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  • 1
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    Journal of superconductivity 13 (2000), S. 617-621 
    ISSN: 1572-9605
    Keywords: thermal conductivity ; (Bi,Pb) 2223 pellet ; thermal conductivity peak ; phonon + electron approach
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Thermal conductivity of superconducting (Bi,Pb)2223 pellet in the temperature range 20–170 K is reported. Electronic contribution to thermal conductivity in the normal state is estimated to be ∼25%. Considering both phonon and phonon + electron approach, we attempted to examine the observed nature of the temperature dependence of thermal conductivity. Our analysis strongly supports the role of phonons as well as electrons in the origin of the thermal conductivity peak in the superconducting state. Some of the microscopic quantities evaluated from the best-fit parameters obtained from phonon + electron approach give reasonable values.
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  • 2
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    Journal of nanoparticle research 2 (2000), S. 199-204 
    ISSN: 1572-896X
    Keywords: nanoscale heat transfer ; nanoparticles ; nanowires ; phonons ; superlattices ; thermal conductivity ; thin films ; microscale effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract Heat conduction in nanostructures differs significantly from that in macrostructures because the characteristic length scales associated with heat carriers, i.e., the mean free path and the wavelength, are comparable to the characteristic length of nanostructures. In this communication, particularities associated with phonon heat conduction in nanostructures, the applicability of the Fourier law, and the implications of nanoscale heat transfer effects on nanotechnology are discussed.
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  • 3
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    Transport in porous media 41 (2000), S. 137-147 
    ISSN: 1573-1634
    Keywords: predictive models ; soils ; thermal properties ; thermal conductivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract An analysis of soil thermal conductivity data shows that, at very low moisture content, this property first varies insignificantly and then begins to increase from a certain critical moisture content, whose value tends to depend on clay mass fraction. Two simple models evaluating the critical moisture content were developed; the first one is a fraction of the permanent wilting point; the second one is a simple linear function dependent on clay mass fraction. An insignificant variation of soil thermal conductivity is observed at 20°C, within a water pressure head ranging from 1 × 103 to 1 × 103 m, while for higher temperatures (45–50°C) from 5000 to 100000 m. Three extensions of the enhanced thermal conductivity model by Sundberg, namely SUN-1, SUN-2 and SUN-3, were proposed and tested. They produce an average root mean square error of 27%, 24% and 30%, respectively, with respect to experimental data. SUN-1and SUN-2 predictions could be further improved if better estimates of thermal conductivity at the dry state and the permanent wilting point were provided. SUN-3 is a simple model which does not require information about the PWP and critical moisture content. All SUN models have a potential for implementing the latent heat transfer component.
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  • 4
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    Journal of superconductivity 13 (2000), S. 417-422 
    ISSN: 1572-9605
    Keywords: (Bi,Pb)2223-PEG composites ; thermal conductivity ; polyethylene glycol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Thermal conductivity measurements have been taken between 20 and 300 K on composites prepared from polyethylene glycol (PEG) containing various amounts of superconducting (Bi,Pb)2223 powder. The nature of temperature variation of thermal conductivity (λC) of the composites and its magnitude depend strongly on the volume concentration of the high-temperature superconductor (HTSC) filler present in the material. The results have been discussed in the light of models known for polymer–metal powder composites. It is shown that for composites with 2223 powder content 〈44 vol. %, the measured data can be accounted well with Hamilton–Crosser model, taking the sphericity factor into consideration. Failure of Hamilton–Crosser expression for composites with higher filler concentration is thought to be associated with direct contact between the superconducting grains, which shortcircuits the acoustic mismatch resistance in the composites.
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  • 5
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    International journal of thermophysics 21 (2000), S. 207-215 
    ISSN: 1572-9567
    Keywords: calorific intensity ; hot probe ; organ or tissue of a living body ; specific heat ; thermal conductivity ; thermal diffusivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new method was developed to determine simultaneously the thermal conductivity, thermal diffusivity, specific heat, and calorific intensity of the organ or tissue of a living body either in vivo or in vitro with a thin hot probe. By using the method, the thermophysical properties and calorific intensities of a human palm and in vivo liver and a kidney, heart, brain, and foreleg and hindleg muscles of an anesthetized canine were measured. It is concluded that there are no significant differences in the thermophysical properties of organ or tissue of a living body either in vivo or in vitro. The measured thermophysical properties are in good agreement with those reported in the literature.
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  • 6
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    International journal of thermophysics 21 (2000), S. 319-328 
    ISSN: 1572-9567
    Keywords: correlation ; R125 ; R134a ; R32 ; refrigerant ; ternary mixture ; thermal conductivity ; transient hot-wire method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The thermal conductivities of ternary refrigerant mixtures of difluoromethane (R32), pentafluoroethane (R125), and 1,1,1,2-tetrafluoroethane (R134a) in the liquid phase have been measured by the transient hot-wire method with one bare platinum wire. The experiments were performed in the temperature range of 233 to 323 K and in the pressure range of 2 to 20 MPa at various compositions. The measured data are correlated as a function of temperature, pressure, and composition. From the correlation, we can calculate the thermal conductivity of pure refrigerants and their binary or ternary refrigerant mixtures. The uncertainty of the measurements is estimated to be ±2%.
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  • 7
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    International journal of thermophysics 21 (2000), S. 367-375 
    ISSN: 1572-9567
    Keywords: correlation ; hard spheres ; liquid ; refrigerants ; thermal conductivity ; viscosity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The viscosity and thermal conductivity of liquid halogenated ethane refrigerants from about 200 K to near the critical temperature, at saturation and also at pressures up to 50 MPa, are shown to be satisfactorily correlated on the basis of a scheme developed by Dymond and Assael from consideration of hard-sphere theory.
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  • 8
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    International journal of thermophysics 21 (2000), S. 465-478 
    ISSN: 1572-9567
    Keywords: heat radiation ; hot wire ; thermal conductivity ; semitransparent material
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new simple analytic model applicable to the measurement system of a hot wire and a semitransparent solid material is developed. An experimental study is carried out on a special glass sample, glass K9, in the temperature range of 297 to 1230 K, and the radiation-free thermal conductivity is reported.
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  • 9
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    International journal of thermophysics 21 (2000), S. 571-583 
    ISSN: 1572-9567
    Keywords: CsPbCl3 single crystal ; heat of transition ; phase transition ; pulse transient method ; specific heat ; thermal conductivity ; thermal diffusivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The main features of the pulse transient method are presented. The method gives the specific heat c and thermal diffusivity a for a single measurement, while thermal conductivity λ is calculated according to λ=caρ, where ρ is the density. The pulse transient method is a dynamic method based on the measurement of the temperature response to a heat pulse produced within a specimen. An apparatus operating in the temperature range from −40 to 100°C is described. Errors are discussed. The thermophysical properties of a CsPbCl3 single crystal are determined using the pulse transient method for a temperature range between 10 and 65°C in the controlled heating and cooling regimes. The data show anomalies in the thermophysical properties around the phase transition temperature at 47°C. Discrepancies in comparison with previously published data are discussed.
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  • 10
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    International journal of thermophysics 21 (2000), S. 639-650 
    ISSN: 1572-9567
    Keywords: empirical correlation ; n-alkane ; propane ; thermal conductivity ; transport properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract New experimental data on the thermal conductivity of propane have been reported since the wide-range correlations proposed by Holland et al. and by Younglove and Ely. These new experimental data, covering a temperature range of 110 to 700 K and a pressure range of 0.1 to 70 MPa, are used together with the previously available data to develop an improved empirical equation for the thermal conductivity of gaseous and liquid propane. The quality of the new data is such that the thermal-conductivity correlation for propane is estimated to have an uncertainty of about ±5% at a 95% confidence level, with the exception of state points near the critical point, where the uncertainty of the correlation increases to ±10%.
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  • 11
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    International journal of thermophysics 21 (2000), S. 927-940 
    ISSN: 1572-9567
    Keywords: calorimetry ; emittance ; fused silica ; hemispherical total emissivity ; refractive index ; spectral emissivity ; thermal conductivity ; virtual mode ; Vycor glass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An attempt to derive the hemispherical total emissivity from the normal emission spectrum is proposed for Vycor and fused silica glasses. The normal emission spectrum from a clear surface has been measured at steady state in the temperature range from 400 to 750 K. The sample is heated on one metal-backed face by thermal radiation from a heater. Temperatures inside the sample were monitored by thermocouples at two points near the surfaces. Evaluation of the hemispherical total emissivity from the normal emission spectrum is determined by means of Kramers–Krönig analysis and virtual mode equations. Assuming a linear temperature distribution within the sample, the thermal conductivities of silicate glasses were obtained at elevated temperatures. The results are comparable with those obtained by previous investigators. The effect of radiation heat transfer in a sample is also discussed.
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  • 12
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    International journal of thermophysics 21 (2000), S. 671-679 
    ISSN: 1572-9567
    Keywords: electrolyte solutions ; potassium chloride aqueous solutions ; thermal conductivity ; transient coated-hot-wire technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract This paper presents new absolute measurements of the thermal conductivity of aqueous potassium chloride solutions using the transient coated-hot-wire technique. The data cover the range from 295 to 360 K at pressures slightly above the vapor pressures and over a concentration range of 0 to 3 mol·kg−1. The instrument can be used to measure the thermal conductivity with a reproducibility of better than 0.2%, and a comparison of the present results with data available in the literature indicates that the uncertainty of the present data is better than 0.5%. An empirical correlation that reproduces the data within the claimed uncertainty is presented.
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  • 13
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    International journal of thermophysics 21 (2000), S. 23-34 
    ISSN: 1572-9567
    Keywords: HFC-32 ; HFC-125 ; HFC-134a ; hard-sphere theory ; mixture ; refrigerant ; thermal conductivity ; viscosity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A recently developed scheme, based on considerations of hard-sphere theory, is used for the simultaneous prediction of the thermal conductivity and the viscosity of binary and ternary HFC refrigerant mixtures, consisting of HFC-32, HFC-125, and HFC-134a. In this prediction scheme, the hypothetical molecular parameters of HFC refrigerant mixtures were assumed to be the molar average of the pure component values. The close agreement between the predicted values and the experimental results of thermal conductivity and viscosity demonstrate the predictive power of this scheme.
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  • 14
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    International journal of thermophysics 21 (2000), S. 35-44 
    ISSN: 1572-9567
    Keywords: aqueous solution ; diffraction ; laser-induced thermal grating ; magnesium chloride ; thermal conductivity ; thermal diffusivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The thermal diffusivity of aqueous solutions of magnesium chloride was determined in the temperature range 294 to 371 K and at atmospheric pressure. Using a noninvasive optical technique—laser-induced thermal grating (LTG)—the measurements were carried out in aqueous solutions of weight fractions of 5, 10, 15, and 20% magnesium chloride. The measurement results for the aqueous solutions are presented as a function of temperature and weight fraction.
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  • 15
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    International journal of thermophysics 21 (2000), S. 445-452 
    ISSN: 1572-9567
    Keywords: evacuated insulations ; opacifier ; powders ; radiative conductivity ; silica powder ; silicon carbide ; thermal conductivity ; thermal radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The thermal conductivity of powder fillings for load-bearing vacuum insulations is investigated. Different opacifiers have been tested in mixtures with perlite powder, precipitated silica, and fumed silica. Using temperature-dependent thermal conductivity measurements, the radiative thermal conductivity and the solid conductivity of the powder samples are separated. Additionally, the influence of the pressure load on the solid conductivity is studied. The thermal conductivities of silica powders with added opacifier powders (carbon black, magnetite, silicon carbide, titanium dioxide) can be as low as 0.003 W·m−1·K−1 if the powder boards are pressed with moderate loads. The use of microporous silica powders as filler materials allows internal gas pressures even beyond 10 hPa with only a moderate increase of the overall conductivity.
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  • 16
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    International journal of thermophysics 21 (2000), S. 1255-1278 
    ISSN: 1572-9567
    Keywords: standard uncertainty ; thermal conductivity ; thermal diffusivity ; transient hot strip method ; transient hot wire method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The standard method for measuring thermal transport properties of dielectric solids such as ceramics and refractories is the transient hot wire (THW) technique. In its simplest arrangement, a thin wire is embedded between two sample halves, where it acts simultaneously as a resistive heat source and a thermometer. From its temperature signal, the thermal conductivity and the thermal diffusivity of the dielectric can be derived. Up to now, there is no uncertainty assessment for this technique strictly following the ISO Guide to the Expression of Uncertainty in Measurement. Here we analyze the ISO standard uncertainty of the THW technique in the same way as in a previous paper on the uncertainty of the closely related transient hot strip (THS) technique. The two papers provide a comprehensive comparison of the most important advantages and disadvantages of these two transient techniques. The results obtained here for the uncertainty (5.8% for the thermal conductivity and 30% for the thermal diffusivity) are nearly the same as those for the THS method. Experiments on a Pyrex standard-reference sample confirm the results.
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  • 17
    ISSN: 1572-9567
    Keywords: R134a ; dilute gas ; refrigerant ; saturation properties ; 1,1,1,2-tetrafluoroethane ; thermal conductivity ; transport properties ; viscosity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract This paper reports the results of an international project coordinated by the Subcommittee on Transport Properties of Commission I.2 of the International Union of Pure and Applied Chemistry. The project has been conducted to investigate the large discrepancies between the results reported by various authors for the transport properties of R134a and culminates the effort which was initially described in 1995. The project has involved the remeasurement of the transport properties of a single sample of R134a in nine laboratories throughout the world in order to test the hypothesis that at least part of the discrepancy could be attributed to the purity of the samples. This paper provides an intercomparison of the new experimental results obtained for the viscosity and thermal conductivity in the vapor, liquid, and supercritical gas phases. The viscosity measurements were made with a variety of techniques including the vibrating wire, oscillating disk, capillary flow, and falling body. Thermal conductivity was measured using transient bare and anodized hot wires, steady-state anodized hot wires, and light scattering. Agreement between a variety of experimental techniques using the standard round-robin sample is necessary to demonstrate that some of the discrepancies in earlier results were due to sample impurities. Identification of disagreement between data using one experimental technique relative to other techniques may suggest modifications that would lead to more accurate measurements on these highly polar refrigerant materials. It is anticipated that the new data which have been measured on this IUPAC round-robin sample will aid in the identification of the reliable data sets in the literature and ultimately allow the refinement of the IUPAC reference-data correlations for the transport properties of R134a.
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  • 18
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    International journal of thermophysics 21 (2000), S. 71-84 
    ISSN: 1572-9567
    Keywords: molten carbonates ; molten nitrate ; thermal conductivity ; thermal diffusivity ; transient short-hot-wire technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A transient short-hot-wire technique has been successfully used to measure the thermal conductivity and thermal diffusivity of molten salts (NaNO3, Li2CO3/K2CO3, and Li2CO3/Na2CO3) which are highly corrosive. This method was developed from the hot-wire technique and is based on two-dimensional numerical solutions of unsteady heat conduction from a short wire with the same length-to-diameter ratio and boundary conditions as those used in the actual experiments. In the present study, the wires are coated with a pure Al2O3 thin film by using a sputtering apparatus. The length and radius of the hot wire and the resistance ratio of the lead terminals and the entire probe are calibrated using water and toluene with known thermophysical properties. Using such a calibrated probe, the thermal conductivity and thermal diffusivity of molten nitrate are measured within errors of 3 and 20%, respectively. Also, the thermal conductivity of the molten carbonates can be measured within an error of 5%, although the thermal diffusivity can be measured within an error of 50%.
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  • 19
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    International journal of thermophysics 21 (2000), S. 217-248 
    ISSN: 1572-9567
    Keywords: linear working equation ; nonlinear working equation ; standard uncertainty ; thermal conductivity ; thermal diffusivity ; transient hot strip method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The transient hot strip (THS) method can be used to measure simultaneously the thermal conductivity λ and diffusivity a of dielectrics within a few minutes. However, although the method has been known for 20 years, there is no complete assessment of its uncertainty. First, the underlying complex mathematical model makes any error analysis a tedious and complicated task. Secondly, the ISO Guide to the Expression of Uncertainty in Measurement does not apply directly because of the classical model's implicit character. In the present paper, the combined standard uncertainty u of the THS method has been determined by applying two different models. First, we start from the classical nonlinear model. The major sources of errors are analyzed, namely, the ideal model errors, the evaluation errors, and the measurement errors. Next, a newly developed numerical procedure combines all the components in a way that the resultant standard uncertainties of the nonlinear model, u(λ)/λ=2.6% and u(a)/a=11%, comply as closely as possible with the principles of the ISO Guide. Second, we start from the recently presented linear expression of the THS mathematical model that is briefly discussed. Since this approximation is explicit in both measurands, the uncertainties, u(λ)/λ=2.5% and u(a)/a=11%, are determined in full accordance with the ISO guide. The uncertainty in thermal conductivity is experimentally assessed against the standard reference CRM 039 (Pyrex). The results obtained are in excellent agreement with the theoretical values.
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  • 20
    ISSN: 1572-9567
    Keywords: molten materials ; self-adaptive finite-element method ; thermal conductivity ; transient hot-strip
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The transient heating in an unsymmetrical, coated, hot-strip sensor was simulated with a self-adaptive finite-element method (SAFEM). The first tests of this model show that it can be used to determine, with a small error, the thermal conductivity of liquids, from the transient temperature rise in the hot strip, which is deposited in a substrate and coated by an alumina spray.
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  • 21
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    International journal of thermophysics 21 (2000), S. 429-443 
    ISSN: 1572-9567
    Keywords: density ; electrical resistivity ; electrostatic levitator ; hemispherical total emissivity ; molten germanium ; specific heat ; surface tension ; thermal conductivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Thermophysical properties of molten germanium have been measured using the high-temperature electrostatic levitator at the Jet Propulsion Laboratory. Measured properties include the density, the thermal expansivity, the hemispherical total emissivity, the constant-pressure specific heat capacity, the surface tension, and the electrical resistivity. The measured density can be expressed by ρ liq=5.67×103−0.542 (T−T m ) kg·m−3 from 1150 to 1400 K with T m=1211.3 K, the volume expansion coefficient by α=0.9656×10−4 K−1, and the hemispherical total emissivity at the melting temperature by ε T, liq(T m)=0.17. Assuming constant ε T, liq(T)=0.17 in the liquid range that has been investigated, the constant-pressure specific heat was evaluated as a function of temperature. The surface tension over the same temperature range can be expressed by σ(T)=583−0.08(T−T m) mN·m−1 and the temperature dependence of the electrical resistivity, when r liq(T m)=60μμΩ·cm is used as a reference point, can be expressed by r e, liq(T)=60+1.18×10−2(T−1211.3)μΩ·cm. The thermal conductivity, which was determined from the resistivity data using the Wiedemann–Franz–Lorenz law, is given by κ liq(T )=49.43+2.90×10−2(T−T m) W·m−1·K−1.
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  • 22
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    International journal of thermophysics 21 (2000), S. 965-980 
    ISSN: 1572-9567
    Keywords: electrical conductivity ; microstructure ; pin fin ; single carbon fiber ; steady-state short-hot-wire method ; thermal conductivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In this paper, the thermal conductivity of a single carbon fiber under different manufacturing conditions is measured using the steady-state short-hot-wire method. This method is based on the heat transfer phenomena of a pin fin attached to a short hot wire. The short hot wire is supplied with a constant direct current to generate a uniform heat flux, and both its ends are connected to lead wires and maintained at the initial temperature. The test fiber is attached as a pin fin to the center position of the hot wire at one end and the other end is connected to a heat sink. One-dimensional steady-state heat conduction along the hot wire and test fiber is assumed, and the basic equations are analytically solved. From the solutions, the relations among the average temperature rise of the hot wire, the heat generation rate, the temperature at the attached end of the fiber, and the heat flux from the hot wire to the fiber are accurately obtained. Based on the relations, the thermal conductivity of the single carbon fiber can be easily estimated when the average temperature rise and the heat generation rate of the hot wire are measured for the same system. Further, the electrical conductivity of the single carbon fiber is measured under the same conditions as for the thermal conductivity using a four-point contact method. The relation between the thermal conductivity and electrical conductivity is further discussed, based on the crystal microstructure.
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  • 23
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    Environment, development and sustainability 2 (2000), S. 277-304 
    ISSN: 1573-2975
    Keywords: Systems of Knowledge ; Local Knowledge ; Fisheries ; Resource Management
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Sociology
    Notes: Abstract During the last 20 years, the existence of rich systems of local knowledge, and their vital support to resource use and management regimes, has been demonstrated in a wide range of biological, physical and geographical domains, such as agriculture, animal husbandry, forestry and agroforestry, medicine, and marine science and fisheries. Local knowledge includes empirical and practical components that are fundamental to sustainable resource management. Among coastal-marine fishers, for example, regular catches and, often, long-term resource sustainment are ensured through the application of knowledge that encompasses empirical information on fish behaviour, marine physical environments, fish habitats and the interactions among ecosystem components, as well as complex fish taxonomies. Local knowledge is therefore an important cultural resource that guides and sustains the operation of customary management systems. The sets of rules that compose a fisheries management system derive directly from local concepts and knowledge of the resources on which the fishery is based. Beyond the practical and the empirical, it is essential to recognise the fundamental socio-cultural importance of local knowledge to any society. It is through knowledge transmission and socialisation that worldviews are constructed, social institutions perpetuated, customary practices established, and social roles defined. In this manner, local knowledge and its transmission, shape society and culture, and culture and society shape knowledge. Local knowledge is of great potential practical value. It can provide an important information base for local resources management, especially in the tropics, where conventionally-used data are usually scarce to non-existent, as well as providing a shortcut to pinpoint essential scientific research needs. To be useful for resources management, however, it must be systematically collected and scientifically verified, before being blended with complementary information derived from Western-based sciences. But local knowledge should not be looked on with only a short-term utilitarian eye. Arguments widely accepted for conserving biodiversity, for example, are also applicable to the intellectual cultural diversity encompassed in local knowledge systems: they should be conserved because their utility may only be revealed at some later date or owing to their intrinsic value as part of the world's global heritage. At least in cultures with a Western liberal tradition, more than lip-service is now being paid to alternative systems of knowledge. The denigration of alternative knowledge systems as backward, inefficient, inferior, and founded on myth and ignorance has recently begun to change. Many such practices are a logical, sophisticated and often still-evolving adaptation to risk, based on generations of empirical experience and arranged according to principles, philosophies and institutions that are radically different from those prevailing in Western scientific circles, and hence all-but incomprehensible to them. But steadfastly held prejudices remain powerful. In this presentation I describe the 'design principles' of local knowledge systems, with particular reference to coastal-marine fishing communities, and their social and practical usefulness. I then examine the economic, ideological and institutional factors that combine to perpetuate the marginalisation and neglect of local knowledge, and discuss some of the requirements for applying local knowledge in modern management.
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  • 24
    ISSN: 1573-0956
    Keywords: (AGI) ; heat flow ; lithosphere ; thermal conductivity ; thermal diffusivity ; models ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Measurements on thermal conductivity and diffusivity as functions of temperature (up to 1150 K) and pressure (up to 1000 MPa) are presented for Archaean and Proterozoic mafic high-grade rocks metamorphosed in middle and lower crustal pressures, and situated in eastern Finland, central Fennoscandian Shield. Decrease of 12–20% in conductivity and 40–55% in diffusivity was recorded between room temperature and 1150 K, which can be considered as typical of phonon conductivity. Radiative heat transfer effects were not detected in these samples. Pressure dependencies of the samples are weak if compared to crystalline rocks in general, but relatively typical for mafic rocks. The temperature and pressure dependencies of thermal transport properties (data from literature and the present study) were applied in an uncertainty analysis of lithospheric conductive thermal modellings with random (Monte Carlo) simulations using a 4-layer model representative of shield lithosphere. Model parameters were varied according to predetermined probability functions and standard deviations were calculated for lithospheric temperature and heat flow density after 1500 independent simulations. The results suggest that the variations (uncertainties) in calculated temperature and heat flow density values due to variations in the temperature and pressure dependencies of conductivity are minor in comparison to the effects produced by typical variations in the room temperature value of conductivity, heat production rate or lower boundary condition values.
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    Journal of superconductivity 12 (1999), S. 497-500 
    ISSN: 1572-9605
    Keywords: Organic superconductors ; Josephson plasma ; thermal conductivity ; upper critical field
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Studies of heat conduction and microwave absorption in the vortex state of κ-(BEDT-TTF)2Cu(NCS)2 reveal some of the specific aspects of superconductivity in this system. Moreover they allow us to probe the destruction of bulk superconductivity by a magnetic field. The two set of results yield identical magnitudes for the upper critical field with a temperature dependence distinctly different from the one suggested by the onset of resistive transition.
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    International journal of thermophysics 20 (1999), S. 375-399 
    ISSN: 1572-9567
    Keywords: coaxial cylinders ; high pressure ; refrigerants ; HFC-125 ; thermal conductivity
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract Measurements of the thermal conductivity of HFC-125 that have been made by a coaxial cylinder cell operating in steady state are reported. The measurements of the thermal conductivity of HFC-125 were performed along several quasi-isotherms between 300 and 515 K in the gas phase and the liquid phase. The pressure range covered varies from 0.1 to 53 MPa. Based on the measurement of more than 600 points, an empirical equation is provided to describe the thermal conductivity outside the critical region as a function of temperature and density. A careful analysis of the various sources of error leads to an estimated uncertainty of approximately ± 1.5%.
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    International journal of thermophysics 20 (1999), S. 665-676 
    ISSN: 1572-9567
    Keywords: density ; myocardium ; swine ; thermal conductivity ; thermal diffusivity
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    Topics: Physics
    Notes: Abstract This paper presents the experimental technique and results for the thermal conductivity, thermal diffusivity, and density of swine myocardial tissue. These properties were measured for freshly excised tissue. Thermal properties were measured using a self-heated thermistor probe, while the density was measured using a water displacement method. Thermistor probes were inserted into the tissue of interest and were used to supply heat within the tissue as well as to monitor the temperature rise in the tissue. An empirical calibration procedure was used to measure the properties of the tissue at different temperatures. The measurement instrument was first calibrated against agar-gelled water and glycerol at each temperature. The measurements were made at temperatures of 25, 37, 50, 62, and 76°C. The uncertainty in the measurement ranges from 2% at lower temperatures to about 5% at higher temperatures (T 〉 50°C). The properties of the tissue depend significantly on the water content. At temperatures higher than 50°C, there is significant water loss from the tissue during the procedure. The water loss is found to vary exponentially with the increase in temperature relative to ambient. Consequently, there is a decrease in the thermal conductivity values with increasing temperature. This decrease, however, is not as much as one would expect from the water loss data. A hypothesis to explain the relationships among water loss, cell damage, and thermal properties is proposed.
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  • 28
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    International journal of thermophysics 20 (1999), S. 1237-1246 
    ISSN: 1572-9567
    Keywords: electrical resistivity ; enthalpy ; high temperature ; liquid alloys ; rhenium alloys ; specific heat ; thermal conductivity ; thermal diffusivity ; tungsten alloys
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    Topics: Physics
    Notes: Abstract Results are reported for the thermal conductivity and thermal diffusivity as a function of temperature for four W–Re alloys (4.0, 21.24, 24.07, and 31.09 mass% of Re) over a wide temperature range covering the solid and liquid states. The measurements allow the determination of specific heat and dependences among electrical resistivity, temperature, and density of the alloys into the liquid phase. The thermal conductivity is calculated using the Wiedeman–Franz law. Additionally, data for thermal conductivity and thermal diffusivity of the constituent elements, tungsten and rhenium, are presented for the first time. Both metals have been previously studied with the same experimental technique.
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  • 29
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    International journal of thermophysics 20 (1999), S. 1403-1415 
    ISSN: 1572-9567
    Keywords: HFC-32/125 ; HFC-32/134a ; binary mixture ; refrigerant ; thermal conductivity ; transient hot-wire method
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    Topics: Physics
    Notes: Abstract The liquid thermal conductivity of mixtures of HFC-32/125 and HFC-32/134a was measured using the transient hot-wire apparatus in the temperature ranges from 213 to 293 K and from 193 to 313 K, respectively, in the pressure range from 2 to 30 MPa and with HFC-32 mass fractions of 0.249, 0.500, and 0.750 for each system. The uncertainty of the thermal conductivity was estimated to be ±0.7%. For practical applications, the thermal conductivity data for the two mixtures were represented by a polynomial in temperature, pressure, and mass fraction of HFC-32 with a standard deviation of 1.0%.
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  • 30
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    International journal of thermophysics 20 (1999), S. 267-277 
    ISSN: 1572-9567
    Keywords: diffusion ; liquid metals ; shear viscosity ; simple liquids ; thermal conductivity
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    Topics: Physics
    Notes: Abstract Several simple approximate hard-sphere relations for transport coefficients are compared with the results of molecular dynamics (MD) simulations performed on Lennard–Jones (LJ) fluids. Typically the individual transport coefficients: self-diffusion coefficients, D, shear viscosity, ηs, bulk viscosity, ηB, and thermal conductivity, λ, agree within a factor of two of the exact results over the fluid and liquid parts of the phase diagram, which seems reasonable in view of the approximations involved in the models. We have also considered the ratio, λ/ηs, and the product, Dηs, for which simple analytic expressions exist in the hardsphere models. These two quantities also agree within a factor of two of the simulation values and hard sphere analytic expressions. Using time correlation functions, Tankeshwar has recently related the ratio λ/D to thermodynamic quantities, in particular, to the differences in specific heats, C p − C V, and to the isothermal compressibility, κT. Using D and thermodynamic values taken solely from LJ MD simulations, his relation was tested and found to give typically better than ~20% agreement at liquid densities, deteriorating somewhat as density decreases into the gas phase. Finally liquid metals are considered. In this case, λ is dominated by its electronic contribution, which is related approximately to the electrical conductivity by the Wiedemann–Franz Law. Some theoretical results for the electrical conductivity of Na are referenced, which allow a semiquantitative understanding of the measured thermal conductivity of the liquid metal. Shear viscosity is also discussed and, following the work of Tosi, is found to be dominated by ionic contributions; Nevertheless, at the melting temperature of Na, a relation emerges between thermal conductivity, electrical resistivity and shear viscosity.
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    International journal of thermophysics 20 (1999), S. 733-742 
    ISSN: 1572-9567
    Keywords: calorimetry ; diffusivity ; emissivity, heat capacity ; radiant exchange ; simultaneous measurement ; thermal conductivity
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    Topics: Physics
    Notes: Abstract Thermal radiation calorimetry has been applied to measure the thermal diffusivity of a solid specimen, along with simultaneous measurements of specific heat capacity and thermal conductivity. In this calorimeter, a disk-shaped solid specimen whose surfaces are blackened is heated and cooled slowly on one face by irradiation in a vacuum chamber. A quasi-steady-state approximation in which a linear temperature gradient within the specimen was assumed is considered in the analysis. The validity of this approximation was confirmed by the results of computer simulation based on the control-volume method. Measurements of Pyroceram 9606 and Pyrex 7740 by use of thermocouples in the temperature range between 250 and 400°C gave values consistent with those obtained by previous authors, within experimental error, for all three thermophysical properties.
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  • 32
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    International journal of thermophysics 20 (1999), S. 977-986 
    ISSN: 1572-9567
    Keywords: ac calorimetry ; CVD diamond ; modified Angstrom method ; reference materials ; thermal conductivity ; thermal diffusivity
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    Topics: Physics
    Notes: Abstract Modified ac calorimetry, a variation of the Angstrom method, has been shown to be a precise tool for measuring the in-plane thermal diffusivity of thin films (thickness less than 300 μm) of a wide variety of materials and layered composites. The property is determined from an analysis of the decay curve of the ac temperature waves generated by irradiation of a specimen using uniform chopped light (at frequencies from 1 to 20 Hz) from a halogen lamp source. To address certain limiting factors, especially to improve the signal-to-noise ratio and to eliminate heat losses, an improved form of measurement instrument has been developed. It is based on the use of a modulated laser beam heating to provide a higher intensity energy source plus a special optical system to ensure that one-dimensional ac temperature wave propagation is obtained. Measurements can now be made using frequencies in the range of 0.01 to 10 Hz, i.e., 10 times lower than in the traditional method. The performance of the improved measurement instrument will be illustrated by results on various materials of known thermal properties such as nickel and stainless steel, proposed reference materials such as a glassy carbon and alumina, plus a comparison of results obtained on CVD diamond films used in an international round-robin series with those obtained by the traditional technique.
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  • 33
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    International journal of thermophysics 20 (1999), S. 1051-1060 
    ISSN: 1572-9567
    Keywords: copper ; liquid metals ; liquid alloys ; Lorenz relation ; resistivity ; thermal conductivity ; thermal diffusivity ; tin
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    Notes: Abstract The thermal properties (heat capacity, thermal diffusivity, and electrical resistivity) of a Cu + 10 wt% Sn alloy in both solid and liquid phases have been reported. Using these values it was confirmed that the Lorenz relation is suitable for obtaining thermal conductivity from electrical resistivity in the liquid phase of this alloy. Also, the temperature differential (dλ/dT) obtained from such an approach was in excellent agreement with the thermal conductivity values calculated from thermal diffusivity.
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  • 34
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    International journal of thermophysics 20 (1999), S. 1279-1288 
    ISSN: 1572-9567
    Keywords: compressibility ; electrical conductivity ; emissivity ; specific heat ; thermal conductivity ; thermal expansion coefficient ; tungsten
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    Notes: Abstract Wire explosion experiments were used to obtain thermophysical properties of tungsten. These properties are specific heat, thermal expansion coefficient, compressibility, and electrical and thermal conductivities and their dependences on temperature. There are strong indications that the emissivity in the liquid range should be dependent on temperature. A proposal has been made for determining the emissivity from comparison of experiments with model calculations. The temperature range is extended up to 10,000 K, and first indications for the near-critical-point behavior were obtained. Other properties such as diffusivity, viscosity, and surface tension may possibly also be derived in this range.
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  • 35
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    Keywords: photothermal radiometry ; roughness effects ; thermal-sprayed coatings ; thermal diffusivity ; thermal conductivity
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    Notes: Abstract Laser infrared photothermal radiometry (PTR) was used to measure the thermophysical properties (thermal diffusivity and conductivity) of various thermal sprayed coatings on carbon steel. A one-dimensional photothermal model of a three-layered system in the backscattered mode was introduced and compared with experimental measurements. The uppermost layer was used to represent a roughness-equivalent layer, a second layer represented the thermal sprayed coating, and the third layer represented the substrate. The thermophysical parameters of thermal sprayed coatings examined in this work were obtained when a multiparameter-fit optimization algorithm was used with the backscattered PTR experimental results. The results also suggested a good method to determine the thickness of tungsten carbide and stainless-steel thermal spray coatings once the thermophysical properties are known. The ability of PTR to measure the thermophysical properties and the coating thickness has a strong potential as a method for in situ characterization of thermal spray coatings.
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    International journal of thermophysics 20 (1999), S. 1653-1666 
    ISSN: 1572-9567
    Keywords: critical parameters ; dielectric constant ; difluoromethane ; dipole moment ; heat capacities ; HFC-32 ; pvT behavior ; refractive index ; saturation densities ; second virial coefficient ; speed of sound ; surface tension ; survey ; thermal conductivity ; vapor pressure ; viscosity
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    Notes: Abstract A survey of experimental data for HFC-32 was prepared at the Institute of Thermomechanics in connection with planned experiments. In tabular form, surveys of thermodynamic, transport, and other property measurements, including pvT behavior, second virial coefficient, vapor pressure, saturation densities, critical parameters, heat capacities, speed of sound, thermal conductivity, viscosity, surface tension, refractive index, dielectric constant, and dipole moment, are presented. Tables include author)s) name(s), reference, year of publication, ranges of measurements, number of points, stated uncertainty, sample purity, and experimental method.
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    International journal of thermophysics 20 (1999), S. 55-62 
    ISSN: 1572-9567
    Keywords: mixture ; R125 ; R134a ; R125+R134a ; refrigerant ; thermal conductivity ; transient hot-wire method
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    Notes: Abstract Thermal conductivities of zeotropic mixtures of R125 (CF3CHF2) and R134a (CF3CH2F) in the liquid phase are reported. Thermal conductivities have been measured by a transient hot-wire method with one bare platinum wire. Measurements have been carried out in the temperature range of 233 to 323 K and in the pressure range of 2 to 20 MPa. The dependence of thermal conductivity on temperature, pressure, and composition of the binary mixture is presented. Measured thermal conductivity data are correlated as a function of temperature, pressure, and overall composition of the mixture. The uncertainty of our measurements was estimated to be better than 2%.
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  • 38
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    International journal of thermophysics 20 (1999), S. 45-54 
    ISSN: 1572-9567
    Keywords: argon ; experimental method ; helium ; low density ; propane ; thermal conductivity
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    Notes: Abstract The paper reports further developments of the transient hot-wire technique. The particular development of interest is the extension of the technique to study polar, or electrically-conducting gases with a relatively low thermal conductivity but a high thermal diffusivity, circumstances which occur at low density and therefore low pressure, for gases of high molecular weight. The theory of the transient hot-wire instrument is examined again in order to guide a revised design of the thermal conductivity cell with this particular application in mind. Test measurements have then been conducted on helium, argon, and propane at low and moderate pressures to confirm that the instrument operates in accordance with the theory of it. The satisfactory completion of these tests demonstrates that the new equipment overcomes many of the defects observed in earlier variants of the instrument for application to the study of refrigerant gases.
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  • 39
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    International journal of thermophysics 20 (1999), S. 63-72 
    ISSN: 1572-9567
    Keywords: 1,1-difluoroethane ; HFC 152a ; liquid ; modified van der Waals model ; thermal conductivity
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    Topics: Physics
    Notes: Abstract Thermal conductivity measurements were performed on 1,1-difluoroethane (HFC-152a) using the polarized transient hot-wire technique in the temperature range of 214 to 294 K and at pressures up to 19 MPa. This technique was used previously for measurements on other halocarbons along the saturation line and in the compressed liquid phase. No dependence of the polarization voltage was found for the thermal conductivity values, demonstrating that the technique was used with success. Also, no influence of heat transfer by radiation or convection was detected, in all the range of densities studied. The samples were supplied with stated purities greater than 99.9%. The reproducibility of the experiments was found to be 0.03%, while the total uncertainty is estimated to be 0.5%. The experimental data were compared with data from other sources. Values for the thermal conductivity along the saturation line for several temperatures were achieved by extrapolating the high-pressure data to the saturation density for each isotherm. The data obtained were also correlated using a modification of the van der Waals model (smooth hard spheres) with an uncertainty of 1.1%, at a 95% confidence level.
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  • 40
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    International journal of thermophysics 20 (1999), S. 73-84 
    ISSN: 1572-9567
    Keywords: azeotropic mixtures ; dynamic viscosity ; prediction method ; quasi-azeotropic mixtures ; refrigerants ; thermal conductivity
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    Notes: Abstract Azeotropic and quasi-azeotropic mixtures of organic compounds could become the most effective candidates as replacement fluids in refrigeration devices and heat pumps. Following the development of effective prediction formulas for several families of pure organic compounds, in this paper the evaluation of transport properties of liquid mixtures is approached from a rather different point of view. Azeotropic and near-azeotropic mixtures are treated as pure compounds rather than as a combination of several pure substances. This is now possible, having developed a single, specialized formula for both the liquid thermal conductivity and the dynamic viscosity. The prediction method requires the knowledge of only a few equilibrium properties of the mixture to be analyzed and thus is a simple and powerful tool for the evaluation of alternative refrigerants. Each formula has been tested against experimental data and shows deviations below those required for engineering purposes. Important results have also been achieved on applying the same equations to quasi-azeotropic mixtures with deviations comparable to those for azeotropic mixtures.
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  • 41
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    International journal of thermophysics 20 (1999), S. 149-161 
    ISSN: 1572-9567
    Keywords: viscosity ; thermal conductivity ; rough-hard-sphere ; refrigerants ; refrigerant mixtures
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    Notes: Abstract Two methods are presented for the correlation and prediction of the viscosities and thermal conductivities of refrigerants R11, R12, R22, R32, R124, R125, R134a, R141b, and R152 and their mixtures. The first (termed RHS1) is a modified rough-hard-sphere method based on the smooth hard-sphere correlations of Assael et al. The method requires two or three parameters for characterizing each refrigerant but is able to correlate transport properties over wide ranges of pressure and temperature. The second method (RHS2) is also a modified rough-hard-sphere method, but based on an effective hard-sphere diameter for Lennard–Jones (LJ) fluids. The LJ parameters and the effective hard-sphere diameter required in this method are determined from a knowledge of the density–temperature behavior of the fluid at saturation. Comparisons with the rough-hard-sphere method of Assael and co-workers (RHS3) are shown. We also show that the RHS2 method can be used to correlate as well as predict the transport properties of refrigerants.
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  • 42
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    Keywords: aqueous solutions ; density ; high pressure ; parallel-plate method ; salt ; thermal conductivity ; water
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    Notes: Abstract Accurate high-pressure thermal conductivity measurements have been performed on H2O+SrCl2 and H2O+Sr(NO3)2 mixtures at pressures up to 100 MPa over a temperature range between 293 and 473 K using a parallel-plate apparatus. The concentrations studied were 0.025, 0.05, 0.10, 0.15, and 0.20 mass fraction of the salts. The estimated accuracy of the method is about ±1.6%. The pressure, temperature, and concentration dependences of the thermal conductivity have been studied. Measurements were made on six isobars, namely, 0.1, 20, 40, 60, 80, and 100 MPa. The thermal conductivity shows a linear dependence on pressure and concentration for all isotherms. Along each isobar, a given concentration shows the thermal-conductivity maximum at a temperature of about 413 K. The measured values of thermal conductivity at atmospheric pressure are compared with the results of other investigators. Literature data at atmospheric pressure reported by Ridel and by Zaitzev and Aseev agree with our thermal conductivity values within the estimated uncertainty.
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  • 43
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    Keywords: absorption measurements ; laser damage ; optical properties ; photothermal measurements ; thermal conductivity ; thermophysical properties ; thin-film properties
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    Notes: Abstract Perspectives and limits of the application of the photothermal technique are given for the measurement of absorption, thermal, and thermoelastic properties in thin films. The peculiarities of this technique in the frequency and time domains are discussed in some detail, and selected important results with respect to laser damage studies in optical coatings are pointed out. Emphasis is placed on the absolute measurement of both optical and thermophysical properties in dielectric materials in thin-film form and, also, on the influence of both absorption and changed thermal properties in thin films on their thermally induced laser damage resistance.
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  • 44
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    Keywords: critical phenomena ; parallel-plate method ; thermal conductivity
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    Notes: Abstract A description is presented of the construction and operating procedure of an improved guarded parallel-plate instrument for measuring the thermal conductivity of fluids in the critical region. With the improved arrangement, it has been possible to reduce the temperature differences across the fluid layer between the two horizontal plates to values as low as 0.3 mK, thus allowing the thermal conductivity of fluids to be measured at temperatures as close as 20 mK to the critical temperature. The instrument has been used to measure the thermal conductivity of methane and of a mixture of methane and ethane in the close vicinity of the critical point.
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  • 45
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    International journal of thermophysics 20 (1999), S. 1379-1401 
    ISSN: 1572-9567
    Keywords: coaxial cylinders ; HFC-134a ; high pressure ; high temperature ; refrigerant ; thermal conductivity
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    Notes: Abstract Measurements of the thermal conductivity of HFC-134a made in a coaxial cylinder cell operating in steady state are reported. The measurements of the thermal conductivity of HFC-134a were performed along several quasi-isotherms between 300 and 530 K in the gas phase and the liquid phase. The pressure ranged from 0.1 to 50 MPa. Based on the experimental data, a background equation is provided to calculate the thermal conductivity outside the critical region as a function of temperature and pressure. A careful analysis of the various sources of errors leads to an estimated uncertainty of ±1.5%.
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  • 46
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    International journal of thermophysics 20 (1999), S. 677-690 
    ISSN: 1572-9567
    Keywords: liquid metals ; liquid alloys ; Lorenz relation ; resistivity ; thermal conductivity
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    Notes: Abstract A four-probe dc technique for measuring liquid-metal electrical resistivities has been developed, and liquid-resistivity measurements on gallium, tin, lead, copper, a lead tin alloy, a copper tin alloy, and a zinc alloy have been presented. The Lorenz relation has been used to calculate thermal conductivities from these resistivity measurements. The thermal conductivities calculated from these resistivity measurements are (where data are available) in good agreement with recommended liquid-metal thermal conductivities.
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  • 47
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    International journal of thermophysics 20 (1999), S. 691-707 
    ISSN: 1572-9567
    Keywords: Composites ; flash method ; orthotropic ; thermal conductivity ; thermal diffusivity ; transient technique
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    Notes: Abstract A generalization of the radial flash technique is presented whereby the thermal diffusivity of an orthotropic solid is measured in directions parallel and perpendicular to the flash source. The theoretical formulation is based on a Green's function approach which assumes a general orthotropic solid with three mutually orthogonal thermal diffusivities (or conductivities). Using this approach, a solution to this problem is presented which can be used to develop solutions for arbitrary pulse waveforms and incident geometries. Analytical and numerical results are presented for two-dimensional and three-dimensional cases of finite and semiinfinite solids. Characteristic equations which describe the ratio of the temperatures at two points along a principal axis are given. The equations show excellent agreement with numerical predictions as well as experimental results. A parameter estimation approach is given which improves on the accuracy of the radial flash technique in the determination of thermal diffusivity from experimental data.
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  • 48
    ISSN: 1572-9567
    Keywords: heat capacity ; high-speed pyrometry ; laser flash ; laser heating, graphite ; thermal conductivity ; thermal diffusivity ; uranium dioxide ; zirconia
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    Notes: Abstract This paper presents a new experimental technique enabling thermophysical measurements to be carried out at very high temperatures in a very simple and small pressurized vessel in which the sample is heated by a continuous wave laser, and subsequently subjected to a short temperature pulse. The adopted method is essentially an extension of the “laser-flash” technique, widely used for thermal diffusivity measurements, whereby, in addition, the heat capacity and, hence, the thermal conductivity, λ, are simultaneously evaluated from the pulse analysis. Results are presented for the thermal diffusivity and heat capacity of graphite, zirconia, and uranium dioxide up to temperatures above 3000 K.
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  • 49
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    International journal of thermophysics 20 (1999), S. 1417-1424 
    ISSN: 1572-9567
    Keywords: HFC-32/125/134a ; refrigerant ; R-407C ; ternary mixture ; thermal conductivity ; transient hot-wire method
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    Notes: Abstract The liquid thermal conductivity of two ternary mixtures of HFC-32/125/134a (23.0/25.0/52.0 and 19.0/43.8/37.2 wt%) was measured using a transient hot-wire instrument in the temperature ranges from 193 to 293 K and from 213 to 293 K, respectively, and in the pressure range from 2 to 30 MPa. The thermal conductivity has an estimated uncertainty of ±0.7%. For engineering purposes, the thermal conductivity data were correlated using a polynomial in temperature and pressure for each mixture with a standard deviation of 0.6%.
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    International journal of thermophysics 20 (1999), S. 237-245 
    ISSN: 1572-9567
    Keywords: critical properties ; data bank ; density ; diffusion coefficients ; evaluated data ; organic mixtures ; solubility ; surface tension ; thermal conductivity ; viscosity
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    Topics: Physics
    Notes: Abstract DIPPR Project 882 was organized to develop a computerized databank of selected and evaluated physical, thermodynamic, and transport properties for mixtures of primarily organic compounds. The properties include: liquid viscosities, liquid thermal conductivities, mutual diffusion coefficients, excess volumes and densities, surface tensions, critical temperatures, critical pressures and densities, and solubilities of sparingly soluble organic compounds. The collection is not complete. It is estimated that the complete collection covers about 90% of the mixture classes, contains about 85% of the binary systems published, references about 80% of the data sources, and is a repository for about 85% of all the data published (these estimates exclude density and solubility where the coverage was not intended to be comprehensive). Exhaustive literature searches were made. The data from the original literature were assessed and differences from the pure component values derived from the DIPPR Project 801 and other reliable evaluated data sources for pure compounds were noted. In cases where the differences were excessive, the data sets were rejected. The total collection consists of about 2140 mixture/property pairs covering 361 mixture classes. The results of the project are distributed as five books in the series Transport Properties and Related Thermodynamic Data of Binary Mixtures published by the American Institute of Chemical Engineers and in electronic form as the DIPMIX Database on Transport Properties and Related Thermodynamic Data for Binary Mixtures distributed by the Thermodynamics Research Center.
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    International journal of thermophysics 19 (1998), S. 379-389 
    ISSN: 1572-9567
    Keywords: energy conservation equations ; finite-element method ; high-thermal diffusivity fluids ; low-density measurements ; thermal conductivity ; transient hot-wire
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    Notes: Abstract The measurement of the thermal conductivity of a fluid by means of the transient hot-wire technique so far has made use of an analytical solution of the energy conservation equation for an ideal model, coupled with a set of approximate analytical corrections to account for small departures from the model. For this solution to be valid, constraints were always imposed on the experimental conditions and the construction of the apparatus, resulting in an inability to measure the thermal conductivity of high-thermal diffusivity fluids. In this paper, the set of energy conservation equations describing the transient hot-wire apparatus is solved using the numerical finite-element method. Because no approximate solutions are involved, this provides a much more general treatment of the heat transfer processes taking part in the real experiment, removing all the aforementioned constraints. In the case of the measurement of the thermal conductivity of liquids (fluids with low thermal-diffusivity values), the numerical solution fully agrees with the existing analytical solution. In the case of the measurement of the thermal conductivity of gases, the present solution allows the extension of the application of the transient hot-wire technique to experimental conditions where the value of the thermal diffusivity of the fluid is high.
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    International journal of thermophysics 19 (1998), S. 437-448 
    ISSN: 1572-9567
    Keywords: alkanes ; carbon dioxide ; diffusion ; mixtures ; molecular dynamics ; thermal conductivity ; viscosity
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    Notes: Abstract Equilibrium molecular dynamics simulations of mixtures of n-decane with methane, ethane, and carbon dioxide and of the mixture carbon dioxide–ethane were performed using the anisotropic united atoms model for n-decane and one-and two-center Lennard–Jones models for the light components. The Green–Kubo relations were used to calculate the viscosity, thermal conductivity, and inter- and intradiffusion. Viscosities are predicted with a maximum deviation of 30% at low gas concentrations and less than 10% deviation at high gas concentrations. The viscosity and thermal conductivity are less sensitive to the cross interactions than the diffusion coefficients, which exhibit deviations between models and with experiments of up to 60%.
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    International journal of thermophysics 19 (1998), S. 749-759 
    ISSN: 1572-9567
    Keywords: aqueous solutions ; capillary-rise method ; surface tension ; thermal conductivity ; transient hot-wire method ; viscosity
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    Topics: Physics
    Notes: Abstract Measurements of the surface tension, viscosity, and thermal conductivity of LiBr and LiSCN aqueous binary solutions have been performed to determine the thermophysical properties near the equilibrium freezing temperature. A differential capillary-rise method for surface tension and the transient hot-wire method for thermal conductivity were employed. Furthermore, a rotational viscometer was utilized for the measurement of viscosity. Correlation equations for the data of the aqueous binary test solutions as a function of temperature and concentration are presented.
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    International journal of thermophysics 19 (1998), S. 15-25 
    ISSN: 1572-9567
    Keywords: aqueous solution ; diffraction ; laser-induced thermal grating ; sodium chloride ; thermal conductivity ; thermal diffusivity
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    Notes: Abstract The laser-induced thermal grating technique was used to determine the thermal diffusivity of aqueous solutions of sodium chloride. In comparison with conventional measurement methods, this noninvasive optical technique has the advantage that no sensors need to be inserted in the sample. Therefore, this technique is especially suitable for the measurement of electrically conducting and corrosive liquids. The aqueous solutions studied have weight fractions of 5, 10, 15, and 20% sodium chloride. Measurement results for the thermal diffusivity are presented for aqueous solutions of sodium chloride in the temperature range 293 to 373 K at atmospheric pressure.
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  • 55
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    International journal of thermophysics 19 (1998), S. 415-425 
    ISSN: 1572-9567
    Keywords: HFC-32 ; HFC-125 ; HFC-134a ; melting point ; refrigerant ; thermal conductivity ; transient hot-wire method
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    Topics: Physics
    Notes: Abstract Measurements of the thermal conductivity of HFC-32, HFC-125, and HFC-134a were carried out for the first time in both solid and liquid phases at the saturation pressure at room temperature and in the temperature ranges from 120 to 263, from 140 to 213, and from 130 to 295 K, respectively. A transient hot-wire instrument using one bare platinum wire was employed for measurements, with an uncertainty of less than ±2%. The experimental results demonstrated that the thermal conductivity of HFC-32, HFC-125, and HFC-134a in the solid phase showed a positive temperature dependence. For HFC-32 and HFC-125, there were big jumps between the solid and the liquid thermal conductivity at the melting point. But for HFC-134a, the solid and liquid thermal conductivity at the melting point is almost-continuous.
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  • 56
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    International journal of thermophysics 19 (1998), S. 511-523 
    ISSN: 1572-9567
    Keywords: chemical vapor deposition (CVD) diamond ; phonon scattering ; specific heat ; thermal conductivity ; thermal diffusivity
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    Topics: Physics
    Notes: Abstract The thermal conductivity κ of natural, gem-quality diamond, which can be as high as 2500 Wm−1 K−1 at 25°C, is the highest of any known material. Synthetic diamond grown by chemical vapor deposition (CVD) of films up to 1 mm thick exhibits generally lower values of κ but under optimal growth conditions it can rival gem-quality diamond with values up to 2200 Wm−1 K−1. However, it is polycrystalline and exhibits a columnar microstructure. Measurements on free-standing CVD diamond, with a thickness in the range 25–400 μm, reveal a strong gradient in thermal conductivity as a function of position z from the substrate surface as well as a pronounced anisotropy with respect to z. The temperature dependence of κ in the range 4 to 400 K has been analyzed to determine the types and numbers of phonon scattering centers as a function of z. The defect structure, and therefore the thermal conductivity, are both correlated with the microstructure. Because of the high conductivity of diamond, these samples are thermally thin. For example, laser flash data for a 25-μm-thick diamond sample is expected to be virtually the same as laser flash data for a 1-μm-thick fused silica sample. Several of the techniques described here for diamond are therefore applicable to much thinner samples of more ordinary material.
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  • 57
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    International journal of thermophysics 19 (1998), S. 615-624 
    ISSN: 1572-9567
    Keywords: photothermal deflection ; thermal conductivity ; thin film
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    Topics: Physics
    Notes: Abstract A three-dimensional theoretical model has been developed to calculate the normal probe beam deflection of the obliquely crossed photothermal deflection configuration in samples which consist of thin films deposited on substrates. Utilizing the dependence of the normal component of probe beam deflection on the cross-point position of the excitation and probe beams, the thermal conductivity of the thin film can be extracted from the ratio of the two maxima of the normal deflection amplitude, which occurs when the cross-point is located near both surfaces of the sample. The effects of other parameters, including the intersect angle between the excitation and the probe beams in the sample, the modulation frequency of the excitation beam, the optical absorption and thickness of the thin films, and the thermal properties of substrates on the thermal conductivity measurement of the thin film, are discussed. The obliquely crossed photothermal deflection technique seems to be well suited for thermal conductivity measurements of thin films with a high thermal conductivity but a low optical absorption, such as diamond and diamond-like carbon, deposited on substrates with a relatively low thermal conductivity.
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  • 58
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    International journal of thermophysics 19 (1998), S. 969-981 
    ISSN: 1572-9567
    Keywords: electrical resistivity ; enthalpy ; high temperature ; liquid alloys ; rhenium alloy ; specific heat ; thermal conductivity ; thermal diffusivity ; tungsten alloy
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    Topics: Physics
    Notes: Abstract In earlier experiments we have studied pure elements with a fast pulse heating technique to obtain thermophysical properties of the liquid state. We report here results for thermophysical properties such as specific heat and dependences among enthalpy, electrical resistivity, and temperature, for four W–Re alloys (3.95, 21.03, 23.84, and 30.82 at % of Re) in a wide temperature range covering solid and liquid states. Thermal conductivity is calculated using the Wiedemann–Franz law for the liquid alloy, as.well as data for thermal diffusivity for the beginning of the liquid phase. Additionally, data for the entire temperature range studied have been analyzed in comparison with those of the constituent elements, tungsten and rhenium, since both metals have been studied previously with the same experimental technique. Such information is of interest in the field of metallurgy since W–Re alloys of low Re content in the region of mutual component solubility in the solid state are widely used as thermocouple materials for the purposes of high-temperature thermometry.
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  • 59
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    Keywords: critical state ; electron concentration ; lead ; shock compression ; spectroscopy ; thermal conductivity
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    Notes: Abstract Experiments were performed to investigate the behavior of lead near its critical point. Emission spectra of shocked lead samples during unloading into helium at different initial pressures were measured by an optical multichannel analyzer (OMA), as well as by a fast optical pyrometer. To describe the obtained experimental data, a model of a thin mixture layer was suggested, in which helium emits due to the presence of external electrons from lead.
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  • 60
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    International journal of thermophysics 19 (1998), S. 1229-1238 
    ISSN: 1572-9567
    Keywords: food properties ; Peltier effect ; thermal conductivity ; thermoelectric heat pump ; tropical foods
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    Topics: Physics
    Notes: Abstract The objective of this work was to test a novel experimental technique to determine the thermal conductivity of low-thermal conductivity materials and tropical foods. The experimental method was based on the Peltier effect and its application to the thermoelectric heat pump. This device became practical recently with the development of semiconductor thermocouple materials. The module assembly used in this work had 127 thermocouples connected in series electrically and in parallel thermally. The heat transfer area of the module was 3.96×3.96 cm2. The equipment was calibrated using standard materials of known thermal conductivity: Plexiglas and Bakelite. Then the κ values were easily computed from a steady-state energy balance equation.
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  • 61
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    International journal of thermophysics 19 (1998), S. 1239-1251 
    ISSN: 1572-9567
    Keywords: criterion of homogeneity ; dispersed composites ; finite element method (FEM) ; laser flash method ; thermal conductivity ; thermal diffusivity ; steady-state comparison method
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    Topics: Physics
    Notes: Abstract The effective thermal conductivity of dispersed composites with a hot-melt-adhesive matrix, measured using the steady-state method, is compared with the apparent thermal conductivity calculated from the average heat capacity and from the thermal diffusivity measured by the laser-flash method. The transient effect has been observed obviously at higher volume percentages for various dispersed particle sizes and ratios of the thermal conductivity values of dispersed and continuous phases. All of the experimental results are compared with those calculated by existing models and by the finite element method (FEM). An attempt has been made to show how the criterion for the homogeneity of dispersed composites under transient conditions is affected by the percentages of dispersed phase, dispersed particle size, and ratio of the thermal conductivity values of dispersed and continuous phases.
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  • 62
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    International journal of thermophysics 19 (1998), S. 259-279 
    ISSN: 1572-9567
    Keywords: alumel ; chromel ; constantan ; thermal conductivity ; thermal diffusivity ; transient technique
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    Notes: Abstract A transient heating technique, improving the constant-rate-heating technique for the measurements of thermal diffusivities of metals, is proposed. For a physical model of a specimen to be measured, the transient heat-conduction equation was solved with some boundary conditions, and the solution obtained was used as the principle of the present transient heating technique for determining the thermal diffusivity of the specimen. Additionally, a thermal analysis was made to satisfy a boundary condition involved in the principle, that is, the condition of radiative thermal insulation at the two end surfaces of the specimen. To verify the validity of the present technique, the thermal diffusivity of iron, whose thermophysical properties are well-known, was measured with the same apparatus as used in our previous work, and the experimental results are discussed. Moreover, thermal diffusivities of thermocouple materials, namely, constantan, chromel, and alumel, were measured by the technique in the temperature range of 360 to 680 K.
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  • 63
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    International journal of thermophysics 19 (1998), S. 281-290 
    ISSN: 1572-9567
    Keywords: GaAs ; impurities ; phonons ; photothermal displacement technique ; semiconductors ; Si ; thermal conductivity ; thermal diffusivity
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    Topics: Physics
    Notes: Abstract Thermal conductivity and thermal diffusivity of Si and GaAs wafers were measured using the photothermal displacement technique, and the temperature dependence of these two quantities was investigated. Thermal diffusivity was obtained from the phase difference between the heating source and the signal, and thermal conductivity was determined from the maximum value of the signal amplitude in the temperature range 80 to 300 K. It was verified that an increase in doping concentration gives rise to a decrease in thermal conductivity at low temperatures. The experimental results obtained on samples with different types and doping concentrations are consistent with those expected from theoretical considerations.
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  • 64
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    International journal of thermophysics 19 (1998), S. 291-304 
    ISSN: 1572-9567
    Keywords: calorimetry ; emissivity ; high temperature ; specific heat capacity ; thermal conductivity
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    Topics: Physics
    Notes: Abstract Thermal radiation calorimetry has been applied to measure the thermal conductivity and the specific heat capacity of an isolated solid specimen simultaneously. The system, in which a disk-shaped specimen and a flat heater are mounted in a vacuum chamber with the specimen heated on one face by irradiation, is presented. A theoretical formulation of the simultaneous measurement at quasi-steady state is described in detail. Noncontact temperature measurement of both specimen surfaces has been performed using pyrometers and a thermocouple set in the gap between the heater and the specimen. Pyroceram 9609 specimens, whose surfaces were blackened with colloidal graphite, were used in the measurement. The largest error involved in the noncontact temperature measurement is ±2°C in the range from 450 to 650°C. The resultant values of the specific heat capacity and the thermal conductivity deviate by about 10% from the recommended values for the Pyroceram specimen.
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  • 65
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    International journal of thermophysics 19 (1998), S. 931-939 
    ISSN: 1572-9567
    Keywords: adhesives ; coatings ; contact conductance ; thermal barrier coatings ; thermal conductivity ; thermal diffusivity ; thin films
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    Topics: Physics
    Notes: Abstract There is an intense and growing demand for knowledge of the thermal transport properties and contact conductances of coatings, thin films, and interfaces. The laser flash technique is uniquely suited for many of the measurements. The usefulness and limitations of this technique for coatings, greases, and joining techniques are described in some detail. Several alternate techniques, namely, step heating, multiproperty, and photoacoustic techniques, are briefly examined.
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  • 66
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    Keywords: analytical model ; glass ; laser-flash method ; radiative heat transfer ; thermal conductivity ; thermal diffusivity
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    Notes: Abstract We have developed an analytical model to determine the thermal diffusivity of nonscattering materials from samples with low optical thickness and opaque boundaries with arbitrary emissivities. The paper outlines the new analytical model and describes measurements on two samples: a microscope slide glass and a high-grade fused quartz plate. Results show that the new model applied to measurements on gold- or graphite-coated samples leads to the same results as if a conventional model is used on gold-coated samples.
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    International journal of thermophysics 19 (1998), S. 557-567 
    ISSN: 1572-9567
    Keywords: photothermal method ; scanning laser ; thermal conductivity ; thermal diffusivity ; thermoelectric effect ; thin film
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    Notes: Abstract This work presents a scanning laser-based thermal diffusivity measurement technique for thin films as well as for bulk materials. In this technique, a modulated laser beam is focused through a transparent substrate onto the film–substrate interface. The generated thermal wave is detected using a fast-responding thermocouple formed between the sample surface and the tip of a sharp probe. By scanning the laser beam around the thermocouple, the amplitude and phase distributions of the thermal wave are obtained with micrometer resolution. The thermal diffusivity of the film is determined by fitting the obtained phase signal with a three-dimensional heat conduction model. Experimental results are presented for a 150-nm gold film evaporated on a glass substrate.
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  • 68
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    International journal of thermophysics 19 (1998), S. 595-601 
    ISSN: 1572-9567
    Keywords: liquid crystals ; phase transitions ; photopyroelectric technique ; thermal conductivity
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    Notes: Abstract The photopyroelectric technique has been used to measure simultaneously the specific heat, the thermal conductivity, and the thermal diffusivity of 9CB liquid crystal in the temperature range 35 to 60°C, where the sample undergoes a weakly first-order phase transition and a second-order one. Measurements of the anisotropy of the thermal conductivity have also been performed, and the data have been used to establish the order of the above-mentioned phase transitions. Pretransitional effects in the isotropic phase in the thermal diffusivity have been found, and they have been associated with similar effects reported for the specific heat.
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  • 69
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    International journal of thermophysics 19 (1998), S. 1099-1109 
    ISSN: 1572-9567
    Keywords: photoacoustic detector ; thermal conductivity ; thermal diffusivity
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    Notes: Abstract A resonant and a nonresonant photoacoustic detector were used to determine thermal diffusivities of gases. With a nonresonant detector thermal diffusivities can be determined in a wide range between 10−3 and 10−7 m2·s−1, whereas experiments with the resonant detector deliver thermal diffusivities in a range that is about a factor of 100 smaller. As refrigerants—HFCs, HCFCs, and hydrocarbons—are absorbents in the infrared at a wavelength of 3.39 μm, their thermal diffusivity can be determined without the addition of a trace gas, particularly at pressures below 0.01 MPa. At pressures above 0.1 MPa, the addition of ammonia as a trace gas is recommended. The absorption wavelength is then 1.531 μm. A simulation model for the nonresonant photoacoustic detector is presented for the design of a detector and for an extended error analysis.
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    Applied mathematics and mechanics 18 (1997), S. 211-220 
    ISSN: 1573-2754
    Keywords: composite ; thermal conductivity ; inhomogeneous interphase ; Mori-Tanaka method
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Mathematics , Physics
    Notes: Abstract Thermal conductivities of carbon/carbon fiber composites with inhomogeneous interphase are studied in thtis paper. The inhomogeneous interphase is modeled approximately as a multilayered structure consisting of many thin layers having homogeneous properties, and close-formed solution of the effective conductivities of the composites is obtained by using the Mori-Tanaka mean-field concept.
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    Journal of statistical physics 82 (1996), S. 1453-1466 
    ISSN: 1572-9613
    Keywords: Kinetic theory ; thermal conductivity ; molecular dynamics ; hard disks ; Enskog's Theory
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    Topics: Physics
    Notes: Abstract The phenomenon of heat conduction in a two-dimensional gas ofN hard disks is studied in the hydrostatic regime by means of nonequilibrium molecular dynamics (N ranging from 100 to 8000). For systems withN≥1500 the temperature and density profiles observed are in excellent agreement with the continuous theory, but the conductivityk differs from the one derived from Enskog's theory in a systematic way. This difference seems to slowly decrease with increasing density.
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  • 72
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    Rheologica acta 35 (1996), S. 103-109 
    ISSN: 1435-1528
    Keywords: Transport properties ; thermal conductivity ; FENE dumbbell model ; polymer solutions ; thermal diffusion
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The phase-space kinetic theory for polymeric liquid mixtures has been further developed for molecular models without internal constraints. The theory provides expressions for the mass, momentum, and energy fluxes, each of which may in general be influenced by concentration, velocity, and temperature gradients. To illustrate the use of these results, the thermal conductivity for a dilute polymer solution is derived; the FENE dumbbell model is used to describe the mechanical behavior of the polymer chains. The Hookean dumbbell results can be obtained by letting the “finite extensibility parameter” b tend to infinity.
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    International journal of thermophysics 17 (1996), S. 597-606 
    ISSN: 1572-9567
    Keywords: binary mixtures ; low temperatures refrigerants ; R22 ; R1426 ; R152a ; thermal conductivity ; transient method
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    Topics: Physics
    Notes: Abstract The paper presents the thermal conductivity of mixtures of liquid refrigerants, The group of systems studied consists of two binary mixtures of R22/R142b and R22/R152a. The measurements have been carried out in the temperature range 160–300 K for pressures From 0.2 to 8.0 MPa in a transient coaxial-cylinder instrument. The uncertainty of the thermal conductivity data is estimated to be ±2%. The experimental method and apparatus were validated by using the measurements of refrigerant R22. The results presented have been used to develop a correlation for the description of the thermal conductivity of refrigerants.
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  • 74
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    International journal of thermophysics 17 (1996), S. 561-571 
    ISSN: 1572-9567
    Keywords: alternative refrigerants ; difluoromethane (HFC-32) ; pentafluoroethane (HFC-125) ; 1,1,1-trifluoroethane (HFC-143a) ; dichloropentafluoropropanes (HCFC-225ca, HCFC-225cb) ; liquid phase ; thermal conductivity
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    Notes: Abstract Measurements ofthe thermal conductivity of five alternative refrigerants. namely, difluoromethane HFC-321. pentafluoroethane (HFC-125), 1,1,1-trifluoroethane (HFC-143a), and dichloropentafluoropropanes (HCFC-225ca and HCFC-225cb). are carried out in the liquid phase, The range of temperature is 253–324 K for HFC-32, 257–305 K for HFC-125, 268–314 K for HFC-134a. 267–325 K for HCFC-225ca, and 286–345 K for HCFC-225cb, The pressure rank is from saturation to 30 MPa, The reproducibility of the data is better than 0.5% and the accuracy of the data is estimated to be of the order of 1%. The experimental results for the thermal conductivity ofeach substance are correlated by an equation which is a function of temperature and pressure. A short discussion is given to the comparison of the present results with literature values for HFC-125, The saturated liquid thermal conductivity values of HFC-32. HFC-125, and HFC-143a are compared with those of chlorodifluoromethane (HCFC-22) and tetrafluoroethane (HFC-134a) and it is shown that the value of HFC-32 is highest, while that of HFC-125 is lowest, among these substances, The dependence of thermal conductivity on number of fluorine atoms among the refrigerants with the same number of carbon and hydrogen atoms is discussed.
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    International journal of thermophysics 17 (1996), S. 695-703 
    ISSN: 1572-9567
    Keywords: AC calorimetry ; CVD diamond film ; Debye phonon model ; grain boundary ; thermal conductivity ; thermal diffusivity ; U-process
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    Topics: Physics
    Notes: Abstract Diamond films 60 and 170 µm in thickness were grown by PACVD (plasma-assisted chemical vapor deposition) under similar conditions. The thermal diffusivity of these freestanding films was measured between 100 and 300 K using AC calorimetry. Radiation heat loss from the surface was estimated by analyzing both the amplitude and the phase shift of a lock-in amplifier signal. Thermal conductivity was calculated using the specific heat data of natural diamond. At room temperature, the thermal conductivity of the 60 and 170 υm films is 9 and 16 W-cm−1. K−1 respectively, which is 40–70% that of natural diamond, The temperature dependence of thermal conductivity of the CVD diamond films is similar to that of natural diamond, Phonon scattering processes are considered using the Debye model, The microsize of the grain boundary has a significant effect on the mean free path of phonons at low temperatures. The grain in CVD diamond film is grown as a columnar structure, Thus, the thicker film has the larger mean grain size and the higher thermal conductivity. Scanning electron microscopy (SEM) and Raman spectroscopy were used to study the microstructure of the CVD diamond films. In this experiment, we evaluated the quality of CVD diamond film of the whole sample by measuring the thermal conductivity.
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  • 76
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    International journal of thermophysics 17 (1996), S. 979-981 
    ISSN: 1572-9567
    Keywords: ceramics ; colloids composites ; conductivity ; pores ; resistivity ; thermal conductivity
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    Topics: Physics
    Notes: Abstract Previous approximations for the effective conductivity of a matrix with inclusions of low conductivity, and for the effective resistivity of a matrix with inclusions of high conductivity, are combined to give the effective conductivity when both types of inclusions are present. This applies, for example, to a ceramic which contains both pores and metallic inclusions.
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    International journal of thermophysics 17 (1996), S. 85-98 
    ISSN: 1572-9567
    Keywords: halocarbon refrigerants ; mixtures ; prediction method ; pure fluids ; saturated liquid state ; thermal conductivity
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    Topics: Physics
    Notes: Abstract A prediction method for the thermal conductivity of halocarbon refrigerants in the saturated liquid state in the reduced temperature range 0.3 to well above 0.9 is presented in this paper. The aim of the method is to present a very simple calculation of the transport property useful for engineering purposes. The method determines thermal conductivity as a sole function of the reduced temperature and requires the knowledge of a parameter dependent upon easily available physical constants characteristic of each compound. The method is validated against experimental data available in the literature, giving average absolute deviations which are usually less than 5%, with maximum absolute deviations generally less than 10%. An extension of the method to estimate thermal conductivity of binary mixtures is also presented, along with a comparison with the few experimental data available in the literature.
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    International journal of thermophysics 17 (1996), S. 239-252 
    ISSN: 1572-9567
    Keywords: metal matrix composites ; thermal conductivity ; titanium
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    Topics: Physics
    Notes: Abstract Thermal conductivity data are presented for titanium-based composites reinforced with 10 and 20%, by volume, of SiC and TiB2 particles and for a composite reinforced by 10%, by volume, of SiC short fibers. In each case the thermal conductivity of titanium would be expected to be enhanced by the presence of the reinforcement. Measurements were made on the composites both as fabricated and after heat treatment. The results clearly show that the thermal conductivity of the Ti-SiC is much lower than predicted and decreases still further after heat treatment. This is attributed to the production of an interfacial contact resistance as a result of crack generation in the reaction products. A smaller effect is noted in the Ti-TiB2 composites.
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  • 79
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    International journal of thermophysics 17 (1996), S. 253-261 
    ISSN: 1572-9567
    Keywords: flash method ; melts ; radiation correction ; slags ; three-layer analysis ; thermal conductivity ; thermal diffusivity
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    Topics: Physics
    Notes: Abstract A high-temperature measuring system has been developed to undertake measurements of thennal difusivity and specific heat up to 1900 K. The overall design allows measurements on solids to be undertaken using the accepted standard techniques and analytical procedures. The specific design for molten materials and especially slags is based on the differential threelayer technique utilizing a special cell which can be accomodated in the system. In this method, the liquid specimen is sandwiched between an upper inner platinum crucible and a lower outer platinum crucible, to provide a three-layered sandwich. A laser pulse irradiates the surface of the upper platinum crucible and the temperature response of the surface of the lower platinum crucible is observed. For the purpose of accurate measurement of specimen thickness at the measuring temperature, two runs are performed in which the thicknesses arel andl+°Dl, wherel is unknown butΔl can be set accurately with a built-in micrometer. The thermal difusivity is obtained through a curve-fitting method by a personal computer using a three-layer analysis with a correction for the radiative component based on the transparent body assumption. Following verification of the basic performance, using solids of known properties and water and ethanol, a continuous casting mixture has been evaluated. The initial results on the fluids are in good agreement with those in the literature.
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    International journal of thermophysics 17 (1996), S. 279-292 
    ISSN: 1572-9567
    Keywords: CFC-alternatives ; HCFC-141b ; HFC-125 ; thermal conductivity ; transient hot-wire method
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    Topics: Physics
    Notes: Abstract The liquid thermal conductivities of the CFC alternatives, HFC-125, and HCFC-141b measured by a transient hot-wire apparatus with one bare platinum wire are reported in the temperature ranges from 193 to 333 K (HFC-125, CHF2, CF3) and from 193 to 393 K (HCFC-141b,CCI2F-CF3), in the pressure ranges from 2 to 30 MPa (HFC-125) and from 0.1 to 30 MPa (HCFC-141b), respectively. The results have been estimated to have an accurancy of ±0.5%. The liquid thermal conductives obtained have been correlated by a polynomial of temperature and pressure which can represent the experimental results within the standard deviations of 0.49% for HFC-125 and 0.46% for HCFC-141b, respectively.
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    International journal of thermophysics 17 (1996), S. 293-328 
    ISSN: 1572-9567
    Keywords: 2,2-dichloro-1,1,1-trifluoroethane ; HCFC-123 ; R123 ; thermal conductivity ; thermal diffusivity ; transport properties ; viscosity
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    Topics: Physics
    Notes: Abstract The thermal conductivity and the viscosity data of CFC alternative refrigerant HCFC-123 (2,2-dichloro-1,1,1-trifluoroethane: CHCI2-CF3) were critically evaluated and correlated on the basis of a comprehensive literature survey. Using the residual transport-property concept, we have developed the three-dimensional surfaces of the thermal conductivity-temperature-density and the viscosity-temperature-density. A dilute-gas function and an excess function of simple form were established for each property. The critical enhancement contribution was taken no account because reliable crossover equations of state and the thermal conductivity data are still missing in the critical region. The correlation for the thermal conductivity is valid at temperatures from 253 to 373 K, pressures up to 30 MPa, and densities up to 1633 kg m−3. The correlation for the viscosity is valid at temperatures from 253 to 423 K, pressures up to 20 MPa. and densities up to 1608 kg·m−3. The uncertainties of the present correlations are estimated to be 50% for both properties, since the experimental data are still scarce and somewhat contradictory in the vapor phase at present.
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  • 82
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    International journal of thermophysics 17 (1996), S. 731-757 
    ISSN: 1572-9567
    Keywords: 1,1-difluoroethane ; correlation ; critical region ; HFC-152a ; R152a ; thermal conductivity ; transport properties ; viscosity
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    Notes: Abstract Based on reliable. carefully selected data sets. equations for the thermal conductivity and the viscosity of the refrigerant R 112a are presented. They are valid at temperatures from 240 to 440 K, pressures up to 20 MPa. and densities up to 1050 kg · m−3. including the critical region.
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  • 83
    ISSN: 1572-9567
    Keywords: cobalt ; electrical resistivity ; low temperatures ; thermal conductivity
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    Notes: Abstract Thermal conductivity and electrical resistivity of 99.99% pure Co sample were measured in the temperature range 2.5–30 K. The annealing, procedure of the sample (either above or below Curie temperature), followed by cooling it down to room temperature at a slow cooling rate, caused an unexpected increase in its thermal resistivity and residual electrical resistivity, contrary to the results obtained for most pure metals. Co samples either not thermally treated or annealed consist only of a HI phase as proved by X-ray and electron diffraction analyses. The result, led to the conclusion that changes of grain structure and physical defects appearing in the Co at Curie temperature and at 690 K, when phase transitions take place, should be taken into account. The electron-magnon scattering, is significant in electrical conductivity but the electron-physical defect and impurity scattering plays a dominant role in thermal conductivity. The electron-physical defect and impurity scattering is elastic (validity of the Wiedemann Franz law)) as demonstrated by the value ofβ th β el = 1.0, obtained in this work.
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  • 84
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    International journal of thermophysics 17 (1996), S. 607-619 
    ISSN: 1572-9567
    Keywords: refrigerants ; pentafluoroethane ; dilluoromethane ; R32 ; R125 ; thermal conductivity ; transient hot-wire method ; transport properties
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    Topics: Physics
    Notes: Abstract Thermal conductivity measurements are reported for the new refrigerants pentafluoroethane (R125) and dilluoromethane (R32), which are suggested to replace chlorodifluoroethane (R22) as components of a mixture. Transient hot-wire experiments were performed which cover both the liquid and the vapor states at temperatures and pressures ranging fromt = −40 to 90°C and fromp = 1 to 60 bar. Uncertainties keep within 1.6% for liquid and 2.0% for vapor states, The results are correlated with density and temperature. In addition, temperature-dependent correlations are presented for practical calculations for (i) saturated liquid, (ii) saturated vapor, and (iii) dilute gas (which approximately equals the vapor state at ambient pressure). Finally, the results are compared with data from the literature and also with the respective thermal conductivities of R22.
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  • 85
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    International journal of thermophysics 17 (1996), S. 631-639 
    ISSN: 1572-9567
    Keywords: microgravity ; critical phenomena ; nonequilibrium ; transport properties ; thermal conductivity ; low temperatures ; superfluid helium ; thermometry ; superconducting instrumentation
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    Topics: Physics
    Notes: Abstract Although many well-controlled experiments have been conducted to measure the static properties of systems near criticality, few experiments have explored the transport properties in systems driven very far away from equilibrium as the transition occurs, Here we propose to measure the thermal gradient across the supertluid (HeII)—normal fluid (HeI interface in microgravity conditions as a function of the heat flux Q used to make the measurements, Microgravity conditions are required (1) to avoid the hydrostatic pressure variation along the height of the helium column t a concern forQ 〈 0.1 µW · cm−2), (2) avoid convection in He-1 forQ 〉 3 µW cm−2 in our apparatus, and (3) to increase theQ=0 interfacial width from its value of a few tens of microns on Earth to about a millimeter in orbit. New technologies described in this paper are under development for this experiment, which is in definition for Space Shuttle flight.
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  • 86
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    International journal of thermophysics 17 (1996), S. 1151-1161 
    ISSN: 1572-9567
    Keywords: alloys ; density ; electrical resistivity ; enthalpy ; heat capacity ; high temperatures ; surface tension ; thermal conductivity ; thermal diffusivity ; viscosity
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    Topics: Physics
    Notes: Abstract Data on the physical properties of alloys at high temperatures are urgently needed for the mathematical modeling of high-temperature processes such as casting, welding, secondary refining, dip melting, spray forming, and metal powder production. Data are required for those properties which are involved in heat and fluid flow in high-temperature processes. Levitated drop methods have been adopted to measure the surface tensions, densities, and enthalpies of commercial alloys, and rapid, transient methods have been developed to measure thermal conductivities to avoid the problem of convection. The results obtained for the properties of commercial alloys for the liquid and “mushy” states are discussed.
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  • 87
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    International journal of thermophysics 17 (1996), S. 1191-1201 
    ISSN: 1572-9567
    Keywords: drop shaft ; levitation ; microgravity ; surface tension ; thermal conductivity
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    Topics: Physics
    Notes: Abstract The effectiveness of 10-s microgravity on thermophysical property measurements on molten materials, such as molten semiconductors, is discussed. The thermal conductivity of molten InSb was successfully measured under microgravity conditions on board the German sounding rocket TEXUS and in a drop shaft in Hokkaido, Japan. Surface tension measurements using an oscillating drop method was attempted in low gravity using a parabolic flight of the NASA KC-135 aircraft. Combined levitation and microgravity, which can provide a contamination-free and undercooled condition. is recommended as a novel approach to obtain missing thermophysical property data on undercooled melts of semiconductors.
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  • 88
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    Journal of superconductivity 8 (1995), S. 445-448 
    ISSN: 1572-9605
    Keywords: High-T c superconductors ; thermal conductivity ; magnetization
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We have investigated heat conduction of single crystal Ba1−xKxBiO3 in the temperature range of 2–300 K and in a magnetic field of up to 6 Tesla. Temperature dependence of thermal conductivityκ(T) reveals the participation of both electrons and phonons with their relative contributions that depend critically on the potassium doping concentration. Crystals underdoped with potassium (samples with higherT c) exhibit a strong suppression ofκ and a glass-like temperature dependence. In contrast, those with a higher potassium content (lowerT c) show an increase as temperature decreases with a peak near 23 K. Field dependence ofκ(H) is also very sensitive to the level of potassium doping. Crystals exhibiting a large phonon contribution show an initial drop inκ(H) at low fields followed by a minimum and then a slow rise to saturation as the field increases. The initial drop is due to the additional phonon scattering by magnetic vortices as the sample enters a mixed state. The high field behavior ofκ(H), arising from a continuous break-up of Cooper pairs, exhibits scaling which suggests the presence of an unconventional superconducting gap structure in this material.
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  • 89
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    Journal of superconductivity 8 (1995), S. 449-452 
    ISSN: 1572-9605
    Keywords: thermal conductivity ; Andreev reflection ; vortex lines ; mixed phase
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The increased thermal conductivity below Tc in YBa2Cu3O7−x (YBCO) is shown to agree with the microwave electrical conductivity, affirming that increase is due to quasiparticle conduction The field dependence, particularly in the conducting plane permits us to separate phonon and quasiparticle contributions for both YBCO and Tℓ2Ba2CuO6 single crystals.
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  • 90
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    International journal of thermophysics 16 (1995), S. 63-78 
    ISSN: 1572-9567
    Keywords: R134a ; dilute gas ; refrigerant ; saturation properties ; 1,1,1,2-tetrafluoroethane ; thermal conductivity ; transport properties ; viscosity
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    Topics: Physics
    Notes: Abstract The paper contains a status report on an international project coordinated by the Subcommittee on Transport Properties of Commission 1.2 of the International Union of Pure and Applied Chemistry. The project has been conducted to investigate the large discrepancies between the results reported by various authors for the transport properties of R134a. The project has involved the remeasurement of the transport properties of a single sample of R134a in nine laboratories throughout the world in order to test the hypothesis that at least part of the discrepancy could be attributed to the purity of the sample. This paper provides an intercomparison of the new experimental results obtained to data in this project for the viscosity and the thermal conductivity in both gaseous and liquid phases. The agreement between the viscosity data from the laboratories contributing to the project was improved with several techniques, now producing consistent results. This suggests that the purity of the samples of R134a used in previous work was at least partly reponsible for the discrepancies observed. For the thermal conductivity in the liquid phase the results of the measurements are also more consistent than before, although not for all experimental techniques. Not all of the previous measurements suffered from significant sample impurities, so the present measurements on a consistent high-purity sample can he used to detect data sets which are outhers, possibly because of impurities. Identification of laboratories and techniques with systematic differences may require the examination of data for several fluids. The implications for future measurements of the transport properties of other refrigerants are significant.
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  • 91
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    International journal of thermophysics 16 (1995), S. 413-422 
    ISSN: 1572-9567
    Keywords: ethanol ; heptane ; nonane ; periodic techniques ; temperature ocillations ; thermal conductivity ; thermal dill'usivity ; water
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    Topics: Physics
    Notes: Abstract Simple temperature ocillation techniques are described for the last measurement of thermal dill'usivity and conductivity of liquids. The liquid specimen is a slab bounded above and below by a reference material. Two Peltier elements mounted on the outer Surfaces of the reference layers generate temperature ocillationS of these surfaces. Temperature waves propagate tluough the reference layers into the specimen. The thermal dilhusivity of the specimen is deduced by measuring all evaluating the amplitude attenuation and or the phase shift between the fundamental temperature oscillations at the surface of the liquid specimen and at a well-defined position inside the specimen. If the thermal diffusivity of the specimen is known. the thermal conductivity is determined by the measured amplitude attenuation and or the phase shill between the fundamental temperature oscillations at the surface of the reference layer and at the surface of the specimen. Slab and semi-infinite body geometries are considered. Measurement cells are designed and experiments are carried out with water, ethanol. heptane. monane. and glycerine. The results of the measurements of thermal dilhusivity asree very well, and those of thermal conductivity reasonably well, with the data obtained from the literature.
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  • 92
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    International journal of thermophysics 16 (1995), S. 195-204 
    ISSN: 1572-9567
    Keywords: ethane ; gas metering ; methane ; natural gas ; prediction ; thermal conductivity ; viscosity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The evaluation of the background transport properties of natural gas multicomponent mixtures over a moderate temperature and pressure range around ambient is considered in the context of the development of certifiable sensors for the measurement of mass and energy fluxes. The best available, theoretically based procedures to predict the properties are compared with experimental information to test the internal consistency, accuracy, and range of validity of the prediction. This is of primary concern to the demonstration of the viability of such sensors. It is shown that for low to moderate pressures, it is possible to achieve an internal consistency of the order of a few parts in a thousand and an accuracy of better than ± I %. At very high pressures the predictive scheme is also satisfactory, with errors of the order of a few percent. However, the procedure employed here systematically underestimates the thermal conductivity of the gas mixtures studied for intermediate pressures owing to the neglect of the critical enhancement even for temperatures quite far removed from the critical. The range of conditions for which the critical enhancement of the thermal conductivity is significant in mixtures is explored with data for binary mixtures of methane and ethane.
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  • 93
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    International journal of thermophysics 16 (1995), S. 821-829 
    ISSN: 1572-9567
    Keywords: a.c. calorimetry ; fluctuation effects ; specific heat ; superconductors ; thermal conductivity ; thermal diffusivity
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    Topics: Physics
    Notes: Abstract The specific heat and thermal conductivity measurements of YBa2Cu3O7−δ high-T c superconductors were performed by an a.c. calorimetry method. Investigations of the specific heat of YBa2Cu3O7−δ ceramics in magnetic fields show that an increase in the magnetic field reduces the jump in the specific heat, broadens the transition region, and shifts the transition temperature downward by about 0.5 K, Temperature dependence of the specific heat of a YBa2Cu3O7−σ high-T c superconducting ceramic reveals that fluctuation affect the specific heat near the superconducting transition, Critical exponentsα =α′ = 0.5, the critical amplitudesC + =C − = 0.5 J · mol−1 K−1, the space dimensionalityd = 3, and the number of components in the order parametern = 3 is calculated, The specific heat and the along-c-axis thermal conductivity of YBa2Cu,3O7−δ single crystal were simultaneously measured.
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  • 94
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    International journal of thermophysics 16 (1995), S. 121-131 
    ISSN: 1572-9567
    Keywords: dilluoromethane ; hydrolluorocarbon ; HFC-32 ; HFC-125 ; pentalluoroethane ; refrigerant ; thermal conductivity ; transient hot-wire method
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    Topics: Physics
    Notes: Abstract The gaseous thermal conductivity of dilluoromethane (HFC-32). pentalluoroethane (HFC-125). and their binary mixtures was measured with a transient hot-wire apparatus in the temperature ranges 283–333 K at pressures up to saturation. The uncertainty of the data is estimated to be within I %. The thermal conductivity as a function of composition of the mixtures at constant pressure and temperature is found to have a small maximum near 0.3–0.4 mole fraction of HFC-32. The gaseous thermal-conductivity data obtained for pure HFC-32 and HFC-125 were correlated with temperature and density together with the liquid thermal-conductivity data from the literature, based on the excess thermal-conductivity concept. The composition dependence of the thermal conductivity at a constant temperature is represented with the aid of the Wassiljewa equation.
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  • 95
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    International journal of thermophysics 16 (1995), S. 237-244 
    ISSN: 1572-9567
    Keywords: critical phenomena ; mixtures ; 2-n-butoxyelhanol ; thermal conductivity ; transient hot-wire ; water
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    Topics: Physics
    Notes: Abstract The thermal conductivity of binary liquid mixtures of water and 2-n-butoxyethanol has been measured within the temperature range 305–350 K at pressures up to 150 MPa. The measurements have been carried out with a transient hotwire instrument suitable for electrically conducting liquids and have an estimated accuracy of ±0.3%. The liquid mixture has a closed-loop solubility and reveals a lower critical solution temperature for a mole fraction of 2-n-butoxyethanol of 0.0478 at a temperature of 322.25 K. The results of the measurements reveal a small, but discernible, enhancement of the thermal conductivity of the solution at the critical composition.
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  • 96
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    International journal of thermophysics 16 (1995), S. 1069-1086 
    ISSN: 1572-9567
    Keywords: flow anisotropy ; forced Rayleigh scattering ; molten salts ; optical method ; polymers ; shear anisotropy ; thermal conductivity ; thermal diffusivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The experimental determination of thermophysical properties has been greatly improved by the introduction of laser technology. The laser beam is used for sensing and also for heating (or exciting) the specimen. The advantage of using a laser beam is most strongly felt in the measurement of the thermal conductivity or the thermal diffusivity, which are some of the most difficult properties to measure. Interesting features of new techniques for investigating various aspects of thermal conductivity in fluids and solids are reviewed. An optical method, the so-called forced Rayleigh scattering method, or the laser-induced optical-grating method, has been developed and used extensively by the present author's group. The method is a high-speed remote-sensing method which can also quantitatively detect anisotropy, namely, direction dependence of heat conduction in the material. It was used for determination of the thermal diffusivity and its anisotropic behavior for high-temperature materials such as molten salts, liquid crystals, extended polymer samples, and flowing polymer melts under shear. Interesting applications of the method were demonstrated also for thermal diffusivity “mapping” and microscale measurement.
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  • 97
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    International journal of thermophysics 16 (1995), S. 761-772 
    ISSN: 1572-9567
    Keywords: density ; high pressure ; refrigerants ; Tail equation ; thermal conductivity ; viscosity
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    Topics: Physics
    Notes: Abstract A recently developed scheme, based on considerations of hard-sphere theory, is used for the simultaneous correlation of the coefficients of viscosity and thermal conductivity for the refrigerants R11, R12, R22, R32. R124, R125, R134a, R141b, and R152a in excellent agreement with experiment, over extended temperature and pressure ranges. Values for the roughness factors and correlations for the characteristic volume are presented. The overall average absolute deviations of the experimental viscosity and thermal conductivity measurements from those calculated by the correlation are 2.1 and 2.3%, respectively, over a temperature range from 200 to about 10 K below the critical temperature and a pressure range from saturation to about 40 MPa. Since the proposed scheme is based on recent and accurate density values, a Tail-type equation was also employed to correlate successfully the density of the refrigerants. The overall average absolute deviation of the experimental density measurements from those calculated by the correlation is ±0.08%.
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  • 98
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    International journal of thermophysics 16 (1995), S. 851-865 
    ISSN: 1572-9567
    Keywords: high pressure ; refrigerants ; R32 ; R124 ; R125 ; R141b ; thermal conductivity ; transient hot-wire technique
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    Topics: Physics
    Notes: Abstract This paper reports measurements of the thermal conductivity of refrigerants R32, R124, R125, and R141b in the liquid phase. The measurements, covering a temperature range from 253 to 334 K and pressure up to 20 MPa, have been performed in a transient hotwire instrument employing two anodized tantalum wires. The uncertainty of the present thermal-conductivity data is estimated to be ±0.5%. The experimental data have been represented by polynomial functions of temperature and pressure for the purposes of interpolation. A comparison with other recent measurements is also included.
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    International journal of thermophysics 16 (1995), S. 1193-1201 
    ISSN: 1572-9567
    Keywords: R134a, R32 ; R32+R134a mixture ; thermal conductivity ; transient hot-wire method
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    Topics: Physics
    Notes: Abstract The liquid thermal conductivity of R32 (CH2F2) and R134a (CF3CH2F) was measured in the range from 223 to 323 K and from 2 to 20 MPa by the transient hot-wire method. The thermal conductivity of the R32+R134a mixture was also measured in the same range by varying the mass fraction of R32. The measured data are analyzed to obtain a correlation in terms of temperature, pressure and composition of the mixture. The uncertainty of our measurements is estimated to be within ±2%.
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  • 100
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    International journal of thermophysics 16 (1995), S. 1203-1211 
    ISSN: 1572-9567
    Keywords: guarded hot-plate apparatus ; polar refrigerant ; R22 ; R123 ; R134a ; R142b ; R143a ; R152a ; thermal conductivity
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    Topics: Physics
    Notes: Abstract The thermal conductivity of the refrigerants R22, R123, R134a, R142b, R143a, and R152a has been determined as a function of temperature in the range from 300 to 460 K. Measurements were carried out at atmospheric pressure with an improved guarded hot-plate apparatus. The width of the instrument's gas layer and the temperature difference across the metering section were varied to detect any stray heat transfer. Radiation correction factors were derived from IR absorption spectra. The uncertainty of the measurements is estimated to be 2% at a standard deviation of less than 0.1%. All values are correlated with respect to temperature in the range covered. The equations are found to represent the results with average deviations of 1%. Our data sets are compared with corresponding hot wire results. In contrast to the generally preferred hot wire technique, with its possible electrical and chemical interactions between the wire and the polar refrigerant, there are no such difficulties using a guarded hot-plate apparatus. Our data sets may thus contribute to the discussions on discrepancies in thermal conductivity values from various authors using hot wire as one particular method.
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