新型空调蓄冷材料四丁基溴化铵-水相变条件和相变热实验研究

四丁基溴化铵水溶液在适当的浓度范围内可在常规空调冷冻水温区内发生固-液相变,形成半笼水合物,是一种潜在的空调蓄冷理想材料.利用实验室的水合物形成实验装置测量了四丁基溴化铵水溶液固-液相变条件,实验结果表明当溶液的质量浓度低于45%时,相变温度随着溶液浓度的增大而增大,但当溶液浓度超过25%,相变温度增加的幅度减小.四丁基溴化铵水溶液的浓度超过45%后,其固一液相变温度反而下降.利用DSC测量了四丁基溴化铵水溶液的相变热,相变热达到195.9kJ/kg.     

水平冷表面上结霜发生随机性研究

水蒸气在冷壁面上的结霜是制冷、低温领域普遍存在的问题。过饱和的水蒸气有两种相变途径，一种是气液固相变；一种是直接气固相变。气液固相变经历气液相变和液固相变两个阶段，实验研究表明其发生具有随机性。在前人实验研究的基础上，从理论上给出了液珠半径随时间的增长规律，并进一步得到了冷壁面自然对流情况下结霜发生概率随时间的变化关系式。     

石蜡微胶囊相变材料与建筑节能

介绍了石蜡相变材料物相变化的特点及其物相变化过程的不定形性，阐述了用微胶囊技术将固-液相变的石蜡转变为固-固相变的石蜡微胶囊的方法。分析了石蜡微胶囊相变材料用于建筑节能领域的现状、存在的问题及其应用前景。     

相变储能材料的研究进展与应用

相变储能技术对于能源的开发和合理利用具有重要意义，在太阳能利用、工业余热回收等方面有着显著的优点。综述了相变材料的研究进展，讨论了固—液相变、固—固相变储能材料的特性及其应用。固—液相变材料一般可分为无机和有机两种类型，其中无机类储能材料主要为无机盐水合物，它具有较大的溶解热和导热系数，但易出现“过冷”和“相分离”现象；有机类储能材料虽然避免了上述缺陷，但其导热性较差、溶解热较低。固—固相变材料种类较少，其中以多元醇应用最为广泛。探讨了这方面研究的发展方向，展望了储能技术市场化应用的前景。     

低温相变材料十二醇-脂肪酸二元体系相变温度的研究

相变恒温材料,目前应用较多的是固液相变材料,而固液相变材料大多数是高温体系.采用步冷曲线法研究了不同组成的十二醇-脂肪酸5组二元体系的相变温度,得到了这5组二元体系的|X相图,这5组体系均为具有最低共熔点的二元体系,其最低共熔温度均小于20℃,具有广泛的应用价值.     

相变贮热材料

本文介绍了相变贮热材料的特点和种类,讨论了固液相变、固固相变贮热材料的性能和应用。     

相变材料的封装定型技术研究进展

相变材料作为能源贮存媒介,能有效地提升太阳能、工业废热等不可再生能源的利用率,成为现今国内外能源领域研究的热点,而相变材料的定型封装技术直接影响到其储能性能及使用耐久性。从基本原理、制备工艺等方面介绍了目前应用范围最广的固-液相变材料的3种主流封装定型技术:多孔载体复合法、微胶囊法和复合纺丝法,以期为相变材料的封装定型提供建议。     

纳米铝粉/石蜡复合相变储能材料的性能研究

针对石蜡作为固-液相变储能材料存在导热系数小、传热性能差的缺点,采用两步法制备了分散性较好的纳米铝粉/石蜡复合相变材料,并对其热物性能进行了实验研究.研究表明,纳米铝粉的加入有效地提高了石蜡相变储能材料的导热系数,而对相变潜热和相变温度影响不大.     

固液相变蓄能的数学模型和自然对流换热系数的实验研究

引入自然对流换热系数 ,将固液蓄能数学模型简化为仅用能量方程加以描述。并通过实验测得相变过程的实际温度场 ,证明了自然对流固液相变换热的影响不可忽略 ,验证了固液相变界面移动速率随自然对流换热系数的增大而增大的定性关系     

硬脂酸相变蓄能模型的改进

引入有效导热系数经验公式，使固液相变蓄能问题得以简化为仅用能量方程加以描述。通过对已有的数学模型加以改进，对有效导热系数经验公式进行修正，使由计算得到相变过程的温度场符合实验测得的温度场，从而验证了改进后的数学模型更加符合固液相变蓄能实际问题。     

Structural analysis of composite bolted joints using the complex potential method

The problem of a pin-loaded hole in a symmetric composite plate with finite dimensions is considered within the scope of the classical laminate theory. The analysis is performed by means of the Lekhnitskii complex potential method. For the given problem, an appropriate power series expansion of the complex potentials is stipulated, where the coefficients are determined from the underlying boundary conditions. The present approach provides an efficient method for the calculation of stresses and displacements in the neighbourhood of the hole where failure is likely to occur.     

A Nonlinear Finite Element Eigenanalysis of Singular Plane Stress Fields in Bimaterial Wedges Including Complex Eigenvalues

A finite element formulation is developed for the analysis of variable-separable singular stress fields in power law hardening materials under conditions of plane stress. The displacement field within a sectorial element is assumed to be quadratic in the angular coordinate and of the power type in the radial direction as measured from the singular point. An iteration scheme that combines the Newton method and matrix singular value decomposition is used to solve the nonlinear homogeneous eigenvalue problem, where the eigenvalues and eigenfunctions are obtained simultaneously. The formulation and iteration scheme apply when the eigenvalue is complex. The examples considered include the single material crack and wedge to demonstrate convergence, and the bimaterial interface crack and the bimaterial wedge to demonstrate geometric versatility and the ability to handle complex eigenvalues. It is found that the real part of the complex eigenvalue for the interface crack agrees with the HRR value. In this case the associated complex eigenfunction is converted into an approximate real-valued eigenfunction that is valid for any mode-mix. In addition, the behavior of separable solutions near certain 'wedge paradox' geometries where non-separable solutions occur is investigated. This revised version was published online in July 2006 with corrections to the Cover Date.     

A novel microwave method for measuring the complex dielectric constant of polymer thin sheets

A new method of measuring the complex dielectric constant of a thin sheet of polymer samples at microwave frequency is presented. In order to obtain the complex dielectric constant in terms of reflection coefficient, a higher order power series solution has been introduced. Application of lower order power series solution to the greater thickness of the sample requires a frequency of less than 1.5 GHz. To overcome this constraint and to extend the range of working frequency, the higher order power series solution is used to obtain the complex dielectric constant. This method is used to measure the complex dielectric constant of poly(ethylene vinyl acetate), polyurethane, polyvinyl acetate, and polystyrene. The results obtained are in good agreement with literature. Electronic Publication     

The dimension splitting and improved complex variable element‐free Galerkin method for 3‐dimensional transient heat conduction problems

In this paper, by combining the dimension splitting method and the improved complex variable element‐free Galerkin method, the dimension splitting and improved complex variable element‐free Galerkin (DS‐ICVEFG) method is presented for 3‐dimensional (3D) transient heat conduction problems. Using the dimension splitting method, a 3D transient heat conduction problem is translated into a series of 2‐dimensional ones, which can be solved with the improved complex variable element‐free Galerkin (ICVEFG) method. In the ICVEFG method for each 2‐dimensional problem, the improved complex variable moving least‐square approximation is used to obtain the shape functions, and the penalty method is used to apply the essential boundary conditions. Finite difference method is used in the 1‐dimensional direction, and the Galerkin weak form of 3D transient heat conduction problem is used to obtain the final discretized equations. Then, the DS‐ICVEFG method for 3D transient heat conduction problems is presented. Four numerical examples are given to show that the new method has higher computational precision and efficiency.     

一种多支撑隔振系统传递功率流测试方法

针对多支撑隔振系统,采用一种间接测试功率流的方法,搭建了功率流测试平台。通过比较直接方法与间接方法获得的隔振系统传递功率流,验证了间接测试方法的有效性,避免了传统隔振系统功率流测试力信号不易获取的问题。功率流间接测试方法在工程中更易实施,对工程中隔振系统及相关结构的功率流获取具有一定的借鉴价值。     

A coupled complex boundary method for the Cauchy problem

Considered in this paper is a Cauchy problem governed by an elliptic partial differential equation. In the Cauchy problem, one wants to recover the unknown Neumann and Dirichlet data on a part of the boundary from the measured Neumann and Dirichlet data, usually contaminated with noise, on the remaining part of the boundary. The Cauchy problem is an inverse problem with severe ill-posedness. In this paper, a coupled complex boundary method (CCBM), originally proposed in [Cheng XL, Gong RF, Han W, et al. A novel coupled complex boundary method for solving inverse source problems. Inverse Prob. 2014;30:055002], is applied to solve the Cauchy problem stably. With the CCBM, all the data, including the known and unknown ones on the boundary are used in a complex Robin boundary on the whole boundary. As a result, the Cauchy problem is transferred into a complex Robin boundary problem of finding the unknown data such that the imaginary part of the solution equals zero in the domain. Then the Tikhonov regularization is applied to the resulting new formulation. Some theoretical analysis is performed on the CCBM-based Tikhonov regularization framework. Moreover, through the adjoint technique, a simple solver is proposed to compute the regularized solution. The finite-element method is used for the discretization. Numerical results are given to show the feasibility and effectiveness of the proposed method.     

Hybrid finite element-Monte Carlo method for coupled conduction and gas radiation enclosure heat transport

A hybrid two-dimensional finite element-Monte Carlo numerical solution method has been developed for solving complex transient non-linear gas radiation enclosure problems. Solid conducting media are coupled to conducting gaseous or particulate participating media and both may be internally energy generating. Bilinear isoparametric elements are used, allowing geometrically complex enclosures with internal objects to be present. Radiative energy transport within the gaseous enclosures is accounted for using a Monte Carlo method which permits a broad range of complexities. Included here are: diffuse-grey and specularly reflecting walls with temperature and spectrally dependent, and non-homogeneous emissivities or absorptivities; absorbing/emitting gases with temperature and spectrally dependent, and non-homogeneous emissivities or absorptivities; and isotropic or anisotropic scattering gases or particles. This method was verified by solving several standard steady state problems and comparing the solutions to those found using the conventional finite element, the P–N and the exchange factor methods. Solution times are comparable to those of the finite element method. A more complex transient problem solution is then given to demonstrate the versatility and power of the method.     

TBD620柴油机低负荷性能研究

以舰用高速大功率柴油机低负荷问题为研究对象，采用试验和理论分析以及计算相结合的方法，对TBD620柴油机进行缸内示功图实机测试和放热规律计算。结果表明，采用主辅双进气道系统是解决舰用大功率柴油机低负荷性能的一种行之有效的方法。     

Solving multi-objective optimal power flow using differential evolution

A differential evolution approach to solve optimal power flow problem with multiple and competing objectives is presented. Two sub-problems of optimal power flow namely active power dispatch and reactive power dispatch are considered. The problem is formulated as a nonlinear constrained true multi-objective optimisation problem with competing objectives. Constrain-domination approach have been used to handle inequality constraints, which eliminates the use of penalty factors. The performance of the proposed approach was tested on standard IEEE 30-bus system and is compared with a conventional method. The result demonstrates the capability of the proposed approach to generate diverse and well-distributed Pareto-optimal solutions.     

Optimal reserve management for restructured power generating systems

This paper presents a technique to determine the optimal reserve structure (reserve providers and the corresponding reserve capacity) for a restructured power generating system (GS). The reserve of a GS can be provided by its own generating units and can also be purchased from other GSs through the reserve agreements. The objective of reserve management for a GS is to minimize its total reserve cost while satisfying the reliability requirement. The reserve management is a complex optimization problem, which requires a large amount of calculations. In order to simplify the evaluation, a complex generating system (CGS) consisting of different GSs and the corresponding transmitting network is represented by its multi-state reliability equivalents. The universal generating functions (UGFs) of these equivalents are developed and the special operators for these UGFs are defined to evaluate the reliability of a particular GS, which has reserve agreements with other GSs in the CGS. The genetic algorithm (GA) has been used to solve the optimization problem. An improved power system-IEEE reliability test system is used to illustrate the technique.