Showing papers in "International Journal of Thermophysics in 2003"

Equations of state for technical applications. III. Results for polar fluids

Abstract: New functional forms have been developed for multiparameter equations of state for non- and weakly polar fluids and for polar fluids. The resulting functional forms, which were established with an optimization algorithm which considers data sets for different fluids simultaneously, are suitable as a basis for equations of state for a broad variety of fluids. The functional forms were designed to fulfil typical demands of advanced technical application with regard to the achieved accuracy. They are numerically very stable and their substance-specific coefficients can easily be fitted to restricted data sets. In this way, a fast extension of the group of fluids for which accurate empirical equations of state are available is now possible. This article deals with the results found for the polar fluids CFC-11 (trichlorofluoromethane), CFC-12 (dichlorodifluoromethane), HCFC-22 (chlorodifluoromethane), HFC-32 (difluoromethane), CFC-113 (1,1,2-trichlorotrifluoroethane), HCFC-123 (2,2-dichloro-1,1,1-trifluoroethane), HFC-125 (pentafluoroethane), HFC-134a (1,1,1,2-tetrafluoroethane), HFC-143a (1,1,1-trifluoroethane), HFC-152a (1,1-difluoroethane), carbon dioxide, and ammonia. The substance-specific parameters of the new equations of state are given as well as statistical and graphical comparisons with experimental data. General features of the new class of equations of state such as their extrapolation behavior or their numerical stability and results for non- and weakly polar fluids have been discussed in preceding articles.

Equations of State for Technical Applications. I. Simultaneously Optimized Functional Forms for Nonpolar and Polar Fluids

Abstract: New functional forms for multiparameter equations of state have been developed for non- and weakly polar fluids and for polar fluids. The resulting functional forms, which were established with an optimization algorithm which considers data sets for different fluids simultaneously, are suitable as a basis for equations of state for a broad variety of fluids. With regard to the achieved accuracy, the functional forms were designed to fulfill typical demands of advanced technical application. They are numerically very stable, and their substance-specific coefficients can easily be fitted to restricted data sets. In this way, a fast extension of the group of fluids for which accurate empirical equations of state are available becomes possible. This article deals with characteristic features of the new class of simultaneously optimized equations of state. Shortcomings of existing multiparameter equations of state widely used in technical applications are briefly discussed, and demands on the new class of equations of state are formulated. Substance specific parameters and detailed comparisons are given in subsequent articles for the non- and weakly polar fluids (methane, ethane, propane, isobutane, n-butane, n-pentane, n-hexane, n-heptane, n-octane, argon, oxygen, nitrogen, ethylene, cyclohexane, and sulfur hexafluoride) and for the polar fluids (trichlorofluoromethane (CFC-11), dichlorodifluoromethane (CFC-12), chlorodifluoromethane (HCFC-22), difluoromethane (HFC-32), 1,1,2-trichlorotrifluoroethane (CFC-113), 2,2-dichloro-1,1,1-trifluoroethane (HCFC-123), pentafluoroethane (HFC-125), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,1-trifluoroethane (HFC-143a), 1,1-difluoroethane (HFC-152a), carbon dioxide, and ammonia) considered to date.

Density Determination of Liquid Copper, Nickel, and Their Alloys

Abstract: A method for the determination of the density of electromagnetically levitated metallic liquids has been developed. This method employs an enlarged beam of parallel laser light to produce a shadow image of the sample. The shadow is recorded by a digital CCD-camera, and the images are analyzed using an edge detection algorithm. The circumference is fitted by Legendre polynomials that can be used for calculations of the volume of the sample. The method has been tested successfully on various alloys of copper-nickel (Ni x Cu y ), as well as on the pure elements, Cu and Ni. Densities were measured for each sample at different temperatures below and above the melting point, and a linear behavior was observed. At the melting point the densities for copper and nickel were 7.9 and 7.93g⋅cm−3, respectively. For T=1270°C liquid copper has a density of 7.75g⋅cm−3 which strongly increases up to roughly 8.1g⋅cm−3 if a small amount (10–40 at.%) of nickel is added to the system. For nickel concentrations larger than 50at.% the density remains nearly constant.

Dielectric Permittivity of Eight Gases Measured with Cross Capacitors

Abstract: A four-ring, toroidal cross capacitor was used to measure accurately the relative dielectric permittivity e(p,T) of He, Ar, N2, O2, CH4, C2H6, C3H8, and CO2. (e is often called the “dielectric constant.”) The data are in the range from 0 to 50°C and, in many cases, extend up to 7 MPa. The accurate measurement of e(p,T) required a good understanding of the deformation of the gas-filled capacitors with applied pressure. This understanding was tested in two ways. First, the experimental values of e(p,T) for helium were compared with theoretical values. The average difference was within the noise, 〈e expt−e theory〉=(−0.05±0.21)×10−6, demonstrating that the four-ring cross capacitor deformed as predicted. Second, e(p,T) of argon was measured simultaneously on three isotherms using two capacitors: the four-ring capacitor, and a 16-rod cross capacitor made using different materials and a different geometry. The results for the two capacitors are completely consistent, within the specifications of the capacitance bridge. There was a small inconsistency that was equivalent to 1×10−6 of the measured capacitances, or, for argon, 3×10−5 A e , where A e is the zero-density limit of the molar polarizability ℘≡(e−1)/[(e+2)ρ].

Surface Tension and Density of Oxygen-Free Liquid Aluminum at High Temperature

Abstract: New values of densities ρ and surface tensions σ of liquid aluminum obtained in the range 1600 to 2360 K by contactless techniques in neutral gases are reported. Conditions for oxygen-free aluminum are fulfilled which allow determination of the surface tension of aluminum. Extrapolation to the melting point, T m = 933 K, confirms the value of σ (T = 933K) = 1.05 N ⋅ m−1.

Viscosity and liquid density of asymmetric hydrocarbon mixtures

Abstract: Although a large body of viscosity data exists for simple mixtures of lighter n-alkanes, available information for heavy or asymmetric systems is scarce. Experimental measurements of viscosity and liquid densities were performed, at atmospheric pressure, in pure and mixed n-heptane, n-hexadecane, n-eicosane, n-docosane, and n-tetracosane from 293.15 K, or above the melting point, up to 343.15 K. The measured densities were correlated using the Peng–Robinson equation of state, and viscosities were modelled using the friction theory.

Accurate determination of liquid viscosity and surface tension using surface light scattering (SLS): Toluene under saturation conditions between 260 and 380 K

Abstract: Earlier reported values of the liquid kinematic viscosity and surface tension of the reference fluid toluene between 263 and 383 K under saturation conditions from surface light scattering have been recalculated. For this, an improved data evaluation scheme based on an exact description of the hydrodynamic capillary wave problem for a liquid-vapor interface has been applied. The maximum adjustments amount to 0.9 and 0.6% for the liquid kinematic viscosity and surface tension, respectively. These changes are within the uncertainties as stated in our original work which demonstrates that for the surface light scattering technique a total uncertainty of better than 1.0% for both properties of interest also holds for the revised data of the present work. Thus, in spite of the additional complexity connected with this very precise data evaluation procedure presented here, the surface light scattering technique could still be used with less complexity for a reliable determination of surface tension and liquid kinematic viscosity with an accuracy comparable or even better than that of conventional methods. While almost all of these conventional methods determine viscosity and surface tension in a relative manner with two completely different sets of experimental equipment, for the surface light scattering technique no calibration procedure is needed and both properties can be determined simultaneously without any extra effort.

Analytical Equation of State for Solid-Liquid-Vapor Phases

Abstract: A simple analytical equation of state has been proposed for describing the phase behavior of three thermodynamic states (solid, liquid, and vapor) of matter. In terms of reduced parameters, it can be written as: $$P_{\text{r}} = \frac{{T_{\text{r}} }}{{V_{\text{R}} - b_{\text{R}} }}\left( {\frac{{V_{\text{R}} - d_{\text{R}} }}{{V_{\text{R}} - c_{\text{R}} }}} \right) - \frac{{a_{\text{R}} }}{{V_{\text{R}}^{\text{2}} }}.$$ Pr and Tr are reduced pressure and temperature with respect to the critical pressure (Pc) and temperature (Tc), respectively, while VR is a reduced molar volume defined as VR=PcV/RTc, where R is the universal gas constant. This may be regarded as an extension of the classical van der Waals's equation of state for fluid (liquid and vapor) only states. The four parameters, aR, bR, cR, and dR in this equation are free adjustable constants, and can be variable with temperature. The basic physical idea underlining the model is presented, and examples applied successfully to actual pure substances and mixtures are demonstrated. Also, applications to the hard-sphere model are examined. Further improvements, limitations, and possible applications of the present model are discussed.

Predicting, Measuring, and Tailoring the Transverse Thermal Conductivity of Composites from Polymer Matrix and Metal Filler

Abstract: The addition of conductive filler in a polymer matrix is an effective way to increase the thermal conductivity of the plastic materials, as required by several industrial applications. All quantitative models for the thermal conductivity of heterogeneous media fail for heavily filled composites. The percolation theory allows good qualitative predictions, thus selecting a range for some qualitative effects on the thermal conductivity, and providing a way to choose a range for some experimental parameters. The design of such composite materials requires a study of its thermal features combined with different mechanical, ecological, safety, technical, and economical restrictions. A specific small guarded hot plate device with an active guard, conductive grease layer, and controlled variable pressure was used for measurement of the transverse thermal conductivity on 15 mm sided samples of composite parts. Extensive thermal and composition measurements on filled thermoplastics show that the conductivity of the filler, its size and shape, and its local amount are, with the degree of previous mixing, the main factors determining the effective conductivity of composites. For injection-molded polybutylene terephtalate plates, the best filler is the short aluminum fiber. With fibers of 0.10 mm diameter, it is possible to obtain conductivities larger by factors of 2, 6, and 10 than those of polymer for aluminum contents of 20, 42, and 43.5 vol%, respectively.

Measurement of the Thermal Conductivity of Stainless Steel AISI 304L Up to 550 K

Abstract: New measurements of the thermal conductivity of stainless steel AISI 304L over the temperature range 300 to 550 K are reported. To perform the measurements, the transient hot-wire technique was employed, with a new wire sensor. The sensor makes use of a soft silicone paste material and of two thin polyimide films, between the hot wires of the apparatus and the stainless steel specimen. The transient temperature rise of the wire sensor is measured in response to an electrical heating step over a period of 40 μs to 2 s, allowing an absolute determination of the thermal conductivity of the solid, as well as of the polyimide film and the silicone paste. The method is based on a full theoretical model with equations solved by a two-dimensional finite-element method applied to the exact geometry. At the 95% confidence level, the standard deviation of the thermal conductivity measurements is 0.6%, while the standard uncertainty of the technique is less than 1.5%.

Pseudo-Pure Fluid Equations of State for the Refrigerant Blends R-410A, R-404A, R-507A, and R-407C

Abstract: Pseudo-pure fluid equations of state explicit in Helmholtz energy have been developed to permit rapid calculation of the thermodynamic properties of the refrigerant blends R-410A, R-404A, R-507A, and R-407C. The equations were fitted to values calculated from a mixture model developed in previous work for mixtures of R-32, R-125, R-134a, and R-143a. The equations may be used to calculate the single-phase thermodynamic properties of the blends; dew and bubble point properties are calculated with the aid of additional ancillary equations for the saturation pressures. Differences between calculations from the pseudo-pure fluid equations and the full mixture model are on average 0.01%, with all calculations less than 0.1% in density except in the critical region. For the heat capacity and speed of sound, differences are on average 0.1% with maximum differences of 0.5%. Generally, these differences are consistent with the accuracy of available experimental data for the mixtures, and comparisons are given to selected experimental values to verify accuracy estimates. The equations are valid from 200 to 450 K and can be extrapolated to higher temperatures. Computations from the new equations are up to 100 times faster for phase equilibria at a given temperature and 5 times faster for single-phase state points given input conditions of temperature and pressure.

Measurement of Specific Heat Capacity and Electrical Resistivity of Industrial Alloys Using Pulse Heating Techniques

Abstract: The determination of the specific heat capacity and electrical resistivity of Inconel 718, Ti-6Al-4V, and CF8M stainless steel, from room temperature to near the melting temperatures of the alloys, is described. The method is based on rapid resistive self-heating of a solid cylindrical specimen by the passage of a short-duration electric current pulse through it while simultaneously measuring the pertinent experimental quantities (i.e., voltage drop, current, and specimen temperature). From room temperature to about 1300 K, the properties are measured using an intermediate-temperature pulse-heating system by supplying a constant current from a programmable power supply and measuring the temperature using a Pt-Pt:13% Rh thermocouple welded to the surface of the specimen. From 1350 K to near the melting temperatures of the alloys, the properties are measured using a millisecond-resolution high-temperature pulse-heating system by supplying the current from a set of batteries controlled by a fast-response switching system and measuring the temperature using a high-speed pyrometer in conjunction with an ellipsometer, which is used to measure the corresponding spectral emissivity. The present study extends the application of these techniques, previously applied only to pure metals, to industrial alloys.

Phase (Liquid/Solid) Dependence of the Normal Spectral Emissivity for Iron, Cobalt, and Nickel at Melting Points

Abstract: Normal spectral emissivities of liquid and solid Fe, Co, and Ni have been determined at their melting points at wavelengths from 650 to 800 nm and from 1000 to 1900 nm using an apparatus that consists of a cold crucible and diffraction grating spectroscopes. For all three metals, the emissivities of the liquid phases are slightly larger than those of the solid phases both in the visible and near-infrared regions. For iron, the near-infrared emissivities decreased progressively with each additional measurement series and settled down after three series. A possible explanation to this behavior is offered. The present results for iron were assessed by comparisons with previously reported results and with predictions based upon the Hagen–Rubens relation for the ratio of the emissivity of the liquid to that of the solid (e Liquid/e Solid). The measured emissivities for all three metals are in good agreement with previous results at and near the melting point. The results for e Liquid/e Solid in the near-infrared region demonstrate that the phase (liquid/solid) dependence of the infrared emissivity is consistent with that of the dc resistivity for all the metals at their melting points.

The Viscosity of Seven Gases Measured with a Greenspan Viscometer

Abstract: The viscosity of seven gases (Ar, CH4, C3H8, N2, SF6, CF4, C2F6) was determined by interpreting frequency-response data from a Greenspan acoustic viscometer with a detailed model developed by Gillis, Mehl, and Moldover. The model contains a parameter ∈ r that characterizes the viscous dissipation at the ends of the viscometer's duct. It was difficult to determine ∈ r accurately from dimensional measurements; therefore, ∈ r was adjusted to fit the viscosity of helium on the 298 K isotherm (0.6 MPa

Thermodynamic Properties of Heavy n-Alkanes in the Liquid State: n-Dodecane

Abstract: A grid algorithm based on sound speed data, was used to calculate the thermodynamic properties of liquid n-dodecane. The density, isobaric expansion coefficient, isothermal compressibility, isobaric and isochoric heat capacities, enthalpy, and entropy of liquid n-dodecane were calculated in the range of temperatures from 293 to 433 K and pressures from 0.1 to 140 MPa. Coefficients of the Tait equation were determined in the above-identified range of parameters. A table of the thermodynamic properties of n-dodecane is presented.

PρT measurements of nonafluorobutyl methyl ether and nonafluorobutyl ethyl ether between 283.15 and 323.15 K at pressures up to 40 MPa

Abstract: In this paper, experimental densities for nonafluorobutyl methyl ether and nonafluorobutyl ethyl ether from 283.15 to 323.15 K at pressures up to 40 MPa are reported. The density measurements were performed by means of a high pressure vibrating tube densimeter. Data reliability was checked by comparing experimental results obtained for tetrachloromethane—whose density is close to those of the fluids studied—with recommended literature data. Furthermore, the isobaric thermal expansion, isothermal compressibility, and internal pressure have been calculated from these density data.

Development of Spectral Selective Multilayer Film for a Variable Emittance Device and Its Radiation Properties Measurements

Abstract: A smart radiation device (SRD) that is a variable emittance radiator has been developed as a thermal control material for spacecraft. The SRD has the unique feature of large variation of the total hemispherical emittance eH near room temperature. The eH of the SRD changes depending on its temperature. However, there is a drawback of a large solar absorptance αS. It is too large to use as a thermal control material for spacecraft. In order to reduce the large αS, spectral selective multilayer film was developed. This multilayer film reflects solar radiation and transmits far-infrared radiation to maintain the variation in the eH of the SRD. This paper presents thermal radiative properties of the SRD with spectral selective multilayer film. The multilayer film was designed by using a genetic algorithm (GA). The designed multilayer film was evaporated on the surface of the SRD by the electron beam evaporation method. The experimental results of αS and eH of the SRD with the multilayer film agreed well with calculated results.

Deviation from Wiedemann-Franz law for the thermal conductivity of liquid tin and lead at elevated temperature

Abstract: The thermal conductivities of tin and lead in solid and liquid states have been determined using a nonstationary hot wire method. Measurements on tin and lead were carried out over temperature ranges of 293 to 1473 K and 293 to 1373 K, respectively. The thermal conductivity of solid tin is 63.9±1.3 W⋅m−1⋅K−1 at 293 K and decreases with an increase in temperature, with a value of 56.6±0.9 W⋅m−1⋅K−1 at 473 K. For solid lead, the thermal conductivity is 36.1±0.6 W⋅m−1⋅K−1 at 293 K, decreases with an increase in temperature, and has a value of 29.1±1.1 W⋅m−1⋅K−1 at 573 K. The temperature dependences for solid tin and lead are in good agreement with those estimated from the Wiedemann–Franz law using electrical conductivity values. The thermal conductivities of liquid tin displayed a value of 25.7±1.0 W⋅m−1⋅K−1 at 573 K, and then increased, showing a maximum value of about 30.1 W⋅m−1⋅K−1 at 673 K. Subsequently, the thermal conductivities gradually decreased with increasing temperature and the thermal conductivity was 10.1±1.0 W⋅m−1⋅K−1 at 1473 K. In the case of liquid lead, the same tendency, as was the case of tin, was observed. The thermal conductivities of liquid lead displayed a value of 15.4±1.2 W⋅m−1⋅K−1 at 673 K, with a maximum value of about 15.6 W⋅m−1⋅K−1 at 773 K and a minimum value of about 11.4±0.6 W⋅m−1⋅K−1 at 1373 K. The temperature dependence of thermal conductivity values in both liquids is discussed from the viewpoint of the Wiedemann–Franz law. The thermal conductivities for Group 14 elements at each temperature were compared.

Thermal Diffusivity Measurements of Liquid Silicate Melts

Abstract: The effect of structure on the thermal diffusivities/conductivities for liquid silicates have been summarized based on recent experimental work carried out by the Royal Institute of Technology, Stockholm and the Tokyo Institute of Technology using the laser-flash and the hot-wire methods, respectively. In the former case, the effective thermal diffusivity was measured by a three-layer method. The relationship proposed by Mills that the thermal conductivity of silicates increases with a decrease in the ratio of NBO/T (number of non-bridging oxygens per tetrahedrally coordinated atom) has been well supported by the effective thermal diffusivity data for the liquid CaO-Al2O3-SiO2 slags. However, it has been shown that for the slags having a higher CaO/Al2O3 ratio, the effective thermal diffusivity is roughly constant independent of the ratios of NBO/T. It has been concluded that when the silicate network is largely broken down, the phonon mean free path is not affected by the structure. It has been found by the hot-wire method that the magnitudes of thermal resistivity are in the hierarchy Li2O-SiO2

PVTx Measurements and Partial Molar Volumes for Aqueous Li2SO4 Solutions at Temperatures from 297 to 573 K and at Pressures Up to 40 MPa

Abstract: Densities of four aqueous Li2SO4 solutions (0.0944, 0.2798, 0.6115, 0.8850 mol⋅kg−1) have been measured in the liquid phase with a constant-volume piezometer immersed in a precision liquid thermostat. Measurements were made for ten isotherms between 297 and 573 K. The range of pressure was from 3.9 to 40 MPa. The total uncertainty of density, pressure, temperature, and concentration measurements were estimated to be less than 0.06%, 0.05%, 10 mK, and 0.014%, respectively. The reliability and accuracy of the experimental method was confirmed with measurements on pure water for two isobars at 10 and 38 MPa. Experimental and calculated (IAPWS formulation) densities for pure water show excellent agreement within their experimental uncertainties (average absolute deviation within 0.02 to 0.05%). Saturated liquid densities were determined by extrapolating experimental P-ρ data to the vapor pressure at fixed temperature and composition using an interpolating equation. Apparent and partial molar volumes were derived using measured densities for aqueous solutions and pure water. Derived apparent molar volumes were extrapolated to zero concentration to yield partial molar volumes of electrolyte (Li2SO4) at infinite dilution. The temperature, pressure, and concentration dependences of partial and apparent molar volumes were studied. A polynomial type of equation of state for specific volume was obtained as a function of temperature, pressure, and composition by a least-squares method using the experimental data. The average absolute deviation (AAD) between measured and calculated values from this polynomial equation for density was 0.02%. Measured values of solution density, and apparent and partial molar volumes were compared with data reported in the literature by other authors.

Transient Behavior of a Thermoelectric Device Under the Hyperbolic Heat Conduction Model

Abstract: The major objective of this work is to describe the dynamic thermal behavior of thermoelectric generators and refrigerators under the effect of the hyperbolic heat conduction model. In practical situations, these devices work under transient operating conditions due to the time change in the imposed current, voltage, and hot or cold temperatures. Results for transient temperature distributions were obtained for different parameters. The coefficient of performance was obtained as a function of time for increasing current flow.

Effect of Heat Treatment on Thermal Conductivity of U-Mo/Al Alloy Dispersion Fuel

Abstract: The molybdenum content of fuel core whose matrix is aluminium 1060, was varied to be 7, 8, and 10 wt% and the volume fraction of U-Mo fuel powders was varied to be 10, 30, and 40 vol%. In this work, thermal conductivities were calculated from measured thermal diffusivities, specific heat capacities, and densities, which were determined using the laser flash, DSC, and Archimedes methods, respectively. The thermophysical properties were measured over a temperature range from room temperature to 500°C. The U-Mo alloy was annealed at between 525 and 550°C for 1 to 36 hours. At high temperature, the U-Mo particles were reacted with aluminium matrix as forming layers of (U-Mo)Al x . These reaction layers have been affected adversely by the thermal conductivity of fuel core. The thermal conductivities of annealed samples appeared to decrease with increasing volume fraction of the reaction layers.

New photopyroelectric technique for precise measurements of the thermal effusivity of transparent liquids

Abstract: A new photopyroelectric methodology for thermal effusivity measurements in transparent liquids is presented. The new methodology involves the thermally thick limit of the pyroelectric signal in the standard front-surface configuration. A signal normalization procedure, which avoids the conventional requirement for transfer function determination, is implemented. The thermal effusivity of five liquids was measured by means of this technique, and very good agreement was found with corresponding values reported in the literature.

Simultaneous Measurement of the Density and Viscosity of Compressed Liquid Toluene

Abstract: A vibrating-wire densimeter described previously has been used to perform simultaneous measurements of the density and viscosity of toluene at temperatures from 222 to 348 K and pressures up to 80 MPa. The density measurements are essentially based on the hydrostatic weighing principle, using a vibrating-wire device operated in forced mode of oscillation, as a sensor of the apparent weight of a cylindrical sinker immersed in the test fluid. The resonance characteristics for the transverse oscillations of the wire, which is also immersed in the fluid, are described by a rigorous theoretical model, which includes both the buoyancy and the hydrodynamic effects, owing to the presence of the fluid, on the wire motion. It is thus possible, from the working equations, to determine simultaneously, both the density and the viscosity of the fluid from the analysis of the resonance curve of the wire oscillation, the density being related essentially to the position of the maximum and the viscosity to its width. New results of measurements of the density and viscosity of toluene in the compressed liquid region are presented, and compared with literature data. The density results extend over a temperature range 222 K≤T≤348 K, and pressures up to 80 MPa. The viscosity results cover a temperature range of 248 K≤T≤348 K and pressures up to 80 MPa. The uncertainty of the present density data is estimated to be within ±0.1% at temperatures 298 K≤T≤350 K, and ±0.15% at 222 K≤T≤273 K. The corresponding overall uncertainty of the viscosity measurements is estimated to be ±2% for temperatures 298 K≤T≤350 K, and ±3% for 248 K≤T≤273 K.

Measurement of Thermal Transport Properties with an Improved Transient Plane Source Technique

Abstract: The transient plane source (TPS) technique has been revised with the aim of developing a simple and fast system to measure the thermal transport properties of materials at low temperatures, especially high-Tc superconductors. To ensure reliable results, any new system should be tested with known samples. Fused silica, 0.9% carbon steel (215/3), and halide crystals (silver chloride) were studied with the new setup to check its performance. Data were taken from room temperature down to liquid nitrogen temperature. The assembly was designed for cryogenic (79 to 300 K) measurements in an atmosphere free of humidity. Dry nitrogen gas was used as a heat transfer medium around the sample holder assembly. The measured values for thermal conductivity and thermal diffusivity of these samples are in excellent agreement with values reported earlier. The thermal conductivity and thermal diffusivity for silver chloride crystals are extended down to 80 K although recommended data were available only down to 220 K. A Ba-doped, Bi-based, high-Tc superconductor was prepared by a solid-state reaction method. The nominal composition used was Bi1.6Pb0.4Sr1.6Ba0.4Ca2Cu3Oy. Large-sized samples (diameter ∼28mm and length ∼11mm) are investigated for thermal transport properties.

Isochoric Heat Capacity Measurements for 0.5 H2O + 0.5 D2O Mixture in the Critical Region

Abstract: The isochoric heat capacity C V of an equimolar H2O+D2O mixture was measured in the temperature range from 391 to 655 K, at near-critical liquid and vapor densities between 274.05 and 385.36 kg⋅m−3. A high-temperature, high-pressure, nearly constant-volume adiabatic calorimeter was used. The measurements were performed in the one- and two-phase regions including the coexistence curve. The uncertainty of the heat-capacity measurement is estimated to be ±2%. The liquid and vapor one- and two-phase isochoric heat capacities, temperatures, and densities at saturation were extracted from the experimental data for each measured isochore. The critical temperature and the critical density for the equimolar H2O+D2O mixture were obtained from isochoric heat capacity measurements using the method of quasi-static thermograms. The measurements were compared with a crossover equation of state for H2O+D2O mixtures. The near-critical isochoric heat capacity behavior for the 0.5 H2O+0.5 D2O mixture was studied using the principle of isomorphism of critical phenomena. The experimental isochoric heat capacity data for the 0.5 H2O+0.5 D2O mixture exhibit a weak singularity, like that of both pure components. The reliability of the experimental method was confirmed with measurements on pure light water, for which the isochoric heat capacity was measured on the critical isochore (321.96 kg⋅m−3) in both the one- and two-phase regions. The result for the phase-transition temperature (the critical temperature, TC, this work=647.104±0.003 K) agreed, within experimental uncertainty, with the critical temperature (TC, IAPWS=647.096 K) adopted by IAPWS.

Thermophysical Property Measurements of Supercooled and Liquid Rhodium

Abstract: The density, the isobaric heat capacity, the surface tension, and the viscosity of liquid rhodium were measured over wide temperature ranges, including the supercooled phase, using an electrostatic levitation furnace. Over the 1820 to 2250 K temperature span, the density can be expressed as ρ(T)=10.82×103−0.76(T−Tm) (kg⋅m−3) with Tm=2236 K, yielding a volume expansion coefficient α(T)=7.0×10−5 (K−1). The isobaric heat capacity can be estimated as CP(T)=32.2+1.4×10−3(T−Tm) (J⋅mol−1⋅K−1) if the hemispherical total emissivity of the liquid remains constant at 0.18 over the 1820 to 2250 K interval. The enthalpy and entropy of fusion have also been measured, respectively, as 23.0 kJ⋅mol−1 and 10.3 J⋅mol−1⋅K−1. In addition, the surface tension can be expressed as σ(T)=1.94×103−0.30(T−Tm) (mN⋅m−1) and the viscosity as η(T)=0.09 exp[6.4×104(RT)] (mPa⋅s) over the 1860 to 2380 K temperature range.

Investigation of the Thermal Diffusivity of Human Tooth Hard Tissue

Abstract: Experiments of two kinds have been performed in which the heat diffusion effects in human tooth hard tissues have been investigated. The first one has been carried out on an incisor tooth as a whole with the use of a bath system. Experiments of the second kind have been done on slice specimens cut out of a tooth. A laser flash apparatus has been utilized. The time dependence of the temperature response has been measured using tiny thermocouples. The experimental data are then used to calculate the effective overall thermal diffusivity of the tooth structures as well as the thermal diffusivity of enamel and dentine alone. A discrepancy between the calculated results and literature data has been discussed.

Viscosity and Density Measurements of Binary Mixtures Composed of Methylcyclohexane + cis-Decalin Versus Temperature and Pressure

Abstract: Viscosity and density measurements have been carried out for binary mixtures composed of methylcyclohexane + cis-decalin in the temperature range 293.15 to 353.15 K and at pressures up to 100 MPa. The viscosity was measured with a falling-body viscometer, except at atmospheric pressure where an Ubbelohde viscometer was used. The experimental uncertainty for the measured viscosities is 2%. The density was measured up to 60 MPa and extrapolated by a Tait-type relationship to 100 MPa. For the reported densities the uncertainty is less than 1 kg⋅m−3. An evaluation of the simple mixing laws of Grunberg and Nissan and of Katti and Chaudhri, which require only the density and viscosity of the pure compounds, showed that they can represent the viscosity of the binary mixtures with an average absolute deviation of 2%, corresponding to the experimental uncertainty.

Non-Contact Measurements of the Thermophysical Properties of Hafnium-3 Mass% Zirconium at High Temperature

Abstract: Several thermophysical properties of hafnium-3 mass % zirconium, namely the density, the thermal expansion coefficient, the constant pressure heat capacity, the hemispherical total emissivity, the surface tension and the viscosity are reported. These properties were measured over wide temperature ranges, including overheated and undercooled states, using an electrostatic levitation furnace developed by the National Space Development Agency of Japan. Over the 2220 to 2875 K temperature span, the density of the liquid can be expressed as ρ L (T)=1.20×104−0.44(T−T m ) (kg⋅m−3) with T m =2504 K, yielding a volume expansion coefficient α L (T)=3.7×10−5 (K−1). Similarly, over the 1950 to 2500 K span, the density of the high temperature and undercooled solid β-phase can be fitted as ρ S (T)=1.22×104−0.41(T−T m ), giving a volume expansion coefficient α S (T)=3.4×10−5. The constant pressure heat capacity of the liquid phase can be estimated as C PL (T)=33.47+7.92×10−4(T−T m ) (J⋅mol−1⋅K−1) if the hemispherical total emissivity of the liquid phase remains constant at 0.25 over the 2250 K to 2650 K temperature interval. Over the 1850 to 2500 K temperature span, the hemispherical total emissivity of the solid β-phase can be represented as e TS (T)=0.32+4.79×10−5(T−T m ). The latent heat of fusion has also been measured as 15.1 kJ⋅mol−1. In addition, the surface tension can be expressed as σ(T)=1.614×103−0.100(T−T m ) (mN⋅m−1) and the viscosity as h(T)=0.495 exp [48.65×103/(RT)] (mPa⋅s) over the 2220 to 2675 K temperature range.