IMEKO Event Proceedings

Page 786 of 855 Results 7851 - 7860 of 8545

B. Nevrlá, M. Vilémová, J. Matejicek
THERMAL AND MECHANICAL PROPERTIES OF TUNGSTEN COMPACTS PREPARED BY SPS

Tungsten is a promising candidate material for use in the tokamak device aimed at future production of nuclear fusion power. Here, tungsten is intended for the application in the part called first wall, with the function of a heat-resistant plasma facing armor. In the present work, two fractions of tungsten powder (2 and 4 µm) were used to prepare two consolidated samples by spark plasma sintering (SPS), using a combination of pressure, temperature and electric power. This sintering technique produces samples of near theoretical density which is positive for the application. Tungsten compacts were then studied to determine some basic thermal and mechanical properties, namely thermal conductivity using the laser-flash method and hardness by Vickers test. The measurements were focused on thermal conductivity of the compacts because high thermal conductivity is crucial for the material of tokamak first wall, loaded by high heat flux from the plasma. High hardness is desirable for good resistance to mechanical erosion. The obtained results pointed out the differences between the two tungsten compacts and provided an idea about suitable production parameters.

S. Lee, S. Kwon
THERMAL CONDUCTIVITY OF ALUMINUM FABRICATED BY EQUAL CHANNEL ANGULAR PRESSING

Equal channel angular pressing (ECAP) has the advantage of enabling an ultrafine grain size. Aluminum 1060 is used as a power plant material because of its favorable electrical properties. However, the weak strength of aluminum limits its application. In this study, the thermal conductivity and electrical conductivity of Al 1060 made by ECAP was investigated. ECAP was conducted through the die having a channel angle of 90° and a corner angle of 20° at a temperature of 473 K with a strain rate of 2 mm·s-1. The specimen was then processed with 1 to 8 passes by the route Bc method with 90° rotation. In the case of eight passes, the grain size was reduced to as small as 300 nm. The thermal conductivity gradually decreased with ECAP passes, because of the decreased grain size by ECAP.

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.

Alexandre Lourenço, Raul Caballero Santos, Javier Diaz De Aguilar Rois
Thermal converter level dependence determination by digital sampling

This paper describes a method to evaluate the low frequency level dependence of Planar Multijuction Thermal Converter (PMJTC) based on digital sampling. The measurement system, the algorithms and the validation are also described. This method is also valid to obtain the absolute value of the ac-dc difference of a thermal converter at low frequency.

Andrea Aquino, Michele Antola, Alessio Pacchini, Stefano Pagnotta, Marco Lezzerini
Thermal decay of monzogranite from Elba Island (western Tuscany, Italy): properties of an ancient building material

Thermal decay may be one of the causes of monzogranite deterioration. In this work, we study the chemical, mineralogical and petrographic characteristics and the physical properties of the monzogranite of Elba Island as a building material, to better understand the main effects of the degradation caused by artificial thermal cycles on this rock.

A. Ryniewicz, M. Kowalski, J, Gawlik
THERMAL DEFORMATION OF MEASURING MACHINES

The paper presents the system for temperature fields analysis of coordinate measuring machines. The system should allow the following operations: temperature measurements on the surface of selected CMM units and elements according to the adopted strategy, controlling the operations of the measurement systems, conducting the calibration and correction of measurement sensors, mathematical analysis with the finite element method and graphic presentation of results.

Zaccaria Silvestri, Patrick Pinot
THERMAL DESORPTION MASS SPECTROMETRY (TDS): APPLICATION ON MASS METROLOGY

A new device has been developed for the study of physisorbed elements on polished and large surface used in mass metrology.
This technique, based on the analysis by mass spectrometry of desorbed molecules caused by heating under vacuum from the analyzed surface, is presented.
The first application of this device is the study of the current and future mass standards to understand the reactivity of their surface depending of the storage conditions, of the cleaning process and polishing method. So, an example of surface contamination analysis by thermal desorption mass spectrometry (about cleaning effect on a super alloy based on cobalt) is given.

Ricardo A. N. Ferreira, Denise M. Camarano, Wilmar B. Ferraz, Pablo A. Grossi, Fábio A. Mansur
THERMAL DIFFUSIVITY OF URANIUM DIOXIDE FUEL PELLETS WITH ADDITION OF BERYLLIUM OXIDE BY THE LASER FLASH METHOD

A research program is in progress at CDTN – Centro de Desenvolvimento da Tecnologia Nuclear, aiming the development of fuel pellets made from a mixture of uranium dioxide microspheres or powder and beryllium oxide powder for increasing the thermal conductivity of the nuclear fuel. This type of fuel promises to be safer than current fuels, improving the performance of the reactor. In previous studies conducted at CDTN, fuel pellets were manufactured and tested considering the following weight percentages: 1, 2, 3, 5, 7 and 14wt.% of beryllium oxide (BeO) in mixture with microspheres of UO2. Continuing this project, new uranium dioxide fuel pellets with addition of 2wt.% of BeO were manufactured and tested. The Laser Flash Method was employed to investigate the variation of thermal diffusivity at room temperature on those new pellets. The results obtained showed an increase of 12% in the thermal diffusivity with addition of 2wt.% of BeO in the uranium dioxide fuel pellets.

Y. Itakura, H. Shinohara, N. Isoda
THERMAL ENVIRONMENT IN A MODEL HOUSE FOR THE AGED

Houses and instruments for the benefit of aged welfare have been developed as one of the solutions to this important problem of the next Century. To live in comfort and to save energy, the thermal environment in a model house for the aged has been monitored. It was made clear that floor heating and ceiling radiant cooling gave a comfortable environment to the aged due to uniform room temperature distribution and that air-conditioning cooling with a ceiling fan was energy efficient.

A. Jakstas, S. Kausinis, A. Kasparaitis, R. Barauskas, A. Barakauskas
THERMAL ERROR ANALYSIS OF PRECISION INTERFEROMETRIC LENGTH MEASUREMENT SYSTEMS

The paper describes the practical application of thermal error analysis for precision length measurement systems operating in non-ideal environments. Finite element analysis and experimental investigations are carried out to examine the essence of thermal process and to demonstrate the existence and feasibility of the thermal modal analysis in precision line scale calibration system.

Page 786 of 855 Results 7851 - 7860 of 8545