Effective heat management is essential for preserving performance and dependability as electronic equipment becomes increasingly powerful and smaller. This project presents the developed system, TeRMeS, which was created to test the thermal resistance of thermal interface materials (TIMs) essential for the thermal management of electronic devices, including battery systems. This work focuses on using steady-state techniques to evaluate TIMs under various operational forces and temperatures in real-world electronic packaging conditions. A noteworthy breakthrough is the creation of a user-friendly graphical user interface (GUI), which offers sophisticated options for real-time thickness measurement and enables researchers to alter parameters and dynamically display outcomes, thereby improving the measuring process. The results of the experiment highlight the importance of TIM thickness and applied force in lowering thermal resistance and increasing thermal conductivity. These elements are necessary to prevent battery packs and electrical parts from overheating. To improve heat management strategies in high-performance computing and electronics, the study provides accurate, reliable data by focusing on steady-state measurements.

Dans le cadre de l’évolution du plus grand accélérateur circulaire de particules « LHC », un important programme de mise à niveau sur l’ensemble des détecteurs qui le constitue a été lancé. Parmi eux, on retrouve la mise à niveau du détecteur LHCb qui comprend le remplacement complet de plusieurs sous-détecteurs. La fréquence de lecture élevée de 40MHz, sans précédent dans une expérience de physique des particules, et l’environnement de rayonnement sévère lié à l’augmentation de l’intensité du LHC, sont les principaux défis à relever par les nouveaux sous-détecteurs. Le travail présenté dans ce manuscrit, décrit une petite partie de l’évolution du détecteur LHCb. Le développement et la construction d’un nouveau trajectographe à grande échelle, basé sur une nouvelle technologie à fibres scintillantes «SciFi», lues avec des photomultiplicateurs au silicium «SiPM», est l’un des projets clés du programme de mise à niveau de LHCb. La première partie, consiste à étudier les échanges thermiques et à concevoir un système de refroidissement pour chaque Read-Out Box « ROB » qui contient deux cartes électroniques frontales « FE », et qui permettent de lire les données du détecteur. Ces dernières possèdent une dissipation thermique d’environ 110W.Pour assurer le bon fonctionnement des composants électroniques, il est obligatoire de mettre en place un refroidisseur. Des contraintes importantes sont prisent en compte dans cette étude, la première représente l’espace limité en regard du besoin du système de refroidissement, des interfaces électroniques et mécanique, la seconde concerne les SiPM. Reliés à l’électronique par des câbles flexibles, elles sont situées à proximité de l’électronique « FE » et leur température de fonctionnement doit être parfaitement réglée autour des -40°C. Des travaux de simulations numériques sur les logiciels FloTHERM et ANSYS ont été menés sur le banc expérimental réalisé au sein du laboratoire, et qui nous ont permis de déterminer la solution de refroidissement la mieux adaptée. Cette étude nous a aussi montré qu’il est plus que nécessaire d’intégrer des interfaces thermiques « IT» telles que des pâtes thermiques afin d’assurer un meilleur transfert de chaleur entre les composants électroniques et le refroidisseur. La deuxième partie, représente une étude approfondie sur les interfaces thermiques qui sont un point délicat de transfert de chaleur, car elles peuvent avoir plusieurs dizaines de pour cent de la résistance thermique globale. Pour garantir une utilisation adéquate et durable de ces matériaux, plusieurs paramètres ont été vérifiés, en particulier la dureté, la consistance (pas de production de graisse ou d’huile) et la conductivité thermique, grâce à un banc de mesures adapté d’après la méthode normalisé ASTM D5470, grâce auquel on a pu mesurer le flux de chaleur qui traverse l’échantillon d’interface thermique testé et qui est généré par une source chaude et un source froide qui sont montées aux extrémités de notre banc.Grâce à l’installation CHARME (CERN) et à la plate-forme PAVIRMA (Campus des Cézeaux), une série de mesure d’irradiations aux neutrons et aux rayons X sont également effectuées, correspondant à l’environnement dans lequel elles seront exposées dans l’expérience, d’un côté pour identifier les dégradations et changements possibles sur les résistances thermiques par l’analyse de l’impédance thermique, de l’autre pour identifier l’interface thermique qui convient le mieux à notre application et qui permet d’assurer un excellent échange thermique et donc un bon refroidissement de l’électronique frontale au sein du trajectographe du détecteur LHCb. / In the context of the evolution of the biggest circular accelerator of particles «LHC», an important program of upgrade on all the detectors which establishes itself was thrown. Among them, we find the upgrade of the detector LHCb which includes the complete replacement of several sub-detectors. The frequency of high reading of 40MHz, an unprecedented in an experiment of physical appearance of particles, and the environment of severe radiation bound to the increase of the intensity of the LHC, are the main challenges by the new sub-detectors. The work presented in this manuscript, described as a small part of the evolution of the LHCb detector. The development and the construction of a new wide-scale tracker, based on a new technology with scintillating fiber «SciFi», read with photomultipliers to the silicon «SiPM», is one of the key projects of the LHCb upgrade program. The first part, consists in studying the thermal exchanges and designing a cooling system for every Read-Out Box «ROB» which contains two electronic front-end « FE », and which allow to read the data of the detector. The latter has a thermal dissipation about 110W. To ensure the smooth running of electronic components, it is compulsory to set up a cooler. Important constraints are taken into account in this study, the first one represents the space limited compared to the need for the cooling system, the electronic interfaces and mechanical, the second concerns the SiPM. Connected with the electronics by flexible cables, they are located near the electronics «FE» and their temperature of operation is perfectly settled around -40 ° C. Works of digital simulations on the software FloTHERM and ANSYS were led on the experimental bench realized within the laboratory, and which allowed us to determine the best adapted solution of cooling. This study also showed to us that he is more than necessity to integrate thermal interfaces «IT» such as thermal pastas to assure a better transfer of heat between electronic components and cooler. The second part, represents an in-depth study on the thermal interfaces which are a delicate point of transfer of heat, because they can have dozens percent of the global thermal resistance. To guarantee an adequate and sustainable use of these materials, several parameters were verified, in particular hardness, consistency (no production of fat or oil) and the thermal conductivity, thanks to a bench of measures adapted according to the method normalized ASTM D5470, with this bench we could measure the flow of heat through the tested thermal interface sample and which is generated by a hot source and a cold source that are mounted at the ends of our bench.With the installation CHARME (CERN) and PAVIRMA (Cézeaux), a series of measure of irradiations at the neutrons and the X-rays are also made, correspond-ing to the environment in which they will be exposed in the experience, on one side to identify the damages and the possible changes on the thermal resistances by the analysis of the thermal impedance, the other one to identify the thermal interface which suits best our application and which allows to assure an excellent thermal exchange and thus a good cooling of the frontal electronics within the trajectographe of the detector LHCb.

Thermoelectric generators (TEG) are re-emerging technology that can be used to recover heat waste from commercial and industrial processes to generate electricity, enhancing fuel utilization and lowering greenhouse gas emissions. TEG modules are solid-state heat engines that produce no noise or vibration during operation. Notably, TEG modules are also able to operate at low-temperature differences, which makes them ideal for a wide range of heat waste recovery applications. Annular thermoelectric generator (ATEG) modules are optimal in applications where either the heat source or sink are round in shape. Bi2Te3 solution-based compounds are of significant interest in the application of thermoelectric materials (TE) used in low-temperature cooling and power generation applications. The main objective of the current work is to design a mechanically reliable ring-shaped ATEG module with a predictable performance using spark plasma sintered Bi2Te3 TE material for low temperature waste heat recovery applications. In terms of structure, this work is divided into two parts. The first part investigates how the use of a powder pre-treatment technique affects the mechanical and thermoelectric properties of P- and N-type Bi2Te3. In addition, part one also presents the measurements of these materials’ mechanical and thermoelectric properties, which serve as inputs for the finite element models used to design thermoelectric modules with parallel and perpendicular configurations vis-a-vis the sintering pressing direction. The second part evaluates the thermoelectric performance and thermal stresses of a ring-shaped ATEG couple that has been integrated between hot-side and cold-side heat exchangers. To this end, two configurations are compared with respect to their heat/electrical current flow paths: one that allows for radial flow (radial configuration), and one that allows for axial flow (axial configuration). The P- and N-type Bi2Te3 powder was treated using a mechanically agitated fluidized powder reduction facility that was built in-house. The characteristic uniaxial tensile strength of the P-type Bi0.4Sb1.6Te3 increased from 13.9 MPa to 26.3 MPa parallel to the sintering pressure, and from 16.3 MPa to 30.6 MPa perpendicular to the sintering pressure following oxide reduction using 5% H2 ˗ 95% Ar at 380 ℃ for 24 h. The figure of merit, ZT, increased from 0.35 to 0.80 and from 0.42 to 1.13 at room temperature (25 ℃) in the parallel and the perpendicular directions, respectively, after the surface oxide reduction treatment. On the other hand, the annealing effects of the oxide reduction pr-treatment of the N-type (Bi0.95 Sb0.05)2(Se0.05 Te0.95)3 using 5% H2 ˗ 95% Ar at 380 ℃ for 24 h were found to be responsible for the majority of the mechanical properties and ZT enhancement. Additionally, the characteristic uniaxial tensile strengths for this material increased from 30.4 to 34.1 MPa and from 30.8 to 38 MPa in the parallel and the perpendicular directions, respectively. The ZTmax (150 ℃) increased from 0.54 to 0.63 in both the parallel and perpendicular directions due to oxide reduction, while annealing led to an increase to 0.58 and 0.62 in the parallel and the perpendicular directions, respectively. An analytical model was constructed to compare the thermoelectric performance of the two configurations under three different hot-side thermal resistances, and a 3D coupled finite element ANSYS model was constructed to study and compare the thermal stresses of the two configurations at different dimensions. The two models were then used to create 2D maps in order to investigate the effects of ATEG couple configuration and dimensions, as well as the hot-side thermal resistance, with the goal of identifying the optimum design. The optimization of module geometry requires a trade-off between performance and mechanical reliability. The results of these investigations showed that increases in the temperature difference across the ATEG couple (ΔT) led to increases in both power and thermal stresses in both configurations. When both configurations were generating the same power at ΔT = 105 ℃, the thermal stresses in the radial configuration were as much as 67 MPa higher than those in the axial configuration due to the formation of additional tensile hoop stresses. The lowest thermal stress obtained for the axial couple configuration was 67.8 MPa, which was achieved when the couple had an outer diameter of 16 mm, an axial thickness of 1 mm, a ΔT of 14.8 ℃, and power generation of 10.4 mW per couple. The maximum thermal stress values were located at the corners of the interface between the solder and the TE rings due to the mismatched coefficient of thermal expansion. This thesis makes a novel contribution to the state-of-the-art literature in ring-shaped ATEG modules, as it details a well-characterised spark plasma sintered Bi2Te3 TE material and a methodology for designing a ring-shaped ATEG module with reliable, robust, and predictable thermoelectric and mechanical performance. The details of the contribution made by this work have been disseminated in the form of three journal publications, which have been integrated into this sandwich Ph.D. thesis. / Thesis / Doctor of Science (PhD)

Diplomová práca sa zaoberá vplyvom termálnych medzivrstiev na tepelnú kontaktnú vodi- vosť a tepelný kontaktný odpor. Práca sa zameriava na aplikáciu termálnych medzivrstiev pre vylepšenie tepelnej kontaktnej vodivosti v tepelnom spínači a v kozmických zariade- niach obecne. Teoretická časť práce stručne skúma rôzne pasívne termálne kontrolné systémy použí- vane v kozmických zariadeniach, vrátane termálnych medzivrstiev, a vysvetľuje pozadie tejto práce. Táto práca ďalej skúma rôzne termálne medzivrstvy, predovšetkým povlaky a fólie, a uvádza výber vhodnej termálnej medzivrstvy. Experimentálna časť práce skúma povrchové parametre, tepelnú vodivosť a mikrotvr-dosť medených vzoriek, ktoré slúžia ako substrát pre povlak čistého striebra. Ďalej rieši podmienky merania, metódy vyhodnocovania a samotné experimentálne merania. Experimentálne merania sú vykonané v termo-vákuovej testovacej komore a na základe výsledkov sú vyvodené závery. Pre ďalšiu prácu sú uvedené doporučenia.