Uticaj kontaktnog otpora pri određivanju toplotne provodnosti metodom zaštićene tople ploče

U radu je opisana aparatura za merenje toplotne provodnosti slaboprovodnih materijala, u koje spadaju stakla, plastike, gume, keramike i sl. Metoda se primenjuje u Labaratoriji za termotehniku i energetiku Instituta za nuklearne nauke “Vinča” od kraja 60-ih godina i daje dobre i pouzdane rezultate u opsegu od 10 do 200 °C. Tokom poslednje godine metoda je podvrgnuta reviziji i unapređena izradom programa za automatizovanu akviziciju, prikaz i obradu podataka pod kontrolom računara. Primena unapređenja ilustrovana je eksperimentima na referentnim uzorcima od Ilford stakla. Nekoliko uzastopnih eksperimenata sa različitim kontaktnim medijumom na površinama uzorka ispitan je uticaj kontaktnog otpora na rezultat merenja

Development of a Single-Sided Guarded Hot Plate Apparatus for Thermal Conductivity Measurements

This work presents the development of an experimental set-up for measurements of thermal conductivity of solid materials, such as ceramics, polymers, rubbers, glasses, biological materials, etc. whose thermal conductivity lies in the approximate range between 0.1 and 2 W/mk The set-up was designed on the principle of the single-sided guarded hot plate method. In order to find the optimal design for generation of traceable 1-D heat flux through an investigated 300 mm x 300 mm specimen, a numerical heat transfer finite element method analysis was performed. The principal components of the measuring apparatus, such as hot plate with thermopile, cold plate, and auxiliary hot plate, were constructed according to the obtained results of simulations. Software for the control of experiment and data acquisition was developed using the LabVIEW programming environment

An in situ temperature calibration of a guarded hot plate apparatus

This paper presents design, development, and testing of a custom-made calibration environment for the calibration of temperature sensors applied in a guarded hot plate apparatus for thermal conductivity measurements. Description of an in situ calibration principle and realization are introduced. Results of numerical simulation, as well as those of experimental validation are given in a separate section of the paper. According to the results, proposed in situ calibration by using the applied guarded hot plate apparatus elements improves both accuracy and traceability the of thermal conductivity measurement. © 2018 Serbian Society of Heat Transfer Engineers

Speeding-up Scientific Knowledge Transfer and Improvement of Capabilities of emerging European National Metrology Institutes and Designated Institutes in the field of thermal measurements: Benefits and Impacts

Within the frame of a European project called Eura-Thermal, the general objective was to upgrade the regional metrological infrastructure (Bosnia & Herzegovina, Croatia, Ireland, Serbia...) with new capabilities, especially in the field of thermal measurements. This paper highlights the strategy used for improving in the short term, scientific knowledge transfer and the capabilities of different emerging institutes. Furthermore, as a main output, the impacts and benefit for Industry and for the end-users are also presented as examples. © 2018 Institute of Physics Publishing. All rights reserved.XXII World Congress of the International Measurement Confederation (IMEKO 2018

Correction on the influence of thermal contact resistance in thermal conductivity measurements using the guarded hot plate method

This work considers the influence of finite thermal contact resistances which exist in thermal conductivity measurements of homogeneous and poor thermal conductive materials using the guarded hot plate method. As an example of correction method proposed in this work, different experimental results obtained from a standard reference material sample (with the conductivity of about 1 W/mK) have been presented

Software solution for control and data acquisition in the pulse calorimetry method

This work presents a software solution for adjusting, controlling, displaying, and acquiring parameters and data in the pulse calorimetry experimental technique for specific heat capacity, electrical resistivity, total hemispherical emissivity, and normal spectral emissivity measurements. The software has been developed under the LabVIEW platform, V.7.11, and an example of its application with measurement results is presented in a separate section. The total expanded uncertainty of obtained results for the specific heat capacity and electrical resistivity of palladium was 5% and 1 - 2%, respectively

Data reduction and uncertainty assessment of the direct pulse heating technique with both contact and radiance temperature measurements

This work presents a data reduction procedure of the direct pulse heating technique with both contact and radiance temperature measurements. The technique is applied for the measurement of thermophysical properties of electroconductive solids over a wide temperature range, i.e., from room temperature up to about 2300°C. Absolute and radiance temperatures of a tested material are measured by thermocouple and radiation thermometer, respectively and these and other experimental data are then reduced to the values of specific heat, specific electrical resistivity, hemispherical total emissivity and normal spectral emissivity of the tested material. The related data reduction and corresponding uncertainty assessment for each property is described in detail. An example of uncertainty assessment is given for the recent measurement of specific heat, specific electrical resistivity, hemispherical total emissivity and normal spectral emissivity at 900 nm of molybdenum alloy TZM specimens

Measurements of Thermophysical Properties of Solids at the Institute VINCA

This paper presents the Metrological Laboratory for Thermophysical Quantities (MLTV) and its actual measurement possibilities. The MLTV is located in the Department of Thermal Engineering and Energy of the Institute of Nuclear Sciences VINCA in Serbia. It was founded in 1963, accredited by the National Accreditation Body in 2007 and became the national designated laboratory for thermophysical quantities and received the status of a EURAMET Associate Member in 2015. Today, the laboratory develops, maintains and disseminates traceability of different national standards, such as those for thermal conductivity of insulations and poorly conductive solid materials from 250 K to 350 K, thermal diffusivity of a large variety of solid materials from 200 K to 1450 K and specific heat and specific electrical resistivity from 250 K to 2400 K of electroconductive solid materials. Total hemispherical and spectral normal emissivity from 1200 K to 2400 K of electroconductive solid materials are also measured in the MLTV. The methods and experimental setups for the realization and measurement of all of these standards and quantities are described with corresponding examples.21st International Meeting on Thermophysics, Oct 12-14, 2016, Terchova, Slovaki

Development of a single-sided guarded hot plate apparatus for thermal conductivity measurements

This work presents the development of an experimental setup for measurements on of thermal conductivity of solid materials, such as ceramics, polymers, rubbers, glasses, biological materials, etc. whose thermal conductivity lies in the approximate range between 0.1 and 2 Wm-1K-1. The setup was designed on the principle of the single-sided guarded hot plate method. In order to find the optimal design for generation of traceable one-dimensional heat flux through an investigated 300×300 mm2 specimen, a numerical heat transfer FEM analysis was performed. The principal components of the measuring apparatus, such as hot plate with thermopile, cold plate and auxiliary hot plate were constructed according to the obtained results of simulations. Software for the control of experiment and data acquisition was developed using the LabVIEW programming environment

Mitigation of urban particulate pollution using lightweight green roof system

As the global population becomes more concentrated in urban environments, higher numbers of people will be exposed to urban air pollution. The environmental and human health benefits of green roofs are widely recognized. The aim of this paper is to promote green roofs as an effective passive technique for pollution mitigation and adaptation to climate change. During the heating season, the ambient concentrations of PM1, PM2.5, and PM10 were measured above a green roof and a reference roof on a school building, located in New Belgrade, the second-most populous municipality and business center of Serbia’s largest city. The percent reduction of PM10, PM2.5 and PM1, in January 2020, above the green roof compared to the reference roof was 7%, 16.6%, and 17.6%, respectively. The results show that lightweight green roof improve air quality in terms of PM concentrations for all months considered. In this paper, correlation analysis and the use of Pearson’s coefficient were used in the process of analysis to determine the relationship between PM10, PM2.5, PM1, and ambient parameters: relative humidity, ambient temperature, and wind speed. It was found that the statistical correlation expressed by the Pearson coefficient between all PM particles and wind speed was statistically significant in all observed months except September. Also, the degree of significance of the correlation between PM particles and humidity and temperature of ambient air varies by month