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 and thermal diffusivity of the R134a refrigerant in the liquid state

Thermal conductivity and thermal diffusivity of “ozone-safe” refrigerant R134a in liquid state within the range of temperatures 295.9–354.9 K and pressures from the liquid — vapor equilibrium line up to 4.08 MPa have been studied by high-frequency thermal-wave method. The experimental uncertainties of the temperature, pressure, thermal conductivity and thermal diffusivity measurement errors were estimated to be 0.1 K, 3 kPa, 1.5 and 2.5 %, respectively. Values of thermal conductivity and thermal diffusivity of liquid R134a on saturated line have been calculated. Approximation dependences for thermal conductivity and thermal diffusivity within the whole studied range of temperatures and pressures as well as on the saturated line have been obtained. The work was financially supported by the Russian Foundation for Basic Research (grant No. 07-08-00295-a).     

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.     

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).     

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.     

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 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.     

Thermal conductivity of R-410A mixture in the vapor phase

Thermal conductivity of R-410A mixture in the vapor phase (314–428 К and 0.1–2.0 MPa) has been studied by the steady-state method of coaxial cylinders. Experimental uncertainties of temperature, pressure, and thermal conductivity measurements did not exceed 0.05 K, 4 kPa, and 1.5-2.5 %, respectively. The approximating equation has been obtained for thermal conductivity depending on temperature and pressure. Thermal conductivity on dew line and in ideal-gas state has been calculated.     

Temperature and concentration dependences of thermal conductivity of solid solutions of gadolinium and dysprosium sulfides

Thermal conductivity of a number of solid solutions of gadolinium and dysprosium sulfides has been studied experimentally within the temperature range 80-400 K. The work offers the data on thermal conductivity coefficient and lattice thermal conductivity of the studied samples. It was found that replacement of gadolinium ions by dysprosium ions leads to significant decrease of the samples?? thermal conductivity and changes its temperature dependence character due to the resonance scattering of phonons by paramagnetic ions of dysprosium. Influence of this mechanism of phonon scattering conditions the area of anomalous change observed on the concentration dependence of thermal conductivity coefficient.     

Theoretical and experimental investigation on enhanced thermal behaviour in chunk-shaped nano ZnO

Thermal properties of chunk-shaped ZnO nanostructures are studied for diffusivity, conductivity, and effusivity by photoacoustics (PA) and simulation methods. Thermal conductivity of nano ZnO was determined from simulation in the temperature range of 100–1000 K. Thermal conductivity of ZnO nanostructures at room temperature is approximately 52 and 128 times lower than that of bulk ZnO for PA and simulation, respectively. For simulation, Tersoff potential is used for the interatomic interaction. The velocity autocorrelation function and Green–Kubo relation are used to compute the thermal conductivity.     

Thermal Diffusivity and Thermal Conductivity of Neodymium in the Temperature Range 293 to 1773 K

Thermal conductivity and thermal diffusivity weremeasured for the first time by the laser flash method in the temperature range of thermal diffusivity of neodymium from 293 to 1773 K, including regions of phase transitions. The results are compared with the available literature data. Reference tables for neodymium heat transfer coefficients are designed for scientific and practical use. The possibility to predict the thermal conductivity of neodymium liquid and β-phase using the Wiedemann–Franz law is shown.     

Temperature and pressure dependences of the thermal conductivity of As2(Se1-xTex)3 solid solutions

The effect of temperature and pressure on the thermal conductivity of solid solutions based on the As₂(Se_{1 - x}Te_x)₃ system was investigated in glassy and polycrystalline samples at 273–450 K and hydrostatic pressures of up to 0.35 GPa. The compound As₂Se₃ was studied in a temperature range of 300–760 K. Analysis showed that the short-cange order structure in As₂Se₃ remains unchanged upon the glass—liquid transition right up to 760 K.     

聚氨酯泡沫液氮温度下热导率的测量

运用稳态径向热流法对液氮温度下聚氨酯泡沫的热导率进行了测定 ,根据 GJB 1875 - 94建立的试验装置确保了使用径向量热法的前提条件。在液氮温度下聚氨酯泡沫的热导率可以达到 0 .86× 10 - 2 W/ m· K ,结果表明 :此材料在液氮的输运系统中是一种优良的绝热材料。另外 ,对聚氨酯泡沫的导热机理进行了讨论 ,最后对试验进行了误差分析 ,得到的最大相对误差为 4 %。     

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.     

HFC-32饱和气导热系数的实验研究

1研究背景自《蒙特利尔议定书》签定后，特别是1992年11月哥本哈根会议以来，HCFCS的替代日程已经确定。目前以含有HFC－32的混合物替代HCFC－22的呼声很高，而且国外正开始着手应用。有关HFC－32的饱和气的导热系数现在还没有见文献报导。在本文中，作者自行开发设计了一套双热线法测量导热系数的实验装置，并对HFC－32的饱和气的导热系数进行了测量，经分析测量结果是令人满意的。2实验装置及实验原理热线法是测量导热系数的瞬态方法之一，其基本原理是Carslaw提出的半径趋于零的无限长线热源在无限大介质中的导热方程的解山文献…     

The effect of pressure on the thermal conductivity of ordered and disordered alloys

A comparison is made between the results from experimental studies into the effect of hydrostatic pressures of up to 400 MPa in the temperature range 273–523 K on the phonon thermal conductivity of CdSnAs₂ alloy and the effective thermal conductivity of granite. Pressure was demonstrated to lead to a change in the degree of structural ordering of the studied specimens.     

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.     

聚双(对甲苯磺酸)-2,4-己二炔-1,6-二醇酯(PTS)的热学性质

应用光声效应研究了聚双(对甲苯磺酸)-2,4-己二炔-1,6-二醇酯(PTS)在175—225K范围内的热学性质随温度的变化关系。发现比热C₃和热导K的积C₃·K在200K附近有一尖锐的峰,第一次由热学性质确定该处存在一个二阶相变。同时通过实验结果分析得到热导K在该温区内存在与温度成正比的反常行为,并对此作了分析。 关键词：     

Structural and thermal properties of the opal-epoxy resin nanocomposite

Thermal conductivity of the opal-epoxy resin nanocomposite is measured in the range 4.2–250 K, and the material is studied by electron microscopy at 300 K. An analysis of the electron microscope images permits a conclusion on the character of opal void filling by the epoxy resin. It is shown that the thermal conductivity of the nanocomposite within the range 40–160 K can be fitted fairly well by the corresponding standard expressions for composites. For T<40 K and T>160 K, the experimental values of the nanocomposite thermal conductivity deviate strongly from the calculated figures.     

Superconducting proximity effect in Ag—Mn

The proximity effect was studied by measuring the thermal conductivity of double layers films made of a normal metal (Ag or Ag—Mn) and a superconductor (Pb–5% Bi), in the temperature range of 0.3–2 K.Thermal conductivity ratios have been used to estimate induced energy gap in silver and in dilute silver manganese alloys. No evidence for bound states in the presence of magnetic impurities was observed.