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Heat Transfer: Volume 4最新文献

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A Partnership Between University’s Engineering Services Departments and Academic Departments for Energy Systems Education 大学工程服务部门和学术部门在能源系统教育方面的合作关系
Pub Date : 1999-11-14 DOI: 10.1115/imece1999-1142
C. Somerton, Laura Genik, Joseph Schroeder, Wayne A. Thelen, Mike Crouch, Michael Hudson, R. Ellerhorst, Roy Gies
Incorporation of plant tours into a laboratory course is discussed. The unique feature of these plant tours is that they are facilities on the university campus and utilize the expertise of the practicing engineers on campus to enhance the students educational experience. Examples of course materials used in these activities are provided.
讨论了将植物参观纳入实验课程的问题。这些工厂参观的独特之处在于它们是大学校园内的设施,并利用校园内实习工程师的专业知识来增强学生的教育体验。提供了这些活动中使用的课程材料示例。
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引用次数: 0
Design and Uncertainty Analysis of a Second-Generation Convective Heat Flux Calibration Facility 第二代对流热流通量校准装置的设计与不确定性分析
Pub Date : 1999-11-14 DOI: 10.1115/imece1999-1104
D. Holmberg, C. Womeldorf, W. Grosshandler
The National Institute of Standards and Technology has developed a convective heat flux facility to allow calibration of heat flux sensors. The facility consists of a small wind tunnel that produces a two-dimensional laminar boundary layer across a heated isothermal copper plate. Sensors are mounted flush in the copper plate alongside a reference to measure the heat leaving the plate. Convective calibrations up to 5 kW/m2 are possible. Sensor output is compared with the reference value, and contrasted with a standard radiation calibration. Recognizing that many sensors are used in mixed radiation and convection environments, this facility provides a unique opportunity to assess a sensor’s convective response. This report describes a second-generation heated plate and provides an analysis of the system uncertainty. Redundant references, improved sensor heating and mounting, improved reference isolation, and a minimized radiation component has reduced the combined relative expanded uncertainty of the reference to ±2.5 %. The benefits of an embedded temperature sensor in the heat flux sensor are described. The facility is available for comparative calibrations and for heat transfer studies by individual researchers.
美国国家标准与技术研究所开发了一种对流热流通量设备,用于校准热流通量传感器。该装置由一个小风洞组成,该风洞在加热的等温铜板上产生二维层流边界层。传感器被平齐地安装在铜板上,旁边是一个参考,用来测量离开铜板的热量。对流校准高达5千瓦/平方米是可能的。将传感器输出与参考值进行比较,并与标准辐射校准进行对比。认识到许多传感器用于混合辐射和对流环境,该设施提供了一个独特的机会来评估传感器的对流响应。本报告描述了第二代加热板,并提供了系统不确定性的分析。冗余参考点、改进的传感器加热和安装、改进的参考点隔离以及最小化的辐射分量将参考点的综合相对扩展不确定度降低到±2.5%。介绍了在热流密度传感器中嵌入温度传感器的优点。该设施可用于比较校准和个人研究人员的传热研究。
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引用次数: 13
An Experimental Correlation of Quenching Temperature Under Top-Down Reflooding in a Vertical Tube 垂直管内自顶向下回流淬火温度的实验关联
Pub Date : 1999-11-14 DOI: 10.1115/imece1999-1129
Yan-ping Huang, Xuemei Lang, Bingde Chen
A quenching experiment under top-down reflooding in a vertical tube was performed by adopting the transient hot block quenching test technique. The temperature history on the inner wall of test tube was calculated by using a quasi-steady-state two-dimension numerical technique, and the intersection of double tangent lines was used to determine the location and the time of the quench front. Based on some theoretical models of quenching temperature, at the same time, the effect of flow parameters in the tube during quenching was taken into account, a semi-empirical correlation for quenching temperature under the low pressure and low mass flow rate is presented in this paper. It is as follows:Tq−TsTo−Ts=11.8362(Ts−Tf,inTo−Ts)−0.0714[(cρk)w]0.2938×G0.0251×(Ts−Tf,in)−0.3145 The parameter range of this correlation is as follows: system pressure: 0.31∼0.88MPa: mass flux: 17.7∼902.kg/m2s; inlet subcooling: 3∼77°C; initial hot-wall temperature: 450∼600 °C.
采用瞬态热块淬火试验技术,进行了垂直管内自上而下回流淬火试验。采用准稳态二维数值计算技术计算了试管内壁的温度历史,并利用双切线的交点确定了淬火锋的位置和时间。在现有的淬火温度理论模型的基础上,考虑淬火过程中管内流动参数的影响,建立了低压低质量流量条件下淬火温度的半经验关系式。Tq−TsTo−Ts=11.8362(Ts−Tf,inTo−Ts)−0.0714[(cρk)w]0.2938×G0.0251×(Ts−Tf,in)−0.3145,该相关性的参数范围为:系统压力:0.31 ~ 0.88MPa;质量通量:17.7 ~ 902 kg/m2s;进口过冷:3 ~ 77°C;初始热壁温度:450 ~ 600°C。
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引用次数: 0
Higher-Order Discretization Method for Computations of Separated Flows 分离流计算的高阶离散化方法
Pub Date : 1999-11-14 DOI: 10.1115/imece1999-1121
B. Song, R. Amano
This paper presents a new higher-order bounded scheme, WACEB, for approximating the convective fluxes in the transport equations. The weighted-average formulation is used for interpolating the variables at cell faces and the weighted-average coefficient is determined from normalized variable formulation and total variation diminishing (TVD) constrains to ensure the boundedness of solution. The new scheme is tested by solving three problems: 1) a pure convection of a box-shaped step profile in an oblique velocity field; 2) a sudden expansion of an oblique velocity field in a cavity, and; 3) a laminar flow over a fence. The results obtained by the present WACEB were compared with the UPWIND and the QUICK schemes and showed that this scheme has at least the second-order accuracy while ensuring boundedness of solutions. Moreover, it was demonstrated that this scheme produces results that better agree with the experimental data in comparison with other schemes.
本文提出了一种新的高阶有界格式WACEB,用于近似输运方程中的对流通量。采用加权平均公式对单元面上的变量进行插值,并根据归一化变量公式和总变差递减(TVD)约束确定加权平均系数,以保证解的有界性。通过解决三个问题对新方案进行了验证:1)斜速度场中箱形阶跃剖面的纯对流;2)空腔内斜速度场的突然膨胀;越过栅栏的层流。与UPWIND格式和QUICK格式进行了比较,结果表明该格式在保证解的有界性的同时至少具有二阶精度。与其他方案相比,该方案的计算结果与实验数据吻合较好。
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引用次数: 0
Temperature/Heat Flux Errors Caused by High Temperature Resistive Shunting Along Mineral-Insulated, Metal-Sheathed Thermocouples 沿矿物绝缘,金属护套热电偶的高温电阻分流引起的温度/热通量误差
Pub Date : 1999-11-14 DOI: 10.1115/imece1999-1102
W. Gill, J. Nakos
Commercially manufactured, mineral-insulated, metal-sheathed (MIMS) thermocouples (TCs) have been used at Sandia National Laboratories (Sandia) and other experimental laboratories for many years to measure temperatures in fires and high-temperature (e.g., 1200°C) radiant-heat environments. These TCs are rugged and relatively inexpensive, which make them ideal for large-scale outdoor testing where factors such as weathering and rough handling are important. A particularly insidious source of TC error is thermal shunting of the TC assembly. This error is caused by a sharp drop in the electrical resistivity of the mineral insulation at elevated temperatures. When a TC assembly is subjected to high temperature along its length, the lower resistivity of the mineral insulation can cause shorting or shunting to occur. This paper describes several cases demonstrating the seriousness of the shunting problem at temperatures previously thought to be immune. Some preliminary experiments designed to clarify the thermal shunting problem are presented. A model developed under previous work but modified specifically for Type K TCs is discussed. Comparisons of measured and predicted temperature error data in additional thermal shunting experiments provide some degree of confidence in the model’s predictive capability. Predictions for several common field test configurations used in Sandia experiments are shown in the hopes of sensitizing other researchers in the field to this problem.
商业制造的矿物绝缘金属护套(MIMS)热电偶(tc)已在桑迪亚国家实验室(Sandia)和其他实验实验室中使用多年,用于测量火灾和高温(例如1200°C)辐射热环境中的温度。这些tc坚固耐用且相对便宜,这使得它们非常适合大规模的户外测试,其中风化和粗糙处理等因素很重要。TC误差的一个特别隐蔽的来源是TC组件的热分流。这种误差是由于矿物绝缘在高温下电阻率急剧下降造成的。当TC组件沿其长度受到高温时,矿物绝缘的低电阻率可能导致短路或分流发生。本文描述了几个案例,证明了在以前认为是免疫的温度下分流问题的严重性。提出了一些初步的实验,旨在澄清热分流问题。本文讨论了在以前的工作基础上开发的一个模型,但专门针对K型tc进行了修改。在额外的热分流实验中,对测量和预测的温度误差数据进行比较,为模型的预测能力提供了一定程度的信心。对桑迪亚实验中使用的几种常见现场测试配置的预测,希望能使该领域的其他研究人员对这个问题更加敏感。
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引用次数: 2
Velocity Statistics of Plane Self-Preserving Buoyant Turbulent Adiabatic Wall Plumes 平面自保浮力湍流绝热壁羽的速度统计
Pub Date : 1999-11-14 DOI: 10.1115/1.1316783
R. Sangras, Z. Dai, G. Faeth
Measurements of the velocity properties of plane buoyant turbulent adiabatic wall plumes (adiabatic wall plumes) are described, emphasizing conditions far from the source where self-preserving behavior is approximated. The experiments involved helium/air mixtures rising along a smooth, plane and vertical wall. Mean and fluctuating streamwise and cross stream velocities were measured using laser velocimetry. Self-preserving behavior was observed 92–156 source widths from the source, yielding smaller normalized plume widths and larger near-wall mean velocities than observations within the flow development region nearer to the source. Unlike earlier observations of concentration fluctuation intensities, which are unusually large due to effects of streamwise buoyant instabilities, velocity fluctuation intensities were comparable to values observed in nonbuoyant turbulent wall jets. The entrainment properties of the present flows approximated self-preserving behavior in spite of continued development of the wall boundary layer. Measurements of temporal power spectra and temporal and spatial integral scales of velocity fluctuations are also reported.
描述了平面浮力湍流绝热壁羽流(绝热壁羽流)的速度特性的测量,强调了远离源的条件,在那里自我保持行为是近似的。实验涉及氦气/空气混合物沿着光滑、平面和垂直的壁面上升。用激光测速仪测量了平均流速和波动流速以及横流流速。在距离源92-156个源宽度处观察到自保行为,得到的归一化羽流宽度较小,近壁平均速度较大,而在更靠近源的流动发展区域内的观测结果较小。与早期观测到的浓度波动强度不同(由于流向浮力不稳定性的影响,浓度波动强度异常大),速度波动强度与在非浮力湍流壁面射流中观测到的值相当。尽管壁面边界层继续发展,但当前流动的夹带特性仍接近自保护行为。还报道了时间功率谱和速度波动的时空积分尺度的测量。
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引用次数: 10
A Method for Estimating Acoustic Implosion Efficiencies for Collapsing Cavities in Nuclear Reactor Systems 估算核反应堆系统塌缩腔声爆效率的方法
Pub Date : 1999-11-14 DOI: 10.1115/imece1999-1130
C. Kullberg
For the last several decades, condensation induced water hammer events have been a concern i n the nuclear industry. With the arrival of passive reactor designs, concerns have arisen about the natural inception of vapor cavity formation in these systems. Several aspects of subcooled bubble cavity implosions are examined. In particular, this paper will focus on spherical cavity implosion transients. Numerical scoping calculations were performed with the compressible version of the Rayleigh-Plesset equation. The calculations revolved around predicting two key parameters, the peak pressure and the net acoustic energy release. Both of these parameters are relevant in quantifying the damage potential of a spherical water hammer event.
过去几十年来,冷凝水诱发的水锤事件一直是核工业关注的问题。随着无源反应堆设计的出现,人们开始关注这些系统中自然形成的汽穴。本文对过冷气泡腔内爆的几个方面进行了研究。本文将特别关注球形空腔内爆瞬态。利用雷利-普莱塞特方程的可压缩版本进行了数值范围计算。计算围绕预测两个关键参数,即峰值压力和净声波能量释放。这两个参数都与量化球形水锤事件的破坏潜力有关。
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引用次数: 0
Laser-Induced Fluorescence Measurements in Venturi-Cascaded Propane Gas Jet Flames 文丘里级联丙烷气体喷射火焰的激光诱导荧光测量
Pub Date : 1999-11-14 DOI: 10.1179/014426010X12682307291542
A. Qubbaj
“Venturi-cascading” technique is a means to control pollutant emissions of diffusion flames by modifying air infusion and fuel-air mixing rates through changing the flow dynamics in the combustion zone with a set of venturis surrounding the flame. A propane jet diffusion flame at a burner-exit Reynolds number of 5100 was examined with a set of venturis of specific sizes and spacing arrangement. The venturi-cascading technique resulted in a decrease of 33% in NO emission index along with a 24% decrease in soot emission from the flame, compared to the baseline condition (same flame without venturis). In order to understand the mechanism behind these results, Laser Induced Fluorescence (LIF) spectroscopy was employed to study the concentration field of the radicals (OH, CH and CN) in the baseline and venturi-cascaded flames. The LIF measurements, in the near-burner region of the venturi-cascaded flame, indicated an average decrease of 18%, 24% and 12% in the concentrations of OH, CH and CN radical, respectively, from their baseline values. However, in the mid-flame region, a 40% average increase in OH, from its baseline value, was observed. In this region, CH or CN radicals were not detected. The OH radical, in the downstream locations, was mostly affected by soot rather than by temperature. In addition, prompt-NO mechanism appeared to play a significant role besides the conventional thermal-NO mechanism.
“文丘里级联”技术是在火焰周围设置一组文丘里管,通过改变燃烧区内的流动动力学,改变空气注入和燃料-空气混合速率,从而控制扩散火焰的污染物排放。用一组特定尺寸和间隔布置的风室对雷诺数为5100的丙烷射流扩散火焰进行了研究。与基线条件(没有文丘里管的相同火焰)相比,文丘里级联技术导致NO排放指数下降33%,火焰的烟尘排放减少24%。为了了解这些结果背后的机制,采用激光诱导荧光(LIF)光谱研究了基线和文丘里级联火焰中自由基(OH, CH和CN)的浓度场。在文丘里级联火焰近燃烧器区域的LIF测量表明,OH、CH和CN自由基的浓度分别比基线值平均下降了18%、24%和12%。然而,在火焰中部区域,观察到OH比基线值平均增加40%。该区域未检测到CH或CN自由基。在下游位置,OH自由基主要受烟灰而不是温度的影响。此外,除了传统的热- no机制外,提示- no机制似乎也起着重要的作用。
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引用次数: 1
Design Competitions Come to Heat Transfer 设计竞赛来到传热
Pub Date : 1999-11-14 DOI: 10.1115/imece1999-1141
C. Somerton, A. Benard, Laura Genik, P. Hoke, Joseph Schroeder, R. Vance
Five different design project competitions focused on heat transfer processes are presented. The projects are design, build, test, and report in nature. These elements are described within the paper for each project. A semester ending design competition is held where the student teams present their devices and their performance is evaluated.
五个不同的设计项目竞赛集中在传热过程。项目本质上是设计、构建、测试和报告。这些元素在每个项目的论文中都有描述。学期结束时举行设计竞赛,学生团队展示他们的设备并对其性能进行评估。
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引用次数: 0
A Thermal Law of the Wall for Separating and Recirculating Flows 分离与再循环流动的壁面热规律
Pub Date : 1999-11-14 DOI: 10.1115/imece1999-1123
D. Cruz, A. P. Silva Freire
The characteristics of the turbulent boundary layer near a separation point are studied here. The emphasis is on providing analytical expressions for the velocity and temperature near wall solutions which are also valid in the region of reverse flow. These expressions can then be used as boundary conditions in numerical schemes that use two-equation differential models. The paper proposes a new expression for the description of the near wall characteristic length which is shown to hold also in the reverse flow region. The specified velocity profiles are based on a previous formulation of the problem by Cruz and Silva Freire (IJHMT, 41, 2097 2111, 1998) but, as written here, they are presented for the first time. The temperature profiles near the wall are also described by a newly proposed expression that reduces to the logarithmic profile in the attached region, and assumes a minus half power law profile at the separation point. In the separated region, the logarithmic profile is recovered. All results are validated through the data of Vogel and Eaton (Trans. ASME JHT, 107, 922 929, 1985).
本文研究了分离点附近湍流边界层的特性。重点给出了速度和温度近壁解的解析表达式,该解析表达式在逆流区也是有效的。然后,这些表达式可以用作使用双方程微分模型的数值格式中的边界条件。本文提出了一种描述近壁特征长度的新表达式,该表达式在逆流区也适用。指定的速度剖面是基于Cruz和Silva Freire (IJHMT, 41, 2097 - 2111, 1998)先前对问题的表述,但正如本文所写的那样,它们是第一次提出。壁面附近的温度分布也用一个新提出的表达式来描述,该表达式在附着区域中简化为对数分布,并在分离点处假设为负一半幂律分布。在分离区域,恢复对数剖面。所有结果都通过Vogel和Eaton (Trans.)的数据进行了验证。中华医学杂志,1997,922 - 929,1985)。
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引用次数: 0
期刊
Heat Transfer: Volume 4
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