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1. chinaXiv:201710.00013 [pdf]

金属泡沫中填充石蜡的相变换热特性实验研究

张嘉杰; 屈治国
分类: 动力与电气工程 >> 工程热物理学

本文对金属铜泡沫填充石蜡的相变换热特征进行了实验研究,通过测试试件加热面及内部的温度响应曲线,分析了金属泡沫填充及自然对流对石蜡非稳态相变换热过程的影响。研究结果表明,采用顶部加热方式时,石蜡内部的换热以纯导热为主,而采用底部加热时,液态石蜡内的自然对流作用使相界面移动速度更快,试件内部温度一致性更好,同时在相变对流区可实现对加热面的温度控制。金属泡沫的填充可强化石蜡内的导热但抑制液态石蜡的自然对流,前者使得试件加热面温升减缓,相界面移动加快,后者则导致底部加热时石蜡的相变区分为相变导热区和相变对流区。金属泡沫的导热强化能力在试件换热中占据主导作用。

提交时间: 2017-10-17 来自合作期刊:《工程热物理学报》 点击量318, 下载量27

2. chinaXiv:201710.00014 [pdf]

聚光光伏与甲醇重整热化学互补发电系统性能研究

李文甲(1,2); 郝勇(1)
分类: 动力与电气工程 >> 工程热物理学

本文提出了太阳能光伏电池与甲醇中低温重整反应相结合的发电系统;通过太阳能的梯级利用以及物理能与化学能之间的品位耦合,太阳能净发电效率较单一光伏或甲醇热化学发电方式获得显著提升。热力学分析表明,在100~250℃C的系统运行温度范围内,系统的理论太阳能净发电效率达43.6%~44.3%(已考虑光学损失),显著高于光伏系统(22.5%)及热化学系统(32.7%)。系统约50%的太阳净发电量来自甲醇重整产物氢气,以化学能形式实现了太阳能的高效储能,且光伏、热化学发电随温度变化的相反趋势间互补达到了稳定输出的效果。此外,系统产生的电能中约25%来自太阳能,高于单一太阳能甲醇热化学发电系统的14%,对化石能源的依赖度降低。光伏与热化学互补发电为太阳能高效综合利用提供了新的思路。

提交时间: 2017-10-17 来自合作期刊:《工程热物理学报》 点击量319, 下载量26

3. chinaXiv:201710.00015 [pdf]

大功率半导体激光器散热研究综述

邓增(1,2); 沈俊(1); 戴巍(1)
分类: 动力与电气工程 >> 工程热物理学

近年来,半导体激光器功率不断提高,由之引发的散热问题已成为限制半导体激光器发展的瓶颈。芯片温度升高引起激光器性能下降,要使激光器在大功率条件下依然保持良好特性就必须强化对激光器芯片的散热。通过分析激光器芯片温度对激光器各项性能指标的影响,说明了降低芯片温度对保证激光器正常工作的重要性。鉴于流体侧的对流传热热阻在总热阻起主导作用,重点分析半导体激光器散热结构中流体侧的散热方法,并将其分为传统散热方法和新型散热方法,传统散热方法包括平板热沉散热、大通道水冷等,新型散热方法包括微通道散热、喷雾冷却、射流冲击、热管散热和液态金属散热。总结了各种方法的优缺点,从热流密度和温差两个指标评价各种散热方法,探讨其在激光器散热上的应用前景。

提交时间: 2017-10-17 来自合作期刊:《工程热物理学报》 点击量325, 下载量35

4. chinaXiv:201710.00008 [pdf]

基于TDTR方法的碳化硅低温导热性能实验研究

张航; 王新伟; 张中印
分类: 动力与电气工程 >> 工程热物理学

低温条件下碳化硅等半导体材料热导率的实验研究极少,数据匮乏,无法满足理论模型的优化需求。现有实验测量以接触式的稳态法导热系数测量为主,实验误差大,且低温测量成本过高。本文通过常规飞秒激光抽运探测热反射法与低温系统的有机结合,完成了4~300 K低温条件下单晶碳化硅热导率的测试及其随温度的变化规律,研究表明单晶碳化硅热导率在100 K左右存在极大值,温度低于100 K时其热导率与温度呈正相关,温度高于100 K时其热导率与温度呈负相关。极值点的位置与理论值的偏差可能是由于样品电子浓度、缺陷分布等因素影响。

提交时间: 2017-10-13 来自合作期刊:《工程热物理学报》 点击量330, 下载量32

5. chinaXiv:201710.00009 [pdf]

轴流压气机等离子体流动控制

吴云; 张海灯; 于贤君
分类: 动力与电气工程 >> 工程热物理学

作者在国际上较早开展了轴流压气机等离子体流动控制研究工作,经过近十年的研究积累,对轴流压气机等离子体流动控制建立了较为深刻的认识。本文首先简要展示了轴流压气机等离子体流动控制的部分研究进展:以压气机叶栅为研究对象,分析了等离子体激励对叶顶泄漏流抑制的规律和机制;通过数值仿真和实验,研究了等离子体激励对高负荷轴流压气机失速的流动控制规律和机制;以高速压气机叶栅为研究对象,探索了吸力面和端壁等离子体激励对高速压气机三维角区分离的流动控制规律;然后介绍了等离子体激励式压气机的概念;最后给出了对未来研究工作的展望。

提交时间: 2017-10-13 来自合作期刊:《工程热物理学报》 点击量316, 下载量28

6. chinaXiv:201708.00366 [pdf]

时变能量网络理论

陈皓勇; 葛海麟; 邱明
分类: 动力与电气工程 >> 电气工程

不同类型的能源系统通过能量转换设备(感应电动机、离心泵等)相互耦合,研究多类型能源系统的动态特性及其仿真方法对多能互补系统优化设计及性能分析具有重要的实际意义。为对时变能量网络进行建模和分析,本文从能量本质的角度出发,通过深入探讨能量传递及转换机理,分别建立时变传递线(管)路和能量转换设备的集中参数模型。在时变能量网络模型的基础上,提出通过构建时变能量网络方程(包括状态方程和输出方程)对多能互补系统的动态特性进行建模仿真的分析方法,最后通过具体算例对本文所提分析方法的有效性及实用性进行验证。本文的研究内容为时变能量网络的建模、分析、优化及规划奠定了基础。

提交时间: 2017-08-28 点击量690, 下载量210

7. chinaXiv:201708.00218 [pdf]

基于连续时间商品模型的电力市场理论

陈皓勇; 韩励佳
分类: 动力与电气工程 >> 电气工程

实时电价理论是许多国家电力现货市场设计的理论基础,但在电力市场实践中也出现了不少问题。实时电价有两个重大缺陷:一是仍然基于传统的分时调度模型,忽略了电能生产和消费的时间连续性这个十分重要的特征,没有认真处理跨时段约束;二是假设同一时段的电能商品都是同质的,无法区别基荷、腰荷和峰荷机组区别明显的技术特征及成本构成。为克服这些缺陷,本文提出连续时间电能商品模型,包括实时电价下和按负荷持续时间定价方式下的电能商品模型,并将两种定价方式下的市场优化问题与数学上的Riemann积分和Lebesgue积分相对应,建立泛函极值优化模型,并基于Euler-Lagrange方程求得市场均衡解,通过严格的数学推导证明了按负荷持续时间定价的可行性。算例计算表明,按负荷持续时间定价能减少市场总购电费用,而且电厂利润分配较为公平。本文所提的理论和方法可为国内外电力市场建设提供全新的思路和理论基础。

提交时间: 2017-08-27 点击量1492, 下载量378

8. chinaXiv:201706.00800 [pdf]

Stereoscopic PIV Measurements of the Flow Field in a Turbine Cascade

Tian Yangtao; Ma Hongwei; Ma Rong
分类: 动力与电气工程 >> 工程热物理学

This paper presents experimental measurements of the flow field in a Low-speed Turbine Cascade using a stereoscopic particle-image velocimetry (SPIV). During the measurements, a pair of frame-straddling-based CCD cameras were configured at different sides of the laser light sheet, and appropriate tracing particles (DEHS) were employed. The measurements were conducted at the incidence angle of 0 degree and exit Reynolds number of 1.7 x 10(5) with the tip clearance 1.18% of blade chord. The tip flow features, such as the evolution and breakdown of tip leakage vortex, the horseshoe vortex, turbulence characteristics of tip leakage flow, were studied for the flow field analysis. The results showed that the tip leakage flow/vortex mainly dominate flow fields in the tip region. The tip leakage vortex performs as a concentrated vortex before its breaking down and splitting into small vortices. The highest turbulence intensity mainly occurs in the tip region along with the trajectory of tip leakage vortex, and when the vortex breaks down, the turbulence intensity reduces rapidly. Additionally, the SPIV with this configuration also shows an advantage in investigating the flow structures and mechanism inside the turbine cascade.

提交时间: 2017-06-26 来自合作期刊:《热科学学报》 点击量1248, 下载量135

9. chinaXiv:201706.00799 [pdf]

An Analysis of the Numerical Model Influence on the Ground Temperature Profile Determination

Jaszczur, Marek; Inga Polepszyc; Aneta Sapińska-Śliwa; Andrzej Gonet2
分类: 动力与电气工程 >> 工程热物理学

The estimation of the ground temperature profile with respect to the depth and time is the key issue in many engineering applications which use the ground as a source of thermal energy. In the present work, the influence of the model components on the calculated ground temperature distribution has been analysed in order to develop an accurate and robust model for the prediction of the ground temperature profile. The presented mathematical model takes into account all the key phenomena occurring in the soil and on its top surface. The impact of individual model elements on the temperature of the soil has been analysed. It has been found that the simplest models and the most complex model result in a similar temperature variation over the simulation period, but only at a low depth. A detailed analysis shows that a larger depth requires more complex models and the calculation with the use of simple models results in an incorrect temperature and a theoretical COP estimation.

提交时间: 2017-06-26 来自合作期刊:《热科学学报》 点击量826, 下载量118

10. chinaXiv:201706.00798 [pdf]

Influence of Filling Ratio and Working Fluid Thermal Properties on Starting up and Heat Transferring Performance of Closed Loop Plate Oscillating Heat Pipe with Parallel Channels

Shi Weixiu; PAN Lisheng
分类: 动力与电气工程 >> 工程热物理学

Using ethanol or acetone as the working fluid, the performance of starting up and heat transfer of closed-loop plate oscillating heat pipe with parallel channels (POHP-PC) were experimentally investigated by varying filling ratio, inclination, working fluids and heating power. The performance of the tested pulsating heat pipe was mainly evaluated by thermal resistance and wall temperature. Heating copper block and cold water bath were adopted in the experimental investigations. It was found that oscillating heat pipe with filling ratio of 50% started up earlier than that with 70% when heating input was 159.4 W, however, it has similar starting up performance with filling ratio of 50% as compared to 70% on the condition of heat input of 205.4 W. And heat pipe with filling ratio of 10% could not start up but directly transit to dry burning. A reasonable filling ratio range of 35%-70% was needed in order to achieve better performance, and there are different optimal filling ratios with different heating inputs - the more heating input, the higher optimal filling ratio, and vice versa. However, the dry burning appeared easily with low filling ratio, especially at very low filling ratio, such as 10%. And higher filling ratio, such as 70%, resulted in higher heat transfer ( dry burning) limit. With filling ratio of 70% and inclination of 75, oscillating heat pipe with acetone started up with heating input of just 24W, but for ethanol, it needed to be achieved 68 W, Furthermore, the start time with acetone was similar as compared to that with ethanol. For steady operating state, the heating input with acetone was about 80 W, but it transited to dry burning state when heating input was greater than 160 W. However, for ethanol, the heating input was in vicinity of 160 W. Furthermore, thermal resistance with acetone was lower than that with ethanol at the same heating input of 120 W.

提交时间: 2017-06-26 来自合作期刊:《热科学学报》 点击量760, 下载量66

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