IMEKO Event Proceedings

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Terry Quinn
Temperature Scales from the early days of thermometry to the 21 century
TEMPMEKO 2004 - 9th Symposium on Temperature and Thermal Measurements in Industry and Science, Cavtat-Dubrovnik, Croatia, 2004

Joachim Fischer, Bernd Fellmuth, Joachim Seidel, Wolfgang Buck
TOWARDS A NEW DEFINITION OF THE KELVIN: WAYS TO GO
The present definition of the kelvin links the unit of temperature with a material property. It would be more consistent with the current approaches to other base units to fix the value of the Boltzmann constant k, in- stead. For this purpose, k must first be determined with distinctly lower uncertainty. This paper considers ex- perimental methods having potential to contribute to the determination of k.
TEMPMEKO 2004 - 9th Symposium on Temperature and Thermal Measurements in Industry and Science, Cavtat-Dubrovnik, Croatia, 2004

P. Marcarino, G. Bonnier
TEMPERATURE AMPLIFIER BY MEANS OF COUPLED GAS-CONTROLLED HEAT-PIPES
BNM-INM and IMGC-CNR have been working during many years in the field of Gas-Controlled Heat-Pipes (GCHPs). These devices have been specifically developed for accurate temperature measurements, with ever improving thermal characteristics during the last 30 years. A GCHP is based on the thermodynamic properties of the liquid-vapor transition of a given working fluid under a controlled pressure. The measuring zones of the more recent GCHPs, connected to an accurate pressure controlled line, present a temperature uniformity and stability at the millikelvin level in a very large range of temperature. The basic principles of GCHPs are reviewed and the most important results achieved by using this device in thermometry are presented. By applying the same pressure to several GCHPs using different working fluids, the temperature in one GCHP is thermodynamically related to the temperature in another GCHP. It means that any temperature of a given working fluid, i.e. between 240 °C and 400 °C for a mercury GCHP, is able to be "amplified" in order to establish an unique and very reproducible higher temperature in another working fluid, i.e. between 660 °C and 962 °C for a sodium GCHP. This instrument, called “Temperature Amplifier” (TA), allows a considerable improvement in the calibration process of SPRTs at high temperature. Indeed, the operating temperature of the reference SPRT in the low temperature GCHP can be limited to 400 °C, and, consequently, the stability and reproducibility in the high temperature GCHP are largely improved. The experimental results lead to the possibility to use the TA above the Aluminum point as a possible alternative instrument in a future temperature scale.
TEMPMEKO 2004 - 9th Symposium on Temperature and Thermal Measurements in Industry and Science, Cavtat-Dubrovnik, Croatia, 2004

Howard W. Yoon, Charles E. Gibson, David W. Allen, Robert D. Saunders, Maritoni Litorja, Steven W. Brown, George P. Eppeldauer, Keith R. Lykke
THE REALIZATION AND THE DISSEMINATION OF THE DETECTOR-BASED KELVIN
In the International Temperature Scale of 1990 (ITS-90), temperatures above the freezing temperature of silver are determined with radiation thermometers calibrated using spectral radiance ratios to one of the Ag-, Au- or Cu-freezing temperature blackbodies and the Planck radiance law. However, due to the use of spectral radiance rats, the temperature uncertainties of the ITS-90 increase as the square of the temperature ratios. Recent acoustic- gas thermometry measurements have also shown that the underlying thermodynamic temperatures used in the radiance ratios in determining the Ag- and Au-fixed point temperatures could be in error. Since the establishment of ITS-90, much progress has been made in the development of radiation thermometers and blackbody sources. Cryogenic electrical-substitution radiometry is widely used in detector and radiometer calibrations, and stable, high-temperature metal-carbon eutectic blackbodies are under development. Radiation thermometers can be calibrated for absolute radiance responsivity, and blackbody temperatures determined from measurement of optical power without the use of any fixed points thus making possible direct dissemination of thermodynamic temperatures. We show that these temperatures can be measured with lower final uncertainties than the ITS-90 derived temperatures. We have shown that these “Absolute Pyrometers” can be used to determine the thermodynamic temperatures of the ITS-90 fixed points as well as also being used in bilateral comparisons of temperature scales. Many leading national measurement institutes are already utilizing detector- based temperatures in establishing spectroradiometric source scales. We believe, that due to these developments, the international temperature scale should be revised so that a thermodynamic temperature scale can be directly disseminated.
TEMPMEKO 2004 - 9th Symposium on Temperature and Thermal Measurements in Industry and Science, Cavtat-Dubrovnik, Croatia, 2004

Bob Hardy
TRUST BUT VERIFY – PRACTICAL APPROACHES TO HUMIDITY GENERATION AND MEASUREMENT
Construction of humidity generators is a common undertaking in many of today's national metrology institutes and commercial calibration laboratories. A generator based on theoretical methods and statistical uncertainty expectations is often trusted as a laboratories primary humidity reference. While it is important to follow sound design theory, and compute statistical estimates of the output from a generator, verification is an equally powerful tool that can help to make even the weakest of designs more trustworthy. Generator designs will be reviewed in an effort to avoid common obstacles while capitalizing on a few simple and practical improvements. Testing and verification will also be considered with a focus on condensation hygrometry.
TEMPMEKO 2004 - 9th Symposium on Temperature and Thermal Measurements in Industry and Science, Cavtat-Dubrovnik, Croatia, 2004

C. A. Nieto de Castro
THERMAL CONDUCTIVITY OF MOLTEN MATERIALS. IS EXPERIMENT NECESSARY?
The knowledge on the thermal conductivity of molten materials (salts, metals, semiconductors, polymers) is very scarce, both from the experimental and theoretical points of view. Knowing of the difficulty in obtaining accurate experimental data for most liquids, the task is uncouthly more difficult when the measurements are to be performed at medium and high temperatures with materials that are corrosive, easily reacting and good heat transfer media. Convective and radiative heat transfer effects affect in particular thermal conductivity measurements at high temperatures. These facts also make difficult theoretical calculations using molecular/ionic theories and drastic approximations, both from the phenomenological side, to the force field between particles, restrict the validity of the results obtained. Computer simulations are a possible alternative to overcome these problems and its development in recent years is noteworthy, induced by the improvements in theory, algorithms and computer hardware. Their applications to the study of molten materials have been very limited and with results of questionable validity. However, it was recently possible to apply equilibrium molecular dynamics simulations to the calculation molten salts thermal conductivity with a reasonable success. In this lecture a short review of the field will be presented, with especially emphasis in the actual situation, challenges faced and foreseen solutions, including microgravity experiments.
TEMPMEKO 2004 - 9th Symposium on Temperature and Thermal Measurements in Industry and Science, Cavtat-Dubrovnik, Croatia, 2004

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