May 25, 2011, Reuters’ headline read: "New York State is prepared for summerelectricity demand". The NY operator forecasts for next summer a peak of 33GW, close to therecord ever reached. With soaring cooling demands, the electricity peak load represents a substantialconcern to the energy system. In the goal of peak shaving, research on alternative solutions based onThermal Energy Storage (TES), for both cooling and heating applications, has been largely performed.This thesis addresses thermal comfort applications with use of active free cooling through implementationof latent heat based TES. Active free cooling is based on the use of the freshness of a source, the outsideair for example, to cool down buildings. This work conceptualizes the implementation of TES basedcooling system with use of Phase Change Material in an in-house-built model. The principle of PhaseChange Material, or Latent Heat TES (LHTES), lies on latent energy which is the energy required for thematerial to change phase. In order to properly size this cooling system, a multi-objective optimization isadopted. This optimization, based on minimization of multi-objective functions, led to optimal designconfigurations. In parallel, the electrical consumption of the system and the volume uptake of the systemwere also considered. Through the obtained optimization studies, we identified non-linearinterdependency between the two objective functions: the cost of the system and the acceptable remainingcooling needs. By remaining cooling needs, we mean the cooling needs that the system cannot meet. As amatter of fact, sizing the system according to these cooling needs would imply a very high cost. It wasfound that for a certain amount of remaining cooling needs, the PCM-based cooling system reveals to bean interesting solution compared to conventional air conditioning in terms of electrical consumption andoverall system cost. / Best Master Thesis Award, granted by French Academic Institute / Cold Thermal Energy Storage

Around 50 million tones hematite iron ores with high iron content at a grade of 68% were found in Muko area of Uganda. Currently, the iron and steel making industry in the country has not yet developed to meet the demand to process the natural ores. Based on the analysis of its composition and mechanical properties, I infer that the natural iron lump ores can charge directly into reduction furnace without any prior treatment, so that the cost of whole process without additional enrichment and sintering will be reduced quite much. Also direct reduction iron (DRI) process use natural gases instead of coals which can greatly reduce the environmental pollution and lower the processes cost. If the raw materials that fit for requirements of majority plants, the seller´s market can get greater control over prices, terms due to the easy and cheap processing. All lump ores were from Butare area which is one occurrence of Muko and named sample A in this work. This research aims to use the lowest cost method to reduce Butare area iron ores and find out the optimum parameters on reduction reactions of Butare iron lump ores, such as flow rate, temperature, size of samples. Base on experiments with different designed parameters, Butare iron lump ores successfully reduced by DR furnace and microstructure was found to be an important parameter that strongly influent reduction degree of Butare iron lump ores.

The thermodynamic properties of the Co-Cr-Mo ternary system have been described. Available experimental data on the system have been assessed and applied to optimize the parameters used in the thermodynamic models within the Calphad method. Meanwhile, samples were made by the powder metallurgical process and heat treated (sintered) at 1573 K to investigate the phase diagram data related to the intermetallic phases, such as σ, μ and R phases present in the system. With the optimized thermodynamic description, we are able to fit most of the experimental data in the literature and from this work. However, the one phase field of R is too narrow in the present description. Furthermore, at 1573 K the extension of the phase boundary of σ toward the Co corner needs to be improved. In addition, the calculated phase diagram at 1573 K shows a fcc-bcc-σ three-phase equilibrium near the Co-Cr binary side. This is not shown in the experimentally determined ternary phase diagram but is necessary in order to match the recent data on the Co-Cr binary system.

This thesis is a study of tailoring amorphous Fe-B-Si based alloy to produce bulk glassy rods by adding Nb. We have prepared rapid quenched thin ribbons (thickness ~12 µm) by melt spinning, and glassy rods of diameter ~1mm by Cu-mold casting based on compositions (Fe0.78B0.13Si0.9)100-xNbx (x=0, 4, 8, 12), and studied their different physical properties. The melt-spun ribbons are found to be X-ray amorphous, whereas some nano-crystallinity is observed in the case of rods. All the ribbons show high saturation magnetization and low coercivity, which are the desirable characteristics of a soft ferromagnet. These ribbons are thus suitable for designing high frequency transformers, and sensors from an applications point of view. With increasing Nb content their saturation magnetization, ferromagnetic Curie temperature, and resistivity are found to decrease as expected. The temperature dependence of electrical resistivity shows small positive temperature co-efficient that is expected for a metallic disordered material. We have also studied the modification of the properties on thermal annealing the (Fe0.78B0.13Si0.9)96 Nb4 ribbon at different temperatures in a neutral atmosphere.

Currently pelletized woody biomass is widely used as a fuel in thermal applications toaccelerate the global transition to renewable energy. Fuel upgrade is one of the key factorsto improve energy conversion processes. Woody biomass can be fractionated into its mainconstituents by steam explosion. Steam-exploded biomass exhibits enhanced heating valueand improves pellet durability. Moreover, there is a significant deviation in thermochemicalbehavior of steam exploded (steam-treated) biomass with respect to the raw material duringpyrolysis. This thesis work concerned combustion characteristics of steam-exploded salix. The steamtreatedmaterial was pelletized and combusted under 21% of oxygen with varying thereactor temperature from 500 to 900°C to study the influence of both surrounding andpretreatment conditions during combustion process. The impact of different pretreatmentseverity factors (Ro) on burning behavior was evaluated: mild (205°C-6min, Ro=3.87),intermediate (205°C-12min, Ro=4.17) and severe (228°C-12min, Ro=4.84). Heterogeneousand homogenous ignition mechanisms were observed, which were dependent on the reactortemperature. The ignition time and devolatilization duration were observed independent onpretreatment severity near 900°C, and slightly influenced near 500°C. Enhanceddevolatilization rate was detected with the increment of Ro from 3.87 to 4.17, whilst themost severe pretreatment conditions (Ro=4.84) weakened biomass reactivity duringdevolatilization. Finally, char reactivity was lowered as a result of the increment ofpretreatment severity.

In order to optimise the ladle treatment mass transfer modelling of aluminium addition and homogenisation time was carried out. It was stressed that incorporating slag-metal reactions into the mass transfer modelling strongly would enhance the reliability and amount of information to be analyzed from the CFD calculations.   In the present work, a thermodynamic model taking all the involved slag metal reactions into consideration was incorporated into a 2-D fluid flow model of an argon stirred ladle. Both thermodynamic constraints and mass balance were considered. The activities of the oxide components in the slag phase were described using the thermodynamic model by Björkvall and the liquid metal using the dilute solution model. Desulphurization was simulated using the sulphide capacity model developed by KTH group. A 2-D fluid flow model considering the slag, steel and argon phases was adopted.   The model predictions were compared with industrial data and the agreement was found quite satisfactory. The promising model calculation would encourage new CFD simulation of 3-D along this direction. / QC 20110414

Constrained optimization is used to derive human postures and movements. In the first study a static 3D model with 30 muscle groups is used to analyse postures. The activation levels of these muscles are minimized in order to represent the individual's choice of posture. Subject specific data in terms of anthropometry, strength and orthopedic aids serve as input. The aim is to study effects from orthopedic treatment and altered abilities of the subject. Initial validation shows qualitative agreement of posture strategies but further details about passive stiffness and anthropometry are needed, especially to predict pelvis orientation. In the second application, the athletic long jump, a problem formulation is developed to find optimal movements of a multibody system when subjected to contact. The model was based on rigid links, joint actuators and a wobbling mass. The contact to the ground was modelled as a spring-damper system with tuned properties. The movement in the degrees of freedom representing physical joints was described over contact time through two fifth-order polynomials, with a variable transition time, while the motion in the degrees of freedom of contact and wobbling mass was integrated forwards in time, as a consequence. Muscle activation variables were then optimized in order to maximize ballistic flight distance. The optimization determined contact time, end configuration, activation and interaction with the ground from an initial configuration. The results from optimization show a reasonable agreement with experimentally recorded jumps, but individual recordings and measurements are needed for more precise conclusions.

With the advent of Self-Compacting Concrete (SCC) that flows freely, under the soleinfluence of gravity, the wish for hassle-free and predictable castings even in complexcases, spurged the simulation of concrete flow as a means to model and predictconcrete workability. To achieve complete and reliable form filling with smoothsurfaces of the concrete, the reinforced formwork geometry must be compatible withthe rheology of the fresh SCC. Predicting flow behavior in the formwork and linkingthe required rheological parameters to flow tests performed on the site will ensurean optimization of the casting process.In this thesis, numerical simulation of concrete flow is investigated, using both discreteas well as continuous approaches.The discrete particle model here serves as a means to simulate details and phenomenaconcerning aggregates modeled as individual objects. The here presented cases aresimulated with spherical particles. However, it is possible to make use of nonsphericalparticles as well. Aggregate surface roughness, size and aspect ratio maybe modeles by particle friction, size and clumping several spheres into forming thedesired particle shape.The continuous approach has been used to simulate large volumes of concrete. Theconcrete is modeled as a homogeneous material, particular effects of aggregates,such as blocking or segregation are not accounted for. Good correspondence wasachieved with a Bingham material model used to simulate concrete laboratory tests(e.g. slump flow, L-box) and form filling. Flow of concrete in a particularly congestedsection of a double-tee slab as well as two lifts of a multi-layered full scale wall castingwere simulated sucessfully.A large scale quantitative analysis is performed rather smoothly with the continuousapproach. Smaller scale details and phenomena are better captured qualitativelywith the discrete particle approach. As computer speed and capacity constantlyevolves, simulation detail and sample volume will be allowed to increase.A future merging of the homogeneous fluid model with the particle approach to formparticles in the fluid will feature the flow of concrete as the physical suspension thatit represents. One single ellipsoidal particle falling in a Newtonian fluid was studiedas a first step. / Med uppkomsten av självkompakterande betong (SKB) och dess möjligheter att flyta ut under inverkan av endast gravitation uppstod ett behov av att kunna förutsäga och kontrollera även mer komplicerade gjutningar. Numerisk simulering av SKBs flöde kan kommma att utgöra ett kraftfullt verktyg för att optimera gjutprocessen, ge möjlighet att förutsäga nödbvändig arbetbarhet och säkerställa kompatibilitet mellan den armerade formen och betongens reologi. I föreliggande avhandling undersöks betongens flöde med både diskreta och kontinuumbaserade simuleringsmetoder. Den diskreta partikelmodellen används för att simulera detaljer och fenomen hos t.ex. ballast i betong. I de här presenterade simuleringarna används sfäriska partiklar, men det är även möjligt att skapa ballastkorn av olika form. Ballastens ytråhet och storlek kan modelleras med parametrar för friktion och storlek medan sammanfogning av ett flertal partiklar kan ge ekvivalent form. Den kontinuumbaserade ansatsen används för att simulera större flödesmängder. Betongen modelleras som ett homogent material, eventuella effekter av ballastens inverkan, till exempel blockering eller separation, ingår ej. God överensstämmelse har uppnåtts med Binghams materialmodell som applicerats på några av SKBs provningsmetoder (bl a flytsättmått och L-låda) liksom även för större gjutningar. Formfyllnad av en hårt armerad sektion av ett STT-element, liksom två pumpade betongleveranser till en hög vägg, har framgångsrikt simulerats. En kvantitativ övergripande analys av betongflödet i formen kan göras med den kontinuumbaserade ansatsen för att upptäcka zoner med eventuella svårigheter. En högupplöst detaljstudie kompletterar sedan analysen på valda delar av och kring dessa zoner för att fånga partikelfenomen kvalitativt med hjälv av den diskreta modellen. Då datorkapaciteten ökar kommer även större volymer med högre detaljrikedom att kunna simuleras. En framtida modell simulerar med stor sannolikhet partiklar i flöde, vilket till fullo kan fånga betongens egenskaper som suspension. Som ett första steg på vägen har en fallande ellipsoid i en newtonsk vätska simulerats.

More efficient and cheaper solar cells are necessary if photovoltaics are to play a major rolein the field of sustainable power generation. Copper indium gallium selenide (CIGSe) is one of the best suited materials for thin film solar cell absorbers. One production method for thin film manufacturing is sputtering, a fast, high-yield, all-dry process that can be performed in an unbroken vacuum chain. The sputter target, which provides the raw material for this process, is an important link to obtain high quality films. Furthermore, the targets stands for the single largest cost in solar cells produced through the method. Hence, driving down the target production costs while maintaining or increasing quality is a vital route towards competitive photovoltaic power generation. In this project, compound CIGSe sputter target material was produced via mechanical alloying of elemental raw materials, followed by hot pressing. The resulting material obtained a relative density above 90% in all samples, with close compositional matching and grain sizes between 20-50 µm. Electrical characterization indicated predominantly p-type majority carriers, and the resistivity was within the range of industrially produced targets. Suitable process parameters are suggested as follows: for ball milling; 600rpm rotational speed, a ball-to-powder ratio of 5:1, and a milling time of 60-120 min. For pressing: 650-750˚C peak temperature, maintained for 1-2 h under 25-60 MPa pressure. 30 min dwell time at peak temperature before pressure application was found to reduce porosity. An initial composition of 23.2/20/6.5/50 at% of Cu, In, Ga, and Se, respectively, was found appropriate to obtain a final composition close to 22.8/20/7/50.2 at%. The project has proven that mechanical alloying combined with hot pressing provides a promising route towards efficient sputter target manufacturing, where the reduction of process operations compared to conventional manufacturing methods entails an optimistic economic outlook.

Thin polymer materials are today widely used in industry and production. An ordinary food package can have around six different layers of materials laminated together to obtain the desired protection. To obtain an efficient usage of these materials simulations are often required. But the simulations require precise and good material models and properties. To obtain these properties through standard tests are difficult as normal strain gauges or extensometers can’t be used. Much research has been done on this kind of material. But still, the knowledge of the behaviour in certain cases is limited. One such area is the tearing of a laminated material.   The first objective of the work is to test a new measurement method, Digital Image Correlation (DIC), for thin polymer films and test if the method is applicable. DIC is a non-contact measurement technique that measure the deformation of a stochastic pattern. The strain is then calculated from this deformation. These strains can then be used to obtain material properties and behaviour. The second objective is to test the tearing behaviour of a laminate.   The material used is a laminate between a PET (100 μm) and LDPE (25 μm) film. When testing the single layers they were carefully delaminated with a plexiglass staff. As the material can be anisotropic the materials were tested in five directions: Machine Direction (MD); 22,5˚; 45˚; 67,5˚ and Cross Direction (CD). The work and tests were performed at BTH Campus Gräsvik.   An experimental setup for DIC with the usage of chalk spray and backlight was tested. Five tests were performed with and without DIC pattern. It was calculated that the DIC specimens were within standard deviation of the reference tests. GOM Correlate was used to evaluate the strains and visualise the distribution. The strains obtained were also used to calculate the true stress of the specimens and estimate the Poisson’s ratio.      Through testing it was concluded that the tearing of the laminate led to delamination in one of the legs. The delamination always appears in the leg where the LDPE film will experience tensile forces. The crack also angels towards 45˚. By testing single layers it was found that the PET film angles when teared, likely caused by the anisotropy of the material.      An experimental setup for the use of DIC for thin polymer has been developed. This method can be used for future measurements and improvement of material models. The behaviour of laminated tearing was observed and some conclusions could be drawn about its behaviour. However, a lot more work is required on this subject.