Thermal conductivity of liquid R507 refrigerant

Thermal conductivity of ozone-safe liquid refrigerant R507 was studied by the method of high-frequency thermal waves within the temperature range of 297.95 … 332.55 K and pressures from the saturation line up to 3.7 MPa. The estimated errors of temperature, pressure, and thermal conductivity measurements are 0.1 K, 3 kPa, and 1.5 %, correspondingly. Thermal conductivity of liquid R507 was calculated on the saturation line. Approximation dependences for thermal conductivity were derived for the whole range of studied temperatures and pressures and on the saturation line. The work was financially supported by the Russian Foundation for Basic Research (Grant No. 07-08-00295-a).     

Thermal conductivity of liquid refrigerant R404A

Thermal conductivity of liquid ozone-safe refrigerant R404A was studied for the first time in the range of temperatures of 297.9–332.6 K and pressures from the saturation line to 3.7 MPa. The uncertainties of temperature, pressure, and thermal conductivity measurements were estimated to be within ±0.1 K, ±3 kPa, and ±0.15%, correspondingly. Values of thermal conductivity were calculated for liquid R404A at the boiling line. Approximating dependences for thermal conductivity were obtained for the whole range of studied temperatures and pressures, and at the boiling line. The work was financially supported by the Russian Foundation for Basic Research (grant No. 04-02-16355).     

Thermal conductivity of ozone-safe C10M1 refrigerant in liquid and gaseous phases

Thermal conductivity of ozone-safe refrigerant C10M1 in liquid (303.9–342.4 K, 1.23–4.257 MPa) and gaseous (324–398.15 K; 0.672–2.107 MPa) states was studied by the methods of high-frequency thermal waves and coaxial cylinders. The estimated measurement errors for the temperature, pressure, and thermal conductivity are ±0.02 K, ±1.5 kPa, and ±1.5–2.5 %, correspondingly. Approximation dependencies for thermal conductivity were obtained over the studied range of temperatures and pressures as well as on the dew and bubble lines. It is shown that thermal conductivity in the liquid state is additive relative to mass concentrations of components. The work was financially supported by the Russian Foundation for Basic Research (grant No. 04-02-16355).     

Thermal conductivity of gaseous refrigerant R 404A

Thermal conductivity of gaseous refrigerant R 404A was studied by the method of coaxial cylinders within the ranges of thermodynamic parameters 309÷422 K and 0.13÷0.184 MPa. The estimated measurement errors for the temperature, pressure, and thermal conductivity are ± 0.05 K, ± 3.75 kPa, and ± 1.5–2.5%, correspondingly. The approximation dependence for thermal conductivity was obtained for the whole studied range of temperatures and pressures. The results obtained were compared with available published data. The work was financially supported by the Russian Foundation for Basic Research (grant No. 04-02-16355).     

Thermal conductivity of refrigerant 507A in gaseous state

Thermal conductivity of refrigerant 507A in gaseous state has been measured with a stationary method of coaxial cylinders in the temperatures range of 315–425 K and pressures 0.105–1.855 MPa. Estimated values of temperature, pressure, and thermal conductivity measurement errors are, respectively, ± 0.05 K, ± 3.75 kPa and ± 1.5–2.5 %. Approximation dependence for thermal conductivity in the whole studied temperature and pressure range has been obtained. Results have been compared with available literature data.     

Experimental study of thermal conductivity of refrigerant R-409A in vapor phase

Thermal conductivity of refrigerant R-409A in vapor phase was studied in the range of temperatures 306–425 K and pressures 0.12–1.33 MPa. Measurements were performed with the stationary method of coaxial cylinders. Uncertainty of experimental data on thermal conductivity was 1.5–2.5 %, and errors of temperature and pressure measurements did not exceed 0.05 K and 4 kPa, respectively. Approximating dependence of thermal conductivity on pressure and temperature was obtained. Thermal conductivity on dew line and in ideal gas state was calculated.     

Heat transfer coefficients of liquid indium in the temperature range 470–1275 K

Thermal conductivity and thermal diffusivity coefficients of liquid indium have been determined in the range of temperatures from 470 to 1275 K by the laser flash method. Errors of heat transfer coefficients are ±(3.5–5) %. Approximating equations and tables of reference data have been developed for temperature dependence of properties. Measurement results have been compared with the data available in the literature. Temperature dependence of Lorentz number has been calculated up to 1000 K.     

Thermal conductivity and thermal diffusivity of tantalum in the temperature range from 293 to 1800 K

Thermal diffusivity of polycrystalline tantalum at the temperature range from 293 to 1800 K has been measured by the laser flash method with the error of 2–4 %. Thermal conductivity has been calculated with the use of reference data on density and heat capacity. Approximating equations and tables of reference data for the temperature dependence of heat transfer coefficients have been obtained; comparison with the published data has been carried out. The work was financially supported by the Russian Foundation for Basic Research (Grant No. 07-08-00071).     

Thermal conductivity of refrigerant R-415A in the vapor phase

Thermal conductivity of refrigerant R-415A in the vapor phase has been studied by the steady-state method of coaxial cylinders in the range of temperatures 308–415 K and pressures 0.12–1.68 MPa. The approximation dependence of thermal conductivity on pressure and temperature was determined. Thermal conductivity on the dew line and in the ideal gas state was calculated.     

国产HFC－134a饱和蒸气导热系数的试验研究

国产ＨＦＣ－１３４ａ饱和蒸气导热系数的试验研究刘明福，韩礼钟，张玉坤，朱明善（清华大学热能工程系北京１０００８４）关键词ＨＦＣ－１３４ａ，导热系数１引言导热系数是研究热量传递过程所需要的基本热物性参数。在ＣＦＣＳ类制冷剂替代物的研究中，获取替代物精确...     

Thermal conductivity of aqueous solutions of salts for high parameters of state

New generalized formulas for calculation of thermal conductivity of aqueous solutions of binary and multicomponent inorganic substances under high values of state parameters were derived. New values of thermal conductivity were calculated for aqueous solutions of salts within the ranges of temperatures of 293–473 K. concentrations of 0–25 mass % and pressures P _s of 100 MPa.     

Thermal conductivity and thermal diffusivity of SiO<Subscript>2</Subscript> nanopowder

A 3ω approach for the simultaneous determination of the effective thermal conductivity and thermal diffusivity of nanopowder materials was developed. A 3ω experimental system was established, and the thermal properties of water and alcohol were measured to validate and estimate the accuracy of the current experimental system. The effective thermal conductivity and thermal diffusivity of the SiO₂ nanopowder with 375, 475, and 575 nm diameters were measured at 290–490 K and at different densities. At room temperature, the effective thermal conductivity and thermal diffusivity of the SiO₂ nanopowder increased with temperature; however, both values decreased as the particle diameter was reduced. An optimum SiO₂ powder density that decreased with decreasing diameter was also observed within the measurement range. The minimum effective thermal conductivity and maximum effective thermal diffusivity were obtained at 85 × 10⁻³ kg/L, when the particle diameter was 575 nm. The optimum densities of the particles with 375 and 475 nm diameters were less than 50.23 × 10⁻³ and 64.82 × 10⁻³ kg/L, respectively.     

Thermal properties of 15-mol% gadolinia doped ceria thin films prepared by pulsed laser ablation

Thermal properties of 15-mol% gadolinia doped ceria thin films (Ce_0.85Gd_0.15 O_1.925) prepared by pulsed laser ablation on silicon substrates in the temperature range 473–973 K are presented. Thermal diffusivities and thermal conductivities were evaluated using photoacoustic spectroscopy. The influence of grain size on thermal properties of the films as a function of deposition temperature is studied. It is observed that the thermal diffusivity and the conductivity of these films decreases up to 873 K and then increases with substrate temperatures. The thermal properties obtained in these films are discussed on the basis of influence of grain size on phonon scattering.     

Experimental and theoretical studies on high-temperature thermal properties of fibrous insulation

In the present paper, an experimental apparatus has been developed to measure heat transfer through high-alumina fibrous insulation for thermal protection system. Effective thermal conductivities of the fibrous insulation were measured over a wide range of temperature (300-973 K) and pressure (10⁻²-10⁵ Pa) using the developed apparatus. The specific heat and the transmittance spectra in the wavelength range of 2.5-25 μm were also measured. The spectral extinction coefficients and Rosseland mean extinction coefficients were obtained from transmittance data at various temperatures to investigate the radiative heat transfer in fibrous insulation. A one-dimensional finite volume numerical model combined radiation and conduction heat transfer was developed to predict the behavior of the effective thermal conductivity of the fibrous insulation at various temperatures and pressures. The two-flux approximation was used to model the radiation heat transfer through the insulation. The experimentally measured specific heat and Rosseland mean extinction coefficients were used in the numerical heat transfer model to calculate the effective thermal conductivity. The average deviation between the numerical results for different values of albedo of scattering and the experimental results was investigated. The numerical results for ω=1 and experimental data were compared. It was found that the calculated values corresponded with the experimental values within an average of 13.5 percent. Numerical results were consistent with experimental results through the environmental conditions under examination.     

Effect of pressure and temperature on the thermal conductivity of siltstone and dolomite

The effective thermal conductivity of rocks (siltstone and dolomite) at high pressures of up to 250 MPa and temperatures of 275–523 K is investigated. It is established that the degree of crystallization of rock-forming substances affects the temperature dependence of thermal conductivity. The thermal conductivity of amorphous and crystalline components in the structure of rock is calculated.     

Specific features of charge carrier scattering mechanisms in Co-Cr alloys at high temperatures

The temperature and concentration dependences of the electrical resistivity π and thermal diffusivity a of Co-Cr alloys have been studied at temperatures of 400–1600 K. It has been shown that, as the temperature increases, the specific features of the electrical properties of the alloys are mainly determined by phonon scattering of carriers, and the character of the polytherms and concentration dependences is determined by the multiband scattering mechanism.     

R134a迁移性质研究

1引言R134a作为一种新工质，有关对其迁移性质的研究目前还进行的不多，已有的迁移性质计算公式适用范围亦不宽。这些都影响了系统的优化设计和动态仿真。针对这一问题，作者在本文对R134a的导热系数、粘度关系式进行了研究。2有关R134a导热系数、粘度系数的实验研究国内外公开发表的有关R134a导热系数、粘度系数实验研究的报告如表1和表2所示。表1近年来对R134a导热系我实验研究表2近年来对R134a粘应的实验研究本文曾于1996年10月在武夷山召开的中国工程热物理学会工程热力学与能源利用学术会议上宣读．表1、表2列出了各研究者对R134a迁…     

Temperature dependence of the thermal conductivity of water: a molecular dynamics simulation study using the SPC/E model

In this study, molecular dynamics simulations of SPC/E (extended simple point charge) water model have been carried out in the canonical (NVT fixed) ensemble over the range of temperatures 300–550 K with Ewald summation. The evaluated thermal conductivity for SPC/E water overestimates the experimental data at 300–550 K. In accordance with experimental data, SPC/E predicts a maximum in the thermal conductivity at 400 K. The temperature dependence of thermal conductivity of SPC/E water was discussed.     

Contribution of thermal radiation in measurements of thermal conductivity of sandstone

The effective thermal conductivity of sandstone at high pressures of up to 400 MPa and temperatures of 273–523 K has been studied. It has been shown that the degree of crystallization of rock-forming minerals substantially influences the temperature and pressure dependences of the thermal conductivity. The contribution of the radiation heat transfer in measurements of the thermal conductivity of sandstone at various temperatures has been analyzed taking into account the reflection and attenuation of the thermal radiation. The results of measuring the reflection and absorption spectra of the thermal radiation have been presented.     

Thermal conductivity of the pine-biocarbon-preform/copper composite

The thermal conductivity of composites of a new type prepared by infiltration under vacuum of melted copper into empty sap channels (aligned with the sample length) of high-porosity biocarbon preforms of white pine tree wood has been studied in the temperature range 5–300 K. The biocarbon preforms have been prepared by pyrolysis of tree wood in an argon flow at two carbonization temperatures of 1000 and 2400°C. From the experimental values of the composite thermal conductivities, the fraction due to the thermal conductivity of the embedded copper is isolated and found to be substantially lower than that of the original copper used in preparation of the composites. The decrease in the thermal conductivity of copper in the composite is assigned to defects in its structure, namely, breaks in the copper filling the sap channels, as well as the radial ones, also filled by copper. A possibility of decreasing the thermal conductivity of copper in a composite due to its doping by the impurities present in the carbon preform is discussed.