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In relation to the increasing interest in implementing smart cities, deployment of widespread wireless sensor networks (WSNs) has become a current hot topic. Among the application’s greatest challenges, there is still progress to be made concerning energy consumption and quality of service. Consequently, this project aims to explore a series of feasible solutions to improve the WSN energy efficiency for data aggregation by the WSN. This by strategically adjusting the position of the receiving base station and the packet rate of the WSN nodes. Additionally, the low-energy adaptive clustering hierarchy (LEACH) protocol is coupled with the WSN state of charge (SoC). For this thesis, a WSN was defined as a two dimensional area which contains sensor nodes and a mobile sink, i.e. a movable base station. Subsequent to the rigorous analyses of the WSN data clustering principles and system-wide dynamics, two different developing strategies, model-based and data-driven designs, were employed to develop two corresponding control approaches, model predictive control and reinforcement learning, on WSN energy management. To test their performance, a simulation environment was thus developed in Python, including the extended LEACH protocol. The amount of data transmitted by an energy unit is adopted as the index to estimate the control performance. The simulation results show that the model based controller was able to aggregate over 22% more bits than only using the LEACH protocol. Whilst the data driven controller had a worse performance than the LEACH network but showed potential for smaller sized WSNs containing a fewer amount of nodes. Nonetheless, the extension of the LEACH protocol did not give rise to obvious improvement on energy efficiency due to a wide range of differing results. / I samband med det ökande intresset för att implementera så kallade smart cities, har användningen av utbredda trådlösa sensor nätverk (WSN) blivit ett intresseområde. Bland applikationens största utmaningar, finns det fortfarande förbättringar med avseende på energiförbrukning och servicekvalité. Därmed så inriktar sig detta projekt på att utforska en mängd möjliga lösningar för att förbättra energieffektiviteten för dataaggregation inom WSN. Detta gjordes genom att strategiskt justera positionen av den mottagande basstationen samt paketfrekvensen för varje nod. Dessutom påbyggdes low-energy adaptive clustering hierarchy (LEACH) protokollet med WSN:ets laddningstillstånd. För detta examensarbete definierades ett WSN som ett två dimensionellt plan som innehåller sensor noder och en mobil basstation, d.v.s. en basstation som går att flytta. Efter rigorös analys av klustringsmetoder samt dynamiken av ett WSN, utvecklades två kontrollmetoder som bygger på olika kontrollstrategier. Dessa var en modelbaserad MPC kontroller och en datadriven reinforcement learning kontroller som implementerades för att förbättra energieffektiviteten i WSN. För att testa prestandan på dom två kontrollmetoderna, utvecklades en simulations platform baserat på Python, tillsamans med påbyggnaden av LEACH protokollet. Mängden data skickat per energienhet användes som index för att approximera kontrollprestandan. Simuleringsresultaten visar att den modellbaserade kontrollern kunde öka antalet skickade datapacket med 22% jämfört med när LEACH protokollet användes. Medans den datadrivna kontrollern hade en sämre prestanda jämfört med när enbart LEACH protokollet användes men den visade potential för WSN med en mindre storlek. Påbyggnaden av LEACH protokollet gav ingen tydlig ökning med avseende på energieffektiviteten p.g.a. en mängd avvikande resultat.

<p>Advancements in future technologies such as artificial intelligence, electric vehicles, and renewable energy create a consistent need for more powerful and smaller electronic devices and systems. As a result, thermal management components such as heat sinks need to remove higher heat loads from more compact spaces to keep electronics within their operational temperature limits. Constraints imposed by conventional manufacturing processes restrict the design of heat sinks to simple geometries with limited cooling performance. Recent widespread commercialization of metal additive manufacturing (AM) tools offers new potential for leveraging the design freedom of these manufacturing technologies to design and fabricate heat sinks with improved performance. </p> <p>In AM, three dimensional parts are created through layer-by-layer depositing of materials, which allows fabrication of complex geometries that would be impossible or too costly using conventional subtractive methods. Many novel heat sink geometries have been proposed in literature which incorporate features such as manifolds, flow mixers, and curved channels using engineering intuition to reduce pressure drop or enhance heat transfer. Although such designs have been shown to offer improved performance, mathematical design algorithms such as topology optimization (TO) have been shown to outperform engineering intuition. Topology optimization optimizes the material distribution within a given design space, guided by physics-based simulations, to achieve a user-defined objective such as minimization of thermal resistance. Previous TO approaches have used penalization methods to ensure the final designs are composed of macroscopic and non-porous features due to the past precedent of fabrication capabilities. This traditional penalization approach is well-suited to the constraints of conventional manufacturing methods; however, microstructures and porous features are easily fabricable with additive manufacturing. There is a need to develop TO approaches that are better suited for leveraging AM for the design of heat sinks. In this thesis, a homogenization approach to topology optimization is proposed wherein the material distribution is represented as parametrized microstructures. This formulation allows design of thermal management components that have sub-grid features and leverages AM for fabrication. The focus of this thesis is the development of the homogenization approach for TO of heat sinks, as well as the exploration of the design problems it can address, the performance benefits made available, and the two-phase flow physics that it uniquely allows to be incorporated into the topology optimization process.</p> <p>A topology optimization algorithm using the homogenization approach is developed by representing the material distribution as arrays of pin fins with varying gap sizes. To this end, the pin fins are modeled as a porous medium with volume-averaged effective properties. Height-averaged two-dimensional flow and non-equilibrium thermal models for porous media are developed for transport in the pin fin array. Through multi-objective optimization, TO designs are generated for an example case involving a hotspot over a uniform background heat input. The resulting topologies have porous-membrane-like designs where the liquid is transported through a fractal network of open, low-hydraulic-resistance manifold pathways and then forced across tightly spaced arrays of pin fins for effective heat transfer. The TO designs are revealed to offer significant performance improvements relative to the benchmark straight microchannel (SMC) heat sink with features optimized under the same multi-objective cost function. A series of microchannel heat sinks are fabricated using direct metal laser sintering to investigate the printing capabilities and to experimentally demonstrate the performance of topology optimized designs. Advantages of the homogenization approach over the penalization approach can be summarized as follows: (1) reduced computational costs due to its ability to create sub-resolution features, (2) intrinsically fabricable parts using available metal AM tools, and (3) easier to use due to significantly reduced number of hyperparameters (e.g., penalization factors) that are controlled by the user. </p> <p>Topology optimization has been applied to thermal management methods involving single-phase flows such as natural convection, forced air cooling, and pumped liquid cooling. Compared to these conventional heat sink technologies, flow boiling offers very high heat transfer coefficients and effective heat capacities, making it a promising candidate for future cooling electronics applications. The final goal of this thesis is to enable topology optimization of flow boiling heat sinks. However, TO of flow boiling heat sinks has been avoided due to difficulties in modeling the boiling phenomena; of note, there are no examples of TO being applied to the design of heat sink under flow boiling throughout the literature. Multi-dimensional two-phase flow models require prior knowledge of friction factor and heat transfer coefficients. Correlations are available in literature but are not universal and depend significantly on channel/fin geometries, surface roughness, and operating conditions. Given that traditional penalization-based TO approach results in fin and channel geometries with unknown shapes, dimensions, and alignment before the optimization is completed, this prohibits their use for optimization of flow boiling heat sinks. However, the homogenization approach to topology optimization developed in this thesis enables the optimization of flow boiling heat sinks. As it relies on user-defined microstructures with known shapes, alignments, and ranges of geometric dimensions, a universal correlation for flow boiling in microchannels is not needed. Instead, correlations for the user-defined microstructures are sufficient to simulate flow boiling in TO designs generated using the homogenization approach. To this end, a predefined microstructure geometry is chosen for which two-phase flow correlations exist and therefore topology optimization can be performed. Topology optimized heat sink designs under flow-boiling are generated and investigated at various heat inputs, topology optimization grid sizes, and maximum vapor quality constraints. Topology optimized heat sinks designed for single-phase versus two-phase flow are compared.  There are significant differences in hydraulic and thermal responses of the single-phase and two-phase designs due to high effective heat capacity rates and high heat transfer coefficients of flow boiling. The algorithm demonstrated in this work extends the capabilities of topology optimization to two-phase flow physics, and thereby enables the design of various two-phase flow components such as evaporators, condensers, heat sinks, and cold plates.</p> <p>The flow and heat transfer of the TO algorithm for microchannel heat sinks under flow boiling use a two-phase mixture model featuring an effective porous medium formulation. However, closure of the governing equations requires empirical correlations for pressure drop and heat transfer that are specific to the operating conditions, microstructure geometry, and surface finish. Therefore, it must be demonstrated these available correlations can be successfully calibrated over a range of microstructural variations present within the homogenization framework, so as to attain the required prediction generality and accuracy needed to ensure the resulting designs achieve Pareto-optimality. To this end, a set of uniform pin fin calibration samples are additively manufactured and experimentally tested under flow boiling at various flow rates and heat inputs for model calibration. All of the unknown/free coefficients in the adopted correlations are determined by minimizing the error between the model predictions and the experimental measurements using gradient-based optimization. The calibrated topology optimization algorithm is then used to generate a Pareto-optimal set of heat sinks optimized for minimum pressure drop and thermal resistance during flow boiling. Experimental characterization of these additively manufactured heat sinks, unseen during the model coefficient calibration process, reveals that the measured Pareto optimality curve matches that predicted by the topology optimization algorithm. Lastly, a heat sink design is generated for a design space involving multiple hot spots and background heating to showcase the capability of the experimentally calibrated two-phase topology optimization algorithm at handling complex boundary conditions. The optimized heat sink intelligently distributes an adequate amount of coolant flow to each of the heated regions to avoid local dry-out. This work demonstrates a complete framework for two-phase topology optimization of heat sinks through experimental calibration of flow boiling correlations to the porous medium used by the homogenization approach. </p> <p>The major contribution of this thesis is the development of a homogenization approach for TO of additively manufactured microchannel heat sinks under single- and two-phase flows. Not only does the homogenization approach provide several advantages over the traditional penalization approaches such as reduced computational costs, intrinsic fabricability using AM, and ease of use, but it also enables TO of heat sinks under flow boiling and potentially TO of other two-phase thermal management components. The work discussed in this thesis serves a comprehensive end-to-end guide on TO of microchannel heat sinks using the homogenization approach with experimental demonstrations for validation.</p>

Motorcyclists are more often involved in accidents with severe harm or even fatal outcome compared to other road users. An experienced motorcycle driver is well familiar with the problem when the day light is reduced. The visibility is of course highly decreased. Allight International develops a light bulb that through a gyroscopic feature allows the light image to always be projected in the same axi-symmetric plane. The low beam head light usually accompanies the drivers movement when cornering, creating a black void ahead that leads to decreased vision. The light bulb has not yet been tested in a headlight and the LED is assumed to have high working temperature, which can lead to a shortened service life and technical errors due to the heat. By comparing empirical tests such as infrared camera and thermocouples on the prototype with theoretical tests such as computer aided design, finite element method, and computational fluid dynamics, a better understanding of how the model can be adapted to counteract the high temperature has achieved. Empirical analysis show that at a lower current of where the light bulb produces a brightness around the lower region of an automotive low beam headlight, the existing solution seems to work with the help of the fan creating forced convection. The improved and evaluated prototype, makes it possible to increase the current for the light bulb when more of the generated heat dissipates from the heat source. / Motorcyklister är mer involverade i olyckor med allvarlig eller dödlig utgång jämfört med generella trafikanter. En erfaren motorcykelförare är väl bekant med problemen som uppstår vid mörkerkörning. Givetvis blir sikten kraftigt försämrad. Allight International utvecklar en typ av lampa som med hjälp av ett gyroskop tillåter ljusbilden att alltid projiceras i samma axialsymmetriska plan. Vanligtvis följer lampan med förarens rörelse när denne svänger vilket skapar ett svart tomrum frammåt som leder till skymd sikt. Lampan har inte testas än i strålkastare och värmen antas ge en för hög arbetstemperatur, vilket kan leda till en forkortad livslängd samt tekniska fel på grund av värmen. Genom att utföra empiriska tester på prototypen som infraröd kamera och thermoelement tillsammans med teoretiska verktyg som computer aided design, finita elementmetoden och computational fluid dynamics fås en bättre förståelse för hur modellen kan anpassas för att motverka den höga temperaturen. Empiriska analyser visar att vid en lägre strömstyrka som motsvarar den ljusstyrka som är kravet för fordonsändamålsenliga halvljus, fungerar den nuvarande prototypen tillsammans med en fläkt som ger forcerad konvektion. Den förbättrade och utvärderade geometrin gör det möjligt att öka strömstyrkan då mer värme kan föras bort från värmekällan.

In this investigation, a single phase fluid is used to study the coupling between natural convection heat transfer within an enclosure and forced convection through computer covering case to cool the electronic chip. Two working fluids are used (water and air) within a rectangular enclosure and the air flow through the computer case is created by an exhaust fan installed at the back of the computer case. The optimum enclosure size configuration that keeps a maximum temperature of the heat source at a safe temperature level (85℃) is determined. The cooling system is tested for varying values of applied power in the range of 15−40𝑊. The study is based on both numerical models and experimental observations. The numerical work was developed using the commercial software (ANSYS-Icepak) to simulate the flow and temperature fields for the desktop computer and the cooling system. The numerical simulation has the same physical geometry as those used in the experimental investigations. The experimental work was aimed to gather the details for temperature field and use them in the validation of the numerical prediction. The results showed that, the cavity size variations influence both the heat transfer process and the maximum temperature. Furthermore, the experimental results ii compared favourably with those obtained numerically, where the maximum deviation in terms of the maximum system temperature, is within 3.5%. Moreover, it is seen that using water as the working fluid within the enclosure is capable of keeping the maximum temperature under 77℃ for a heat source of 40𝑊, which is below the recommended electronic chips temperature of not exceeding 85℃. As a result, the noise and vibration level is reduced. In addition, the proposed cooling system saved about 65% of the CPU fan power.

В данной магистерской диссертации представлены разработки и результаты исследования влияния конструктивных решений на теплоотвод при точении резцом с внутренним воздушным охлаждением. Разработана конструкция резца с увеличенным теплоотводом. Она позволяет существенно расширить область использования резцов с внутренним воздушным охлаждением вместо традиционных резцов с охлаждением СОЖ. Результаты диссертационной работы опубликованы в V номере инженерного журнала «Справочник». Также по результатам проведенного исследования был получен патент на полезную модель №209971 «Металлообрабатывающий инструмент с внутренним охлаждением». Магистерская диссертация состоит из введения, 5 глав, заключения. Объем диссертационной работы – 72 страниц, в том числе 33 рисунка, 6 таблиц. Библиографический список содержит 25 источников. / This master's thesis presents the developments and results of a study of the influence of design solutions on heat removal when turning with a cutter with internal air cooling. A cutter design with increased heat sink has been developed. It allows you to significantly expand the scope of use of cutters with internal air cooling instead of traditional cutters with coolant. The results of the dissertation work were published in the 5th issue of the engineering journal Spravochnik. Also, based on the results of the study, a patent for utility model No. 209971 "Metalworking tool with internal cooling" was obtained. Master's thesis consists of introduction, 5 chapters, conclusion. The volume of the dissertation work is 72 pages, including 33 figures, 6 tables. The bibliographic list contains 25 sources.

The purpose of the study is to contribute knowledge about how 2-4-year-oldsexplore the physical phenomena of floating and sinking, and how a practicalactivity can contribute to development and learning. To respond to the study,observation was chosen as the method where a designed activity with thevariation theory as support was conducted in three groups of children, theactivity was then divided into four phases for us students to get a clearerstructure. The theory was made visible by making the phenomena the objectof learning in the exploration. The children themselves got to explore and thinkabout which aspects determined whether something floated or sank usingvariations on similar objects. The three activities were filmed and lateranalyzed using the research questions and categories that emerged using theanswers from the four phases.The result shows that it is possible to perform a float and sink activity with theyounger children in preschool. Something that connects to Jean Piaget´s stagetheory was that the youngest children stopped their exploration when theycame up with a hypothesis and they saw what was happening. Our result showsthat, when they are four years old, they start to come up with explanations forthe hypotheses they have given about how an object behaves in a certain wayin water. The most common thing that the children referred to was the weightof the object. They concluded that an object sank because it was heavy, butthey also reasoned that an object floated because it was heavy. This shows thatthey don’t have the answers fully but the thoughts and the will to understand. / Syftet med studien är att bidra med kunskap om hur 2–4-åringar utforskar defysikaliska fenomenen flyta och sjunka samt hur en praktisk aktivitet kan bidratill utveckling och lärande. För att möta studiens syfte valdes observation sommetod där en designad aktivitet med variationsteorin som stöd genomfördes itre barngrupper, aktiviteten delades sen in i fyra faser för oss studenter för attfå en tydligare struktur. Teorin synliggjordes genom att fenomenen blevlärandeobjektet i utforskandet. Barnen fick själva utforska och fundera på vilkaaspekter som avgjorde om något flöt eller sjönk med hjälp av variationer påföremål som liknade varandra. De tre aktiviteterna filmades och analyseradessenare med hjälp av studiens frågeställningar och kategorier som uppkom medhjälp av det som resultatet visade från de fyra faserna.Resultatet visar att det är möjligt att utföra en flyta och sjunka-aktivitet med deyngre barnen i förskolan. Något som knyter an till Jean Piagets stadieteori varatt de yngsta barnen stannar sitt utforskande vid att komma med en hypotesoch ser vad det är som händer. Först när de fyllt fyra år börjar de komma medförklaringar till de hypoteser de gett om hur ett föremål beter sig på ett visstsätt i vatten. Det vanligaste som barnen refererade till var föremålets vikt, dekom fram till att ett föremål sjönk för att det var tungt men de resonerade ävenatt ett föremål flöt för att det var tungt. Detta visar på att de inte har svaren heltmen funderingarna och viljan att förstå finns.

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Heat sinks are used mainly to take away the excessive heat which are produced in a component. This transfer of heat enables a smooth operation of the system with the heat generating component. The efficiency of heat sink is often dependent on the amount of heat it can take away within the smallest duration of time. Several designs and manufacturing techniques have been developed to improve this performance of heat sinks. This project aims at building a test rig which can be used to test the efficiency of heat sinks. The test rig should be designed to be modular, i.e. it should be able to test heat sinks of different sizes and also adhering to the design requirements. The project started with a broad information search on heat sinks and different testing methods. A system architecture was formulated for this test rig as a beginning stage and to find the different architectural components. The main principal components were selected fulfilling the design requirements. A chiller with pump, a flow meter with controller, temperature and pressure sensors and piping’s including a flexible pipe were the main components of the system created. When the specific components were chosen, the design was embodied and the components were arranged in a compact manner as a SolidEdge CAD-model. After several design iterations, a final design was selected. The experimental test rig was then built in the flow lab. The built experimental test setup is able to be adjusted to install heat sinks of different sizes making it modular in design. Future work to improve the performance of the test rig is also suggested. / Värmesänkor, som exempelvis kylflänsar, används främst för att transportera bort värme som orsakas av förluster i en komponent. Denna värmeöverföring möjliggör en smidig drift av systemet där den värmegenererande komponenten ingår. Värmesänkans effektivitet beror på hur mycket värmeeffekt den kan transportera bort. Flera olika konstruktioner och tillverkningstekniker har utvecklats för att förbättra värmesänkors kylprestanda. Målet med detta projekt är att bygga en testrigg som kan användas för att testa kylflänsars effektivitet. Testriggen ska utformas så att den är modulär, dvs. den ska kunna användas för att testa kylflänsar av olika storlekar. Projektet startade med en bred informationssökning om kylflänsar och olika testmetoder. En systemarkitektur skapades som ett början och för att hitta systemets olika principkomponenter. De viktigaste huvudkomponenterna som uppfyllde designkraven valdes sedan. En kylare med pump, en flödesmätare med regulator, temperatur- och tryckgivare och rörledningar, inklusive ett flexibelt rör var de viktigaste komponenterna i det system som skapades. De specifika komponenterna valdes sedan och de representerades och arrangerades på ett kompakt sätt som en system-CAD-modell i SolidEdge. Efter flera iterationer valdes en slutlig konstruktion, och den experimentella testriggen byggdes sedan i flödeslaboratoriet. Den experimentella testriggen kan justeras för att installera kylflänsar av olika storlekar, vilket innebär att den, i viss mån, är modulär. Framtida arbeten för att förbättra testriggens prestanda föreslås också.