D.C. scanning thermal microscopy: Characterisation and interpretation of the measurement

The used Scanning Thermal Microscopy (SThM) probe is a thin Pt resistance wire acting as a heat source and as a detector simultaneously. Its energetic balance is investigated by the study of the temperature profile along the probe. A theoretical approach of the measurement, based on this investigation, is then proposed. Simulations with this modelling are shown to predict how the heat, electrically produced in the probe, is dissipated in the probe-sample system. In particular, it is shown that the steady-state of conduction losses to the thermal element support varies versus the thermal conductivity of the sample and can lead to bad interpretations of the measurement.     

Ground water level influence on thermal response test in Adana,Turkey

For optimum design of borehole thermal energy storage (BTES) and ground sources heat pump (GSHP) applications, determination of underground thermal properties is required. The design and economic feasibility (number and depth of boreholes) of these systems need thermal conductivity of geological structure, λ (W m^?1 K^?1), and thermal resistance of ground heat exchanger, R (K W^?1 m). Thermal properties measured in laboratory experiments do not coincide with data of in situ conditions. Therefore, in situ thermal response test equipment has been developed and used in Canada, England, Germany, Norway, U.K., U.S.A. and Sweden to ensure precise designing of BTES systems. This paper describes the results and evaluations of the Adana continual thermal response test measurements. Copyright © 2007 John Wiley & Sons, Ltd.     

活塞热疲劳分析

用Pro/E建立活塞几何模型,在ANSYS单元库里选取热结构耦合单元,对模型网格进行优化,并对活塞温度场进行标定,然后进行热机耦合分析计算,得到活塞温度场、热应力场和变形。计算结果表明,在低频热疲劳下,活塞循环次数最少约是1 120 000次,这为活塞的结构改进和优化提供了依据。     

非共晶相变材料应用于太阳能吸热蓄热器的数值分析

通过计算分析发现对于目前的吸热蓄热器结构，采用相变发生在一个温度区间的非共晶熔盐混合物作为相变材料可以较好的提高吸热蓄热器的整体性能。主要表现在明显地提高相变材料的利用率、减小换热管工质出口温度波动、减小容器表面最大温度及容器表面温度变化，经过合理的设计还可以减小整体系统的质量。分析结果可以作为吸热器设计的参考。     

A review on thermal management techniques for lithium-ion battery

随着新能源汽车的广泛使用,动力锂离子电池的热安全性问题日益突出。本文以Bernardi生热机理为基础,耦合不同物理量,分别从电化学-热耦合模型、电-热耦合模型和热滥用模型来介绍单体电池的热特性。由于电池能量密度的增加与行驶工况复杂程度的提高,动力锂离子电池容易发生热量堆积,甚至造成热失控,对此,文中梳理了商用动力电池包的常用冷却方式。最后,根据对影响电池模组安全性的热失控蔓延机理及实测结果,介绍了阻断单体及基本模块热失控传播的有效方法。     

A mobile thermal battery resembling a solar receiver: Innovative design and performance assessment

An innovative design of a mobile thermal battery resembling the solar receiver is presented. A ternary salt mixture consisting of 52% KNO₃, 18% NaNO₃, and 30% LiNO₃ by wt% is used as the thermal energy storing medium inside the thermal battery. Since the thermal conductivity of the ternary salt mixture is low, aluminum meshes are introduced to create a thermal conduction tree inside the thermal energy storing medium. The actual field data are used in the simulations to resemble the solar irradiation emanating from the parabolic trough and focusing onto the thermal battery outer surface. To improve the uniform heating at the outer surface, the thermal battery rotation along the centerline of the trough is considered. The temperature parameter is introduced to assess the uniform‐like temperature distribution inside the ternary salt mixture. It is found that the use of aluminum meshes improves the heat diffusion in the phase change material of the ternary salt mixture; in which case, it acts like a thermal conduction tree inside the thermal battery. The rotation of the thermal battery results in uniform‐like temperature distribution across the thermal battery cross section and suppresses the excessive temperature rise because of the local heating in the close region of the thermal battery outer surface.     

A model study for cyclic thermal loading and thermal performance of a thermoelectric generator

Thermal cyclic loading influences the life cycle of the thermoelectric device pins because of the thermal stress developed in the pins. Although thermal efficiency improves for different geometric configurations of the device pins, development of thermal stresses limit the selection of pin geometry in practical applications, particularly under cyclic thermal loading. Consequently, in the present study, thermal stress analysis of thermoelectric pins under cyclic thermal loading is carried out. The influence of thermoelectric pin geometry on the stress levels is examined when the device is subjected to the thermal cyclic loading. The predictions of thermal stress distribution are validated with the data presented in the open literature. It is found that pin geometric configuration has a significant effect on the stress levels developed in the pin when subjected to cyclic thermal loading. The pin configuration R_A = 1 (parallel pins) results in the minimum value of the maximum von Mises stress in the pins as compared to that corresponding to other configurations. Copyright © 2014 John Wiley & Sons, Ltd.     

THERMAL RELAXATION TIMES EFFECT ON RAYLEIGH WAVES IN GENERALIZED THERMOELASTIC MEDIA

Rayleigh waves in a half-space exhibiting generalized thermoelastic properties based on Green-Lindsay (G-L), Lord-Shulman (L-S), and classical dynamical coupled (C-D) theories are discussed. The phase velocity of Rayleigh waves in the previous three different theories has been obtained. A comparison is carried out between the phase velocities of Rayleigh waves, displacements, stresses, and temperature as calculated from the different theories of generalized thermoelasticity. The C-D theory is recovered as a special case. It appears, in particular, that the results obtained from G-L theory tend to those of L-S theory as the values of the two relaxation times become closer to each other. The second relaxation time is well pronounced when it becomes larger than the first one. Furthermore, it is found that the thermal relaxation times decrease the speed of the elastic waves and modify the phase velocities of the Rayleigh waves. The results obtained and the conclusions drawn are discussed numerically and illustrated graphically. Relevant results of previous investigations are deduced as special cases.     

热网络法概论

对应用于温度场分析的热网络方法进行了系统的介绍。介绍了热网络法的原理及其应用领域,总结了该方法在卫星、航空航天、建筑、油田等更多领域的应用成果,对基于热网络法的软件SINDA/FLUINT也进行了详细介绍。     

地源热泵岩土热物性测试简介与分析

地源热泵系统作为利用可再生能源的暖通空调技术,具有节能、环保等优点,在世界范围内被广泛使用。土壤作为地源热泵系统的冷热源,对整个系统有着至关重要的影响。不同建筑负荷特性要求系统对土壤的取放热量不同,二者的不平衡会使土壤的温度发生变化,影响整个系统的运行。对特定建筑地源热泵系统土壤的热物性测试是设计地埋管系统的重要依据。本文对热物性测试的理论依据进行了简单介绍,并对具体事例进行了分析计算,得出岩土体的导热系数等具体热物性参数,为地源热泵系统的精确设计提供了依据。     

水合物导热系数和热扩散率实验研究

基于Hot Disk热常数分析系统的单面测试功能,建立了一套新的天然气水合物热物性测试系统,并实验研究了I型水合物（甲烷）、H型水合物（甲烷和甲基环己烷）的导热系数和H型水合物的热扩散率。结果显示甲烷水合物样品导热系数随温度的变化非常小,平均导热系数约为0.53 W/(m•K)。结合文献报道和实验分析发现零孔隙率甲烷水合物的导热系数大约为0.7 W/(m•K),水合物样品在压缩过程中虽然减少了孔隙,但是却引起晶体破碎,导致导热系数与理想值差距较大。水合物的导热系数与水合物的类型及客体分子有关,大体顺序为I型 > II型 > H型 > 半笼型水合物。甲烷−甲基环己烷生成的H型水合物热扩散率为0.205 ~ 0.26 mm2/s,和其他类型的水合物相当;水合物的热扩散率大约为水的两倍,而导热系数和水相近。     

Research on the thermal corridor of a hypersonic vehicle

The establishment of a reasonable physical model and an effective solution scheme for the thermal corridor is very important to thermal protection structure design, trajectory selection, aerodynamic configuration optimization design, etc. The concept of a thermal corridor for a hypersonic vehicle was analyzed and a physical model was proposed in this paper. Furthermore, the governing equations and the corresponding algorithm for the thermal corridor were discussed. The envelopes of the height–velocity curves at typical positions of the vehicle X43 were calculated, the characteristics of the thermal corridor were summarized, the effect of the thermal protection material on the thermal corridor was discussed, and the emission coefficient of the thermal protection material was defined. The results indicate that the thermal corridor depends on the emission coefficient of the surface material, the flow conditions, and turbulence transition position. © 2008 Wiley Periodicals, Inc. Heat Trans Asian Res, 37(4): 218–223, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20203     

热力除氧技术研究及其发展

水中溶解氧的存在是导致锅炉及汽轮机通汽部分设备腐蚀发生的重要原因,也影响给水系统以及整个热力系统的运行安全。随着高参数大容量发电机组的发展,对给水品质的要求不断提高。除氧技术也伴随着热力系统对除氧要求的提高而不断发展。热力除氧过程中加热蒸汽与除氧水之间传热传质过程的强化是确保和提高热力除氧器除氧性能的关键,也是热力除氧器结构改进与优化的基本原则。     

储热混凝土单元设计与储热模拟

设计两种储热结构单元,采用ansys动态模拟方法模拟了在储热过程中储热单元温度最低点温度与时间的关系。研究发现：热导率越大储热速度越快,把钢管由平行排列改为三角错排,储热单元截面则由正方形变为正六边形,面积保持不变,传热性能有所提高;在混凝土中加入5％石墨片强化传热,等效热导率提高了4．7倍,与加5％石墨粉的混凝土相比,等效热导率提高了一倍。     

工业热负荷最佳热化系数的计算

最佳热化系数是反映热电联产系统热源最佳结构的一个再要参数。本文通过对实际工业热负荷特性的分析整理得到有代表性的几种热负荷特性,以此为基础,以热电联产系统单位供热能力节能量为优化目标,建立了适用于业热负荷的最佳热化系数计算公式。     

Thermal wave measurements in superfluid helium II

In this paper, a thermal wave in the bath of superfluid helium II is measured by a new type of superconductor temperature sensor under different heat fluxes and bath temperatures, and at the same time, a thermal shock wave is also studied experimentally and theoretically. © 2001 Scripta Technica, Heat Trans Asian Res, 30(5): 419–425, 2001     

Assessment of Thermal Properties via Nanosecond Thermoreflectance Method

Nanosecond time-domain thermoreflectance (ns-TDTR) is an all optical method of determining independently a variety of thermal parameters of both homogeneous and layered materials. Despite its relative experimental simplicity, the sensitivity of the temperature decay (measured by the transient reflectivity signal) to the relevant thermal properties has yet to be fully characterized. In principle, it is possible to simultaneously extract multiple thermal parameters from a single measurement. In practice, however, changes to several of these parameters may result in experimentally indistinguishable variations to the transient reflectivity signal. In this work, we focus on investigating thermal properties of bulk material and the contact resistance between the thin-film coating that is needed for the ns-TDTR method and the bulk substrate. To extract multiple properties from one temperature decay trace, we divide the data into temporal sub-regions known to be influenced to different degrees by each individual thermal parameter and iteratively fit with a 1-D heat conduction model to independently determine the contact resistance and cross-plane thermal conductivity.     

等离子喷涂热障涂层组织结构及热导率研究

采用扫描电子显微镜（SEM）、激光脉冲等方法研究了204NS和204NS-G粉末对等离子喷涂热障涂层组织结构及热导率的影响。结果表明：相比204NS-G粉末,204NS粉末制备的YSZ涂层具有较高的密度和较低的孔隙率。在1 000℃下,204NS粉末制备的YSZ涂层热导率为0.78 W/m·K,比204NS-G粉末制备的YSZ涂层热导率高约20%。     

室内动态热舒适的影响因素分析

析了室内动态热环境下人体热舒适的主要影响因素,并探讨了不同因素的影响程度,指出室内动态热环境下人体热舒适性是各种因素综合作用的结果,室内空气温度、气流速度、空气相对湿度、平均辐射温度、人体生理心理特点、人体活动量、服装参数等均对动态热舒适有影响,其中空气温度及气流速度的动态化是其影响的主要客观因素,人体条件及服装参数是主要主观因素。     

基于ABAQUS软件的CB250汽油机活塞热分析

活塞作为内燃机的主要受热零部件之一,由于受热面积大,散热条件差,承受非常大的热负荷。在进行设计改进时,需考虑其热负荷问题,应对其进行热场预测及数值分析,研究其热应力和热变形。笔者运用有限元分析软件Hypermesh和Abaqus,仿真分析得到活塞三维温度场,并计算其热变形,为活塞的结构改进和优化提供了重要依据。