Assessment of methods for determining the impurity concentration in mercury cells

Kalemci, M. | Ince, A.T. | Bonnier, G.

Article | 2011 | International Journal of Thermophysics32 ( 01.02.2020 ) , pp.269 - 277

The uncertainty arising from chemical impurities is the principle contribution in the uncertainty budget of primary level temperature measurements. Impurities in any substance generally decrease the freezing (or triple) point temperature of a substance, and their influence is governed primarily by their behavior at low concentrations in the host material. The depression in temperature due to impurities is theoretically expressed by Raoult's law which, at final analysis, expresses the linearity between ?T (T observed-T pure) and the inverse of the melted fraction (1/F). Recently, TUBITAK UME carried out a new project on the construct . . .ion of new reference mercury fixed-point cells. Within the scope of this study, three different sets of mercury cells with different purity values were fabricated. Three methods were employed to assess the impurity concentration in the cells. The first method is known as the mole fraction sum of impurity components, and the chemical assays form the basis for this kind of assessment. The second method of evaluation is based on a 1/F versus ?T curve, and the slope values obtained from these curves are important. The final method is to directly compare the new cells with a national (or reference) standard mercury cell. The results obtained from three methods of evaluation showed consistency in terms of qualitative analysis. © 2011 Springer Science+Business Media, LLC Daha fazlası Daha az

Use of salt baths in the temperature range from 175 °c to 540 °c with uncertainties of less than 30 m°C

Alper, F.M.P. | Ince, A.T. | Aiordachioaiei, M.

Article | 2011 | International Journal of Thermophysics32 ( 01.02.2020 ) , pp.505 - 512

Calibration of thermometers in the temperature range from -80 °C to 550 °C requires liquid baths; alcohol, water, silicon oil, salt baths and dry block furnaces. In this study, the use of salt baths outside of their usual range of 250 °C to 540 °C for calibrating thermometers in the range between 175 °C and 250 °C is proposed. The calibration range from 150 °C to 250 °C is usually covered by an oil bath, but utilizing a salt bath saves calibration time and resources, improves stability and homogeneity, allows longer term usage of the liquid, and reduces hazardous chemical vapors evaporated at temperatures above 175 °C. This proposal . . . is based on a study of the uncertainty contributions at varying salt bath temperatures in the range from 175 °C to 540 °C which was carried out in this study. Results achieved and analyzed in this study indicate that the implementation of salt baths in this lower temperature range provides opportunities to calibrate reference and/or working thermometers with an uncertainty below 30 m°C, almost the same as the oil-bath uncertainty in the range of 175 °C to 250 °C. The main components of uncertainty contributed by a salt bath over this temperature range are discussed in this study. © 2011 Springer Science+Business Media, LLC Daha fazlası Daha az

Construction of Home-Made Tin Fixed-Point Cell at TUBITAK UME

Kalemci, M. | Arifovic, N. | Bağçe, A. | Aytekin, S.O. | Ince, A.T.

Article | 2015 | International Journal of Thermophysics36 ( 8 ) , pp.1968 - 1979

TUBITAK UME Temperature Laboratory initiated a new study which focuses on the construction of a tin freezing-point cell as a primary temperature standard. The design is an open-cell type similar to the National Institute of Standards and Technology design. With this aim, a brand new vacuum and filling line employing an oil diffusion pump and two cold traps (liquid nitrogen and dry ice) was set-up. The graphite parts (crucible, thermometer well, etc.) have been baked at high temperature under vacuum. Each cell was filled with approximately 1 kg of high-purity tin (99.9999 %) in a three-zone furnace. Then several melting and freezing . . .curves were obtained to assess the quality of the home-made cell, and also the new cell was compared with the existing reference cell of the laboratory. The results obtained are very close to the reference cell of UME, indicating that the method used for fabrication was promising and satisfactory and also seems to meet the requirements to have a primary level temperature standard. © 2015, Springer Science+Business Media New York Daha fazlası Daha az

Spectroscopy for the Analysis of Nanoporous Silicon Gas and Humidity Sensors

Oguz Aytekin, S. | Ince, R.

Article | 2018 | International Journal of Thermophysics39 ( 10 ) , pp.1968 - 1979

In this work, a Raman spectroscopic study of nanoporous silicon sensor samples demonstrated its use as a method of gauging the sensor potential via quantitative data it provides on the sensor nanostructure dimensions. This special property of the Raman spectroscopy technique also showed its potential to determine mechanical stability of the samples over 3 months. This work also shows that the Raman spectroscopy technique is sensitive to step changes in relative humidity in all the sensor samples via its measurement of the strain-free crystalline silicon (c-Si) Raman peak. Since the Raman technique is non-destructive and senses remot . . .ely on the fragile nanoporous sensor samples it will be the ideal replacement of the presently used electrical capacitance techniques as the primary determination of relative humidity. © 2018, Springer Science+Business Media, LLC, part of Springer Nature Daha fazlası Daha az

A New Generation of Open Zinc Freezing Point Cells at TUBITAK UME

Kalemci, M. | Bağçe, A. | Ince, A.T. | Arifoviç, N.

Article | 2018 | International Journal of Thermophysics39 ( 9 ) , pp.1968 - 1979

The Temperature Laboratory at TUBITAK UME initiated a study which focused on the construction of freezing point cells of ITS-90 as primary temperature standards. The first cell constructed within the scope of this study was an open tin freezing point cell and the results were in good agreement with the reference tin fixed point cell of UME. The second set of cells constructed was two open zinc freezing point cells. The design of these cells is similar to the tin freezing point cell. After construction, all the home-made cells were evaluated by analyzing their melting and freezing curves. Finally comparison measurements were performe . . .d between the current laboratory reference zinc cell and all newly constructed cells. © 2018, Springer Science+Business Media, LLC, part of Springer Nature Daha fazlası Daha az

Thermodynamic analysis of some industrial applications with variable ambient conditions

Çamdali, Ü. | Tunç, M.

Article | 2004 | International Journal of Thermophysics25 ( 6 ) , pp.1965 - 1979

In this study, the general exergy balance equation of an open system is obtained based on the variable ambient temperature and pressure. Using this result, the mathematical equations regarding both the reversible work given to the system in the electric arc furnace used in steel production and the exergy loss in the rotary burner used in cement production are derived. In obtaining these equations, it is assumed that the ambient temperature has a sinusoidal variation. The effects of varying ambient parameters on calculated exergy values in industrial applications are discussed, and the obtained results are analyzed and demonstrated.

Fabrication and Characterization of Nanoporous Silicon Relative Humidity Sensors

Aytekin, S.O. | Ince, R.

Article | 2015 | International Journal of Thermophysics36 ( 12 ) , pp.3421 - 3439

This work describes a porous, silicon-based humidity sensor operating under the capacitive transduction principle. One of the aims of this work is to determine the main parameters such as sensitivity, linearity, hysteresis, and time response to step humidity changes of four samples via measurements of their capacitance. The parameters gauged by capacitance measurements were used to explain the dynamics of its operation. The most sensitive sample caused changes in relative humidity of 74nF·%rh-1. Hysteresis of at least 3.6 % to 4.6 % was found to occur. Humidity sensor samples synthesized from nanoporous silicon were also analyzed by . . . scanning electron microscopy, image processing, and Raman spectra red shifts. As a result of these measurement and analysis of this work, the best synthesis conditions and nanopore surface and sub-surface diameters for producing high performing humidity sensors were identified. Another aim of this work is to find the optimal pore size from the analysis of image processing and Raman spectra. The optimal porous sizes in relation to the analyzed sensor’s characteristics were found to be between 4 nm and 26 nm. The novelty of this work is to establish the relationship between the capacitance measurements with image processing of SEM images and Raman spectral measurements. The mechanical stability of the samples was also gauged over 3 months utilizing both capacitance and Raman spectral measurements. © 2015, Springer Science+Business Media New York Daha fazlası Daha az

Development of a system for temperature profile characterization of baths

Torun, M.K. | İnce, A.T.

Article | 2011 | International Journal of Thermophysics32 ( 11.12.2020 ) , pp.2370 - 2378

Liquid baths are the main calibration equipment to directly affect the measurement uncertainty in temperature calibrations. Therefore, the characteristics of baths need to be well investigated and understood. The temperature profile and stability of liquid baths are one of the most important contributions to the calibration uncertainty of platinum resistance thermometers, digital thermometers, liquid-in-glass thermometers, and thermocouples. Commercial baths only present stability and uniformity data in two dimensions in general; however, thermometers and thermocouples are immersed into the body of the bath, so the depth or z-axis i . . .s also very important. In this study, a measurement system has been designed using three-stepper motors and a data acquisition system (DAS). The DAS is developed using object-oriented algorithms to form a three-dimensional (3-D) scanning system. The 3-D scanning system is home-made and used in conjunction with a reference platinum thermometer. The temperature profiles and stability of several types of baths: water, oil, and salt were obtained in the temperature range from 30°C to 450°C. Therefore, this contributed toward a more accurate uncertainty budget evaluation. © 2011 Springer Science+Business Media, LLC Daha fazlası Daha az

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