysics and professional programming to describe the momentum,energy and Maxwell's equations.The evaluations of the electromagnetic field,the temperature distribution and the velocity field are simulated for the fluids dynamically heated by singleand multi-feed microwave system,respectively.Both the pilot experimental investigations and numerical results of microwave with single-feed heating for fluids with different effective permittivity and flow rates show that the presented numerical modeling makes it possible to analyze dynamic process of multi-feed microwave heating the industrial liquid.The study aids in enhancing the understanding and optimizing of dynamic process in the use of multi-feed microwave heating industrial continuous flow for a variety of material properties and technical parameters.

Simultaneous Optimization of Synthesis and Scheduling of Cleaning in Flexible Heat Exchanger Networks

A novel methodology is presented for simultaneously optimizing synthesis and cleaning schedule of flexible heat exchanger network(HEN)by genetic/simulated annealing algorithms(GA/SA).Through taking into account the effect of fouling process on optimal network topology,a preliminary network structure possessing two-fold oversynthesis is obtained by means of pseudo-temperature enthalpy(T-H)diagram approach prior to simultaneous optimization.Thus,the computational complexity of this problem classified as NP(Non-deterministic Polynomial)-complete can be significantly reduced.The promising matches resulting from preliminary synthesis stage are further optimized in parallel with their heat exchange areas and cleaning schedule.In addition,a novel continu- ous time representation is introduced to subdivide the given time horizon into several variable-size intervals according to operating periods of heat exchangers,and then flexible HEN synthesis can be implemented in dynamic manner.A numerical example is provided to demonstrate that the presented strategy is feasible to decrease the total annual cost(TAC)and further improve network flexibility,but even more important,it may be applied to solve large-scale flexible HEN synthesis problems.