Les futurs réacteurs expérimentaux comme ITER ou JT-60SA réaliseront des réactions de fusion thermonucléaire au sein de plasmas de plusieurs millions de degrés. Le confinement de la réaction au centre de la chambre est assuré par des champs magnétiques très intenses générés par des aimants supraconducteurs. Ces bobines sont refroidies à 4.4 K via une circulation forcée d’hélium supercritique. Le fonctionnement cyclique des machines engendre des charges thermiques pulsées qui devront être absorbées par les réfrigérateurs de plusieurs mégawatts de puissances électriques. L’expérience HELIOS, construite au CEA Grenoble, est une maquette à échelle réduite du système de distribution d’hélium du tokamak JT-60SA constituée d’un bain d’hélium à saturation et d’une boucle en hélium supercritique. Les travaux de thèse présentés ici explorent les possibilités d’HELIOS afin de réaliser les études expérimentale et numérique de trois stratégies de lissage de charges thermiques : l’utilisation du bain saturé en tant que volant thermique ouvert, la variation de la vitesse du circulateur et l’utilisation de la vanne de by-pass de la charge thermique. Le modèle EcosimPro développé ici rend bien compte des phénomènes de couplage transitoire entre le dépôt d’énergie, la montée en pression et en température de la boucle de circulation, de même que le couplage entre la boucle de circulation et le bain saturé. Des contrôles avancés ont été testés numériquement puis validés expérimentalement pour améliorer la stabilité du réfrigérateur et optimiser la puissance de réfrigération. / Future fusion reactor devices such as ITER or JT-60SA will produce thermonuclear fusion reaction inplasmas at several millions of degrees. The confinement in the center of the chamber is achieved byvery intense magnetic fields generated by superconducting magnets. These coils have to be cooleddown to 4.4 K through a forced flow of supercritical helium. The cyclic behavior of the machinesleads to pulsed thermal heat loads which will have to be handled by the refrigerator.The HELIOS experiment built in CEA Grenoble is a scaled down model of the helium distributionsystem of the tokamak JT-60SA composed of a saturated helium bath and a supercritical helium loop.The thesis work explores HELIOS capabilities for experimental and numerical investigations on threeheat load smoothing strategies: the use of the saturated helium bath as an open thermal buffer, therotation speed variation of the cold circulator and the bypassing of the heated section. Thedeveloped model describes well the physical evolutions of the helium loop (pressure, temperature,mass flow) submitted to heat loads observed during experiments. Advanced controls have beentested and validated to improve the stability of the refrigerator and to optimize the refrigerationpower.

The thesis deals with simulation of solar gains in highly glazed administration building of Microsoft company on Vyskocilova Street in Prague. Effects of the geographical orientation and types of shading are compared on the base of the current simulation. For a more precise description of the effect of geographical orientation is simulation of solar gains in fictive office room with constant dimension together with applying different types of shielding. All the simulations are performed in TRSNYS 16.1 software.

This thesis aims to investigate if the hourly heat load consumptiondata can be used to approximate the daily consumptions patterns forbuildings connected to Göteborg Energi’s district heating network. Theapproximated data shall act as foundation for dimensioning of thedistrict heating network. In this work, it is studied how theconsumption approximation are due to changes in the outdoortemperature between different years.The aim is to develop an approximation model for hourly heat loadpatterns, heat output, water flow and return temperature from thedistrict heating substations of individual buildings regardless ofbuilding types. The approximation methods used in the hourlyapproximation model is multiple ridge regression. Regression trees areused to define breaking points such as the building balance pointtemperature from the consumer heat load pattern. Two separateregression intervals were defined based on breaking points from theregression tree. Outdoor temperature data, solar radiation data,weekday and weekends data used as predictors.The approximation model is evaluated against a reference model usingthe daily mean heat load consumption data. Evaluation between themodel and reference is made on six different building and buildingtypes during the outdoor temperature of -16, which is the designoutdoor temperature of the district heating system of Göteborg Energi.The approximated maximum heat output and water flow during the daywhere 18 % and 10 % above the approximated daily mean. Theapproximated return temperature where 43-51 °C compared to the dailymean of 42 °C for a warm year and 47-52,5 °C compared to 50 °C dailymean for a cold year.The hourly approximation model where able to capture the heat loadpatterns of different building types. However, higher demands on dataquality needs to be addressed to ensure the use of the hourlyapproximation model. / I detta examensarbete har en undersökning angående värmelastapproximationer baserade påtimupplöst kundlastdata gjorts. Värmelasterna som approximerades var värmeeffekt,vattenflöde och returtemperatur. Data för utomhustemperatur, helg och vardag samtsolinstrålningsdata har använts för att kunna approximera värmelasterna. Resultat avapproximationer har visualiserats i relation till utomhustemperaturen och har utvärderats fördimensionerande utomhustemperatur. Utvärdering gjordes på olika byggnader ochbyggnadstyper. Resultat av approximationsmodell med timupplöst kundlastdata utvärderadesmot modell baserad på dygnsmedeldata. Modellerna testades för två olika år med skildautomhustemperaturer, ett kall-år och ett varm-år.Resultat visar att det är möjligt att fånga den timvisa värmelasten hos enskilda kunder och skulleinnebära ett bättre underlag vid dimensionering. Detta då högsta värmelasten under ett dygnskiljer sig från dygnsmedellasten. Att implementera modell med timdatat ökar känsligheten imodellen och ställer högre krav på den inhämtade kundlastdatat. Mätare i fjärrvärmecentralerbör ses över för säkerställning av god mätupplösning och mätprecision.

The trend in the electronic and electrical equipment industry towards denser and more powerful product requires a higher level of performance from cooling devices. In this context, passive cooling techniques such as latent heat storage systems have attracted considerable attention in recent years. Phase change materials (PCMs) have turned out to be extremely advantageous in this regard as they absorb high amount of latent heat without much rise of temperature. But unfortunately, nearly all phase change materials (PCMs) with high latent heat storage capacity have unacceptably low thermal conductivity, which makes heating and cooling processes slow during melting and solidification of PCMs. Augmentation of heat transfer in a PCM is achieved by inserting a high thermal conductivity material, known as thermal conductivity enhancer (TCE), into the PCM. The conglomeration of PCM and TCE is known as a thermal storage unit (TSU). In this thesis, detailed and systematic analyses are presented on the thermal performance of TSUs subjected to two types of thermal loading- (a) constant power loading in which a constant power level is supplied to the chip (heater) for a limited duration of time, and (b) cyclic loading. Eicosane is used as the PCM, while aluminium pin or plate fins are used as TCEs. First, a 1-D analytical model is developed to obtain a closed-form temperature distribution for a simple PCM domain (without TCE) heated uniformly from the bottom. The entire heating process is divided into three stages, viz. (a) sensible heating period before melting, during which heat is stored in the solid PCM in the form of specific heat, (b) melting period, during which a melt front progresses from the bottom to the top layer of the PCM and heat is stored in latent as well as in sensible forms, and (c) post melting period, during which energy is stored again in the form of sensible heat. For each stage, conduction energy equation is solved with a set of initial and boundary conditions. Subsequently, a resistance capacitance model of phase change process is developed for further analysis. For transient performance under constant thermal loading, experimental investigations are carried out for TSUs with different percentages of TCE. A numerical model is developed to interpret the experimental results. The thermal performance of a TSU is found to depend on a number of geometrical parameters and boundary conditions. Hence, a systematic approach is desirable for finding the best TSU design for which the chip can be operated for a longer period of time before it reaches a critical temperature (defined as the temperature above which the chip starts malfunctioning). As a first step of the approach, it is required to identify the parameters which can affect the transient process. It is found that the convective heat transfer coefficient, ‘h’ and the exposed area for heat transfer have little effect on the chip temperature during the constant power operation. A randomized search technique, Genetic Algorithm (GA), is coupled with the CFD code to find an optimum combination of geometrical parameters of TSUs based on the design criteria. First, the optimization is carried out without considering melt convection within the PCM. It is found that the optimum half-fin width remains fixed for a given heat flux and temperature difference. Assuming a quasi steady process, the results of optimization are then explained by constructing and analyzing a resistance network model. The resistance network model is then extended to include the effect of melt convection, and it is shown that the optimum pitch changes with the strength of convection. Accordingly, numerical analysis is carried out by considering the effect of melt convection, and a correlation for optimum pitch is developed. Having established the role of melt convection on the thermal performance of TSUs, rigorous computational and experimental studies are performed in order to develop correlations among different non-dimensional numbers, such as Nusselt number, Rayleigh number, Stefan number and Fourier number, based on a characteristic length scale for convection. The enclosures are classified into three types, depending on the aspect ratio of cavity, viz. shallow, rectangular and tall enclosures. For a shallow enclosure, the characteristic length is the height of cavity whereas for a tall enclosure, the characteristic length is the fin pitch. In case of rectangular enclosure, both pitch and height are the important characteristic lengths. For cyclic operation, it is required that the fraction of the PCM melting during the heating cycle should completely solidify back during the cooling period, in order that that TSU can be operated for an unlimited number of cycles. If solidification is not complete during the cooling period, the TSU temperature will tend to rise with every cycle, thus making it un-operational after some cycles. It is found that the solidification process during the cooling period depends strongly on the heat transfer coefficient and the cooling surface area. However, heat transfer coefficient does not play any significant role during the heating period; hence a TSU optimized for transient operation may not be ideal for cyclic loading. Accordingly, studies are carried out to find the parameters which could influence the behaviour of PCM under cyclic loading. A number of parameters are identified in the process, viz. cycle period and heat transfer coefficient. It is found that the required heat transfer coefficient for infinite cyclic operation is very high and unrealistic with air cooling from the surface of the TSU. Otherwise, the required cooling period for complete re-solidification will be very high, which may not be suitable for most applications. In an effort to bring down the cooling period to a duration that is comparable to the heating period, a new design is proposed where both ‘h’ and area exposed to heat transfer can be controlled. In this new design, the gaps between the fins in a plate-fin TSU are alternately filled with PCM, such that only one side of a fin is in contact with PCM and the other side is exposed to the coolant (air). In this arrangement, the same heat flow path through the fin which is used for heating the PCM (during the heating stage) can also be used for cooling and solidifying the PCM during the cooling part of the cycle. Natural or forced air cooling through the passages can be introduced to provide a wide range of heat transfer coefficient which can satisfy the cooling requirements. With this arrangement, the enhanced area provided for cooling keeps the ‘h’ requirement within a realistic limit. This cooling method developed is categorized as a combination of active and passive cooling techniques. Analytical and numerical investigations are carried out to evaluate the thermal performance of this modified PCM-based heat sink in comparison to the ones with conventional designs. It is found that, the performance of new PCM-based heat sink is superior to that of the conventional one. Experiments are performed on both the conventional and the new PCM-based heat sinks to validate the new findings.

This thesis deals with the heat loss and the heat loads simulation of A1 building in the area of The Faculty of Mechanical Engineering, Brno University of Technology and with the measures of the energy saving. The measures of the thermo-technical charakteristics for the winter and summer operations are provided on the base of the current state simulation. These measures include increasing of thermal resistence (of the building case), the radiation shielding, the sun blinds and the passive cooling by the night ventilation. All the simulation are performed in TRNSYS 16.1 software.

Master’s Thesis deals with utilization of energy simulation software in area of classic brick buildings and measures to decrease heat consumption. Introduction deals with historic development of heat loss demands in Czech Republic and ways how to decrease heat loss through different types of building elements. Next chapter is focused on indoor microclimate and it’s affecting factors. Last but not least are mentioned environmental and financial aspects of these adjustments. Final part shows examined buildings, simulation configurations and output evaluations.