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438 Uppsatser om Numerical grid - Sida 9 av 30
Analys av turbulensmodeller för CFD
This thesis has been a part of Forsmarks Kraftgrupp AB's evaluation of a turbulencemodel used in simulation of turbulent flow called PRNS (Partially Resolved NumericalSimulation). This model has promising properties and may be of use in savingcomputational resources. The purpose of this thesis was to analyze this model andcompare it with industrially applied models such as k-omega SST and LES (Large EddySimulations).PRNS works as a hybrid of the k-omega SST and DNS (Direct Numerical Simulation)where a constant, RCP (Resolution Control Parameter) with a value between 0 and 1are selected. This constant is then used in the calculations and determines thebehavior of the simulation. When RCP is set to zero the equation are the same as fora DNS simulation and when RCP is set to one the equations for k-omega SST issolved.
Det energiproducerande huset
We are heading towards a huge switch of how energy is produced with fossil fuels being replaced by renewable energy sources. It is not difficult to replace the energy you use in the house and there is no need for futuristic technology. There are already many established products on the market such as high efficiency vacuum solar collectors, heat pumps & small wind power stations that can supply the energy being used in a house. The company Sol & Energiteknik SE AB in Huskvarna has many different products which can reduce the need for an outside energy distributor. An average house in Sweden uses 15 000 kWh for heating, 5000 kWh for tap water and 5000 kWh for electricity.
Solenergisystem i Hammarby Sjöstad
Problems with the current energy system, which partially relies on non-renewable fuels, are increasingly recognized. Emissions of greenhouse gases from fossil fuels may speed up global warming, which in turn leads to a number of negative consequences. Nuclear energy is risky and relies on consumption of a scarce resource. This leads to a demand of renewable energy that is also economically feasible. One possible renewable source of energy is solar energy.
Effektivisering av mellanspänningsnät med enkla medel : Feldetektorer och sommardriftläge
Renewable energy and the charging of electrical vehicles will increase in the future. Therefore the risk of outages is also increasing, partly because renewable energy is intermittent and the production amount can change fast. Charging electrical vehicles is often demanding high effect in short time, which could make faults occur. It takes more advanced technology to short the outage time. Today Övik Energi has high reliability in the power grid, but in order to maintain the reliability, it is time to prevent problems that can occur in the future. This thesis has presented a suggestion for the placement of fault detectors Protrol IPS2, in which a total of four detectors is proposed.
Leg SSk
Syftet med denna studie var att go?ra en bedo?mning av den postoperativa fo?rloppet i hemmet hos dagkirurgiska ljumskbra?cksopererade patienter. Data insamlade med hja?lp av ho?gstrukturerade telefonintervjuer. En enka?t med standardiserade fra?gor och ikryssbara svarsalternativ som kommer har anva?nts vid telefonintervjuerna.
Resultaten fra?n de 52 intervjuerna visade att de flesta patienter inte o?verskred Numerical Rating Scale (NRS) 3 i vila eller ro?relse dag ett.
GPS-baserad virtuell geografisk inhägnad för mobil enhet
The aim of this paper is to find an algorithm to establish and maintain a virtual enclosure around a mobile unit. The area may take any form and should be scalable up to and including national borders. The enclosure is managed on the mobile unit. The target system is Android. Smartphones, tablets and more recently, cameras is examples of mobile units.
Utredning av frekvensregleringens påverkan på mekanisk utrustning i en kaplanturbin
As a consequence of increasing wind power installations in the Nordic grid the last years, the need for regulating power has become larger. In the Nordic grid, regulating power is mainly provided by hydro power. One part of the regulating power is called frequency control, which ensures that the grid frequency is stable and close to 50 Hz.However, setting the turbine into frequency controlled operation may cause stress and wear of the components in the mechanical control system. Frequency controlling implies large and frequent servo forces and longer travelling distance of the sliding bearings in the Kaplan turbine.Based on one selected Kaplan turbine, Selsfors G1, measurements and MATLAB calculations have been performed in order to determine forces and movements of the linkage system. With these forces and movements as input, stresses and fatigue have been determined as well as sliding distances, bearing pressures and wear of bearings during a typical lifetime of 40 years.The results indicate that no severe wear exists on the bearings during 40 years of service.
Samspel, etablering och koppling mellan naturgas och biogas
Sweden has a natural gas grid extending along the west coast, from Trelleborg to Stenungsund. There are also several smaller local networks where a planned natural gas pipeline from Skutskär to Hofors prompted the need for a comprehensive study. This study examines the linkages that exist in terms of technology and market of natural gas and biogas in Sweden. Sweden has set high targets for the future with ambition to become independent of coal and oil as energy sources. Since 1985, a part of the solution has been import of Danish natural gas.
En ledares egenskaper : En undersökning i Stockholm
Ledarskap är ett aktuellt ämne sedan flera årtionden tillbaka, det talas och skrivs om det nästan varje dag. Det finns många olika teorier om ledarskap och varje årtionde har haft sin egen prägel på ämnet. Än idag har forskningen inte kommit fram till en idealisk ledarskapsstil, varför vi fann det intressant att undersöka vad människor som dagligen kommer i kontakt med ledarskap anser utgör en bra ledare. Utifrån detta vill vi se om åsikterna passar in på de valda teorierna. Vi avgränsade oss till de anställda på Clas Ohlson då de ansågs relevanta för undersökningen.Syftet med detta arbete är att se vad personalen på Clas Ohlson i Stockholmsområdet anser utgör en bra ledare.
Självförsörjande elgenerering : Kan Orust bli självförsörjande på förnybar el?
Orust Kretsloppsakademi is a nonprofit organisation, with a goal of annually generate the same amount of electrical energy that is consumed. Orust is an island on the west coast of Sweden, north of Gothenburg. The population of 15 000 reaches 40 000 during summer, due to the large amount of vacationer. The total electricity demand is 174 GWh a year with a maximum power need of 32 MW. This report presents an analysis for the plausibility of their plan and from a power system stability perspective, the effects on the electrical grid.The conclusion is that the restraints for development of power generation from wind, solar and wave generation, are the power systems capability to transfer power, primarily in the transformers of the grid.
Internprissättning : En studie av svenska företag
Begreppet ekonomistyrning innefattar många aktiviteter som i grunden handlar om att uppnå ekonomiska mål. Internprissättning är ett av dessa. När ett företag växer i storlek uppkommer ofta en diskussion om hur organisationen ska decentraliseras och vem som ska fatta beslut. Vanligt idag är att företagen decentraliseras och fler och fler beslut fattas lokalt.1967 gjordes en enkätundersökning som innefattade totalt 235 svenska företag varav bland annat alla börsnoterade. Man ville undersöka vad man i svenska företag vill åstadkomma med sin internavräkning.
Ledarskap och frisknärvaro : en kvalitativ intervjustudie
Frågan om chefers ledarskaps påverkan på de anställdas hälsa har aktualiserats under senare tid. Dock finns inte mycket forskning på området, vilket gör att denna uppsats kan komma att fylla en funktion i detta sammanhang. Uppsatsen har som syfte att ta reda på hur förskolechefer i en svensk kommun utövar sitt ledarskap och om det går att se någon koppling till medarbetarnas frisknärvaro. Med hjälp av kvalitativ metod där fem semistrukturerade intervjuer genomfördes besvaras följande frågor i kandidatuppsatsen: Vilket slags ledarskap utövar förskolecheferna?Vilka likheter finns i ledarskapsstilarna mellan de förskolechefer som har hög frisknärvaro bland medarbetarna?Skiljer sig ledarskapet åt, i så fall hur, mellan de chefer som har hög frisknärvaro och de med mellanhög och låg dito? Min slutsats är att det finns likheter i hur cheferna utövar sitt ledarskap.
Reading space. Möbel för läsning till Göteborgs nya stadsbibliotek
Reading spaceFurniture for reading for the new city library of GöteborgThe main purpose of my project has been to inspire people to read books at the library. I wanted to create something very site specific and chose a room on the second floor of the new city library to work with. To be able to relax, feel inspired and to concentrate on reading, the visitors of the library need to experience a sense of security. My solution to the different conditions or problems in the room and the needs I identified is a seat hanging inside a frame. When sitting down in the seat, the frame is low enough to see over but it is still experienced as a private spatiality.
GPS-baserad virtuell geografisk inhägnad för mobil enhet
The aim of this paper is to find an algorithm to establish and maintain a
virtual
enclosure around a mobile unit. The area may take any form and should be
scalable
up to and including national borders. The enclosure is managed on the mobile
unit.
The target system is Android.
Smartphones, tablets and more recently, cameras is examples of mobile units. A
modern mobile unit is part of a computer network.
Tidssynkroniserade mätningar i vattenkraftstationer
Vattenfall and Svenska Kraftnät perform start-up tests, where hydropower generators are used to power up the electrical grid in case of a blackout. To monitor the electrical grid, Phasor Measurement Units (PMU) are used. Each PMU is individually equipped with a GPS-receiver to precisely timestamp the data relative to the official time UTC. During the test, it is also of interest to timestamp the measurement signals from individual hydropower generators to later compare with PMU-data, and thus study the power grids impact on the generator. The aim is to work out an appropriate method to make these measurements and to build a data acquisition system, capable of timestamp data relative to UTC, from a generator in one of Vattenfalls hydroelectric power stations. The problem is that the generator is located in an underground station which hampers the reception of GPS-signals and wiring should be avoided if possible. Time synchronization has been solved by using Vattenfalls network, which is synchronized by the network protocol NTP.