含有冷却水管混凝土结构温度场的三维仿真分析

研究了水管冷却混凝土结构温度场的三维仿真计算方法，并将子结构技术应用到温度场的计算中，算例表明，该方法对于含有大量冷却水管混凝土结构的温度场精确求解问题是可行和有效的。     

基于Comsol Multiphysics的通水冷却热流耦合数值分析

当前针对大体积混凝土通水冷却热流耦合问题的数值分析还存在许多不足，面临着简化较多、精细模拟十分困难的局面。为此，基于Comsol Multiphysics多场耦合有限元软件中的流体流动模块和传热模块，进行了通水冷却热流耦合精细化数值分析，将计算结果与理论解、通水冷却等效算法进行对比，验证了Comsol耦合精细化算法的正确性和可行性。结果表明，Comsol耦合精细化算法在模拟水管沿程温度变化和水管附近的温度值变化方面比等效算法更加精确，更能体现真实的温度梯度，为后续的热应力分析奠定了基础。     

基于冷却水管离散算法的重力坝温控研究

应用精度较高的水管冷却混凝土温度场离散迭代算法对某混凝土重力坝进行全坝段仿真计算,结果揭示了坝体准稳定温度场、坝体温度和应力变化规律.提出的温控防裂措施合理可行、效果明显,对设计和施工具有重要的参考价值.     

考虑水管冷却及表面保温的闸墩施工期温度应力场仿真分析

鉴于施工期的混凝土内外温差及变形约束是闸墩产生温度裂缝的主要原因,基于温度应力场和水管冷却算法等基本理论,通过与施工现场的温度监测数据的对比分析,反演混凝土热学计算参数,利用三维有限元计算软件进行闸墩施工期考虑水管冷却的温度场及应力场仿真计算。结果表明,水管冷却温控效果良好,但混凝土表面因降温幅度较大而产生早期较大的拉应力,应进一步做好表面保温措施,降低混凝土内外温差。     

基于ANSYS的冷却水与混凝土之间对流换热模拟方法

热流耦合算法计算含有冷却水管的大体积混凝土温度场时,无需在水管处细化网格,网格划分方便,且可精细模拟水温的沿程温升及水管附近混凝土温度场,但需逐对耦合流体单元的附加节点与同一位置的混凝土节点来模拟冷却水与混凝土之间的对流换热,比较麻烦。对此,特描述了热流耦合算法模拟冷却水与混凝土之间对流换热的本质,并提出了一种新的方法来模拟冷却水与混凝土之间的对流换热,即用nummrg,all命令代替耦合来模拟冷却水与混凝土之间的对流换热。实例应用结果表明,新方法与传统耦合方法的计算结果相差不超过2%,由此验证了新方法可行、正确,为热流耦合算法在实际工程中的应用提供了参考。     

锅筒翻边开孔交变应力范围捷算法研究

为解决我国固定式水管锅炉计算标准和相关研究中锅筒翻边开孔交变应力范围计算的复杂性。按该标准计算方法并结合计算工况下锅炉运行中峰谷应力变化特点,对捷算法计算公式进行了推导和实例验证;对固定式水管锅炉国家标准法计算步骤和计算物理量进行了比较,并对其在船舶动力锅炉上应用的可行性进行了分析;结合已有研究成果,对我国标准规定的锅筒五种开孔型式的捷算法交变应力范围计算公式进行了的适用分类。与我国标准相比,捷算法仅需对每一计算工况下考核点处峰谷值环向应力及其合成主应力进行计算,省略了每一计算工况下三个方向间主应力差的峰谷值计算、主应力差变化范围计算和交变应力范围取值计算。捷算法也适用于具有相同开孔结构和计算应力种类不多于我国标准中的船舶动力锅炉,克服了我国标准法的不足,具有理论和应用价值。     

基于改进鲸鱼优化算法的大体积混凝土热学参数反演

为提高混凝土热学参数反演分析时的计算效率和精度,引入Logistic映射和惯性权重对鲸鱼优化算法进行改进,并结合有限元仿真计算,提出一种基于改进鲸鱼优化算法的混凝土热学参数反演分析方法。结合上海ZJH泵闸工程开展现场非绝热温升试验,采用该方法对大体积混凝土试块的导温系数和表面散热系数进行了反演分析,并与粒子群算法反演结果进行比较。结果表明,改进鲸鱼优化算法在计算精度及迭代效率方面均较粒子群算法有明显提高,该算法在求解混凝土热学参数反演问题方面具有可行性和有效性,能够满足工程精度要求。     

特高混凝土拱坝水管冷却效果评价

为评价混凝土拱坝水管冷却温控效果,根据混凝土浇筑到接缝灌浆各个阶段的不同特征,确立了评价指标体系,采用熵权法确定指标权重,并根据现有的温控标准,结合实际温度控制情况,运用模糊综合评价法确定水管冷却效果的评价等级。实例应用结果表明,该方法能有效判断本周水管冷却的薄弱环节,可为下周通水调整提供参考依据。     

基于热流耦合算法的含有冷却水管的大体积混凝土温度场仿真技术

针对采用等效算法求解含有冷却水管的大体积混凝土温度场时无法考虑水管中水温沿程变化、不能精细计算靠近水管处的混凝土温度场问题,特提出改进的热流耦合算法,并基于ANSYS软件中的solid70单元、fluid116单元、mass flow等子程序,构建了含有冷却水管的大体积混凝土热流耦合算法的单元选择、网格划分、自由度耦合、载荷施加等关键技术,并将其应用于锦屏一级拱坝#14坝段1~4仓含有冷却水管的大体积混凝土温度场仿真计算中。仿真结果表明,采用改进的热流耦合算法的计算值与实测值十分接近,从而验证了改进算法的可行性。     

水管冷却技术在大型渡槽防裂中的应用研究

针对大型渡槽施工期间常见裂缝问题,采用三维有限元仿真分析软件,以南水北调某大型渡槽为例,对混凝土浇筑全过程进行了模拟,分析了一期水管冷却效果,并对水管冷却的通水温度进行敏感性分析.计算结果表明,水管冷却具有良好的导热降温作用,不同的通水温度对混凝土温度降幅基本一致,在确保降温效果的同时可适当提高通水温度以降低水管附近混凝土的拉应力,同样能有效防止施工早期和后期其他部位出现温度裂缝,可供类似工程在施工期的温控措施借鉴.     

Thermal Buckling of Piezolaminated Plates Subjected to Different Loading Conditions

A thermal buckling analysis is presented for simply supported rectangular laminated composite plates that are covered with top and bottom piezoelectric actuators, and subjected to the combined action of thermal load and constant applied actuator voltage. The thermomechanical properties of composite and piezoelectric materials are assumed to be linear functions of the temperature. The formulations of the equations are based on the higher-order laminated plate theory of Reddy and using the Sanders nonlinear kinematic relations. The closed-form solutions for the buckling temperature are obtained through the Galerkin procedure and solving the resultant eigenvalue problem, which are convenient to be used in engineering design applications. Numerical examples are presented to verify the proposed method. The effects of the plate geometry, fiber orientation in composite layers, lay-up configuration, different utilized piezoelectric materials, temperature dependency of material properties, thermal conductivity, and energy generation on the buckling load are investigated.     

Experimental and numerical study of unsteady non-periodic wall heat transfer under step,ramp and cosine temperature perturbations

An experimental and numerical study of the transient non-periodic wall heat transfer problem is presented. A computer-controlled indoor/outdoor environment simulation system produces any desired variation of the air temperature, thus allowing measurement of the dynamic thermal behaviour of any test wall under the desired boundary conditions. Measurements of the temperature field within the wall, of the heat flow and of the convection coefficients at the wall surfaces are performed during step, ramp and cosine perturbations of the outdoor air temperature. The measurements are in very good agreement with the numerical predictions obtained by a developed finite difference solution procedure. The results showed that in building heat transfer applications, for example in air conditioning, the usual assumption of periodic outdoor conditions may lead to considerable errors in case of a significant temporary deviation of the temperature from periodicity.     

The potential drop method for monitoring crack growth in real components subjected to combined fatigue and creep conditions: application of FE techniques for deriving calibration curves

The potential drop technique is a robust method to provide continuous in situ crack growth monitoring of real power-plant components. For a correct assessment of the crack depth, accurate calibration curves for the geometry at hand are required. The problem entails determining the electrical potential field in a body usually characterised by a complicated geometry as a function of the growing crack. Finite element analysis procedures are first applied to optimise the technique (i.e. to determine the best location for the PD leads) and secondly to provide theoretical calibration curves. The validity of this procedure has been assessed in laboratory component tests under both thermal fatigue and multiaxial creep loading. Post-test measurements of the crack depth underline the accuracy of the FE calibration technique.     

A design optimization tool of earth-to-air heat exchanger using a genetic algorithm

Advancement in genetic algorithm (GA) optimization tools for design applications, coupled with techniques of soft computing, have led to new possibilities in the way computers interact with the optimization process. In this paper, the concept of goal-oriented GA has been used to design a tool for evaluating and optimizing various aspects of earth-to-air heat exchanger behavior. A new optimization method based on GA is applied as a generative and search procedure to optimize the design of earth-to-air heat exchanger. The GA is used to generate possible design solutions, which are evaluated in terms of passive heating and cooling of building, using a detailed thermal analysis of non air-condition building environment The results from the simulations are subsequently used to further guide the GA search to find the high-energy solutions for optimized design parameters. The specific problem addressed in this study is the sizing of earth-to-air heat exchanger in a non air-conditioned residential building. The developed algorithm is suitable for the calculation of the outlet air temperature and therefore of the heating and cooling potential of the earth-to-air heat exchanger system. This methodology is applicable to a wide range of design optimization problems like choice of building such as green house, solar house, or heating and cooling of buildings by mechanical system.     

二冲程舷外机簧片阀阀片材质的检测与分析

为了解决舷外机簧片阀阀片在工作一定的时间后容易出现断裂的现象，本文经过对材料成分的检测和分析对比，指出产生该现象的主要原因，并提出解决该问题的方法。     

反演计算不同炉气温度下非灰气体的当量吸收系数的方法

提出了一种反演计算不同炉气温度下非灰气体的当量吸收系数的方法。此方法以实验数据反演得到的非灰气体的当量吸收系数作为物性参数,由正演算计算不同条件下的炉气温度,并以此为定解条件,反演不同炉气温度下的非灰气体的当量吸收系数,反复迭代,直至收敛。反演计算过程中采用区域法与求目标函数最小值的共轭梯度法相结合的方法。与实验结果比较表明,该方法可以较为准确地反演不同炉气温度下的非灰气体的当量吸收系数。最后,用该方法计算并比较了非灰气体的当量吸收系数随炉气温度的变化。图2表2参9     

低温环境中空冷器的设计

针对低温环境中空冷器使用所遇到的问题，提出了解决防止流体在管内凝固和冻结的方法，并对防冻防凝的几种方法进行了比较。     

Multiple transient point heat sources identification in heat diffusion: application to experimental 2D problems

This paper deals with an inverse problem, which consists of the experimental identification of line heat sources in a homogeneous solid in transient heat conduction. The location and strength of the line heat sources are both unknown. For a single source we examine the case of a source which moves in the system during the experiment. The identification procedure is based on a boundary integral formulation using transient fundamental solutions. The discretized problem is non-linear if the location of the line heat sources is unknown. In order to solve the problem we use an iterative procedure to minimize a cost function comparing the modelled heat source term and the measurements. The proposed numerical approach is applied to experimental 2D examples using measurements provided by an infrared scanner for surface temperatures and heat fluxes. In some particular examples, internal thermocouples can be used. A time regularization procedure associated to future time-steps is used to correctly solve the ill-posed problem.     

大顶子山溢流坝长闸墩温度应力仿真计算分析

应用非稳定温度场和温度应力场仿真程序ANSYS对闸墩的温度应力进行了模拟分析,从材料、温度控制、施工方法和养护等方面采取措施,以降低混凝土的内外温差、防止混凝土外表面因温度变化太快而产生裂缝,具有工程实际意义。     

Computational Design of Microstructural Composites with Tailored Thermal Conductivity

This article presents a numerical procedure to design two-phase periodic microstructural composites with tailored thermal conductivities, which is generalized as a topology optimization problem. The objective function is formulated in a least-square of the difference between the target and effective conductivities. The effective values are derived from homogenization method with periodic boundaries; whereas, the target points locate in the Milton-Kohn bounds. The bound-based interpolation scheme and nonlinear diffusion technique are explored to regularize the original problem for attaining mesh-independent, edge-preserving, and checkerboard-free results. Various microstructures both in 2- and 3-dimensions are presented to demonstrate such a systematic procedure of conductive material design.