Showing papers in "International Journal of Thermophysics in 1990"

Thermophysical properties of ice, snow, and sea ice

Abstract: The paper reviews and discusses data and information on the thermophysical properties of ice, snow, and sea ice. These properties include thermal conductivity, specific heat, density, thermal diffusivity, latent heat of fusion, thermal expansion, and absorption coefficient. The available data are shown graphically for convenience in conjunction with the recommended correlation equations.

Thermophysical properties of solid and liquid tungsten

Abstract: The thermophysical properties of solid and liquid tungsten have been measured up to an enthalpy ofH = 1.4 MJ · kg−1 using an isobaric expansion technique. These measurements give the pressure, temperature, volume, enthalpy, electrical resistivity, and sound velocity as fundamental quantities. From these, other properties may be calculated, such as specific heat at constant volume and pressure, heat of fusion, isothermal and adiabatic bulk moduli and compressibilities, and thermodynamicγ. Results of these calculations are presented for liquid tungsten and compared with literature values where such data exist. These data will help in understanding liquid-metal phenomenology theoretically and in the design and modeling of exploding wires, foils, and fuses.

Thermal diffusivity measurements of thin films and multilayered composites

Abstract: This review discusses the following methods for measuring thermal diffusivity of thin materials: ac calorimetric method, flash method, mirage-effect method, picosecond time-resolved thermoreflectance method, photoacoustic method, etc. The measurements are classified into the following three cases: (a) that yield thermal diffusivity parallel to the surface of a thin material, (b) that yield thermal diffusivity perpendicular to the surface, and (c) that yield thermal diffusivity perpendicular to the surface of a thin material but deposited on a solid substrate. The contribution of inhomogeneity in the spatial distribution of the imparted thermal energy and obscureness at the edge of the restricted region, to which uniform thermal energy is imparted, is considered in each case. The contribution of temporal distortion of the temperature pulse, waves, etc., is considered in each measurement. The proper thickness of samples required for the measurements is discussed. In some of the measurements, the applicable materials are restricted, for instance, thermoreflectance measurements are applicable to metallic samples only.

Correlation of high-pressure thermal conductivity, viscosity, and diffusion coefficients for n-alkanes

Abstract: Thermal conductivity, viscosity, and self-diffusion coefficient data for liquid n-alkanes are satisfactorily correlated simultaneously by a method based on the hard-sphere theory of transport properties. Universal curves are developed for the reduced transport properties λ*, η*, and D* as a function of the reduced volume. A consistent set of equations is derived for the characteristic volume and for the parameters Rλ, Rη, and RD, introduced to account for the nonsphericity and roughness of the molecules. The temperature range of the above scheme extends from 110 to 370 K, and the pressure range up to 650 MPa.

Thermodynamic and transport properties of 1, 2-dichloroethane

Abstract: (p, V, T) data for dichloroethane (DCE) have been obtained at 278.15, 288.15, 298.15, 313.15, 323.15, and 338.15 K for pressures either slightly below the freezing pressure or up to a maximum of 280 M Pa, together with densities at 0.1 MPa. A high-pressure self-centering falling-body viscometer method has been used to measure shear viscosities at 278.15, 288.15, 298.15, 313.15, and 323.15 K for pressures either slightly below the freezing pressure or up to a maximum of 330 MPa. Self-diffusion coefficients for DCE are reported at 278.15, 288.15, 298.15, and 313.15 K for maximum pressures up to 300 MPa. Isothermal compressibilities, isobaric expansivities, and internal pressures have been evaluated from the volumetric data. The shear viscosities and self-diffusion coefficients have been interpreted in terms of a modified rough hard-spheres theory. The anomalous behavior observed for p-V-T, shear viscosities, and self diffusion at higher temperatures and pressures is suspected to be the result of temperature and pressure altering the population ratio of the two molecular conformers, trans and gauche.

Thermal expansion of tungsten in the range 1500–3600 K by a transient interferometric technique

Abstract: The linear thermal expansion of tungsten has been measured in the temperature range 1500–3600 K by means of a transient (subsecond) interferometric technique. The tungsten selected for these measurements was the standard reference material SRM 737 (a standard for thermal expansion measurements at temperatures up to 1800 K). The basic method involved rapidly heating the specimen from room temperature up to and through the temperature range of interest in less than 1 s by passing an electrical current pulse through it and simultaneously measuring the specimen temperature by means of a high-speed photoelectric pyrometer and the shift in the fringe pattern produced by a Michelson-type interferometer. The linear thermal expansion was determined from the cumulative shift corresponding to each measured temperature. The results for tungsten may be expressed by the relation $$\begin{gathered} (l - l_0 )/l_0 = 1.3896 \times 10^{ - 3} - 8.2797 \times 10^{ - 7} T + 4.0557 \times 10^{ - 9} T^2 \hfill \\ - 1.2164 \times 10^{ - 12} T^3 + 1.7034 \times 10^{ - 16} T^4 \hfill \\ \end{gathered} $$ whereT is in K andl0 is the specimen length at 20°C. The maximum error in the reported values of thermal expansion is estimated to be about 1% at 2000 K and approximately 2% at 3600 K.

Effects of detector nonlinearity and specimen size on the apparent thermal diffusivity of NIST 8425 graphite

Abstract: With the use of a graphite thermal conductivity standard it is demonstrated that optical detector non-linearity, coupled with excessive laser pulse energies, is primarily responsible for the anomalous specimen size dependence of the thermal diffusivity measured by the laser-pulse technique. High laser pulse energies also result in an anomalous positive temperature dependence for thin specimens near room temperature, in contrast to the expected negative temperature dependence. Using moderately thick specimens and attenuated laser pulses yields excellent agreement with thermal diffusivity calculated from standard thermal conductivity data.

Dual-wavelength radiation thermometry: Emissivity compensation algorithms

Abstract: The traditional contact methods of temperature measurement for metal processing applications provide accuracies of ±10 K. Noncontact methods based upon emissivity compensation techniques have the potential for improved accuracy with greater ease of use but require prior knowledge of the target emissivity behavior. The features of the basie spectral and ratio methods and five dualwavelength methods are reviewed. Experiments were conducted on a series of aluminum alloys with different surface treatments characterized by x-ray photoelectron spectroscopy in the temperature range 600 to 750 K. Compensation algorithms that account for surface characteristics are required to achieve improved accuracy.

Thermodynamic analysis of manganese

Abstract: A description of the Gibbs energy of the various solid modifications of manganese at 101325 Pa has been obtained for the whole temperature range from 298 K to the melting point. The present analysis accounts for the effect of a magnetic transition in α-, γ-, and δ-Mn, which is treated using the Inden-Hillert-Jarl phenomenological model for the magnetic Gibbs energy. Our description involves smaller magnetic contributions to the entropy of these phases than suggested in the classical work by Weiss and Tauer. An expression for the Gibbs energy of the liquid phase is also reported.

Viscosity, thermal conductivity, and surface tension of high-temperature melts

Abstract: High-temperature melts are substances which are solids at room temperature and liquids at high temperatures. They include liquid metals, molten salts, and other melts such as molten semiconductor materials. Although they show scientifically interesting behavior and have industrially important characteristics, the thermophysical properties of these substances at high temperature are not sufficiently known due to experimental difficulties. Many melts show strong chemical activity and therefore are corrosive to materials of container and sensors. Applicable sensors are limited also because of the high temperature and the electrical conductivity of melts. In this paper the present status of available data for the viscosity, the thermal conductivity, and the surface tension of high-temperature melts is reviewed. Limited experimental information is available and these properties are difficult to predict theoretically. The transport properties are important for predicting heat transfer and flow patterns. For the prediction of the behavior of melts under microgravity condition, the temperature dependence of the surface tension plays a major role.

The properties of liquid carbon

Abstract: A model for the transport properties of liquid carbon based on Ziman liquid metal theory with refinements for polyvalent liquid metals and Fermi surface blurring is applied to calculate the electrical resistivity of liquid carbon at the melting temperature. The thermal and electrical properties predicted by the model are compared to experimental results using numerical heat flow calculations and found to be in good agreement with pulsed-current heating experiments on the resistivity of carbon fibers.

Measurement of the radiance temperature (at 655 nm) of melting graphite near its triple point by a pulse-heating technique

Abstract: Measurements of the radiance temperature of graphite at 655 nm have been performed in the vicinity of its triple point by means of a rapid pulse-heating technique. The method is based on resistively heating the specimen in a pressurized gas environment from room temperature to its melting point in less than 20 ms by passing an electrical current pulse through it and simultaneously measuring the radiance temperature of the specimen surface every 120 μs by means of a high-speed pyrometer. Results of experiments performed on two different grades of POCO graphite (AXM-5Q1 and DFP-1) at gas pressures of 14 and 20 MPa are in good agreement and yield a value of 4330±50 K for the radiance (or brightness) temperature (at 655 nm) of melting graphite near its triple point (triple-point pressure, ∼ 10 MPa). An estimate of the true (blackbody) temperature at the triple point is made on the basis of this result and literature data on the normal spectral emittance of graphite.

Equation of state and critical point of cesium

Abstract: Equation-of-state measurements for cesium at temperatures from 350 to 2200 K and pressures from 1 to 60 MPa by means of a hermetically sealed two-zone dilatometer are presented. The experimental range includes the liquid and gaseous phases together with the coexistence curve up to critical point and supercritical region. The critical parameters are 1938 K, 9.4 MPa, 0.39 g · cm−3. The data were used for the calculation of tables of the density and its derivatives for cesium. The results are discussed.

Thermal conductivity of composites

Abstract: A general expression for the effective thermal conductivity of inhomogeneous media in terms of the Fourier components of the spatial variation of the conductivity is applied to composites consisting of inclusions in a continuous matrix. It is reformulated in terms of the mean square fluctuations of the conductivity. Specific cases treated are spherical inclusions and long cylinders, both random and with preferred directions. The results hold provided the difference in thermal conductivities is small or provided the concentration of inclusions is not too large. The theory fails if the thermal conductivity of the matrix is much smaller than that of the inclusions. The same considerations also apply to electrical conductivity.

Measurement of thermophysical properties of lead by a submicrosecond pulse-heating method in the range 2000–5000 K

Abstract: A submicrosecond ohmic pulse-heating technique with heating rates of more than 109K· s−1 allows the determination of such thermophysical properties as heat capacity and the mutual dependences among enthalpy, electrical resistivity, temperature, and volume up to superheated liquid states for lead. Also, an estimation of the critical point data is given from investigations at elevated static pressures.

Thermodynamic properties of 2,2,4-trimethylpentane

Abstract: p, V, T data for 2,2,4-trimethylpentane (TMP) have been obtained in the form of volume ratios for six temperatures in the range 278.15 to 338.15 K for pressures up to 280 MPa. Isothermal compressibilities, isobaric expansivities, and internal pressures have been evaluated from the volumetric data. There are strong indications that the combination of the present results with literature data at 348 and 373 K enable accurate extrapolations in the liquid range up to 473 K, and possibly to as low as 170 K, for pressures up to 980 MPa; use of only the present results with the requirement that the B coefficient of the Tait equation should become equal to the negative of the critical pressure at the critical temperature provides interpolations and extrapolations of comparable accuracy. It is suggested that 2,2,4-trimethylpentane is a suitable secondary reference material (because of its large liquid range at atmospheric pressure and the similarity of its volumetric properties to a wide range of fluids) for calibration of measuring cells used for determining volumes of fluids under pressure.

Thermal conductivity by a pulse-heating method: Theory and experimental apparatus

Abstract: A new dynamic technique for the measurement of thermal conductivity at high temperatures has been developed at the IMGC. The specimen is brought to high temperatures with a current pulse; during cooling the heat content is dissipated by radiation and by conduction. The differential equation describing this process contains terms related to the heat capacity, the hemispherical total emittance, and the thermal conductivity of the material. If the first two properties are determined using the same specimen during subsecond pulse heating experiments, thermal conductivity may be evaluated by accurate measurements of the round-shaped temperature profiles established on the specimen during cooling. High-speed scanning pyrometry makes possible accurate measurements of temperatures and of temperature derivatives (with respect to space and time), which enables the differential equation describing the power balance at each point of the specimen to be transformed into a linear equation of the unknown thermal conductivity. A large overdetermined system of linear equations is solved by least-squares techniques to obtain thermal conductivity as a function of temperature. The theory underlying the technique is outlined, the experimental apparatus is described, and details of the measurement technique are given.

Present research on thermal radiation properties and characteristics of materials

Abstract: This paper reviews the recent advances in our spectroscopic research on radiation properties and characteristics of solid and liquid materials, from thermal engineering point of view. The topics discussed are optical constants of metallic materials, radiation characteristics of the real surfaces in actual industrial environments, those of semi-transparent scattering-absorbing media, and those of human body and environmental surfaces of human living space. The review also includes the algorithm for radiation pyrometry and the demand for radiation data of new materials and for new engineering techniques. It is concluded that the development of engineering models is important for the systematic research of the complicated radiation phenomena and that generation and compilation of pertinent data are necessary.

Measurements of the compressibility and sound velocity in methane up to 1 GPa, revisited

Abstract: New density measurements of methane (CH4) at 298.15 K up to 1 GPa are reported. The precision of the measurements is 0.03%, while the estimated accuracy is between 0.05 and 0.1%. Velocities of sound have been remeasured between 148.15 and 298.15 K at intervals of 25 K and at pressures up to 1 GPa, with an estimated accuracy of 0.12% at 100 M Pa, 0.10% at 150 MPa, and 0.08% above 150 MPa. Comparisons with experimental results and equations of state of other workers are presented. The isothermal and the adiabatic compressibility and the ratio of specific heats have been calculated at 298.15 K.

Thermodynamic properties of aqueous solutions at high temperatures: Needs, methods, and challenges

Abstract: Needs exist for thermophysical data on aqueous solutions at high temperatures and pressures in many different areas of science and engineering. These needs are reviewed and references are given to recent relevant conference proceedings, reviews, and papers. Aspects and drawbacks are discussed of current methods, which are most often extensions to high temperatures of methods developed for liquid water. The challenges posed by engineering needs and by new phenomena resulting from experimental breakthroughs are discussed. Some examples are given of alternative approaches more suitable for highly compressible media.

The melting points of ultralong paraffins and their homologues

Abstract: Because of the recent availability of the melting points of several ultralong normal paraffins, the melting behavior of normal paraffins has been investigated. Taking the melting point of polyethylene to represent the melting point of an ultralong paraffin, a new function has been established to represent the melting points of alkanes from the carbon number 32 onwards. Adopting the same value for the limiting melting point of an ultralong paraffin, equations are derived for the melting points of several homologous series.

The thermal conductivity of the mixtures of liquid hydrocarbons at pressures up to 400 MPa

Abstract: The paper presents the results of measurements of the thermal conductivity of three binary mixtures of normal heptane and 2,2,4-trimethyl pentane. The measurements were carried out within the temperature range 308–359 K and over the pressure range 0.1–410 MPa with a transient hot-wire instrument. The experimental data have an estimated uncertainty of ±0.3%. The experimental data have been represented by simple polynomials along isotherms as a function of pressure for each composition for the purpose of interpolation. However, an alternative scheme of representation, based upon an heuristic extention of the hard-sphere theory, is shown to give a much more concise representation capable of extrapolation. Indeed, a procedure for the prediction of the thermal conductivity of the mixtures, based on the same theory, which uses no information derived from the present measurements, is shown to yield results of an accuracy sufficient for many purposes.

An interim analytic equation of state for sulfurhexafluoride

Abstract: An interim analytic equation of state for Sulfurhexafluoride is given in the form of a reduced Helmholtz energy function. It represents the thermodynamic properties over the temperature range 222.38 to 525 K for pressures up to 55 MPa. The data selected for determining the linear coefficients of the equation are given, which includes some values predicted using the principle of corresponding states. The method used for the multiproperty fitting is given and, in particular, the functions used for fitting isobaric heat capacities as primary data. Comparisons with values predicted by the equation of state are given for saturation properties, second virial coefficients, densities, and isobaric and isochoric heat capacities. The accuracy of the representation of the equation of state is discussed and, also, the problems arising from inconsistencies between the different data sets. The interim status of this equation of state is due to these inconsistencies.

Cubic equations of state for transport properties: An equation for the thermal conductivity of oxygen

Abstract: A scheme for the development of equations for the transport properties in terms of pressure and temperature, so-called transport equations of state, is presented. The surfaces of transport properties and density as a function of pressure and temperature reveal similarities, which become even more evident when the residual transport property as a function of pressure and temperature is considered. Even the spinodals of transport and thermal properties coincide in the p, T plane, as can be shown mathematically and as was already empirically found for water and oxygen. Based on these similarities a cubic transport equation of state is evaluated for the residual thermal conductivity of oxygen. The new equation is only a little less accurate than the already established virial transport equation of state for oxygen. It is, however, much simpler and needs only a few parameters. The accuracy is still good enough for practical applications. The results demonstrate that cubic equations of state can describe transport properties and are a basis for generalized estimation methods for the transport properties of fluids.

Thermal properties of aqueous solutions of polyvinylpyrrolidone in the temperature range 20–80°C

Abstract: The thermal properties (thermal diffusivity a, thermal conductivity λ, and volumetric heat capacity ρCp) of aqueous solutions of polyvinylpyrrolidone (PVP) were measured in the temperature range 20–80°C. The measurements were carried out using the hot-wire (strip) technique. Three different average molecular weights of PVP were used [M = 10,000 (PVP-10), M = 24,500 (PVP-24.5), and M = 40,000 (PVP-40)], i.e., the average degrees of polymerization are 90, 220, and 360, respectively. The results show that the values of the thermal properties depend on the temperature and the concentration of PVP in the medium. The mechanism of heat transfer was discussed. The role of convection and radiation were taken into consideration.

Measurement of the heat of fusion of tungsten by a microsecond-resolution transient technique

Abstract: A microsecond-resolution pulse-heating technique was used for the measurement of the heat of fusion of tungsten. The method is based on rapid (100 to 125μs) resistive self-heating of a specimen by a high-current pulse from a capacitor discharge system and measuring current through the specimen and voltage across the specimen as functions of time. Melting of a specimen is manifested by changes in the slope of the electrical resistance versus time function. The time integral of the power absorbed by a specimen during melting yields the heat of fusion. Measurements gave a value of 48.7 kJ · mol−1 for the heat of fusion of tungsten with an estimated maximum uncertainty of ±6%. The electrical resistivity of solid and liquid tungsten at its melting temperature was also measured.

Issues and future directions in subsecond thermophysics research

Abstract: The key issues and anticipated future directions in subsecond thermophysics research are presented and discussed. The main emphasis is placed on experimental techniques for measurements of selected thermophysical properties utilizing rapid volume heating (resistive self-heating) and rapid surface heating (laser pulse-heating) methods. The time regime covered is from 1 to 10−12s. Specific research topics and key research areas are identified and discussed.

Sound speed measurements on gas mixtures of natural gas components using a cylindrical resonator

Abstract: A description of a fixed-path length acoustic resonator which uses electrostatic transducers for sound generation and detection is given. Also, a summary of the measurements on 13 binary and 4 multicomponent gas mixtures of natural gas components is given. Data were obtained at pressures to 10 MPa for five isotherms at 25 K increments from 250 to 350 K. The binary mixtures are primarily methane-rich, with either ethane, nitrogen, carbon dioxide, or propane as the second constituent. The multicomponent mixture compositions represent four naturally occurring natural gas mixtures.

Thermodynamic properties of n-pentane

Abstract: Specific volumes and isobaric heat capacity measurements are reported for n-pentane. The measurements were made in the liquid and vapor phases at temperatures ranging from the triple point (173 K) to the onset of dissociation temperature (700 K) and pressures up to 100 MPa including a wide region around the critical point. We are able to fit our data, as well as those of a number of other authors, to a single equation of state with 30 constants. This equation yields the density of n-pentane in the temperature range from 280 to 650 K at pressures up to 80 MPa and the caloric properties up to 500 K. Additional experimental investigations of the thermodynamic properties are required for temperatures above 500 K. Interpolating equations for the caloric properties on the saturated line and in the critical region are also presented.

Composition dependence of binary diffusion coefficients in alkane mixtures

Abstract: The binary diffusion coefficients of mixtures of n-heptane with n-hexane and 2,2,4-trimethylpentane with n-hexane have been measured at various compositions at 308.1, 312.2, and 316.5 K using the Taylor dispersion technique. The experimental results for the n-hexane/n-heptane system were in good agreement with the literature values (<1.5%). The observed binary diffusion coefficients for this system exhibit a linear dependence on composition. On the contrary, the results of the n-hexane/2,2,4-trimethylpentane system reveal an interesting behavior of the composition dependence of the binary diffusion coefficients, presenting a slight maximum, for composition at a molar fraction of n-hexane of 0.86. In order to explain this difference in behavior, the influence of branching of molecules on diffusion is discussed. It was found that although the Enskog hard-sphere model for binary diffusion can reproduce the experimental results for the n-hexane/n-heptane system within 3%, it failed to predict the composition dependence of the n-hexane/2,2,4-trimethylpentane system within the experimental accuracy. The results showed that there is significant effect of branching in alkane molecules on the diffusion coefficient. This effect has been quantified using the roughness parameter, which represents the magnitude of coupling between translational and rotational motions.