共查询到19条相似文献,搜索用时 156 毫秒
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《纳米技术与精密工程》2017,(4)
本文基于瞬态平面热源(TPS)法测量物质导热系数的原理,针对探头温升模型中贝瑟尔函数的积分运算求解复杂的问题,修正了文献[9]中方形探头简化模型的参数,使其适用于TPS法国际标准规定的圆形探头.该模型和原有模型的误差分析表明,二者具有很好的相关性,可以替代原有模型进行导热系数的计算,而且多项式的运算效率明显高于贝瑟尔函数的积分运算效率.基于该简化模型,针对热物理性能标准材料奥氏体不锈钢和Pyroceram 9606在常温、常压下的导热系数进行了测量,结果表明,测量结果和标准值的误差分别为2.1%和1.8%,验证了该模型的有效性. 相似文献
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为研究接触热阻对瞬态平面热源(transient plane source,TPS)法测量高聚物薄膜热导率的影响规律以便提高测量准确度,阐述TPS法基本测量原理,根据串联热路中热阻的关系建立接触热阻的简化计算模型,以不同厚度硅橡胶薄膜为对象,通过回归分析的方法获得接触热阻随压力的变化规律,利用此规律测量单一厚度聚四氟乙烯薄膜和聚酯薄膜的热导率。结果表明:当未施加压力时,接触热阻的存在导致测量结果的相对误差为10%~30%,接触热阻会随压力的增大近似呈非线性关系减小,当压力达到200 k Pa时,可减小测量误差到6%以内。同种材质的高聚物薄膜还可通过改变厚度来减小接触热阻。 相似文献
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假想热源法是基于瞬态平面热源(transient plane source,TPS)法测量平板样品导热系数的理论基础,但是其没有考虑测量过程中背景材料本身的有限热阻所导致的边界热损失,从而直接影响导热系数的测量精度。该文基于假想热源法和热探测深度理论,建立一种可实现边界热损失补偿的数学模型。该数学模型揭示探头尺寸、样品厚度以及背景材料的导热系数和热扩散率对边界热损失的影响。为验证该数学模型的有效性,通过变换背景材料和探头尺寸对不锈钢、铅、45钢、Q235A.F钢、黄铜、6061铝合金、纯铝以及紫铜的导热系数进行测量。结果表明:该数学模型能够对不同的探头尺寸、平板样品以及背景材料进行有效的热损失补偿,使导热系数的测量误差从热损失补偿前的2.14%~3.49%减小到补偿后的-1.39%~0.80%,显著提高平板样品导热系数的测量精度。 相似文献
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Svetozár Malinarič 《International Journal of Thermophysics》2013,34(10):1953-1961
The transient plane source method of measuring the thermal conductivity and thermal diffusivity uses a sensor in the shape of a thin disk, which simultaneously serves as the heat source and thermometer. This study describes improvements of the experimental apparatus, providing some details of the electrical bridge with the aim to obtain maximum reliability of the measurement results. The aim of the temperature function analysis is to find the optimal time of measurement. The relation between the data time window used for fitting, the uncertainty of the sensor temperature measurement, and the uncertainty of the results is presented and graphically illustrated using numerical simulation of the experiment. The theory was confirmed by the evaluation of real measurements on polymethylmetacrylate. The temperature function analysis revealed that a decrease of the temperature measurement uncertainty need not always lead to a fall in the total uncertainty of the results but to shorter experiments and smaller specimens. 相似文献
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Nasser Hamdami Jean-Yves Monteau Alain Le Bail 《International Journal of Refrigeration》2003,26(7):809-816
The modelling of heat transfer within materials with high porosity is complicated by evaporation-condensation phenomena. The aim of this work is to develop a model for apparent thermal conductivity in these products. The effective thermal conductivity of a porous food model (sponge) having 0–60% moisture contents and 0.59–0.94 porosity was measured by a line-source heat probe system in the range −35 to 25 °C. Two predictive models of the effective thermal conductivity of porous food were developed (Krischer and Maxwell models). The effective thermal conductivity predicted by Krischer model were in good agreement with the experimental data. Also, it was shown that the model including the effect of evaporation-condensation phenomena in addition to heat conduction was useful to predict the effective thermal conductivity of sponges. 相似文献
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Songping Mo Peng Hu Jianfeng Cao Zeshao Chen Hanlin Fan Fei Yu 《International Journal of Thermophysics》2006,27(1):304-313
The effective thermal conductivity of capillary structures is an important parameter in the thermal performance analysis of loop heat pipes (LHP). In this paper, the effective thermal conductivity of porous sintered nickel material filled with water, ethanediol, and glycerin were measured by means of the hot disk thermal constant analyzer. The measured data were compared with similar measured data and calculated values from models in the literature. The results indicate that the thermal conductivity of the porous material depends on the thermal conductivity of the fluid, the filled ratio, and the porosity of the material.Paper presented at the Seventh Asian Thermophysical Properties Conference, August 23–28, 2004, Hefei and Huangshan, Anhui, P. R. China 相似文献
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F. Arpino V. Fernicola A. Frattolillo L. Rosso 《International Journal of Thermophysics》2009,30(1):306-315
Surface-temperature measurements by means of contact probes require a detailed investigation of the probe-surface interaction.
For an accurate calibration of such probes, the heat transfer processes involved in contact measurements must be well known
and the impact of any influence parameters must be taken into account. At present, contact probes are generally calibrated
by means of a temperature-controlled hot plate. A calibration system for contact surface-temperature probes, based on such
a hot plate, was developed at INRIM. It covers the temperature range from ambient to 350 °C. The reference temperature is
available on the upper surface of a metal block and is determined by linear extrapolation of the readings of three calibrated
thermometers embedded into the block at different depths. However, the actual temperature of the reference surface largely
depends on the sensor-to-surface interaction. The contact thermal resistance, the thermal conductivity of the block, the geometry
of the probe, and the temperature of the surrounding fluid are just some of the parameters that affect a calibration and that
may cause measurement errors if they are not properly taken into account and corrected for. Better insight into the interaction
between the surface and the probe is therefore required. Since the experimental evaluation of measurement errors is not straightforward,
mathematical modeling could represent a crucial tool to better understand the interactions between the probe and the calibration
system. In this paper, a finite-element numerical model of the INRIM calibration system was developed in order to investigate
the temperature field across the reference block as well as on its surface during a calibration. The thermal load introduced
by a commercial contact probe during a calibration was also included in the simulation and its effect on the temperature field
was studied. In order to obtain a detailed mathematical model, the surrounding air was also included in the simulation, avoiding
the imposition of boundary conditions at the interface between solid parts and fluid. The proposed model was validated by
comparing the results obtained with the available experimental data. 相似文献
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建立了地源热泵岩土导热系数现场测试系统的三维数值模型,基于所建数值模型分析了测试时间、舍弃初始小时数、钻孔半径、岩土体初始温度、加热器输入功率等因素对岩土导热系数测试结果的影响。研究结果表明:热响应测试时间应大于70h;对于柱热源模型,随着钻孔尺寸的增大,辨识得到的导热系数逐渐减小;岩土初始温度对岩土导热系数辨识结果没有影响,但采用参数估计法作为辨识方法时,岩土初始温度的测试精度对辨识结果有较大影响;对于纯导热模型,加热器输入功率对岩土导热系数辨识结果没有影响。 相似文献
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分析了测量导热系数传统模型与相关文献中的修正模型的原理与不足,提出一个较为严密的三维传热学模型,利用MATLAB数值模拟验证了其合理性。推导出计算圆柱型试样导热系数的公式,并得到了适合实际应用的简化公式。以真空橡皮盘为例,定量分析了侧壁散热对导热系数测量值的影响程度,给出了试样规格与测算精度的关系曲线。当试样半径与厚度的比值大于28.9时,侧壁散热的影响将小于5%,故可忽略。 相似文献
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S. W. Kim K. Park S. H. Lee K. H. Kang K. T. Lim 《International Journal of Thermophysics》2008,29(6):2179-2188
The temperature distribution, the thermal deformation, and the thermal stress of automotive brake disks have quite close relations
with car safety; therefore, much research in this field has been performed. However, successful and satisfactory results have
not been obtained because the temperature-dependent thermophysical properties of brake disk materials are not sufficiently
known. In this study, the thermophysical properties (thermal diffusivity, the specific heat, and the coefficient of thermal
expansion) of three kinds of iron alloy series brake disk materials, FC250, FC170, and FCD50, and two kinds of aluminum alloy
series brake disk materials, Al MMC and A356, were measured in the temperature range from room temperature to 500 °C, and
the thermal conductivity was calculated using the measured thermal diffusivity, specific heat capacity, and density. As expected,
the results show that the two series have significant differences in respect of the thermophysical properties, and to reduce
the thermal deformation of the brake disk, the aluminum alloys with a high thermal conductivity and the iron alloys with low
thermal expansion are recommended. 相似文献
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Qingqing Zhang Wei Zhu Jie Zhou Yuan Deng 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(32):2300968
Quantitative thermal performance measurements and thermal management at the micro-/nano scale are becoming increasingly important as the size of electronic components shrinks. Scanning thermal microscopy (SThM) is an emerging method with high spatial resolution that accurately reflects changes in local thermal signals based on a thermally sensitive probe. However, because of the unclear thermal resistance at the probe-sample interface, quantitative characterization of thermal conductivity for different kinds of materials still remains limited. In this paper, the heat transfer process considering the thermal contact resistance between the probe and sample surface is analyzed using finite element simulation and thermal resistance network model. On this basis, a mathematical empirical function is developed applicable to a variety of material systems, which depicts the relationship between the thermal conductivity of the sample and the probe temperature. The proposed model is verified by measuring ten materials with a wide thermal conductivity range, and then further validated by two materials with unknown thermal conductivity. In conclusion, this work provides the prospect of achieving quantitative characterization of thermal conductivity over a wide range and further enables the mapping of local thermal conductivity to microstructures or phases of materials. 相似文献