Thermophysics

This work involves the determination of transport coefficients and equation of state of supercritical fluids by molecular dynamics (MD) simulations on parallel computers using the Green-Kubo formulae and the virial equation of state, respectively. The MD program uses an effective Lennard-Jones potential, linked cell lists for efficient sorting of molecules, periodic boundary conditions, and a modified velocity Verlet algorithm for particle displacement. Previously, simulations had been carried out on pure argon, nitrogen and oxygen, and this has now been extended to ethylene, C^H^, at various supercritical conditions, with shear viscosity and thermal conductivity coefficients, and pressures computed for most of the conditions. The results compare well with experimental and National Institute of Standards and Technology (NIST) values.

A new photopyroelectric (PPE) methodology, for optical characterization of general liquids, was used for the assessment of hemoglobin in human blood. The optical absorption coefficient of a hemoglobin reference was measured with this PPE methodology and its corresponding absorptivity, at 532 nm, was obtained. This last reference was used for hemoglobin quantification of blood from a healthy man.

New absolute measurements, by the transient hot-wire technique, of the thermal conductivity of n-hexadecane and binary mixtures of n-hexadecane with ethanol and n-decane with butanol are presented. The temperature range examined was 295-345 K and the pressure atmospheric. The concentrations of the mixtures studied were 92% (by weight) of n-hexadecane and 30 and 70% (by weight) of n-decane. The overall uncertainty in the reported thermal conductivity data is estimated to be _+0.5%, an estimate confirmed by the measurement of the thermal conductivity of water. A recently extended semiempirical scheme for the prediction of the thermal conductivity of mixtures from the pure components is used to correlate and predict the thermal conductivity of these mixtures, as a function of both composition and temperature.

Photoacoustic spectroscopy (PAS) is widely used for diverse applications in different areas. These include studies in material, environmental, and life sciences. In the present work the study of pigments from pottery surfaces and volumes of Mexican (Aztec) and Poblana cultures that were developed in central Mexico from 1325 to 1521 and 1521 to 1800, respectively, is reported. The optical absorption spectra from each archeological sample was obtained using PAS. The superficial spectra were also compared with standard color pigments and archeological registers. Complementary energy dispersive spectroscopy (EDS) analysis of these archeological potteries gave us their elemental composition which agreed with other studies about their composition and technology of the pottery manufacturing.

Accurate molecular partition functions are required to determine both thermodynamic properties for equilibrium and nonequilibrium flow field calculations, and energy level populations for radiative heat transfer in high enthalpy flows, for instance. Thermodynamic functions of diatomic molecules are computed in this study at high temperatures and for nonequilibrium media in the framework of multitemperature models. Partition functions, average energies, and specific heats of N 2 , N + 2 , NO, O 2 , CN, C 2 , CO, and CO + are calculated up to 50,000 K by direct summation over energy levels using recent and accurate spectroscopic data and dissociation energy values. Estimates are made for the error introduced by neglecting the highest considered electronic states. For nonequilibrium media, the sensitivity of the multitemperature thermodynamic functions to different schemes for energy partitioning is discussed. In particular, the effects of vibration-rotation coupling are investigated. The tabulated results are available upon request.

The isochoric heat capacity of pure methanol in the temperature range from 482 to 533 K, at near-critical densities between 274.87 and 331.59 kg · m −3 , has been measured by using a high-temperature and high-pressure nearly constant volume adiabatic calorimeter. The measurements were performed in the singleand two-phase regions including along the coexistence curve. Uncertainties of the isochoric heat capacity measurements are estimated to be within 2%. The single-and two-phase isochoric heat capacities, temperatures, and densities at saturation were extracted from experimental data for each measured isochore. The critical temperature (T c = 512.78 ± 0.02 K) and the critical density (ρ c = 277.49 ± 2 kg · m −3 ) for pure methanol were derived from the isochoric heat-capacity measurements by using the well-established method of quasi-static thermograms. The results of the C V V T measurements together with recent new experimental PVT data for pure methanol were used to develop a thermodynamically self-consistent Helmholtz free-energy parametric crossover model, CREOS97-04. The accuracy of the crossover model was confirmed by a comprehensive comparison with available experimental data for pure methanol and values calculated with various multiparameter equations of state and correlations. In the critical and supercritical regions at 0.98T c T 1.5T c and in the density range 0.35ρ c ρ 1.65ρ c , CREOS97-04 represents all available experimental thermodynamic data for pure methanol to within their experimental uncertainties.

In this paper, the advantages, design possibilities, performance of the Multi-Entrance Fixed Point (MEFP) concept are described. The purpose of MEFP is to replace equalizing blocks in any temperature-controlled zone with phase transition of matter during melting or freezing. The phase transition in such a calibration is not intended to be the temperature standard itself, but only provides for spatial thermal homogeneity and temporal stability during comparison calibration. Knowing that some of the main uncertainty components in the uncertainty budget of the comparison calibrated thermometer are the radial and axial gradients in the isothermal zone and knowing that comparisons comprise by far the majority of all calibrations, the improvement of speed and quality of calibration is of significant importance. The tin-filled MEFP with multiple entrance tubes, designed in the Laboratory for Process Measurements allows for simultaneous calibration of several thermometers against a standard thermometer. MEFP prototypes filled with other materials and with other design characteristics are pending production. This concept allows the use of modest purity materials to fill the cell, since a standard thermometer is used as the calibration reference. During this investigation, thermometers were calibrated against a standard in the same furnace, using both the standard equalizing block and the MEFP. The measurement results indicate that the use of MEFP decreases the uncertainty contributions from temperature gradients and the stability of the bath by an order of magnitude, compared to the standard equalizing block.

A comprehensive thermal conductivity (λ) database of three dry standard sands (Ottawa C-109, Ottawa C-190, and Toyoura) was developed using a transient line heat source technique. The database contains λ data representing a variety of soil compactions and temperatures (T) ranging from 25 • C to 70 • C. The tested standard sands, due to their repeatable physical characteristics, can be used as reference materials for validation of thermal probes applied to similar dry granular materials. The measured data show an increasing trend of thermal conductivity at dryness (λ dry) against T in spite of declining quartz λ with T. The air content (porosity) controls the λ of dry sands by acting as a very effective thermal insulator around solid soil particles. As a result, a diminutive increase of λ dry with T is driven by increasing λ of air. The experimental λ data of dry sands were exceptionally well predicted by de Vries and Woodside-Messmer models, and also by a thermal conductance model, a product of λ of solids and the thermal conductance factor.

We report the first experimental detailed study of laser induced surface melting on the nanoscale time scale of amorphous silicon carbide layers produced by ion implantation. Time-resolved reflectivity has been used to observe the fast liquid-solid-liquid transition features, and transmission electron microscopy (TEM) was used in order to study the structure resulting after the fast solidification following the laser induced melting. By means of the evaluation of the laser fluences required to induce melting of amorphous layers of different thickness on top of a crystalline substrate, we evaluated the thermal diffusion coefficient and the melting point of the amorphous material which occurred much lower than for crystalline material. Moreover, we give evidence of amorphous-to-crystal transitions occurring in the solid phase on the nanosecond time scale, for laser irradiation at fluences below the melting threshold. A quite different crystalline structure is observed for crystallization from the liquid phase than from the solid phase.

Experimental densities at (293.15, 298.15, 303.15, 308.15, and 313.15) K and refractive indices at 298.15 K are reported for the binary liquid mixtures of ethanol with benzene and pyridine over the entire range of compositions and atmospheric pressure. From these experimental data, the excess molar volumes V E and deviations in molar refractivity Δ R were derived and fitted by the Redlich–Kister polynomial to determine the adjustable fitting parameters and the standard deviations. The number of adjustable parameters to be included in a Redlich–Kister polynomial for fitting the derived properties was optimized with the F -test. V E values are found to be negative over the entire composition range in ethanol + pyridine mixtures, without considerable changes over the temperature range studied. In the ethanol + benzene mixtures, the V E results show an S-shaped composition dependence, and the temperature contribution was found to be very important. The variation of V E with composition and temperature has been interpreted in terms of molecular interactions between the components of the mixture and structural effects. Δ R values are found to be negative for both mixtures with a minimum located between 0.45 and 0.5 volume fractions of ethanol. Furthermore, several theoretical and empirical mixing rules were applied to predict refractive indices of mixtures in order to test their validity for the present systems.

Combining the well-known Bruggeman theory and Nan et al. results, formulas for predicting the effective thermal conductivity of anisotropic particulate composites with an interface layer are derived. These formulas are valid for a composite material containing arbitrarily oriented ellipsoidal particles with any aspect ratio, and they can be expected to be suitable mainly for large volume fractions, when the thermal interaction between neighboring particles needs to be considered. Results of the present approach are reduced to simpler formulas for some limiting cases in the particle shape. Theoretical analysis of the effective thermal conductivity as a function of volume fraction and shape of the particles is performed. Comparison of the obtained formulas with previously reported experimental data for the effective thermal conductivity is also presented.

Investigations of Type A (W-5%Re/W-20%Re) thermocouples were performed at several laboratories to validate their reference function before its standardization in the new issue of the international standard IEC 60584. The Type A thermocouples investigated were equipped with sealed protection tubes made of sapphire which were filled with an inert gas (argon). The investigations at Russian laboratories were performed mainly in carbon-free high-temperature furnaces. The calibration results obtained in the temperature range (600-1850) °C in the carbon-free environment were within the (0.5%) of tolerance limits and confirmed the suitability of Type A thermocouples for industrial applications. In contrast, the Type A thermocouple 89/95-P investigated at PTB (Germany) was exposed to carbon environment when annealed at 1850 ° and when it was calibrated at metal-carbon eutectic (Me-C) fixed points. Measurements made at Me-C fixed points did not deviate from the reference function by more than about 6 K at the first stage when temperatures were below 1500 °C. However, the inhomogeneity of the thermoelements increased continuously after the calibration at the Me-C eutectic fixed points. The additional measurements at the Cr3C2-C peritectic fixed point (1826 °C) resulted in a continuous emf drift to deviations from the reference function of about -(100-150) µV which corresponds to a temperature equivalent of about -(9-14) K. The thermoelectric stability and homogeneity of the thermocouple 89/95-P during these investigations was checked by repeated measurements at the freezing point of copper (1084.62 °C).

The isobaric ideal-gas heat capacity for HFO-1234yf, which is expected to be one of the best alternative refrigerants for HFC-134a, was determined on the basis of speed-of-sound measurements in the gaseous phase. The speed of sound was measured by means of the acoustic resonance method using a spherical cavity. The resonance frequency in the spherical cavity containing the sample gas was measured to determine the speed of sound. After correcting for some effects such as the thermal boundary layer and deformation of the cavity on the resonance frequency, the speed of sound was obtained with a relative uncertainty of 0.01 %. Using the measured speed-of-sound data, the acoustic-virial equation was formulated and the isobaric ideal-gas heat capacity was determined with a relative uncertainty of 0.1 %. A temperature correlation function of the isobaric ideal-gas heat capacity for HFO-1234yf was also developed.

Type R (Pt-13 %Rh versus Pt) and type S (Pt-10 %Rh versus Pt) thermocouples are widely used as reference and working standards for temperature measurements both in calibration laboratories and in industry for temperatures up to 1600 • C. Many laboratories claim that the best achievable uncertainty is 0.1 • C up to 1000 • C and 0.3 • C up to 1550 • C, and international comparisons confirm that this is achievable practically. However, due to (i) preferential Rh oxidation of the Pt-Rh alloy thermoelement and (ii) defect quenching effects, these thermocouples suffer from reversible hysteresis in their calibration. As a result, calibration laboratories usually perform some heat treatment of the wire prior to calibration to attain a specific 'annealing state', at which the calibration is performed. Internationally, there are two commonly used annealing states for these thermocouples: the '450 • C annealed state' and the '1100 • C quenched state'. High-level comparisons between laboratories in the calibration of type R or type S thermocouples will rigorously specify the annealing state in the protocol, so any systematic differences due to the choice of annealing state will be masked. This article compares the calibration of several thermocouples using the two common annealing states, finding that the difference can be as large as 0.2 • C at 961 • C, larger than the best calibration uncertainties reported. The article examines the advantages and disadvantages to the user of calibrations performed in each state, and the implications for the uncertainty analysis for calibration and use of type R and type S thermocouples.

The flash point is an important indicator of the flammability of a chemical. For safety purposes, many data compilations report the lowest value and not the most likely. This practice, combined with improper documentation and poor data storage methods, has resulted in compilations filled with fire-hazard data that are inconsistent with related properties and between members of homologous chemical series. In this study, the flash points reported in the DIPPR 801 database and more than 1,400 other literature values were critically reviewed based on measurement method, inter-property relations, and trends in chemical series. New measurements for seven compounds illustrate the differences between experimental flash points and data commonly found in fire-hazard compilations. With a critically reviewed set of experimental data, published predictive methods for the flash point were evaluated for accuracy.

In the temperature range (900-2800) K there has been confirmed a compliance with the existing national standards for thermocouple wires W5%Re/W20%Re (type A) produced in Russia. The homogeneity within a lot of wires was evaluated by measuring the emf deviations from the corresponding reference function of thermocouples constructed from the front and the rear sections of paired coils of wires. The diameter of the wires amounted to 0,35 and 0,5 mm. Stability indicators were thermal EMF changes after two-hours annealing at 1773 K.

This paper discusses a mathematical model for computing the thermodynamic properties of propane, n-butane, isobutane, and their mixtures, in the fluid phase using a method based upon statistical chain theory. The constants necessary for computations such as the characteristic temperatures of rotation, electronic state, etc. and the moments of inertia are obtained analytically applying a knowledge of the atomic structure of the molecule. The paper presents a procedure for calculating thermodynamic properties such as pressure, speed of sound, the Joule-Thomson coefficient, compressibility, enthalpy, and thermal expansion coefficient. This paper will discuss, for the first time, the application of statistical chain theory for accurate properties of binary and ternary mixtures including propane, n-butane, and isobutane, in their entire fluid phases. To calculate the thermodynamic properties of Lennard-Jones chains, the Liu-Li-Lu model has been used. The thermodynamic properties of the hydrocarbon mixtures are obtained using the one-fluid theory.

In this work, fruit of the collaboration between two laboratories, we present different techniques to measure thermal diffusivity. At first a brief description of every technique both in the experimental layout and in the processing algorithms is given. After that, results obtained on samples cut from the same block of stainless steel AISI 304, are reported. Uncertainties evaluation of any measurement is reported together with a discussion on the pros and cons of the related technique.

Molten salts are one of the few remaining classes of fluids for which standardquality (±1% accuracy) data on thermal conductivity have not hitherto been available. We have therefore developed a new apparatus based on the transient hot-wire technique to obtain reference-quality measurements of the thermal conductivity of molten salts at high temperatures. Liquid metal-filled quartz capillaries served as insulated hot wires in our method, and in addition, a two-wire technique was used in order to obtain absolute values of the thermal conductivity. New data for the NaNO3-KNO3 eutectic between 525 and 590 K are reported in this paper and comparisons with other recent measurements are shown.

We show how the successful empirical results of the past century for the compressibility of liquids can be obtained from a recent statistical-mechanical theory that includes dense fluids as well as low-density gases and vapors. The theory also shows to what extent the results for liquids can be extended to dense supercritical fluids and how they can be generalized to any number of dimensions. For simplicity only argon and a Lennard-Jones (12,6) fluid are examined in detail, but the results can probably be extended to real molecular fluids.

A newly designed experimental apparatus has been used to measure the speed of sound u in high-purity water on nine isotherms between 274 and 394 K and at pressures up to 90 MPa. The measurement technique is based on a traditional double-reflector pulse-echo method with a single piezoceramic transducer placed at unequal distances from two stainless steel reflectors. The transit times of an acoustic pulse are measured at a high sampling rate by a digital oscilloscope. The distances between the transducer and the reflectors were obtained at ambient temperature and pressure by direct measurements with a coordinate measuring machine. The speeds of sound are subject to an overall estimated uncertainty of 0.05 %. The acoustic data were combined with available values of density ρ and isobaric heat capacity c p along one isobar at atmospheric pressure to calculate the same quantities over the whole temperature and pressure range by means of a numerical integration technique. These results were compared with those calculated from the IAPWS-95 formulation with corresponding relative deviations which are within 0.1%.

The Dortmund Data Bank (DDB) was started in 1973 with the intention to employ the vast store of vapor-liquid equilibrium (VLE) data from the literature for the development of models for the prediction of VLE. From the beginning, the structure of the DDB has been organized in such a way that it was possible to take advantage of the full potential of electronic computers. With the experience gained in fitting and processing VLE data, we extended the DDB system to other types of mixture properties, i.e., liquid-liquid equilibria (LLE), gas solubilities (GLE), activity coefficients at infinite dilution (7 ~), heats of mixing (hE), and excess heat capacities. Besides the files for mixture properties, the DDB contains pure-component data and program packages for various applications. New experimental data are checked for consistency before they are stored. For data retrieval user-specified search masks can be used. The data files are available via an online data service and through the Dechema Chemistry Data Series. For the purpose of data correlation and model testing, parameter fitting is performed with an optimization routine (Nelder-Mead). In the past years the DDB system has been successfully employed for the development of prediction methods for VLE, LLE, GLE, 7~, and h z (UNIFAC, mod. UNIFAC, etc.).

New experimental results are reported for the surface tension of normal pentane, hexane, heptane, and octane. The data were obtained with a differential capillary-rise method and cover the entire liquid range from the triple-point temperature to the critical temperature. Equations for calculating the surface tension of these n-alkanes as a function of temperature are presented.

The flash point is an important indicator of the flammability of a chemical. For safety purposes, many data compilations report the lowest value and not the most likely. This practice, combined with improper documentation and poor data storage methods, has resulted in compilations filled with fire-hazard data that are inconsistent with related properties and between members of homologous chemical series. In this study, the flash points reported in the DIPPR 801 database and more than 1,400 other literature values were critically reviewed based on measurement method, inter-property relations, and trends in chemical series. New measurements for seven compounds illustrate the differences between experimental flash points and data commonly found in fire-hazard compilations. With a critically reviewed set of experimental data, published predictive methods for the flash point were evaluated for accuracy.

The viscosity and thermal conductivity of acetic acid-water mixtures were measured over the entire composition range and at temperatures ranging from 293 to 453 K. Viscosity measurements were performed with a high-pressure viscometer and thernaal conductivity was measured using a modified transient hot-wire technique. A mercury filled glass capillary was used as the insulated hot wire in tile measurements. The viscosity data showed unusual trends with respect to composition. At a given temperature, the viscosity was seen to increase with increasing acid coqcentration, attain a maximum, and then decrease. The thermal conductivity, on the other hand, decreased monotonically with acid concentration. A generalized corresponding-states principle using water and acetic acid as the reference fluids was used to predict both viscosity and thermal conductivity with considerable succes.

In this paper we propose a new procedure of simultaneous estimation of the effective infrared optical absorption coefficient and the thermal diffusivity of solid state samples using the photothermal infrared radiometry method in the transmission configuration. The proposed procedure relies on the analysis of the frequency dependent signal obtained from the samples covered with thin aluminum foil. This method can be applied for both optically opaque and transparent samples. The proposed method is illustrated with the results of the thermal diffusivity and the effective IR absorption coefficient obtained for several Cd 1Àx Mg x Se crystals.

The thermal conductivity of polymethyl methacrylate (PMMA) and borosilicate crown glass BK7 has been studied. The transient hot-wire technique has been employed, and measurements cover a temperature range from room temperature up to 350 K for PMMA and up to 500 K for BK7. The technique is applied here in a novel way that minimizes all remaining thermalcontact resistances. This allows the apparatus to operate in an absolute way and with very low uncertainty. The method makes use of a soft silicone paste material between the hot wires and the solid under test. Measurements of the transient temperature rise of the wires in response to an electrical heating step over a period of 20 µs up to 5 s allow an absolute determination of the thermal conductivity of the solid, as well as of 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 deviations of the thermal conductivity measurements are 0.09% for PMMA and 0.16% for BK7, whereas the standard uncertainty of the technique is less than 1.5%.

At present, the South African national humidity measurement standards, maintained by NMISA, consist of two chilled-mirror hygrometers operating from (−75 to 20) • Cdp and unsaturated salt solutions covering the range (5 to 95) %rh. To reduce measurement uncertainties and to obtain traceability to local measurement standards for temperature and pressure, it is desired to replace the salt solutions by a dew-point generator for relative humidity calibrations from (5 to 95) %rh (5 to 60) • C, equivalent to a dew-point range of (−30 to 59) • Cdp. Required uncertainties in relative humidity (at a coverage factor of k = 2) are (0.1 to 1.2) %rh. This article describes the design and evaluation of a two-pressure humidity generator intended to satisfy this requirement. The saturator consists of a coil of stainless steel tubing immersed in a 70 l stirred water bath. Pressure reduction is accomplished using a throttling valve adjusted by a stepper motor, and hygrometers being calibrated are sealed into a small test chamber contained in a larger temperature-controlled chamber. The results of the following performance tests are presented:

A group-contribution method has been developed to estimate the heat of sublimation (?Hsub) at the triple point for organic solids. The correlation was developed using ?Hsub values from a training set of 218 compounds, and it was tested by comparing predicted and solid vapor pressures for 87 compounds (1103 data points). The predicted solid vapor pressures were obtained from the

The objective of the present investigation was the determination of the melting temperatures of the eutectic compounds Fe-C, Co-C, and Ni-C. Six eutectic fixed-point cells of the Physikalisch-Technische Bundesanstalt (PTB) (Fe-C1, Fe-C2, Co-C1, Co-C2, Ni-C1, and Ni-C2) and two cells of the Brazilian National Metrological Institute (Inmetro) (Fe-C1V and Ni-C1V), useable for the calibration of contact thermometers, were investigated. Their melting temperatures were calculated by extrapolation of the emf-temperature characteristics of four stable Pt/Pd thermocouples, which were calibrated at the eutectic fixed points and at conventional fixed points of the International Temperature Scale of 1990 (ITS-90). On the basis of the eight eutectic fixed-point cells and seven independent calibration runs, the melting temperatures of the Fe-C, Co-C, and Ni-C eutectics resulted in 1153.67 ± 0.15 • C, 1323.81 ± 0.27 • C, and 1328.48 ± 0.20 • C, respectively, with expanded uncertainties corresponding to a coverage factor of k = 2.

A vibrating-wire instrument for simultaneous measurement of the density and viscosity of liquids under conditions of high pressure is described. The instrument is capable of operation at temperatures between 298.15 and 473.15 K at pressures up to 200 MPa. Calibration was performed by means of measurements in vacuum, air, and toluene at 298.15 K. For n-dodecane measurements were made along eight

New, absolute values of the thermal conductivity of two refrigerants, R134a and R141b, in the liquid phase at saturation are reported. The measurements have been performed in transient hot-wire instruments making use of electrically insulated tantalum wires within ...

The thermal conductivity of three thermal-conductivity reference materials, Pyrex 7740, Pyroceram 9606, and stainless steel AISI 304L, has been studied. The technique employed is the transient hot-wire technique, and measurements cover a temperature range from room temperature up to 570 K. The technique is applied here in a novel way that eliminates all remaining contact resistances. This allows the apparatus to operate in an absolute way. The method makes use of a soft silicone paste material between the hot wires of the technique and the solid of interest. Measurements of the transient temperature rise of the wires in response to an electrical heating step in the wires over a period of 20 ms up to 20 s allow an absolute determination of the thermal conductivity of the solid, as well as of 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 0.1% for Pyrex 7740, 0.4% for Pyroceram 9606, and 0.2% for stainless steel AISI 304L, while the standard uncertainty of the technique is less than 1.5%.

This document summarises the uncertainties in the realisation of the standard platinum resistance thermometer (SPRT) subranges of ITS-90 between the triple point of neon (24.5561 K) and the freezing point of silver (961.78 ºC). The document provides users of ITS-90 with guidance for assessing the uncertainty in their SPRT calibrations and temperature measurements. A secondary purpose is to promote harmonisation of the assessment of calibration and measurement capabilities as defined under the CIPM's arrangement for the mutual recognition of national measurement institutes (CIPM 1999). The document describes all known sources of uncertainty and influence variables, identifies key references in the literature that discuss, model or evaluate each effect, gives an indication of the typical magnitudes of the uncertainties, and gives propagation laws so that total uncertainty may be determined.

The Boltzmann constant k will be re-determined by using the simple, exact connection between the speed of sound in noble gases (extrapolated to zero pressure) and the thermodynamic temperature T , the molar mass of the gas M, and the universal gas constant R. The speed of sound will be determined in a spherical cavity of known volume V by measuring the acoustic resonance frequencies. This acoustic method led to the CODATA-recommended value of k; however, the CODATA value of k came from measurements using an almost perfectly spherical, stainless-steel-walled cavity filled with stagnant argon. The steel cavity's volume was determined by weighing the mercury of well-known density required to fill it. In contrast, a copper-walled, quasispherical cavity (intentionally slightly deformed from a sphere), filled with helium gas that is continuously refreshed by a small helium flow that will mitigate the effects of outgassing, will be used. The volume of the copper cavity will be determined by measuring the microwave resonance frequencies and/or by three-dimensional coordinate measurements. If the microwave method is satisfactory, the measurement of k will be based on the ratio of the speed of sound in helium-obtained by acoustic resonance measurements-to the speed of light, obtained by microwave resonance measurements. This method exploits the theorem that the frequency ratios are independent of the details of the shape of the quasi-spherical cavity. Here, progress at LNE-INM/CNAM towards a better mechanical design and better understanding of the excess of the half-widths of the acoustic and microwave measurements are reported.

The construction, the calibration, and the use of the NIST Thermodynamic Radiation Thermometer (TRT) to measure the temperature of the gold freezing temperature blackbody and a variable-temperature blackbody from 800 to 2,700°C are described. These temperature determinations are detector-based and derived from the electrical substitution radiometer and length units. The TRT is constructed using a cooled, near-infrared enhanced silicon detector with a room-temperature-stabilized five-position filter wheel. The characteristics of the TRT, such as the size-of-source effect and preamplifier linearity, are determined. The measured temperatures are compared with those obtained using the NIST Absolute Pyrometer 1 (AP1) and the current NIST standard radiation thermometer, the Photoelectric Pyrometer (PEP). After the performance assessments, the TRT will become the standard radiation thermometer for disseminating radiance temperature scales in the United States.

Type R thermocouples are widely used and convenient high-temperature transfer standards; however, the achievable accuracy is limited by the effects of inhomogeneity and hysteresis. In this article, we summarize the results of the recent international comparison APMP-T-S1-04 and discuss the results of the thermoelectric scanning, spatially resolved over the length of the thermocouples. The thermoelectric signatures show both reversible (hysteresis) and irreversible inhomogeneities introduced by the calibration processes used by the participants. The results demonstrate that although the reversible hysteresis of Type R thermocouples limits their performance as a transfer standard in thermometry, this can be managed by appropriate design of the comparison protocol. By performing all calibrations from lower to higher temperatures from an initial 450 • C anneal state, a pilot laboratory reproducibility of typically 0.03 • C (k = 2) and a reference value uncertainty of 0.03-0.06 • C (at k = 2) over 0-1,100 • C were achieved. This allowed statistically significant testing of the calibration capabilities of all the participants.

The fugacity coefficients of hydrogen in binary mixtures with isobutane were measured using a physical equilibrium technique. This technique involves the use of an experimental chamber which is divided into two regions by a semipermeable membrane through which hydrogen, but not isobutane, can penetrate. Measurement of the gas pressures inside and outside the membrane allow a direct measurement of the hydrogen component fugacity at a given temperature, binary mixture mole fraction, and mixture pressure. In this paper, results are reported at 120, 140, 160, and 180°C. In each case, the total pressure of the mixture was maintained at an average value of 3.40 MPa. The general qualitative features of the data are discussed, and comparisions are made with predictions obtained from the Redlich-Kwong and the Peng-Robinson equations of state.

The equation of state (EOS) data for physical and chemical mixtures have been studied in terms of the Simha-Somcynsky hole theory. In a previous paper, individual group attraction energy and repulsive volume quantities necessary for the description of interactions between the chemical constituents of alkanes and alkylbenzene were proposed. The previous method has now been extended to physical mixtures of alkanes and alkane-alkylbenzene through suitable decomposition equations for physical and chemical mixtures. A comparison of the theoretical EOS data, predicted by means of the proposed scaling parameters, and the experimental data is in reasonable agreement. The results confirm a basis for the EOS predictions and promote applications of the methodology to further systems.

The fundamental structure of the model is based upon a detailed and innovative conformality analysis of the viscosity surfaces of pure fluids similar to that proposed for thermodynamic properties [G. Scalabrin et al. Fluid Phase Equilib. 170:23 (2000); Int. J. Refrig. 26:35 (2003)], resulting in the introduction of a new specific scaling parameter ψ for viscosity, defined by a single experimental viscosity value. The model structure is based on two reference fluids for which pure-fluid viscosity dedicated equations (VDE) are available, which in this work are ethane and propane. The model is then extended to mixtures following the classical corresponding states (CS) one fluid model using mixing rules without interaction parameters. This gives the model a predictive character. It can be reliably applied in a wide range of pressure-temperature values, in both liquid and vapor phases, due to the validity ranges of the reference equations. The investigated mixtures include binary and multicomponent systems of both light and heavy n-alkanes and halogenated alkanes including R134a, R125, R152a, R143a, R22, R142b, R32, and R124 as components. For both families of fluids, the accuracy in terms of absolute average deviation (AAD) is within 2.68% in the vapor phase and 3.0% in the liquid phase. The model has also been validated for strongly azeotropic mixtures such as R32-R290 and R134a-R290 giving interesting results by fitting the interaction parameters on a limited subset of data. The effectiveness of the proposed procedure is enhanced by the comparison with a recently published advanced theoretical model.

A bilateral comparison between Centro Español de Metrología (CEM) and Laboratorio Costarricense de Metrología (LACOMET) in the range from 83.8058 K to 933.473 K was carried out during 2009, and it is aimed to provide linkage of the CCT key comparisons K3 and K4 to LACOMET. This comparison gives support to the calibration measurement capabilities requested by LACOMET. The participation of CEM in the EURAMET regional comparisons EUROMET-T.K3 and EUROMET-T.K4 is the basis of the link. Two 25 standard platinum resistance thermometers (SPRTs) were used as travelling standards and were hand carried. One of them was used only in the aluminum freezing point while the other one covered the remaining fixed points. At the temperature of the argon triple point (83.8058 K), CEM performed the measurements in an argon triple-point apparatus, but LACOMET calibrated the SPRT at a temperature close to the argon point using a liquid-nitrogen boiling-point apparatus. Both SPRTs were provided by LACOMET, and LACOMET measured them before and after CEM. The SPRTs showed no significant drifts during the comparison. The results for both laboratories agreed within their expanded uncertainties and are summarized. A proposal for the linkage to the results of CCT-K3 and CCT-K4 is presented.

The thermal conductivity of three (0.239, 0.499, and 0.782 mol·kg −1 ) and the viscosity of four (0.0658, 0.2055, 0.3050, and 0.4070 mol·kg −1 ) binary aqueous K 2 SO 4 solutions have been measured with coaxial-cylinder (steady-state) and capillary-flow techniques, respectively. Measurements were made at pressures up to 30 MPa, and the range of temperature was 298-575 K. The total uncertainties of the thermal conductivity, viscosity, pressure, temperature, and composition measurements were estimated to be less than 2%, 1.6%, 0.05%, 30 mK, and 0.02%, respectively. The measured values of the thermal conductivity and viscosity of K 2 SO 4 (aq) were compared with data and correlations reported in the literature. The reliability and accuracy of the experimental method was confirmed with measurements on pure water with well known (IAPWS standards) thermal conductivity and viscosity values (deviations, AAD, within 0.31 % and 0.52 %, respectively). The values of the viscosity A-, B-, and D-coefficients of the extended Jones-Dole equation for the relative viscosity (η/η 0 ) of aqueous K 2 SO 4 solutions as a function of temperature were studied. The maximum of the Bcoefficient near 340 K has been found. The derived values of the viscosity A-and B-coefficients were compared with results predicted by the Falkenhagen-Dole theory of electrolyte solutions and calculated with the ionic B-coefficient data. The behavior of the concentration dependence of the relative viscosity of aqueous K 2 SO 4 solutions is discussed in terms of the modern theory of transport phenomena in electrolyte solutions.