辐射角系数计算边界元法及奇异积分处理

运用Stokes公式及边界元理论，导出了辐射换热计算中的辐射角系数与相互辐射面积的计算基本公式。分析了影响计算准确度有关因素，对所遇到的奇异积分给予了有效的处理。通过四个典型例子的计算，结果与精确解加以对比，表明本方法计算可靠、稳定，具有输入数据少、准确度高等优点。为辐射系数和空间热阻的求解开辟了新的途径。     

单轴旋转跟日式多平面镜反射聚光器的设计

主要设计了一种新型的单轴旋转跟日式多镜面聚光系统,该系统与目前常见的聚光器相比,价格低廉、易于维护,仅通过单轴的转动来实现反射聚光,耗能较小.对系统中各镜面的位置及尺寸进行了详细的讨论和计算,并通过实验验证了其可行性和有效性,该方法能实现4倍以上的聚光,能有效减少跟踪系统消耗的能量,从而提高整个跟踪聚光系统的性价比.     

固定磁场对旋转火焰旋转特性影响的研究

通过对固定磁场作用下旋转火焰动量方程的分析和实验研究，得到不同强度磁场作用下旋转火焰的旋转强度变化的规律性。通过研究可以得到，当磁场的强度大干0．357T时，随着磁场强度的增加．火焰的旋转强度会有所下降；当磁场的强度小于0．357T时，随着磁场强度的增加，火焰的旋转强度会有所增加。     

水平旋转筒反应器内的换热

本文研究了直径１５～１００μｍ的碳水化合的颗粒在水平旋转筒反应器中的传热．用“渗透模型”机理讨论了粉体颗粒与旋转筒内壁面间的换热,推导出换热系数α与筒旋转速度、物料填充度之间的理论分析解。换热系数理论值和实验所得数据较为吻合。     

步进炉内方坯间综合角系数计算的研究

从步进炉内方坯间综合系数计算的实际问题出发，推导了非透明介质有限封闭区域综合角系数的精确计算公式，并以Ｔｕｃｋｅｒ的精确数值计算结果为依据，比较了面间透过率的五种近似算法的计算精度，最终获得了可用于实际计算的较为准确的综合角系数近计算方法。     

涂层导热系数变化对换热器传热的影响

采用换热器效能法,对不同种类换热器进行校核计算.研究换热工质为气气、气液、液液时,不同种类换热器的换热性能随涂层导热系数的变化趋势.结果表明,各种换热器的总传热系数皆随涂层导热系数的增加而增大,且在不同低温侧流体雷诺数下增加程度不同,雷诺数越大,增加程度越大.设定涂层厚度为200.000 μm,涂层导热热阻所占比例随着...     

四角切圆锅炉炉内等温气流旋转特性的研究

通过数学解析、数值模拟和模型试验的手段对四角切圆锅炉炉内等温气流旋转特性进行研究,获得的一些结论对燃煤电站锅炉向高参数大容量发展及安全经济运行有促进作用。图5表2参3     

矩形鳍片膜式水冷壁辐射角系数的求解

文中结出矩形鳍片模式水冷壁温度场计算所必需的辐射角系数的求解方法，从而可求出表面热流密度分布的精确群。     

发动机壁面瞬态换热系数的试验求取与分析

本文在对表面温度法进行深入分析研究的基础上，作者利用新研制的一种特殊表面热电偶，提出了发动机缸内局部换热系数的试验求取法。此法可以避免表面温度法中气体容积平均温度假定所带来的不确定性。     

采暖建筑外表面热流及换热系数现场测试研究

建筑表面换热系数是建筑热工与节能及暖通空调领域的重要基础计算参数.为研究实际建筑表面热流与换热系数的波动趋势,为换热系数的取值和边界条件的设置提供合理的实测依据,采用一种新型超薄热流传感器,利用直接热平衡法,实测了西安采暖季期间的某办公建筑外墙,获取了外表面的辐射、对流及总热流,对流与辐射换热系数的变化曲线.结果表明,...     

利用Monte Carlo方法对循环流化床锅炉炉膛传热的数值计算

作者对循环流化床锅炉炉膛传热进行数值研究,所建模型考虑轴向和径向颗粒浓度分布的影响。模型计算揭示烟气温度和热流密度在炉膛内的分布变化,计算结果表明在循环流化床锅炉炉膛传热计算中,颗粒相对流换热不能忽略。     

Discussion on the Network Method for Calculating Radiant Interchange Within an Enclosure

ＤｉｓｃｕｓｓｉｏｎｏｎｔｈｅＮｅｔｗｏｒｋＭｅｔｈｏｄｆｏｒＣａｌｃｕｌａｔｉｎｇＲａｄｉａｎｔＩｎｔｅｒｃｈａｎｇｅＷｉｔｈｉｎａｎＥｎｃｌｏｓｕｒｅ￥Ｈ．Ｊ．Ｋａｎｇ；Ｗ．Ｑ．Ｔａｏ（ＳｃｈｏｏｌｏｆＥｎｅｒｇｙａｎｄＰｏｗｅｒＥｎｇｉｎｅｅｒ...     

圆管状内壁面管口辐射传递的方向分布特性

为了得到圆管状内壁面通过管口辐射传递的方向分布特性,给出了圆管状内壁面单元间辐射传递系数RD的蒙特卡罗求解方法,研究了当内壁为等温灰体、漫发射、漫反射时,管内壁发射率、管长与半径比的变化对管口表面当量定向发射率的影响,结果表明：总趋势为管长与半径比增加,管口表面当量定向发射率极值点向小角度的天顶角方向移动,在管长与半径比较大时,随管长增加、管内壁发射率ε减小,管出口表面较小天顶角方向当量定向发射率增大。     

Monte Carlo method for simulating the radiative characteristics of an anisotropic medium

This study introduces a Monte Carlo method for predicting the radiative characteristics of a semitransparent medium containing small particles and presents an analytical model of independent, multiple scattering. The anisotropic characteristics of the cloud of particles are considered directly using the Mie phase function. The bidirectional reflectivity and bidirectional transmittance of a flat plate containing the small particles are predicted. The calculated results are satisfactorily in agreement with the experimental data and the calculated results using the discrete-ordinate method. © 1999 Scripta Technica, Heat Trans Asian Res, 28(3): 201–210, 1999     

Evaluation of a three-dimensional model for the prediction of heat transfer in power station boilers

This paper reports an evaluation of a full three-dimensional mathematical model of a power station boiler with emphasis on the heat transfer phenomena. The model is based on the numerical solution of the equations governing conservation of mass, momentum and energy and transport equations of scalar quantities. The radiative heat transfer is modelled using the discrete transfer method. The model was applied to a power station boiler of the Portuguese Electricity Utility where an experimental study was recently carried out. Measurements of gas temperature, species concentrations and incident heat fluxes to the walls were compared with the predictions for standard operating conditions, partial load operation and low excess air conditions. Comparison of the results with the measurements has shown that in general a good agreement was achieved, but in some cases only qualitative agreement was found. More detailed measurements would be needed to allow a better evaluation of the model and to identify the sources of discrepancy. Nevertheless, the model proved to be a useful tool for the analysis of the heat transfer in utility boilers.     

Performance of hemisphere algorithm for fast form factor calculation

A fast and accurate algorithm is required for carrying out radiative heat transfer simulations designing thermally efficient devices. This paper describes the performance of the hemisphere algorithm, which was originally developed for fast form factor calculation for obtaining photorealistic three‐dimensional computer graphics. We compare the performance of the hemisphere algorithm with that of two conventional algorithms that are widely used for radiative heat transfer simulations. The hemisphere algorithm is found to be significantly faster than the other algorithms, but it has an absolute error of 1.0×10^?5. In addition, the result indicates that the hemisphere algorithm is suitable for simulating the trial and error process in the practical analysis of large‐scale models due to its tolerable visualization of form factor distribution. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20259     

基于逆向Monte Carlo法的腔内小接受体红外辐射传递研究

针对MC方法在计算三维大辐射腔内小接受体所受到辐射时存在的耗时长难收敛等问题,采用三维逆向能束跟踪MonteCarlo方法(BMC),结合CFD数值模拟技术,分析了不同介质参数以及燃烧工况下,腔体内不同高度上红外辐射能传感器所接受的辐射能特性,并与正向MC方法进行了对比。模拟计算结果表明:BMC方法对于处理小接受体大发射源辐射传递问题具有明显的时间优越性,同时该方法可以用于基于辐射能的腔体内燃烧过程分析。     

Development of a finite element radiation model applied to two‐dimensional participating media

A finite element method (FEM) for radiative heat transfer has been developed and it is applied to 2D problems with unstructured meshes. The present work provides a solution for temperature distribution in a rectangular enclosure with black or gray walls containing an absorbing, emitting, isotropically scattering medium. Compared with the results available from Monte Carlo simulation and finite volume method (FVM), the present FEM can predict the radiative heat transfer accurately. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 34(6): 386–395, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20076     

Numerical simulation of the heat flux distribution in a solar cavity receiver

In the solar tower power plant, the receiver is one of the main components of efficient concentrating solar collector systems. In the design of the receiver, the heat flux distribution in the cavity should be considered first. In this study, a numerical simulation using the Monte Carlo Method has been conducted on the heat flux distribution in the cavity receiver, which consists of six lateral faces and floor and roof planes, with an aperture of 2.0 m×2.0 m on the front face. The mathematics and physical models of a single solar ray’s launching, reflection, and absorption were proposed. By tracing every solar ray, the distribution of heat flux density in the cavity receiver was obtained. The numerical results show that the solar flux distribution on the absorbing panels is similar to that of CESA-I’s. When the reradiation from walls was considered, the detailed heat flux distributions were issued, in which 49.10% of the total incident energy was absorbed by the central panels, 47.02% by the side panels, and 3.88% was overflowed from the aperture. Regarding the peak heat flux, the value of up to 1196.406 kW/m² was obtained in the center of absorbing panels. These results provide necessary data for the structure design of cavity receiver and the local thermal stress analysis for boiling and superheated panels.     

View factor calculation using the Monte Carlo method for a 3D strip element to circular cylinder

The discussion includes the application of the Monte Carlo method to determine view factor for the plate including strip elements to circular cylinder as a case in heating and cooling processes in material processing. The results involving the relationships between different discretization schemes, number of rays used for the view factor calculation, CPU time and accuracy are presented. The analysis also displays the differences between the numerical results obtained and analytical solutions for the 20, 30 and 45 element discretized figures and for (30⁴), (50⁴) and (70⁴) rays per element. The results obtained from the Monte Carlo solution indicate that smaller elements require more effort to obtain an accurate view factor.