均匀散射介质参与体系辐射换热分析

在辐射换热网络法基础上,定义了容积散射热阻并导出其表达式,区别容积辐射体对不同表面段的发射率及逸散系数,分析了均匀散射介质参与辐射换热时空间热阻的变化,并绘制出散射介质参与的三元体系辐射换热网络图.介质的散射使得容积段与表面段之间的总热阻增大,因而削弱了容积段与表面段之间的辐射热交换.     

均匀散射介质参与体系辐射换热分析

在辐射换热网络法基础上，定义了容积散射热阻并导出其表达式，区别容积辐射体对不同表面段的发射率及逸散系数，分析了均匀散射介质参与辐射换热时空间热阻的变化，并绘制出散射介质参与的三元体系辐射换热网络图．介质的散射使得容积段与表面段之间的总热阻增大，因而削弱了容积段与表面段之间的辐射热交换．     

考虑炉气散射特性的加热炉内辐射换热分析

考虑加热炉内燃烧产物的散射作用,借助辐射换热网络分析法,给出了吸收、发射和散射介质中炉膛系统黑度及辐射换热的基本公式,模拟计算了散射介质中系统黑度的变化.数值模拟结果表明,与忽略介质散射作用的简化描述相比,散射使得系统黑度值降低,炉膛总换热强度减弱.介质的散射作用越强,忽略介质散射导致的误差越大.     

考虑炉气非灰特性的辐射全交换面积

考虑加热炉内炉气的非灰特性,区别了炉气对不同表面的发射率及其对不同表面有效辐射中各分量的吸收率,通过求解反射热流密度推导三元辐射体系(炉气-炉壁-钢坯表面)中辐射全交换面积的简化表达式。以某轧钢厂的一座步进梁式加热炉为例,对辐射全交换面积沿炉长方向的分布进行模拟计算,并研究了炉壁发射率对炉壁表面段与钢坯表面段间辐射全交换面积的影响。推导的辐射全交换面积表达式,耗费机时较少,可用于加热炉在线控制数学模型中钢坯表面辐射热流的准确计算。     

散射性介质辐射传热的数值模拟

利用有限容积法采用C语言模拟了三维圆柱体内吸收、散射性介质的辐射传热温度场：通过辐射传递过程的数值计算，分析了介质本身性质、各向异性散射对温度分布的影响。与光线踪迹法相比较，有限容积法计算速度快具有较好的精度，是目前辐射传递过程数值模拟的一种较好的方法。计算结果表明，由于径向辐射射程比轴向辐射射程小，所以各向异性散射在径向对温度场的影响要比在轴向的大；此外反照率对温度场的影响不大。     

逸散系数及接受系数在求解辐射直接交换面积中的应用

基于逸散系数定义,给出了直角坐标系下逸散系数积分表达式.采用积分简化公式推导了逸散系数及接受系数的降重积分表达式,并应用高斯数值积分进行求解.应用逸散系数及接受系数对气体段对自身及气体段对相邻表面段的直接交换面积进行求解验证.结果表明,采用降重积分求解逸散系数及接受系数计算结果更精确,用于求辐射直接交换面积时精度更高,并可以节省一定的机时.     

热线法实验中半透明介质内部导热和辐射分析

对热线法实验条件下半透明介质的积分-微分能量方程进行了数值求解。着重分析各个辐射项对内部总热流的贡献,研究了介质吸收系数以及热线黑度对热线温升的影响,引入了介质的等效平均吸收系数和热线的等效表面黑度2个新概念,并讨论了简化模型。     

基于炉气非灰辐射特性的钢坯表面热流研究

 基于加热炉内炉气的非灰辐射特性,指出三元辐射体系(炉气 炉壁 钢坯表面)中炉气存在2种发射率和6种吸收率。应用射线跟踪方法推导钢坯表面热流表达式,解除了Τимофеев公式中炉壁为零热流和炉气为灰体的限制。以某轧钢厂的一座步进梁式加热炉为例,对其钢坯表面热流进行了模拟计算。推导的钢坯表面热流表达式为加热炉在线控制数学模型中钢坯表面热流的简化算法提供了理论依据。此外,给出了炉气为非灰时的辐射全交换面积的一种计算方法,为准确求解加热炉炉膛内的辐射热交换创造了条件。     

长方体火焰炉辐射传热特性的段法分析

本文阐述了长方体火焰炉辐射传热特性的段法分析,较详细地进行了燃烧气体黑度计算公式、直接交换面积公式的推导,利用直接交换面积导出热平衡方程,并进行了全交换面积计算公式、热平衡式的推导,指出上述给出的计算公式完全适应无焰燃烧场合。     

封闭体系内表面区域间辐射总交换面积的Monte—Carlo方法计算

本文讨论了用Monte-Carlo方法直接计算辐射总交换面积及光子数,伪随机数,发射点位置分布等因素对计算精度的影响.     

辐射直接交换面积数论网格法与Monte-Carlo法的比较研究

针对辐射直接交换面积,分别用数论网格法与Monte-Carlo法进行了比较计算。结果表明,与Monte-Carlo法相比,数论网格法具有计算速度快,计算精度高及使用方便等优点。     

Surface Characteristics of Sorptive-Filtration Storm Water Media. I:?Low-Density (ρs < 1.0) Oxide-Coated Buoyant Media

Control strategies for storm water that combine unit operations and processes can offer distinct advantages for many in situ applications in the built environment. Examples include a variety of control strategies that utilize engineered buoyant media to provide filtration and adsorption for heavy metals transported by storm water. With the goal of producing such media, methods were developed to coat iron and manganese oxide onto the surface of common polymeric media. Surface characteristics of coating media were determined by powder X-ray diffraction, infrared spectroscopy, and scanning electron microscopy analyses. Results indicated that oxide coatings ranged from 20 to 200 μm in depth, and surface areas were increased from 0.05 m2∕g for uncoated spherical polymeric media to 27 m2∕g for the same media after oxide coating. All manganese oxide coated media generated a net negative surface charge in the typical storm water pH range of 6–8. Media specific gravity (ρs) remained less than 0.93 even with oxide coatings. A multiple-layer oxide coating provided surface characteristics that enhance filtration and adsorption of heavy metals using coated buoyant polymeric spherical media in storm water treatment systems such as sorptive buoyant media clarifiers.     

钻井水溶法开采矿区地表移动随机介质理论预计研究

钻井水溶法开采流程简单、操作方便、劳动负荷轻、投资少、见效快，是一种很有发展前途的采矿方法。钻井水溶法开采形成的地下采空区可能会使地表发生移动和变形。随机介质预计理论概率积分法是建立在上履岩层软弱、顶板跨落基础上的非连续介质理论。由于沉积成矿的特点，岩盐矿床的地质条件决定了其岩石力学性质整体表现为顶、底板强度较低，适应于采用随机介质理论预计地表移动与变形。文章结合某钻井水溶法开采矿山实例，探讨地表移动与变形预计随机介质预计方法。     

钻井水溶法开采矿区地表移动随机介质理论预计研究

钻井水溶法开采流程简单、操作方便、劳动负荷轻、投资少、见效快,是一种很有发展前途的采矿方法。钻井水溶法开采形成的地下采空区可能会使地表发生移动和变形。随机介质预计理论概率积分法是建立在上覆岩层软弱、顶板跨落基础上的非连续介质理论。由于沉积成矿的特点,岩盐矿床的地质条件决定了其岩石力学性质整体表现为顶、底板强度较低,适应于采用随机介质理论预计地表移动与变形。文章结合某钻井水溶法开采矿山实例,探讨地表移动与变形预计随机介质预计方法。     

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A 2D temperature model was proposed for heating rules and real-time calculation during heating process on billet reheating furnace, which included furnace temperature calculation along furnace length, billet surface fluxes calculation and conduction calculation inside billet. First, furnace temperature was accomplished according to thermocouple. Then fluxes on the above and below surfaces were calculated by total heat exchange factor method, as well as lateral fluxes. ADI and TDMA algorithms were adopted to calculate billet internal temperature distribution. Validation was carried out by thermocouple experiments and a model system was established in a hot rolling plant to provide appropriate heating rules and real-time temperature prediction. It shows precision and responsibility during reheating furnace production.     

Comparison of finite-difference transport and diffusion calculations for photon migration in homogeneous and heterogeneous tissues

We analyse the limits of the diffusion approximation to the time-independent equation of radiative transfer for homogeneous and heterogeneous biological media. Analytical calculations and finite-difference simulations based on diffusion theory are compared with discrete-ordinate, finite-difference transport calculations. The influence of the ratio of absorption and transport scattering coefficient (mu(a)/mu'(s)) on the accuracy of the diffusion approximation are quantified and different definitions for the diffusion coefficient, D, are discussed. We also address effects caused by void-like heterogeneities in which absorption and scattering are very small compared with the surrounding medium. Based on results for simple homogeneous and heterogeneous systems, we analyse diffusion and transport calculation of light propagation in the human brain. For these simulations we convert density maps obtained from magnetic resonance imaging (MRI) to optical-parameter maps (mu(a) and mu'(s)) of the brain. We show that diffusion theory fails to describe accurately light propagation in highly absorbing regions, such as haematoma, and void-like spaces, such as the ventricles and the subarachnoid space.     

Influence of the gas exchange function through the middle ear mucosa on the development of sniff-induced middle ear diseases

To investigate the influence of gas exchange function through the middle ear mucosa on the development of sniff-induced middle ear diseases, the authors examined the mastoid pneumatization among patients with sniffing habit using computed tomography, and also examined the change of negative middle ear pressure induced by sniffing using tympanogram. In 20 ears with cholesteatoma or adhesive otitis media, the areas of mastoid cavity measured at the level of the lateral semicircular canal were significantly smaller than those in 26 ears with otitis media with effusion (OME) or attic retraction and in eight normal ears with sniffing habit (P < .01 and P < .0001, respectively). In 26 ears with OME or attic retraction, the areas of mastoid cavity were significantly smaller than those in eight normal ears with sniffing habit (P < .0001). By contrast, in the four ears with sniff-induced middle ear disease, the recovery of negative middle ear pressure in 5 minutes without swallowing was less than 10 mm H2O, whereas in all seven ears with normal eardrum, negative middle ear pressure recovered by more than 20 mm H2O in 5 minutes. These findings suggested that impairment of gas exchange function through the middle ear mucosa, as well as eustachian tube dysfunction, might be closely related to the development of sniff-induced middle ear diseases.     

Poly(4- and 5-acrylamidosalicylic acids). Part V. Effect of counter anion and salicylate complex stability on cation exchange from aqueous solution

Poly(5-acrylamidosalicylic acid) acts as a monobasic acid with a dissociation constant of 3.13 × 10^?4 moles l^?1 derived from the direct titration of monomeric 5-acrylamidosalicylic acid. The polymer exhibits very low solubility in acid media but is appreciably soluble above pH 6, when it is almost wholly dissociated. Studies with acetate, chloride, nitrate and sulphate ions show that the exchange characteristics of the polymer are little affected by the nature of the counter anion present in the case of strongly bound cations, but exchange levels are markedly depressed by the presence of sulphate in the case of weakly bound cations. Possible reasons for this change in behaviour are discussed.