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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.

Institute VINCA, respectively French National Metrology Institute and Serbian Designated Institute for thermal properties metrology, on thermal conductivity measurements by the guarded hot plate method. The main objective was to validate the measurement capabilities of VINCA in terms of thermal conductivity in the temperature range from 10 degrees C to 50 degrees C by using the facility improved in the frame of the European project Eura-Thermal. The measurements were carried out on expanded polystyrene boards using guarded hot plate apparatuses (two-specimen GHP apparatuses) in accordance with the international standard ISO 8302. The measurement programme was defined taking into account the major characteristics of the guarded hot plate apparatuses used, such as specimen dimensions and temperature and thermal conductivity ranges. Specimens were machined by LNE from a same batch for both participants. Prior to the measurements, the homogeneity of the set of specimens, as well as the influence of a variation of density of the expanded polystyrene on the thermal conductivity measurements were studied by VINCA. The obtained results showed good agreement between the two laboratories, with relative deviations within the uncertainties of measurement. Also, the results validated the level of uncertainty assessed by VINCA for its thermal conductivity measurements to around 2.5 % (with a coverage factor of 2) between 10 degrees C and 50 degrees C.

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.

Ова докторска теза обухвата истраживачки рад на унапређењу мерења топлотне проводности термоизолационих чврстих материјала у Метролошкој лабораторији за температуру и термофизичке величине (МЛТВ) Института за нуклеарне науке ВИНЧА. Топлотна проводност се, као једна од најзначајнијих термофизичких величина чврстих материјала, мери различитим експерименталним методама. Метода која код слабо проводних материјала може обезбедити резултате са најмањом могућом мерном несигурношћу је метода заштићене топле плоче и она се као референтна користи у свим најзначајнијим националним метролошким лабораторијама у свету. Експериментална поставка којом се примењује ова метода је установљена у Институту ВИНЧА још 60-их година прошлог века и била је функционална до средине 80-их. Топлотна проводност термоизолационих материјала се у том периоду мерила са релативном мерном несигурношћу од 3 % до 10 %. У складу са убрзаним развојем МЛТВ почетком овог века, као и њеним каснијим признавањем као именоване националне лабораторије за термофизичке величине, приступило се ревитализацији експерименталне поставке и унапређењу поступка одређивања топлотне проводности. У оквиру рада на овој дисертацији је унапређена како сложена мерна апаратура кроз моделовање, израду и тестирање нових елемената и система, тако и калибрациони и мерни поступак и начин обраде мерних сигнала. Као резултат широког унапређења, данас се у Институту ВИНЧА топлотна проводност термоизолационих чврстих материјала може мерити са високом тачношћу и прецизношћу, тј. малом релативном мерном несигурношћу која достиже ниво од 2 %. Тим резултатом, који је потврђен преко међународног међулабораторијског поређења извршеног у оквиру Eura-Thermal пројекта, Метролошка лабораторија за температуру и термофизичке величине Института ВИНЧА се сврстала у ред значајних светских лабораторија те врсте., This PhD thesis implies research on improving the thermal conductivity measurement of thermal insulations in the Metrological Laboratory for Temperature and Thermophysical Properties (MLTV) of the Institute of Nuclear Sciences VINČA. Thermal conductivity, as one of the most important thermophysical properties of solid materials, is measured by various experimental methods. A method that may provide results with a lowest possible measurement uncertainty for poorly conductive materials is the guarded hot plate method and it is used as a reference technique in all most important national metrology laboratories in the world. A related experimental setup was established at the Institute VINČA in the 1960s and was functional until the mid-80s. Thermal conductivity of thermal insulation materials was measured in this period with a relative uncertainty of 3 % to 10 %. In accordance with a fast development of MLTV at the beginning of this century, as well as its subsequent recognition as the designated laboratory for thermophysical properties, a revitalization of the experimental setup and an improvement of the corresponding measurement process began. Within the scope of this dissertation, the measurement apparatus was improved through modelling, designing and testing of new elements and systems, as well as through new calibration, measuring and data reduction procedures. As a result of these improvements, today, the Institute VINČA is capable to measure the thermal conductivity of insulation materials with a high accuracy and precision, i.e. with small relative uncertainties down to a level of 2 %. With this result, which was confirmed through an international inter-laboratory comparison performed within the framework of the Eura-Thermal project, the MLTV of the Institute VINČA has been ranked among the world's leading laboratories of this kind.

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.

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.

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.

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.

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.