辐射器漫反射定向管表面热辐射方向性

为了得到辐射能的方向分布特性,利用蒙特卡罗法,研究了定向管内壁面为不等温灰体、其底部假想圆型辐射器为黑体时,管内壁发射率、管长与半径比、管内空气流速等参数的变化对管口表面当量定向发射率的影响,计算结果表明:管长与半径比增加,管口表面较大的当量定向发射率向小角度的天顶角方向移动,空气流速仅影响当量定向发射率数值大小。     

Generalised radiant emittance in the phase-space representation of planar sources in any state of spatial coherence

The physical meaning of the generalised radiant emittance is not trivial. Indeed, its energy values should describe the local emission properties of planar sources in any state of spatial coherence, but they can take on positive and negative values mainly within the non-paraxial region. The recent phase-space modelling of optical fields in terms of radiant and virtual layers of point sources is used as framework for analysing the nature of the generalised radiant emittance in order to give more insight on its physical meaning.     

动态黑洞的瞬时辐出度

选取超前爱丁顿坐标，采用统计的方法，计算出动态黑洞的瞬时辐出度.结果表明，动态黑洞的瞬时辐出度不仅与假定黑洞处于热力学平衡时的辐出度有关，还与黑洞的事件视界变化率、事件视界温度、事件视界附近的熵密度及黑洞的吸收和辐射系数有关.对于球对称动态黑洞，任一时刻黑洞的瞬时辐出度总是正比于黑洞事件视界温度的四次方. 关键词： 熵密度 事件视界温度 薄膜模型 瞬时辐出度     

Local correlation of current density,radiant emittance and temperature within GaAsP light-emitting diodes

Two experimental methods are described which allow local and temporal investigations of radiant emittance and temperature within the active area of GaAsP lightemitting diodes. Resolution is in the order of 1 μm and 10 μs, respectively. The measurements are correlated with theoretical calculations of the local current density. Non-uniformity and saturation are observed under pulsed operating conditions. The results demonstrate the importance of local measurements, especially in the case of degradation studies, where current density and temperature are supposed to play a major role.     

An improved model to calculate radiative heat transfer in hot combustion gases

Radiative heat transfer plays an important role in the chemical reactions in the combustor. The widely used WSGG model proposed by Smith is established for normal pressure, which shows inevitable computational errors when dealing with radiative heat transfer problems at reduced or elevated pressures. In this paper, an improved global model is established to calculate the radiant energy exchanges between combustion gases and combustor chamber walls. Compared with the Smith model, the new model shows better performance in a wide range of pressure regions. The model accuracy is examined by computing the emissivity, radiative heat flux as well as the radiative source of H₂O–CO₂ gas mixtures at different pressure values. Finally, the radiative heat transfer inside a 3D TBCC(turbine-based combined cycle) engine exhaust system where strong gradients of pressure and temperature exist, is also addressed. The computational results show that the developed model provides approximate results at much less computational costs than the high-precision MSMGFSK-c8 model, which makes it competitive in complicated combustion systems.     

加速运动动态黑洞的瞬时辐出度

利用加速黑洞视界面附近的熵密度，导出黑洞的瞬时辐出度，得到了任一时刻黑洞沿某一方向的瞬时辐出度总是正比于在该方向上黑洞事件视界温度的四次方的结论. 导出的广义Stefan-Boltzmann系数不再是一个恒量，而是一个与黑洞视界的变化率、黑洞视界面附近的时空度规及黑洞的吸收与辐射系数有关的动比例系数. 揭示了黑洞周围的引力场与其热辐射之间存在着必然的内在联系. 关键词： 薄膜模型 瞬时辐出度 广义Stefan-Boltzmann系数     

低温地板辐射采暖系统的传热分析与仿真

建立了低温地板辐射供暖系统的传热过程的数学模型,用有限元法对数学模型进行求解。以一个动态仿真程序得出了不同供回水平均温度和排管间距下的地板表面最高温度和单位面积的热流量,阐明了系统的舒适和节能特性,为工程设计提供了理论依据。     

测量组织局部血液灌注率的表面热干扰法

1日u云去正常的血液灌注是机体组织重要的生理要素之一，组织所需的氧、营养和药物靠灌注的血液来运输供应。心肌缺血（即冠心病）是当前困扰人们的发病率高的严重疾病之一。脑对血液的供应则更是敏感，脑血管的局部栓塞将导致局部脑组织缺血甚至坏死。因此，组织灌注状况的检测不仅对于生理和病理研究是重要的，对临床医学也是十分重要的。事实上，某些非缺血性疾病的治疗（例如癌瘤的热疗）过程也直接或间接地涉及到组织的灌注率。寻求一种测量组织灌注率的方法一直是人们孜孜以求的。近年来，各种测量方法的研究已有相当的发展山，其中热…     

高速碰撞诱发闪光辐射温度的测量及误差分析

为实现对高速碰撞诱发的闪光辐射温度进行实验测量及误差分析,建立了二级轻气炮加载系统及闪光辐射温度测量系统。采用聚碳酸酯弹丸分别以6 km/s、3.9 km/s的速度垂直撞击2A12铝靶,利用瞬态光纤高温计采集闪光信号,通过比色法计算不同碰撞条件下的闪光辐射强度及辐射温度。依据普朗克辐射定律计算了不同波长及温度条件下的闪光辐射强度理论值,与实验测量结果相比较并进行了误差分析;分别采用双色测温法的不同波长组合及四色测温法计算了闪光辐射温度及其平均温度,通过计算标准差分析了波长的选取对闪光辐射温度的影响。结果表明：与理论计算结果相比较,实验测量得到的闪光辐射强度值偏低,采用双色测温法计算闪光辐射温度时波长的选取对计算结果影响很大,波长间隔越大计算结果误差越小（误差最小值实验No.1为68.25 K,实验No.2为30.67 K）;四色测温法计算得到的闪光辐射温度与平均温度相近（误差实验No.1为72.88 K,实验No.2为63.66 K）,因此采用比色法计算闪光辐射温度时应尽量选取大间隔波长或多个波长参与计算以降低误差。     

Paraxial Approximation of Modern Radiometry for Beamlike Wave Propagation

A new approach to the construction of a system of the generalized radiometric quantities expressed in terms of the cross-spectral density function of the wave field is proposed. The key distinction of this approach lies in the fact that the initial hypothesis of beamlike wave propagation allows to invoke the paraxial approximation when deducing the generalized radiant flux. Within the framework of this approach the new expressions for the generalized radiant emittance, the generalized radiant intensity and the generalized radiance are derived. All the proposed generalized radiometric characteristics represent physically measurable quantities and, hence, may be used in practical radiometry. The results obtained in this paper can be regarded as a particular case of the modern radiometry theory in paraxial approximation for beamlike wave propagation.On leave from Kiev Polytechnic Institute, Ukraine.     

Radiometry and Radiation Efficiency of Twisted Gaussian Schell-Model Sources

Wavefields endowed with the coherence-induced property of optical twist have recently attracted a good deal of theoretical and experimental attention. We present the generalized radiometric theory of fields generated by twisted Gaussian Schell-model sources. The effects introduced by the novel, rotationally symmetric, twist phenomenon in the radiant intensity, generalized radiance, radiant emittance (irradiance), and the radiation efficiency are assessed. The radiance becomes directionally skewed as a result of the twist, whereas the radiant intensity remains axially symmetric. The twist reduces the radiation efficiency and broadens the radiation distribution, in agreement with the notion that the twist decreases the effective coherence. Several special cases, such as quasihomogeneous sources, are analyzed in detail. The radiometric results, which are physically consistent with the superposition models of twisted sources, are demonstrated by illustrative examples.     

Heat transfer in boundary layer stagnation-point flow towards a shrinking sheet with non-uniform heat flux

In this paper, the effect of non-uniform heat flux on heat transfer in boundary layer stagnation-point flow over a shrinking sheet is studied. The variable boundary heat fluxes are considered of two types: direct power-law variation with the distance along the sheet and inverse power-law variation with the distance. The governing partial differential equations (PDEs) are transformed into non linear self-similar ordinary differential equations (ODEs) by similarity transformations, and then those are solved using very efficient shooting method. The direct variation and inverse variation of heat flux along the sheet have completely different effects on the temperature distribution. Moreover, the heat transfer characteristics in the presence of non-uniform heat flux for several values of physical parameters are also found to be interesting.     

空间屏打孔多层隔热材料热计算模型

分析了空间屏打孔多层隔热材料中导热和辐射的复合传热问题,在一定假设的基础上,根据反射屏能量平衡方程,建立了反射屏稳态温度计算模型和投射辐射数值分析模型。结合AD I法,对两个方程组进行迭代求解,得到材料屏间投射辐射热流和反射屏的温度。将文中模型的预测结果与文献中实验值进行比较,验证了模型在工程上应用的可行性。同时分析了当量导热系数、各种热流以及内部温度分布随层密度的变化规律,对材料的优化设计具有积极的指导意义。     

列车客车用低温电地板辐射供暖传热模拟

以传热学理论为基础,建立了低温电地板辐射供暖非稳态过程的二维传热数学模型,并应用有限元分析软件ANSYS对数学模型进行了求解;通过实测及理论计算,得出地板内温度及热流密度分布特点;计算值与实测值相对误差小于10％。     

Radiative transfer with anisotropic scattering in an isothermal slab

Two types of anisotropic scattering, linear anisotropic scattering and Rayleigh anisotropic scattering, are considered in the analysis of radiative transfer for an isothermal, plane-parallel medium confined between gray, diffuse walls. The problem is formulated in terms of a coupled pair of integral equations containing the intensity-moments as the unknown variables. These intensity-moments are shown to be the components of the source function. The set of equations is then solved both numerically and in closed form. The results reveal clearly the effects of anisotropic scattering on important characteristics such as heat flux directional emittance and incident radiant energy per unit area. These effects are well predicted by the approximate closed-form solution.     

四色高温测量中最佳化参数的选择

本文从黑体辐射定律出发,计算了物体辐射谱在四个不同波长处辐射强度的比率。结果表明,适当选取四个测量点的波长,四波长之差值及测量点波长带宽,该比率与被测辐射体温度之间有良了的单值关系,并可一定程度上消除物体单色辐射率对测温的影响。根据结果用图示出了各参数对四色高温测量的影响。     

Pulsed Heating of Carbides

Experimental studies of carbides are briefly reviewed. The high-temperature properties of carbides used in nuclear power and aerospace engineering are considered. Temperature is measured from either plane surface emittance or the emittance of thin samples prepared in the form of a melting blackbody model. The following quantities are measured: Joule energy, heat capacity (predominantly С_p), electrical resistance, and phase-transition heat versus temperature (up to 5000 K). The pre-melting heat capacity exceeds the equilibrium value, but temperatures measured at the characteristic points of the phase diagram correspond to the design diagram.     

复合相变材料应用于电子散热的热分析

基于显热容法,建立复合相变材料应用于电子散热的传热模型及相应的数值计算方法,利用Icepak软件进行数值计算,分析了温度场及流场分布。模拟结果与实验测量值相接近,其最大相对误差为8.8%,说明所采用的数值模型及相关简化处理正确。借助热分析方法可以真实地模拟系统的热状况,从而为电子设备的热设计和热管理提供依据。     

基于遗传算法混合工质热泵多参数优化

本文将人工智能之一的遗传算法应用于混合工质热泵系统,在对热泵进行模拟的基础上构造了系统性能函数,对冷凝压力、蒸发压力以及回热度进行了多参数的优化,得到了使系统COP最大时的各参数的最佳值。发现在进行制冷/热系统多参数组合优化时,遗传算法全局寻优以及收敛能力与传统的优化方法相比,性能有了较大的提高。     

静态球对称黑洞Dirac场的Stefan-Boltzmann定律

利用静态球对称黑洞Dirac场的统计熵，导出静态球对称黑洞的Stefan-Boltzmann定律，得 到黑洞的辐出度与视界温度的四次方成正比的结论.发现Stefan-Boltzmann常数不同于平直 时空的值，并且在不同时空度规中该常数有不同的值. 关键词： 黑洞 统计熵 薄层模型 辐出度