METHODOLOGY TO GENERATE ACCURATE SOLUTIONS FOR VERIFICATION IN TRANSIENT THREE-DIMENSIONAL HEAT CONDUCTION

This article describes the development of accurate solutions for transient three-dimensional conductive heat transfer in Cartesian coordinates for a parallelepiped which is homogeneous and has constant thermal properties. The intended use of these solutions is for verification of numerical computer programs which are used for solving transient heat conduction problems. Verification is a process to ensure that a computer code is free of errors and accurately solves the mathematical equations. The exact solutions presented in this article can have any combination of boundary conditions of specified temperature, prescribed heat flux, or imposed convection coefficient and ambient temperature on the surfaces of the parallelepiped. Additionally, spatially uniform nonzero initial condition and internal energy generation are treated. The methodology to obtain the analytical solutions and sample calculations are presented.     

Insulated solar storage tanks

This paper presents the theoretical and experimental investigation of an insulated parallelepiped, outdoor solar, water-filled storage tank of size 1 m × 0.5 m × 0.3 m, that is made from galvanized iron. The absorption coefficient of the insulating material has been determined. The effects of plastic covers and insulation thickness on the water temperature and the energy gained or lost by water are investigated. Moreover, the effects of insulation thickness on the temperature profiles of the insulating material are discussed. The results show that the absorption coefficient decreases as the insulation thickness increases. Also, it is found that the glass wool insulation of 2.5 cm thickness has the best results compared with the other thicknesses (5 cm, 7.5 cm, and 10 cm) as far as the water temperature and the energy gained by water are concerned.     

Fast-converging steady-state heat conduction in a rectangular parallelepiped

A Green's function approach for precisely computing the temperature and the three components of the heat flux in a rectangular parallelepiped is presented. Each face of the parallelepiped may have a different, but spatially uniform, boundary condition. Uniform volume energy generation is also treated. Three types of boundary conditions are included: type 1, a specified temperature; type 2, a specified flux; or type 3, a specified convection boundary condition. A general form of the Green's function covering all three types of boundary conditions is given. An algorithm is presented to obtain the temperature and flux at high accuracy with a minimal number of calculations for points in the interior as well as on any of the faces. Heat flux on type 1 boundaries, impossible to evaluate with traditional Fourier series, is found by factoring out lower-dimensional solutions. A numerical example is given. This research and resulting computer program was part of a code verification project for Sandia National Laboratories.     

Estimation of steady state ground losses from earth coupled structures by simulation

A thermal simulation method for estimating the ground losses from earth coupled structures has been described. The accuracy of the method has been evaluated by comparing the experimental results obtained for a sphere with the corresponding analytical results. The method has been used to determine the shape factor, which can be used to evaluate the heat loss to the ground for (i) slab-on-grade buildings, (ii) a sunken cylindrical structure, and (iii) sunken and buried parallelepiped structures for different ratios of their dimensions.     

1 000 MW核电汽轮机低压内缸3D建模与轴封变形分析

对某1 000 MW核电汽轮机低压内缸进行了三维建模,并进行有限元分析,计算了稳定运行工况下,负荷、上下缸温差以及抽真空过程对轴封变形的影响。计算结果表明:在温度、压力的综合作用下,并受汽缸变形影响,轴封变形膨胀,向内倾斜。其中低压内缸内外压差是造成轴封向内倾斜的主要原因,同时上下缸温差也是造成轴封内倾的原因之一。汽缸受热膨胀会减轻轴封的向内倾斜程度。     

形状记忆可展桁架在轨热变形分析研究

本文借助I-DEAS软件建立了针对形状记忆可展桁架的热-结构耦合分析模型,并试验验证了分析模型的准确性。在此基础上,采用多层隔热复合材料作为热控措施,计算分析有/无热控措施及预紧力大小对桁架温度与热变形的影响。结果表明,包覆多层隔热材料效果明显,可将桁架在轨周期内的温度差减小85%,位移差减小80%,有利于对可展桁架进行温控,实现展开与收拢,减小运行期间振动的影响。桁架变形大小由预紧力和热应力共同决定,随着预紧力增大,桁架位移差逐渐减小。     

燃气轮机压气机静叶环电子束焊接变形研究

针对燃气轮机压气机静叶环电子束焊接数据进行了收集、整理和分析,得出影响电子束焊接变形的一般规律,提出相应的改进措施,实现了焊接变形的量化控制,达到了控制变形的目的。     

Numerical solution of the three-dimensional diffusion equation in leaching processes

A mathematical model is presented to account for the leaching of a solute during the heating of a parallelepiped solid with the diffusion coefficient being a function of temperature. The alternating direction implicit method developed by Douglas and Brian was chosen to solve the resulting equations. Details of the finite difference scheme are given with special reference to the variable diffusion coefficient and the third kind boundary condition. The model was applied to predict the retention of water soluble vitamins during the blanching of potato parallelepipeds.     

THERMAL SHOCK IN A VISCOELASTIC HALF-SPACE

Abstract

Thermal shock due to sudden heating of the bounding surface of a viscoelastic half-space is discussed. Coupling of the temperature and strain fields has been taken into account, and the effects of thermal relaxation on the shock propagation have also been considered. The linear standard model has been used to represent the viscoelastic behavior of the solid in shear which is elastic in hulk deformation. The analysis, although valid for small times, shows that the stress and temperature fields have discontinuities at two points at a given instant of lime. It is further noted that attenuation takes place more rapidly than in the corresponding case of an elastic continuum. The stress and temperature fields are the result of superposition of two shock waves: one is mechanical in origin, the other is due to thermal relaxation. An estimate of the finite speed of the heat signal is also obtained for a specific case.     

边坡变形影响下锦屏一级拱坝安全性分析

锦屏一级高拱坝左岸边坡断层较多且持续变形不收敛,从而对坝体安全稳定运行造成不利影响,为合理分析左岸边坡变形对坝体安全性的影响,建立了锦屏一级拱坝三维有限元仿真模型,运用小生境与遗传模拟退火耦合算法搜索左岸边坡最危险潜在滑动面,在搜索到的潜在滑动面施加三角形位移荷载模拟左岸边坡的变形并进行持续超载,同时考虑坝体自重、水压力等荷载作用下坝体的应变情况。结果表明,边坡变形的极限超载系数在9~10之间,靠近坝体左岸岸肩1 769m高程以上的部位在边坡持续变形中会较早进入塑性屈服阶段,在不出现塑性屈服区贯通情况下,坝体弦长最大压缩变形可达到205.32mm,从而可为坝体安全运行提供参考。     

An analytical solution for two-dimensional inverse heat conduction problems using Laplace transform

An analytical method has been developed for two-dimensional inverse heat conduction problems by using the Laplace transform technique. The inverse solutions are obtained under two simple boundary conditions in a finite rectangular body, with one and two unknowns, respectively. The method first approximates the temperature changes measured in the body with a half polynomial power series of time and Fourier series of eigenfunction. The expressions for the surface temperature and heat flux are explicitly obtained in a form of power series of time and Fourier series. The verifications for two representative testing cases have shown that the predicted surface temperature distribution is in good agreement with the prescribed surface condition, as well as the surface heat flux.     

Eigenvalue Approach to Two-temperature Generalized Thermoelastic Interactions in an Annular Disk

Two-temperature generalized thermoelasticity theory has been applied to determine the conductive and thermodynamic temperature as well as the deformation and stresses in an annular disk. The basic equations have been written in the form of a vector-matrix differential equation in the Laplace transform domain and solved for the field variables in closed form. Finally, the time variation and space variation of temperatures, deformation and stresses have been estimated by numerical methods and presented in several graphs and the analysis of the results have been made.     

基于补偿模糊神经网络的灰循环系统控制研究

针对循环系统回料量对循环流化床锅炉床温的影响,采用补偿模糊神经网络的建模方法,建立灰循环系统回料控制模型,选取锅炉床温变化及变化率作为输入、回料风量作为输出进行了仿真研究,并与常规控制进行比较．结果表明：补偿模糊神经网络控制器对参数变化的适应性明显优于常规控制器,补偿模糊神经网络方法对灰循环系统控制优化有实际意义．     

Hyperthermia and Cancer Treatment

Hyperthermia has been used as one of the therapies for cancer treatment since the early 1970s. This condition is reached when temperature of a cell (or larger mass) is elevated to 43°C, about 6 degrees above body temperature, causing the destruction of the mass. With fewer complications than chemotherapy and radiation this thermotherapy has been used as an assisting therapy in conjunction with chemo or radiation therapies. Because of nanotechnology and its medical applications, there have been many recent developments in making hyperthermia more effective in treatment of many forms of cancers.     

中心进气旋转盘的冷却效果实验研究

对涡轮发动机热部件冷却的主要指标目的是使热部件的总体温度尽可能低和热部件内部的温差尽可能小,因此对涡轮发动机涡轮盘的冷却除研究转盘表面的对流换热系数外,还应对以上两个指标进行研究。本文将发动机的涡轮盘简化成中心进气施转盘模型,用实验的方法研究了旋转雷诺数、进气雷诺数、盘罩间隙比和出气间隙比对转盘无量钢过余体平均温度和无量纲径向温差的影响,并给出了相应的准则关系式。     

Three-dimensional numerical simulation of the movement of the flexible body under different constraints

For the large deformation of the flexible body may cause the fluid grid distortion,which will make the numerical calculation tedious,even to end,the numerical simulation of the flexible body coupling with the fluid is always a tough problem.In this paper,the flexible body is under two kinds of constrained conditions and the ratio of length-diameter is 1：30.The Reynolds number of the airflow is 513,belonging to the area of low Reynolds number.The control equations of the coupling of flexible body with airflow are built and the adaptive grid control method is adopted to conduct the three-dimensional numerical simulation of the movement of the flexible body.The numerical results show that it is possible to simulate the characteristics of the flexible body＇s movement in the low Reynolds number airflow when the appropriate control equations are modeled and suitable equation-solving method is adopted.Unconstrained flexible body would turn over forward along the airflow＇s diffusion direction,while constrained flexible body in the flow field will make periodic rotation motion along the axis of the flexible body,and the bending deformation is more obvious than that of unconstrained flexible body.The preliminary three-dimensional numerical simulation can provide references for further research on the characteristics of the yam movement in high Reynolds number airflow.     

应用计算机控制系统预防危险废物回转窑焚烧结渣的研究

危险废物回转窑焚烧处置工艺具有诸多优点,但是当危险废物焚烧产生的灰渣熔融温度较低时,窑内的高温气氛会将灰渣颗粒熔融成液相,导致回转窑的结渣。灰渣的熔融实验结果证明,灰渣的熔融温度比较低,变形温度仅有1000℃左右。化学组分对灰渣熔融温度的影响研究表明,SiO2、Al2O3、CaO和CaSO4都对灰渣的熔融温度起到了升高的作用。采用计算机控制系统对整个系统进行监测、控制和管理,控制回转窑的温度在略低于灰渣熔融温度的水平运行,或者对危险废物在焚烧前进行合理的预混配伍,都能起到较好的预防回转窑结渣的作用。     

高强度柴油机活塞温度与应力场有限元分析及其结构改进

结合柴油机活塞发展现状,针对某型号高强度柴油机,利用SolidWorks建立该柴油机活塞的三维模型,并用ANSYS对活塞进行有限元分析,讨论活塞在高温环境、最高燃烧压力或最大侧向力作用下的温度场、应力分布和变形情况。分析结果表明,活塞主要承受热应力和热变形,最大耦合应力在油道顶部,约270MPa,最大变形出现在活塞顶部边缘,变形量约0.08%,变形随活塞高度降低而减小,在裙部略有上升。活塞头部在销孔方向上热变形大于耦合变形,两者差值随活塞头部高度降低而减小。活塞在垂直于销孔轴线方向上的耦合变形总体上大于平行于销孔方向的耦合变形。同时,燃烧室喉口、环槽和销座处应力集中明显,针对上述薄弱区域进行结构改进,发现改进后应力值均显著降低,这些结构改进对高强度柴油机活塞设计开发具有重要指导意义。     

三峡水库蓄水条件下树坪滑坡变形特征及稳定性分析

为了解三峡水库蓄水对树坪滑坡的影响,基于监测资料分析了滑坡位移随水库蓄水变化的规律,采用有限元分析软件Geo-studio分析了各蓄水阶段树坪滑坡的渗流场、位移场和稳定性变化特征。结果表明,水库蓄水过程可分为125~139~135m、135~156~145m和145~175~145m三个阶段,每个蓄水阶段对树坪滑坡的影响程度不同;库水位上升时滑体内地下水浸润线呈内凹趋势,库水位下降时滑体内地下水浸润线呈外凸趋势,且凹凸程度与运行水位差正相关;第一阶段蓄水过程主要引起树坪滑坡前缘局部变形,第二阶段蓄水过程中滑坡前缘变形量增大且变形逐步向滑坡中部发展,第三阶段蓄水过程中滑坡前缘及中部变形量明显增大,变形逐渐向后发展。最后根据树坪滑坡变形机理,提出了防治措施。研究成果可为三峡库区管理提供理论依据。     

Solution of an initial-boundary value problem for heat conduction in a parallelepiped by time partitioning

An initial-boundary value problem for transient heat conduction in a rectangular parallelepiped is studied. Solutions for the temperature and heat flux are represented as integrals involving the Green's function (GF), the initial and boundary data, and volumetric energy generation. Use of the usual GF obtained by separation of variables leads to slowly convergent series. To circumvent this difficulty, the dummy time interval of integration is partitioned into a short time and a long time subintervals where the GFs are approximated by their small and large time representations. This paper deals with the analysis and implementation of this time partitioning method.