The thesis deals with the creation for a numerical model of a solar collector with a phase change material as a heat storage medium. The model was implemented in Python. Using the created model, design optimization of several problems was carried out with the use of selected methods of heuristic optimization. The results of the behaviour of the created model and of design optimization were then analysed and evaluated.

Tato diplomová práce se zabývá předehřevem spalovacího vzduchu a jeho vlivem na parametry spalovacího procesu. V teoretické části je zpracován přehled nejčastějších znečišťujících látek z průmyslového spalování. Je popsána aktuálně platná relevantní legislativa v Evropské unii a jsou porovnány její implementace do národní legislativy v České republice a v Německu. Dále je provedena klasifikace hořáků z hlediska různých kritérií a rešerše předchozí práce v oblasti předehřevu spalovacího vzduchu. Na zkušebně hořáků byla provedena experimentální studie dvou různých hořáků na zemní plyn při konstantním tepelném příkonu 750 kW se spalovacím vzduchem předehřátým až na 250 °C. Výsledky odhalily pozitivní vliv předehřevu na účinnost spalování. Množství emisí NOx a CO naopak rostlo s teplotou spalovacího vzduchu.

This study focuses on the numerical solution of a fourth-order cell problem obtained through a two- scale expansion approach applied to a higher gradient heat equation microscopic problem involving temperature distributions. The main objective is to investigate the temperature field within the macroscale domain and compute the effective conductivity using finite element methods. The research utilizes numerical techniques, specifically finite element methods, to solve the fourth-order cell problem and obtain the temperature distribution.

E-bikes, often known as electric bicycles, are becoming more and more well-liked as green modes of mobility. High-capacity lithium-ion (Li-ion) batteries are utilised to power these e-bikes because of their extended cycle life, high energy density, and low self-discharge rate. The performance and longevity of these batteries may be impacted by temperature fluctuations, however. To guarantee the safe and dependable functioning of Li-ion batteries used in e-bikes, it is crucial to do temperature analysis on the batteries. In this dissertation, the thermal behaviour of a 48V 60AH Li-ion battery used in an e-bike will be studied under various cooling scenarios. The research specifically contrasts forced convection cooling using fans with broad and limited outlet ports to natural air convection cooling with large and reduced outlet ports. The study sheds light on the ideal cooling setups that might increase battery longevity and performance. The results of this study have important ramifications for e-bike producers and designers, battery producers, and energy storage system researchers. Simulations based on computational fluid dynamics (CFD) are used to simulate the thermal behaviour of the Li-ion battery under various cooling settings for the investigation. 25°C has been selected as the ambient temperature. For forced convection, the airflow rate is set at 3.5 m/s, whereas the airflow rate for natural convection is set at 0.1 m/s. The study's findings demonstrate that both natural and forced convection cooling methods may successfully lower the temperature of a Li-ion battery. However, forced air convection cooling using fans is more efficient than natural air convection at dispersing heat. These findings suggest that, owing to the higher air velocity, shrinking the outlet ports in both cooling approaches improves thermal performance.

Continuous caster moulds are the last and most important stage in the steelmaking process, where inclusions can either be generated or removed. With increasing casting speed using conventional immersion nozzles critical problems, such as unstable bulk mould flow have been noticed. Mould flux entrapment due to vortex and shearing action from the oscillating surface waves have become of particular concern. It is therefore necessary to have a calm inlet flow at the entrance of the mould. Recently, it has been acknowledged that a swirl blade placed at the upstream of the immersion nozzle effectively resolves the problems arising from unstable bulk mould flow. Therefore, to increase the knowledge of effect of swirling flow on the flow pattern in the mould, fundamental mathematical models of a billet mould equipped with a swirl blade in the nozzle have been developed. The model was used to study the effect of divergent angle of the immersion nozzle and mould aspect ratio on the flow field and temperature distribution inside billets moulds. Data from water model experiments were used to verify the mathematical model predictions. A fairly good agreement was found between physical modeling data and predictions, which ensured that the numerical model is reliable. Thereafter, the differences between square and round billet moulds were studied. Next, the effect of changing aspect ratio of the rectangular mould on the fluid flow and heat transfer, while keeping mould surface area constant, was studied. Two types of immersion nozzles, bottomless and conventional, were also analyzed during the research. The model moulds were changed gradually from a square billet with an aspect ratio of 1x1 to a rectangular billet with an aspect ratio of 3x1. First, the temperature and velocity distributions were calculated. Later, unsteady calculations were done to determine velocity fluctuations on the meniscus level for two types of nozzles and several moulds geometries. / <p>QC 20101110</p>

No / This paper presents experimental results of temperature distribution in fire in four typical types of steel-concrete composite joint (web cleat, fin plate, flush endplate and flexible endplate) with different fire-protection schemes. The test specimens were unloaded and the steelwork of each joint assembly was exposed to a standard fire condition [ISO 834, 1975: Fire Resistance Tests, Elements of Building Construction, International Organization for Standardization, Geneva] in a furnace. In total, 14 tests were conducted, including 4 tests without any fire protection and 10 tests with different schemes of fire protection. The main objective of these tests was to investigate the effects of three practical fire-protection schemes as alternatives to full fire protection of the entire joint assembly. The three alternative methods of fire protection were: (1) protecting a segment, instead of the entire length, of the beams; (2) unprotected bolts and (3) protecting the columns only. The main results of these tests are: (1) if all the steel work (excluding the bolts) in the joint assembly was protected, whether or not protecting the bolts had very little effect on temperatures in the protected steelwork other than the bolts. The bolt temperatures were higher if they were not protected than if they were protected, but the unprotected bolt temperatures in a joint with fire protection to other steelwork were much lower than bolt temperatures in a totally unprotected joint; (2) as far as joint temperatures are concerned, protecting a segment of 400 mm of the beam was sufficient to achieve full protection and (3) if only the column was protected, only the joint components that were in the immediate vicinity of the column (such as welds) developed noticeably lower temperatures than if the joint assembly was unprotected, but due to heat conduction from the unprotected steel beams, these temperature values were much higher than if the joint assembly was protected. Furthermore, the column temperatures in the joint region were much higher than the protected column temperatures.

Les travaux présentés dans cette thèse se focalisent sur l'étude de l’effet de dégradations des composants de puissance, plus particulièrement au niveau de l’environnement proche des puces (métallisations, connexions, brasures puces/DCB), sur le comportement électrique et thermique des puces ainsi que de leur assemblage. Pour ce faire nous avons cherché à étudier la répartition des courants et des températures à la surface de la puce à l’aide d’un modèle électrothermique 2D distribué. Nous avons aussi évalué l’effet de la dégradation des brasures dans le volume de l’assemblage, à l’aide cette fois d’un modèle thermique relié à la constitution de l’assemblage. La première partie de cette thèse consiste à mettre en place un modèle électrothermique distribué de puce MOSFET, qui tient compte à la fois du caractère distribué de la dissipation de la puissance et du couplage électrothermique en régime transitoire. Ce modèle électrothermique s’appuie sur un modèle électrique aux variables d’états et un modèle thermique par éléments finis couplé au modèle électrique. Les modèles électriques et thermiques ont été développés respectivement sous Matlab et sous CAST3M, et le couplage des deux modèles a été fait sous Simulink. Dans une deuxième partie, pour la validation des résultats des températures et pour l’analyse de l’effet du vieillissement et des dégradations (sur la distribution et la dynamique de température de la surface supérieure de la puce), une méthodologie de mesure rapide de température et un banc expérimental pour thermographie infrarouge ont été mis en place. Les difficultés rencontrées lors des mesures thermiques IR sous variation rapide de la température nous ont poussé à envisager d’autres méthodes d’analyse thermique. Enfin, nous avons cherché à évaluer la réponse impulsionnelle du composant testé en estimant, par des simulations thermiques, la fonction de transfert dans le domaine fréquentiel à l’aide du logiciel COMSOL Multiphysics. Nous avons également étudié la pertinence de modèles RC équivalents (réseau RC de Cauer). Ces modèles ont ensuite été utilisés pour rendre compte de différents modes de dégradation notamment cette fois au niveau des couches de brasures entre puce et DCB et entre DCB et semelle. Mots clef : Modules de puissance à semi-conducteur, Vieillissement, Métallisation, Modélisation électrothermique, Court-circuit, Distribution de courant et de température, Problème inverse, Caméra IR, Réseaux de Cauer. / The work presented in this thesis focus on the study of the effect of degradation of power components, especially at the near environment of chips (metallization, connections, solder chips / DCB), on the electrical and thermal behavior of the chips and their assembly. As a consequence, we studied the distribution of currents and temperatures on the chip surface with a 2D electrothermal distributed model. We also evaluated the effect of solder degradation in the volume of the assembly. Firstly, we developed an electrothermal distributed model of the MOSFET chip, which takes into account both the distributed power dissipation and the electrothermal coupling transient. This electrothermal model is based on an electrical model of state variables and thermal finite element model coupled to the electric model. Electrical and thermal models were developed respectively in Matlab and CAST3M whereas the two models coupling was done in Simulink . In the second part, to validate the results of temperatures and to analyze the effect of ageing and degradation on the distribution and dynamics of temperature of the upper surface of the chip, methodology rapid temperature measurement and an experimental bench for infrared thermography were established. The difficulties encountered in IR thermal measurements with rapid temperature change led us to consider other thermal analysis methods. Eventually, we assessed the impulse response of the tested component by estimating with thermal simulations, the transfer function in the frequency domain using the COMSOL Multiphysics software. Moreover we evaluated the relevance of RC equivalent models (RC Cauer network). These models were then used to account for different modes of degradation this time especially on the solder layer between the chip and DCB and between the DCB and sole. Keywords: Power Modules semiconductor, Ageing, Metallization, electrothermal modeling, Short Circuit, Power and temperature distribution, inverse problem, IR Camera, Cauer networks.

The aim of this thesis is to design the water-cooling system for a synchronous motor with an output of 10kW. The power loss was analytically determinated. For the initial water-cooling system and for two design proposals, thermal models were calculated in Ansys. The same boundary conditions were set for all three models. Then the analysis results of the temperature distribution on the machine surface and in the slots were compared. The comparison also includes the economical cost of the production and service of the machine. Then the production documentation was created, consisting of the assembly drawings and a simplified technological process.

Environmental concerns, resource depletion, energy security, technological advancements, and global policies are just a few of the variables influencing the global energy perspective. In the case of technological advancement, lithium batteries play a key role in the development of a more sustainable energy infrastructure. The high energy density and long lifespan of lithium batteries make them ideal for usage in a broad range of applications, such as portable electronics, electric vehicles, and grid-scale energy storage for renewable energy sources. However, there are certain possible concerns regarding the safe operation and performance of lithium batteries, most of which are associated with the temperature sensitivity of lithium batteries. Hence, battery thermal management systems are an essential component of a battery package for regulating the temperature level in lithium batteries to avoid the aging process, poor performance, and safety issues.   Many studies have been conducted to develop battery thermal management systems with improved cooling performance. Within this framework, Paper A in this licentiate thesis considers how the design of a lithium battery cell may be improved to reduce the thermal load on the thermal management system. An analytical model based on the integral transform technique is developed to accurately and efficiently predict the thermal behavior of a cylindrical lithium battery cell. Following model validation, the thermal behavior of cylindrical lithium-ion battery cells with different jelly-roll layers and can sizes are compared. The results demonstrate that 21700 cylindrical battery cells outperform other types of cylindrical battery cells in terms of thermal performance. Furthermore, the thermally optimal thicknesses for positive active material, negative active material, positive current collector, and negative current collector are 180, 34, 21, and 20 um, respectively. After learning about design considerations to reduce thermal issues in lithium-ion battery cells and developing a proper tool for further studies, the focus was set on the flow behavior surrounding a cylindrical battery cell in an air-based cooling system. The cooling system under consideration is a wall-bounded cross-flow heat exchanger, the most common air-based cooling system for battery applications. Despite the importance of the cooling system in battery safety, few studies have been conducted to investigate the thermo-flow characteristics of wall-bounded cross-flow heat exchangers. Hence, in the battery research field, it is common to estimate the performance of wall-bounded cross-flow heat exchangers using the thermal characteristics of free cross-flow heat exchangers due to their geometrical similarities. In Paper B, this assumption is scrutinized by comparing the thermo-fluid characteristics of free and wall-bounded cross-flow heat exchangers. According to the results, flow through both heat exchangers shows almost similar thermo-fluid behavior in areas sufficiently far from the bounding walls. A turbulence model study suggests that the k-kl-omega transition model is a time-efficient and reliable turbulence model for capturing thermo-fluid characteristics in such heat exchangers. Moreover, it is observed that the two different heat exchangers have an almost identical area-averaged heat transfer rate despite the local changes in Nusselt number along the height of cells. This finding shows that it is possible to do two-dimensional simulations for applications that only require an area-averaged heat transfer rate on the battery cells. The findings in Paper A and Paper B may be used to investigate the cooling performance of a battery thermal management system with a practical design. Hence, in Paper C, a comprehensive yet simplified model is developed that can be used to study the thermal field of lithium battery cells in a large-scale air-based battery thermal management system. The model consists of the CFD model derived in Paper B, which predicts the flow behavior around cells in the inner region of the battery package, and the analytical model described in Paper A, which determines the thermal field within the battery cells. The area-averaged heat transfer coefficient interconnects the models, and a system of equations is employed to estimate the row-to-row variation of the thermal field. The model is employed to assess the effect of transverse and longitudinal pitch ratios on the thermal performance of an air-based battery thermal management system used in a hybrid electric vehicle.

<div>Powder Bed Fusion Additive Manufacturing enables the fabrication of metal parts with complex geometry and elaborates internal features, the simplication of the assembly process, and the reduction of development time. However, the lack of consis-tent quality hinders its tremendous potential for widespread application in industry. This limits its ability as a viable manufacturing process particularly in the aerospace and medical industries where high quality and repeatability are critical. A variety of defects, which may be initiated during the powder-bed fusion additive manufacturing process, compromise the repeatability, precision, and resulting mechanical properties of the final part. The literature review shows that a non-uniform temperature distribution throughout fabricated layers is a signicant source of the majority of thermal defects. Therefore, the work introduces an online thermography methodology to study temperature distribution, thermal evolution, and thermal specications of the fabricated layers in powder-bed fusion process or any other thermal inherent AM process. This methodology utilizes infrared technique and segmentation image processing to extract the required data about temperature distribution and HAZs of the layer under fabrication. We conducted some primary experiments in the FDM process to leverage the thermography technique and achieve a certain insight to be able to propose a technique to generate a more uniform temperature distribution. These experiments lead to proposing an innovative chessboard scanning strategy called tessellation algorithm, which can generate more uniform temperature distribution and diminish the layer warpage consequently especially throughout the layers with either geometry that is more complex or poses relatively longer dimensions. In the next step, this work develops a new technique in ABAQUS to verify the proposed scanning strategy. This technique simulates temperature distribution throughout a layer printed by chessboard printing patterns in powder-bed fusion process in a fraction of the time taken by current methods in the literature. This technique compares the temperature distribution throughout a designed layer printed by three presented chessboard-scanning patterns, namely, rastering pattern, helical pattern, and tessellation pattern. The results conrm that the tessellation pattern generates more uniform temperature distribution compared with the other two patterns. Further research is in progress to leverage the thermography methodology to verify the simulation technique. It is also pursuing a hybrid closed-loop online monitoring (OM) and control methodology, which bases on the introduced tessellation algorithm and online thermography in this work and Articial Neural Networking (ANN) to generate the most possible uniform temperature distribution within a safe temperature range layer-by-layer.</div>