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发泡绝热液氮传输管道绝热层导热系数的测量 总被引:1,自引:0,他引:1
为了对实际发泡绝热液氮传输管道进行性能评价,通过建立蒸发率与平均导热系数之间的关系式,由蒸发率的测量来获得平均导热系数,建立了一套低温液体传输管道绝热性能检测装置,并对若干根2 m长发泡绝热液氮传输管道进行了测试,从而在不破坏发泡绝热层的条件下得出了实际管道绝热层真实平均导热系数.平均导热系数测量结果与发泡层取样导热系数测量结果对比表明:该测试装置所得数据准确可信,可作为发泡绝热低温流体输送管道无损绝热性能测试的标准测试台.详细描述了该测试装置的测量原理、方法和构成、以及数据采集和处理,最后讨论了影响平均导热系数测量的主要因素. 相似文献
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热带法测量材料导热系数的实验研究 总被引:8,自引:0,他引:8
根据瞬态热带法的基本原理,建立了测量非导电固体材料以及松散材料导热系数的实验装置,采用热电偶直接测量热带的温度变化,整个测量系统更加方便实用、易于实现。对一批试样进行的测试结果表明,本测量装置具有较好的重复性和准确性,可应用于相关的科研部门和工业部门。 相似文献
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中国计量科学研究院正在建立保护热板法测量固体材料导热率的标准装置,本文对实验原理、装置与实验过程作了简单的介绍,在室温至80 ℃温度范围内对PTB提供的标准参考物质进行了多次导热率测量,对测量结果进行拟合的相对标准偏差为0.6×10-2W/(m·K),并与欧洲实验室的测量结果进行对比;在80 ℃~530 ℃温度范围间测量了花岗岩材料的导热率,测量的结果随着温度的上升而下降. 相似文献
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The thermal conductivity of olivine, dry and mixed with water, up to saturation, has been measured with a thermal probe, using the step heating method. The olivine is composed of solid particles with dimensions in the range from 0.8 to 1 mm. Dry olivine has been measured in the range of temperatures between –17° to +50°C. Olivine mixed with water has been measured at +50°C. The cubic cell model has been used to make predictions to compare with the measured data. Comparisons of the experimental thermal conductivities and the predicted values of dry and water-mixed olivine show good agreement. The cubic cell model can be used to evaluate the porosity of olivine and the thermal conductivity of the solid particles, from the values measured at dryness and saturation, with reasonably good agreement. In this way, it is not necessary to measure the mineral composition of the particles of the porous media. Also, the porosity of the medium is predicted with reasonable agreement, which takes into account the phenomenon of the porosity increase near the probe, since the diameter of the probe is smaller than that of the solid particles. 相似文献
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本文在Campbell模型和de V-1模型的基础上,以Campbell模型为主,对该模型中的两个参数形状因子(ga)和土壤固相热导率( )采用de V-1模型中的计算方法,提出了一种新的预测土壤热导率温度关系的模型。该模型土壤固相热导率和形状因子均考虑了土壤颗粒组成成分,也包含了温度对土壤固相热导率的影响。此外,与前两种模型进行比较,该模型与实验值吻合较好,能够更好地预测土壤热导率。基于该模型,分析了土壤温度和体积含水率两个变量对不同类型土壤热导率的影响。研究表明:在同一温度及体积含水率工况下,土壤热导率是砂土>壤土>粘土。该研究为地埋管换热器周围非饱和土壤热湿耦合迁移模型的建立提供新的思路。 相似文献
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Based upon the theory that the thermal conductivity can be determined by measuring the speed of the propagation of the solid/liquid phase interface during a phase transition, a system was developed to investigate the thermal conductivity of metals and alloys at the liquid/solid phase transformation point. Furthermore, a mathematical method was applied to represent the melting and solidifying process in the phase transformation chamber, by which the error could be analyzed. In order to test the feasibility of the method and the measuring system, a series of verification experiments on lead have been performed to estimate the precision and the applicability of the measuring system. From comparisons with recommended data from the literature, the uncertainty of the experimental results is estimated to be about 5% which means the measuring method is suitable to determine the thermal conductivity of eutectic alloys and metals at the liquid/solid phase transformation point. This work provides a relatively precise method for thermal conductivity measurements on new materials such as lead-free solders.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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D. P. H. Hasselman 《International Journal of Thermophysics》2018,39(9):109
It is suggested that a possible explanation for the “anomalous” thermal conductivity of nanofluids measured by the hot-wire method is the positive temperature dependence of the heat transfer coefficient of the hot-wire–nanofluid interface, which results from the positive temperature dependence of the energy exchanged during the particles’ collisions with the wire. It is shown qualitatively that this effect can result in an overestimate of the nanofluid’s thermal conductivity. It is concluded that the interpretation of the experimental data for the thermal conductivity of nanofluids, obtained by the hot-wire method, requires independently determined data for the heat transfer coefficients and their temperature dependence of the hot-wire nanofluid and the particle–fluid interfaces. 相似文献
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We have been studying on ice slurry in a dynamic type ice storage system. The ice slurry has many good characteristics. The ice slurry can be made from a solution. When designing the ice storage system using this ice slurry, thermal conductivity of the ice slurry is essential.When thermal conductivity of the ice slurry made from a solution is measured by a transient line heat-source technique, a measurement value of thermal conductivity is affected by a latent heat of fusion of ice. Therefore, the thermal conductivity measured is apparent thermal conductivity. In this study, influences of Stefan number, initial concentration of the solution, initial solid fraction (initial IPF) and Fourier number on the thermal conductivity was analytically discussed to improve measurement accuracy of the thermal conductivity of ice slurry in the transient line heat-source technique. 相似文献
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A. A. Tarzimanov F. R. Gabitov I. N. Ponikarova F. D. Yuzmukhametov 《Journal of Engineering Physics and Thermophysics》1992,63(4):1004-1008
An experimental device is described, which uses the pulse heating method for a low-inertia transducer with an automatic system of information gathering and processing. The possibility of measuring the thermal conductivity of the liquid, gaseous, and solid materials by linear and planar transducers is shown. The thermal conductivity of n-tetracosane at the phase transition is measured. A method of measuring the thickness of layers is proposed.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 63, No. 4, pp. 436–441, October, 1992. 相似文献
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In this paper, we investigate the radiative properties and the effective thermal conductivity (ETC) of the opacified silica aerogel by theoretical method. The radiative properties of the opacified silica aerogel are obtained by the modified Mie Scattering Theory that is used for particle scattering in absorbing medium. The modified gamma distribution is used to take account of the non-uniformity of the particle size. The solid thermal conductivity of the composite material is obtained by considering the scale effect of the particles. Based on these calculated thermophysical properties the coupled heat conduction and radiation through the evacuated opacified aerogel are solved by the finite volume method. And the radiation flux is computed by the P-1 approximation combined with the gray-band model. Results show that, the calculated thermophysical properties of the TiO2-doped silica aerogel are close to the experimental data. The optimal mean radius for the largest radiation extinction of the SiC particles is about 1μm. The presented data of optimal doping amount of the SiC particles at different temperature conditions for the evacuated silica aerogel is very useful for thermal insulation material design. 相似文献
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Conventional heat transfer fluids have intrinsically poor heat transfer properties compared to solids. Enhancing the efficiency of heat transfer is of great interest for various industrial applications. Suspending solid particles in a fluid increases the thermal conductivity of the resulting suspension and enhances the heat transfer properties. In this work, changes in thermal conductivities of fluids upon the addition of magnetic nanoparticles have been investigated. Fe(3)O(4) nanoparticles are synthesized using different synthesis methods and are suspended in various oils. The effect of the base fluid and the type of magnetic particle on the thermal conductivity is investigated in detail. Up to 28% increase in the thermal conductivity is obtained with 2.5 wt% magnetic particles in hexane. The thermal conductivity enhancement is found to depend on the particle concentration, method of preparation and base fluid. The enhancements obtained are higher than those estimated using any theoretical model present in the literature. 相似文献