The diploma thesis is focused on creating a calculation software for designing heat exchanger. The software will not calculate one single heat exchanger but will recommend all heat exchangers which meet the requirements. Then, user can decide which heat exchanger is best suited for the specific application and make a comprehensive calculation. Part of the diploma thesis is to verify correctness of the software and make a parametric studies. Parametric studies will be focused on baffle cut, baffle spacing, tube pitch, and tube thickness and its effect on heat transfer and pressure drop.

The aim of this thesis was to investigate the effect of clearance and tolerance in bolted joints when there is a mismatch between the bolt holes. A parametric study with seven different cases was analyzed in this project; four double bolt configuration and three triple bolt configuration, with variation of the size of the bolt hole misalignment, the diameter of the bolt and the thickness of the plates. All analyses were performed with the aid of the FEM commercial software Abaqus, all the models were modelled with 3D brick elements. Despite bolted connections being subject of several investigations, no study about this matter for structural engineering purposes had been performed before. The results indicate that for connections with a low number of bolts a misalignment of the bolt clearance can cause a serious reduction in the ultimate bearing capacity of a joint and it indicates that the Eurocode 1993 1-8 might be overestimating the ultimate bearing capacity for some cases.

The automotive sector finds itself undergoing a significant and substantial transformation, propelled by the pronounced proliferation of electric vehicles (EVs) and autonomous driving technologies. As the industry proactively adapts to embrace this, an increasingly pressing demand becomes evident for higher performance, reliability, sustainability, and speed. Semiconductor packages emerge as primary catalysts within this ongoing revolution, positioned squarely at the forefront to assume a critical and indispensable function in facilitating the realization of these fundamental objectives. Commercial vehicle manufacturers are taking steps to respond to these demands for sustainability and speed, the driving force in facilitating this being the shift from Si IGBTs to SiC MOSFETs. Silicon Carbide is an increasingly popular choice in inverter module fabrication for electric vehicle applications owing to its inherent characteristics such as reduced on resistance, higher blocking voltage, and higher temperature stability that enable high power density, increased efficiency, and speeds. This work focuses on developing and fabricating a high-density 1.7 kV, 300 A SiC MOSFET half-bridge power module tailored for a 280-320 kW, 2-level inverter configuration. Co-designed with the busbar and gate driver, the custom power module stresses efficient heat dissipation, minimized parasitic inductance, and a compact footprint. Key target parameters to achieve optimal performance include a Rdson below 20 mΩ, Rthjc under 0.2 K/W and a switching time below 20 ns. The proposed module features a double-sided cooling sandwiched structure, an integrated thermistor for health and degradation monitoring, and incorporates three Wolfspeed 3rd generation 1.7 kV, 18 mΩ devices per switch position. The simulated power loop inductance is 14.5 nH, the simulated parasitic resistance is 0.265 m, and the simulated junction-to-case thermal resistance is 0.12182 ℃/W. To keep the die temperature below 150 ℃, a cooling coefficient of 5500 W/m2 is necessary. / Master of Science / The automotive sector is in the midst of a major transformation, propelled by the noticeable spread of electric vehicles (EVs) and autonomous driving technologies. As the industry actively evolves to accommodate this, an increasingly pressing demand becomes apparent for higher performance, reliability, sustainability, and speed. Semiconductor packages are at the forefront of this transformation, playing a crucial role in achieving these goals. Commercial vehicle makers are taking steps to respond to these demands for sustainability and speed, the driving force for this being the shift from Si IGBTs to SiC MOSFETs. Silicon Carbide is an increasingly popular choice in inverter module fabrication for electric vehicle applications owing to its inherent characteristics such as reduced resistance, higher blocking voltage, and higher temperature stability that enable high power density, increased efficiency, and speeds. This study focuses on creating a compact and efficient power module for commercial electric vehicle applications. The designed module is capable of handling high power levels while remaining compact, thus prioritizing power density. This is carefully designed to ensure it cools down effectively, minimizes unnecessary energy losses, and has a small footprint. Certain key features, such as its commutation speed, current carrying capacity, and thermal and mechanical limitations, were also studied. A temperature sensor was incorporated to monitor its health and performance over time. Simulations were performed to validate that this module performs well in terms of its resistances in the electrical conduction path and the oath of heat dissipation.

Yes / Hot spotting is a thermal localisation phenomenon in which multiple hot regions form on a brake disc surface during high energy and/or high speed braking events. As an undesired problem, hot spots can result in high order brake judder, audible drone and thermal cracking. This paper presents a finite element model for hot spot modelling which introduces the classical axisymmetric assumptions to the brake pad in 3D by scaling the material properties combined with a subroutine to simulate the heat generation instead of modelling the rotation of the brake pad. The results from the initial feasibility models showed significant improvement in computing efficiency with acceptable accuracy when compared to a traditional FE model without such simplifications. This method was then applied to the 3D simulation of hot spotting on a realistic ventilated brake disc/pad pair and the results showed good correlation with experiments. In order to improve the understanding of the hot spotting mechanism, parametric studies were performed including the effects of solid and ventilated disc geometry, rotational speed and energy, pins, disc run-out, and brake pad length. Based on the analysis of the results, it was identified that the vents and pins affected the hot spot distribution. Speed was shown to be more important on the hot spot generation time and distribution than either the pressure or total energy input. Brake disc run-out was shown to affect the magnitude of both hot spot temperature and height due to the non-linear relationship between local deformation, contact pressure and heat generation. Finally, increasing the brake pad length generated fewer hot spots but the temperature of each hot spot increased.

The influence of the hanger configuration in the arch and deck bending moments under asymmetric loads is widely used nowadays for improved designs of arch bridges. In this work, by means of a parametric study, those hanger configurations that most efficiently increase both the natural frequencies and buckling factors are identified, simultaneously evaluating the dynamic and static performance of timber arch footbridges. A parametric FEM model allows to evaluate the performance of vertical, Nielsen, fan and network hanger configurations together with combinations of them among others for a three-hinge timber arch. The impact of other relevant design choices such as the number of hinges in the arch or the arch slenderness ratio is jointly addressed allowing for design recommendations. The results show a convergence of the natural frequencies regardless of the configuration of the hangers when increasing the number of them. Moreover, the performance of the studied hanger configurations is improved by introducing inclined hangers significantly increasing natural frequencies and buckling factors of the system. This highlights the importance of the stabilizing horizontal reaction appearing at the deck hanger anchor points and thereby improving the bending moment distribution at the arch. Furthermore, the analyses show that the combination of Nielsen and vertical hangers achieves both the largest natural frequency and buckling factor for a reasonable number of hangers. This contrasts with the low sensitivity of the static and dynamic performance that the vertical hanger configuration shows in relation to changes in the number of hangers, arch rise or arch stiffness among others. Additionally, an important consideration when designing three hinge arch bridges is found to be to prevent a local buckling mode from appearing at the crown of the arch. This can also be done by the right choice of the number and configuration of hangers, as has been shown in the thesis. The results produced in this work can be used to guide engineers towards designing arch bridges with higher static capacity and better dynamic performance while reducing at the same time the material consumption. Furthermore, the findings of the work open up the way towards optimization of arch bridge structures.

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