用有限体积法研究二维矩形散射介质辐射传递

用直角坐标系下有限体积法研究了二维矩形介质内辐射传递,散射相函数采用Legendre多项式展开.与其他文献的计算结果比较证明了本文有限体积法模型是可靠的.研究表明,相函数及反照率等对温度分布有影响.比较了线性各向异性散射与各向同性散射矩形介质内的温度场,对于不同的误差要求对应存在一个衰减系数及反照率取值区域,在该区域内选取物性参数则可以将线性各向异性散射简化处理为各向同性散射,从而方便了计算.     

微粒散射对半透明流体层光谱吸收特性的影响

通过数值模拟分析了微粒散射对半透明流体层光谱吸收特性的影响 .采用MonteCarlo法模拟辐射能被半透明流体和微粒的吸收与散射以及在半透明镜反射面处的折射、反射和不透明漫反射壁面处的反射过程 ,用H -G相函数考虑了微粒的各向同性、前向及后向散射几种典型的散射分布 .模拟了各种散射分布下含微粒水层对垂直入射辐射的光谱吸收率及水层内部的吸收分布 ,分析了散射分布、吸收因子、衰减系数和反照率等对半透明流体层吸收特性的影响     

有限体积法解多场耦合下散射性非灰介质内的辐射换热

将有限体积法与谱带模型结合 ,求解了吸收、散射性非灰介质内的耦合换热 .经与光线踪迹法、离散传递法的计算结果比较表明 :提出的数值方法具有较高的精度 ;有限体积法适合辐射导热的多场耦合计算 ;对非灰介质建议选用谱带模型 ;并应考虑折射率对传热的影响     

苯妥英钠-Pb2＋体系共振散射光谱的研究与分析应用

在弱酸性介质中,苯妥英钠与硝酸铅结合形成的离子缔合物导致体系的共振散射强度急剧增强,并产生特征散射峰,最强散射峰位于488nm。在适宜的条件下,苯妥英钠浓度在1．25～32．5μg／mL范围内与体系散射强度的增加（△I）有良好的线性关系,方法的检出限为0．89μg／mL（30r）。本法用于药物制剂中苯妥英钠的含量测定,操作简便、快速,灵敏度高。     

用离散传递法求解辐射全交换面积

用离散传递法计算辐射换热量,然后反算求解辐射全交换面积,计算过程方便可行.利用降维后的离散传递法计算了二维封闭体系的辐射全交换面积,与基本算法计算结果的比较表明该算法能够在保证计算精度的前提下大幅度减少所耗机时,同时计算结果很好地满足了全交换面积的互换性和完整性原则,这也进一步证明了离散传递法是求解辐射全交换面积的一种好方法.     

二氧化钛的相对散射力

介绍了相对散射力的概念，并对比分析了国内外部分金红石型二氧化钛的相对散射力。研究了煅烧时间、粒度及粒度分布、介质中的分散性以及后处理包膜等因素对金红石型二氧化钛在一定颜料体积浓度(PVC)下的相对散射力的影响。     

复杂炉型内有非均质参与的热过程数学模型

实现了用均匀离散射线法计算二维复杂炉型内有非均质参与的辐射直接交换面积．对高次非线性段能量平衡方程组采用了主变量修正法．在解决辐射与对流混合传热的问题上,提出了新的双重网格技术．仿真计算结果表明,本文提出的一系列计算辐射换热的方法能够满足工程精度要求．     

热辐射成像法测量大型炉膛内三维温度场的算法新进展

大型炉膛内三维燃烧场与炉内燃烧过程的安全性、经济性和污染物排放水平密切相关。相对于其他大型炉膛内三维温度场可视化监测技术(声学层析成像法和吸收光谱层析成像法),热辐射成像法具有系统紧凑、易于实施等特点,且时间分辨率和空间分辨率较高,具有较大的应用潜力。介绍了大型炉膛内热辐射成像原理;分析了辐射传递反问题的不适定性;综述了辐射传递反问题求解方法研究进展。构建大型炉膛内热辐射成像模型即利用热辐射成像矩阵,将炉膛边界传感器接收的辐射能量分布与炉内温度场、介质和壁面辐射特性联系起来;计算热辐射成像矩阵的关键在于获得介质和壁面单元散射或反射份额的分布,目前通常使用DRESOR法、逆向蒙特卡洛法等进行求解。通过热辐射成像矩阵的条件数判定可知,热辐射传递反问题是不适定性的,导致解的不唯一性甚至不存在性,以及微小测量误差会引起温度场重建的不稳定。目前求解该类不适定问题,主要有优化方法和正则化方法2类。优化方法可分为传统优化方法和智能优化方法。传统优化方法基于梯度计算,通过反复迭代计算减小目标函数,常见有最小二乘法、共轭梯度法等;但该类方法对初值依赖大,需要对目标函数求导数且无法获得全局最优解。智能优化...     

聚合物球晶SALS图样的计算机模拟

介绍了用计算机模拟并绘制聚合物球晶的小角度激光散射图样（包括Hv散射、Vv散射、拉伸试样）的原理和方法，并对模拟得到的散射图样和实验中得到的散射图样进行了比较和分析。     

激光偏振散射法测量钢化玻璃应力的分析

介绍了表面应力及内部应力分布对钢化玻璃各项性能的影响,给出了激光偏振散射法的详细理论推导,结合计算机数字图像处理技术,该方法可方便快捷地获得钢化玻璃表面应力与板厚方向的应力分布,是一种比较理想的钢化玻璃应力测量方法,利用四点弯曲试验对激光偏振散射法的准确性进行核验,结果表明该方法可以满足测试要求.     

Microwave combination heating: Coupled electromagnetics‐ multiphase porous media modeling and MRI experimentation

The work includes development of a multiphase porous media model and magnetic resonance imaging (MRI) experiments to study microwave combination heating. Combination of electromagnetic, convective and radiant heating was considered. The material being heated was modeled as a hygroscopic porous medium with different phases: solid matrix, water and gas, and included pressure driven flow, binary diffusion and phase change. The three‐dimensional transport model was fully coupled with electromagnetics to include the effect of variable properties. MRI was used to obtain spatial temperature and moisture distributions to validate the model. The model demonstrated that high and low moisture materials behave differently under different combinations of heating and general guidelines for combining heating modes were obtained. Low moisture materials can be heated effectively using higher microwave power which is not possible in high moisture material. Cycling of microwave was found to be useful in distribution of excessive volumetric heat generated by microwaves. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

APPLICATION OF THE PRECONDITIONED CONJUGATE GRADIENTS METHOD IN THE SIMULATION OF RELATIVE PERMEABILITY PROPERTIES OF POROUS MEDIA

A model that is after the determination of the relative permeability characteristics of porous media is presented. It is part of a general model that deals with the simulation of capillary phenomena and immiscible fluid flow behaviour in porous media. The relative permeability characteristics in a water wet porous medium are simulated with the use of three-dimensional (3-D) network models of pore structure with pore body and pore throat size distributions. The major assumption involved is that a cubic network of pore bodies connected by pore throats with pore body and pore throat size distribution respectively, is a realistic representation of the pore structure of a porous medium. The physical laws that apply in real media are simulated in the network analysis, and the computed results are compared with experimental findings. A new algorithm was developed that leads to the solution of a large set of linear equations, with a sparse and positive definite coefficient matrix. Results obtained with the application of the Preconditioned Conjugate Gradients method and numerical aspects of the simulation are presented and discussed. Comparison of this method with other available numerical methods is also made. It is concluded that the Preconditioned Conjugate Gradients method is advantageous for large networks with regards to time of solution, convergence, and accuracy. The validity of the algorithm is tested against other methods in the literature.     

Numerical analysis of a catalytic radiant burner: effect of catalyst on radiant efficiency and operability

In this paper we study a new class of porous direct-fired radiant burners which burn part of the fuel catalytically. The burner consists of a multiple-layer porous medium, with one layer that is partially coated with an oxidizing catalyst. Simulations are performed to investigate the effect of platinum catalyst loading, location of catalyst layer, and its thickness on burner performance for single layer and bilayer porous media. Significant efficiency gains are found, but only when the catalyst was placed on the downstream edge of the porous medium. The porous medium was generally not hot enough to cause significant deterioration of the catalyst. Only a thin layer of catalyst is required for efficiency improvements. Enlarging the catalytic zone into cold temperature regions has almost no effect on burner performance. Heat release due to the catalyst occurs inside the porous medium, thus resulting in a higher radiant efficiency.     

Exact solutions of nonlinear heat- and mass-transfer equations

The method of generalized separation of variables for solving nonlinear steady and unsteady heat- and mass-transfer equations is outlined. New exact solutions of one-, two-, and three-dimensional heat equations are obtained. Anisotropic media with a nonlinear heat source of general form are considered for the case in which the main thermal diffusivities show a power or an exponential dependence on the spatial coordinates. Equations with a logarithmic heat source are analyzed in detail. The results obtained are applied to the problem of thermal explosion in an anisotropic medium.     

Surface radiant-energy balance for structural thermal analysis

The development of computer programs to model the effects of fire on structures has led to an increase in the variety of problems to which they are applied. Programs which provide the thermal analysis for such problems must determine the energy exchange between the structure and the fire environment, and this paper addresses the radiation aspect of this exchange. The radiant energy exchange of a surface exposed to any fire environment is considered in relation to equations used in such programs. With the aid of a simple model an alternative generalized expression is derived, which takes a simple form. Two equations, typical of those used in such programs, are compared with this generalized form and their shortcomings discussed. It is proposed that the expression derived in this work should be the preferred choice.     

Nonlinear coupled heat and mass exchange in a cross-flow regenerator

Simultaneous heat and mass exchange in a cross-flow regenerator has been formulated using Schumann's model. A generalized equilibrium relationship at the gas—solid interface led to a non-linear coupling between the heat and mass transfer processes. The Green's matrix, obtained for the problem of heat transfer alone, has been used to set up integral equations to represent this problem of nonlinear coupled heat and mass exchange. A numerical scheme has been developed for solving the resulting system of multidimensional, nonlinear, Volterra-type integral equations using a modified block-by-block method.It is shown that cross-cooled dehumidifiers can be both smaller and require less power than corresponding adiabatic exchangers.     

多孔介质/纯流体耦合区域内可压缩气体的流动

采用统一形式的修正N-S方程描述多孔介质/纯流体耦合区域的流动,提出了方程中用于处理多孔介质内流动的源项确定方法,并利用成熟的CFD技术对圆管内具有前后台阶的耦合区域内可压缩气体的流动进行了数值模拟,得到了与实验吻合的计算结果.