The Thermal Conductivity, Thermal Diffusivity, and Heat Capacity of Gaseous Argon

This paper presents new absolute measurements for the thermal conductivity and thermal diffusivity of gaseous argon obtained with a transient hot-wire instrument. Six isotherms were measured in the supercritical dense gas at temperatures between 296 and 423 K and pressures up to 61 MPa. A new analysis for the influence of temperature-dependent properties and residual bridge unbalance is used to obtain the thermal conductivity with an uncertainty of less than 1% and the thermal diffusivity with an uncertainty of less than 4%. Isobaric heat capacity results were derived from measured values of thermal conductivity and thermal diffusivity using a density calculated from an equation of state. The heat capacities presented here have a nominal uncertainty of 4% and demonstrate that this property can be obtained successfully with the transient hot wire technique over a wide range of fluid states. The technique will be useful when applied to fluids which lack specific heat data.     

Intercomparison of Measurements of the Thermophysical Properties of Polymethyl Methacrylate

Results of an intercomparison of measurements of thermal conductivity, thermal diffusivity, specific heat capacity, and density of polymethyl methacrylate (PMMA) in the temperature range between –70°C and +80°C are presented. The purpose of this comparison is to investigate the variability of the results among guarded hot-plate (GHP) and guarded heat-flow meter (GHF) techniques on the one hand and among GHP/GHF and other measuring instruments on the other. The primary objectives are to characterize the material properties mentioned and to quantify the effects of thermal contact resistances and temperature measurements. With regard to future use of PMMA as a reference material, reference data for the thermal conductivity are derived.     

Ca2YO(BO3)3晶体的热物理性质研究

测量了新型非线性激光晶体Ca2YO(BO3)3（YCOB）的比热及其沿a,b,c三个方向的热膨胀系数，热扩散系数，导热系数，声子平均自由程和等效声速等热物理性质；讨论了属于单斜晶系的YCOB晶体的热物性的各向异性行为；实验结果表明YCOB晶体具有较大的比热和导热系数，其热膨胀系数各向异性相对较小，具有良好的热物理和力学性能。     

Thermophysical Properties of Solid Phase Zirconium at High Temperatures

This paper presents experimental results on the thermophysical properties of relatively pure polycrystalline zirconium samples in the solid phase from room temperature up to near the melting point. The specific heat capacity and specific electrical resistivity were measured from 290 to 1970 K, the hemispherical total emissivity from 1400 to 2000 K, the normal spectral emissivity from 1480 to 1940 K, and the thermal diffusivity in the range from 290 to 1470 K. From these data, the thermal conductivity and Lorentz number were computed in the range from 290 to 1470 K. For necessary corrections the most recent values of the linear thermal expansion from the literature have been used. Subsecond pulse calorimetry for measuring heat capacity, specific electrical resistivity, and both emissivities and the laser flash method for measuring thermal diffusivity were applied. Samples in the form of a thin rod and in the form of a thin disk were used in the first and second methods, respectively. Measurement uncertainties were generally about 3% for heat capacity, 1.6% for specific electrical resistivity, 3–10% for the two emissivities, and from less than 1% up to 6% for thermal diffusivity. All the results are discussed in reference to available literature data.Paper presented at the Seventeenth European Conference on Thermophysical Properties, September 5–8, 2005, Bratislava, Slovak Republic.     

Thermophysical Properties of Solid Phase Hafnium at High Temperatures

The thermophysical properties of several hafnium samples with a content of zirconium below 1% were experimentally studied over a wide temperature range. The specific heat capacity and specific electrical resistivity were measured from 300 to 2340 K, the hemispherical total emissivity from 1000 to 2130 K, while the thermal diffusivity was measured in the range from 300 to 1470 K. The thermal conductivity and Lorentz number were computed from measured properties for the range from 300 to 1470 K. The specific heat capacity, specific electrical resistivity, and hemispherical total emissivity were measured by subsecond pulse calorimetry, and the thermal diffusivity using the laser flash method. Samples in the form of a thin rod or wire, and in the form of a thin disk were used in the first and second methods, respectively. For data reduction and computation of relevant parameters, recent literature values of the linear thermal expansion were used. The results are compared with literature data and discussed.     

The thermal conductivity and heat capacity of gaseous argon

This paper presents new absolute measurements of the thermal conductivity and of the thermal diffusivity of gaseous argon obtained with a transient hot-wire instrument. We measured seven isotherms in the supercritical dense gas at temperatures between 157 and 324 K with pressures up to 70 MPa and densities up to 32 mol · L^–1 and five isotherms in the vapor at temperatures between 103 and 142 K with pressures up to the saturation vapor pressure. The instrument is capable of measuring the thermal conductivity with an accuracy better than 1% and thermal diffusivity with an accuracy better than 5%. Heat capacity results were determined from the simultaneously measured values of thermal conductivity and thermal diffusivity and from the density calculated from measured values of pressure and temperature from an equation of state. The heat capacities presented in this paper, with a nominal accuracy of 5%, prove that heat capacity data can be obtained successfully with the transient hot wire technique over a wide range of fluid states. The technique will be invaluable when applied to fluids which lack specific heat data or an adequate equation of state.     

The Thermal Conductivity, Thermal Diffusivity, and Specific Heat of Liquid n-Pentane

The thermal conductivity and thermal diffusivity of liquid n-pentane have been measured over the temperature range from 293 to 428 K at pressures from 3.5 to 35 MPa using a transient hot-wire instrument. It was determined that the results were influenced by fluid thermal radiation, and a new expression for this effect is presented. The uncertainty of the experimental results is estimated to be better than ±0.5% for thermal conductivity and ±2% for thermal diffusivity. The results, corrected for fluid thermal radiation, are correlated as functions of temperature and density with a maximum uncertainty of ±2% for thermal conductivity and ±4% for thermal diffusivity. Derived values of the isobaric specific heat are also given.     

Theoretical considerations of the effects of rapid heating of solids on their apparent thermal properties

The conditions are investigated for thermal properties to change from their normal values when solids are heated very rapidly. The properties considered are specific heat, thermal expansion, thermal conductivity, and thermal diffusivity. Over times which may be as long as a microsecond, the heated solid is unable to expand: the appropriate values of specific heat and thermal conductivity are then those at constant volume rather than constant pressure. In those alloys where thermal equilibrium requires diffusion, its establishment is delayed, and if solids do not have time to expand, the diffusion coefficient is reduced. For heating times below nanoseconds, the electrons and the lattice may be at different temperatures, particularly if the energy is initially imparted to the electrons. The temperature of the electron gas of metals may then approach the degenerary temperature. The apparent specific heat of a decoupled system departs from the steady-state value in a manner which depends on how temperature is measured. In such a decoupled system the concepts of thermal conductivity and thermal diffusivity must be used with care.Paper presented at the First Workshop on Subsecond Thermophysics, June 20–21, 1988, Gaithersburg, Maryland, U.S.A.     

The Thermal Conductivity, Thermal Diffusivity and Isobaric Heat Capacity of Toluene and Argon

This paper presents absolute measurements for the thermal conductivity and thermal diffusivity of toluene obtained with a transient hot-wire instrument employing coated wires over the density interval of 735 to 870 kgm^–3. A new expression for the influence of the wire coating is presented, and an examination of the importance of a nonuniform wire radius is verified with measurements on argon from 296 to 323 K at pressures to 61 MPa. Four isotherms were measured in toluene between 296 and 423 K at pressures to 35 MPa. The measurements have an uncertainty of less than ±0.5% for thermal conductivity and ±2% for thermal diffusivity. Isobaric heat capacity results, derived from the measured values of thermal conductivity and thermal diffusivity, using a density determined from an equation of state, have an uncertainty of ±3% after taking into account the uncertainty of the applied equation of state. The measurements demonstrate that isobaric specific heat determinations can be obtained successfully with the transient hot wire technique over a wide range of fluid states provided density values are available.     

The investigation of thermophysical properties of fluids by an alternating current hot-wire method

A method and an instrument for the measurement of a number of the thermophysical properties (thermal conductivity, thermal activity, volumetric specific heat, thermal diffusivity) are described. The results obtained for thermal conductivity and specific heat of toluene, over a temperature range 30–350°C and pressures of up to 30 MPa, are presented.     

Thermophysical properties of ice,snow, and sea ice

The paper reviews and discusses data and information on the thermophysical properties of ice, snow, and sea ice. These properties include thermal conductivity, specific heat, density, thermal diffusivity, latent heat of fusion, thermal expansion, and absorption coefficient. The available data are shown graphically for convenience in conjunction with the recommended correlation equations.Paper presented at the Second U.S.-Japan Joint Seminar on Thermophysical Properties, June 23, 1988, Gaithersburg, Maryland, U.S.A.     

无机纳米流体的热物性及其测试新方法的研究

研究了一种能同时测量纳米流体导热系数λ、导温系数α和比热C_p的非稳态多功能测试新方法,它结合了单丝法准确测量导热系数和双丝法准确测量导温系数的优点.对几种液体的导热系数和导温系数的实测值与TPRC推荐值进行比较,最大偏差分别为-0.4％和-2.7％.导热系数和导温系数测试均方根误差分别<±0.5％和±3％.并用此法测量了纳米Al₂O₃流体和纳米TiO₂流体的热物性参数,结果表明在流体中加入无机纳米粉体后其入和α较分散介质均有明显提高,加和原理不完全适用于纳米流体比热计算.     

Thermal Conductivity,Thermal Diffusivity,and Heat Capacity of Gaseous Argon and Nitrogen

Low-pressure thermal conductivity and thermal diffusivity measurements are reported for argon and nitrogen in the temperature range from 295 to 350 K at pressures from 0.34 to 6.9 MPa using an absolute transient hot-wire instrument. Thermal conductivity measurements were also made with the same instrument in its steady-state mode of operation. The measurements are estimated to have an uncertainty of 1% for the transient thermal conductivity, 3% for the steady-state thermal conductivity, and 4% for thermal diffusivity. The values of isobaric specific heat, derived from the measured thermal conductivity and thermal diffusivity, are considered accurate to 5% although this is dependent upon the uncertainty of the equation of state utilized.Paper presented at the Sixteenth European Conference on Thermophysical Properties, September 1–4, 2002, London, United Kingdom     

Thermophysical Properties of U–Mo/Al Alloy Dispersion Fuel Meats

Uranium–molybdenum alloy dispersion fuel meats are being studied for utilization as a research reactor fuel. Thermophysical properties of U–Mo/Al dispersion fuel, where U–Mo was dispersed in aluminum in research reactor fuel for the study, were determined by computing the thermal conductivity through measurements of the specific heat capacity and thermal diffusivity. Uranium molybdenum powder was first fabricated and utilized as U–Mo/Al dispersion fuel; the molybdenum-to-uranium ratios were 6, 8, and 10 mass% to produce the initial powder, which was then combined with aluminum (Al 1060). The volume fractions of U–Mo powder to aluminum were 10, 30, 40, and 50 vol.% to fabricate the dispersion fuel. The thermal diffusivity and specific heat capacity were measured by the laser-flash and differential scanning calorimetry (DSC) methods, respectively. Although the thermal diffusivity showed a decreasing trend with the U–Mo volume fraction when the dispersion quantity was insignificant, the trend reversed with a higher dispersion level. The specific heat capacity increases monotonically with temperature; its value is larger for a smaller dispersion level. Additionally, the overall thermal conductivity increases with temperature. Finally, the thermal conductivity decreases with an increase in the amount of U–Mo powder in the dispersion fuel. Paper presented at the Seventeenth European Conference on Thermophysical Properties, September 5–8, 2005, Bratislava, Slovak Republic.     

Evaluation of Thermophysical Properties of Functionally Graded Materials

In this work, by considering four-layered functionally graded material (FGM) specimens of Cu/Ni and PSZ/NiCrAlY, the transient characteristics and homogeneity of heat conduction media have been studied. The thermal diffusivities of the considered specimens have been measured by the laser flash method. As the temperature response curve of a FGM is very similar to that of a homogeneous material, it is difficult to distinguish a FGM from a homogeneous material by the shape of the temperature responses. Therefore, the thermal diffusivity obtained from the half-time method is usually taken as the corresponding value of the thermal diffusivity. The apparent thermal conductivity, obtained from the corresponding value of the thermal diffusivity and the average of the heat capacity of each layer, is different from the effective thermal conductivity, obtained from the sum of the heat resistances of each layer. As the values of the heat capacity of materials exist over a certain range, and the heat capacity distribution can be predicted when the materials in a FGM are known, the amount of error that will be caused when the effective thermal conductivity is replaced by the apparent value can be determined. Also, the heterogeneity of a FGM, based on an evaluation of thermophysical properties, has been discussed.Paper presented at the Seventh Asian Thermophysical Properties Conference, August 23–28, 2004, Hefei and Huangshan, Anhui,P. R. China.     

Determination of the Thermophysical Properties of Halogenated Hydrocarbons in a Heat-Conducting Calorimeter

The values of the coefficients of thermal expansion and compressibility, isobaric heat capacity and thermal diffusivity of three brominated saturated hydrocarbons of butyl bromide, hexyl bromide and heptyl bromide are measured in a heat-conducting calorimeter at a temperature of 298–363 K in the pressure range of 0.098–147 MPa. The experimental data on the isobaric heat capacity are compared to the calculation results. Generalized dependences are suggested to determine the heat capacity and thermal diffusivity.     

Characterization of Sodium Nitrate as Phase Change Material

In this article the results of material investigations of sodium nitrate (NaNO₃) with a melting temperature of 306 °C as a phase change material (PCM) are presented. The thermal stability was examined by kinetic experiments and longduration oven tests. In these experiments the nitrite formation was monitored. Although some nitrite formation in the melt was detected, results show that the thermal stability of NaNO₃ is sufficient for PCM applications. Various measurements of thermophysical properties of NaNO₃ are reported. These properties include the thermal diffusivity by the laser-flash, the thermal conductivity by the transient hot wire, and the heat capacity by the differential scanning calorimeter method. The current measurements and literature values are compared. In this article comprehensive temperature-dependent thermophysical values of the density, heat capacity, thermal diffusivity, and thermal conductivity in the liquid and solid phases are reported.     

Thermophysical Properties of Automotive Metallic Brake Disk Materials

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.     

Normal Spectral Emissivity at a Wavelength of 684.5 nm and Thermophysical Properties of Solid and Liquid Molybdenum

Polarimetric emissivity measurements adapted for a rapid pulse heating setup and recent results of normal spectral emissivity at 684.5 nm for molybdenum at melting and in the liquid phase are presented. Also reported is a complete set of thermophysical data (specific enthalpy, isobaric heat capacity, electrical resistivity, thermal conductivity, and thermal diffusivity) for molybdenum for both solid and liquid states. The results for all mentioned thermophysical properties are discussed and furthermore compared to literature values. The normal spectral emissivity and the electrical resistivity of molybdenum show opposite trends in the liquid phase, leading to the conclusion that a prediction of normal spectral emissivity at the given wavelength of 684.5 nm based on the Hagen–Rubens-relation and electrical resistivity measurements is not applicable.     

Thermal conductivity,heat capacity,and thermal diffusivity of selected commercial AlN substrates

The thermal transport properties of four commercially available AlN substrates have been investigated using a combination of steady-state and transient techniques. Measurements of thermal conductivity using a guarded longitudinal heat flow apparatus are in good agreement with published room temperature data (in the range 130–170 W · m^–1 · K^–1). Laser flash diffusivity measurements combined with heat capacity data yielded anomalously low results. This was determined to be an experimental effect for which a method of correction is presented. Low-temperature measurements of thermal conductivity and heat capacity are used to probe the mechanisms that limit the thermal conductivity in AlN.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.