Ejector systems have been a field of research for many years. One of the latest topics are transcritical cycles with R744 refrigerant. The main reason of installing ejectors in that type of systems is the recovering of the pressure energy, lost in the classic cycles during the throttling processes.The thesis consists basically of two parts, which both of consider the topic of parallel ejector operation. In the third part conclusions are presented.The first part is a simplified feasibility study for a concept R744 cycle with three different ejector geometries working in parallel. MS Excel spreadsheet was created for general parameters calculations and for specific motive nozzles mass flow estimations.The second part contains results of measurement procedures on the SINTEF test facility. First, single ejector operation was examined. Basing on the test results, characteristic of P2GGC ejector geometry has been created. Later on, a new module with two different geometries (P2GGC and A2CDC) working in parallel has been built on the rig. The parallel ejector operation has been examined, as well as single operation of each geometry. The results has been compared, considering the influence of each operation on the system parameters.In the third part final conclusions are presented. Some ideas of further work are mentioned as well.

AISI 316/316L has traditionally been used in offshore topside environments when operating under low temperatures. It has been observed that the AISI 316/316L piping suffer from severe attacks of pitting and crevice corrosion on external surfaces. It is therefore important to emphasise the comments within the statements that give the limitations on the use of the material. While temperature is the main parameter in the standards, there seem to be others, such as location, presence of tags and coating, which affect the initiation and propagation of pitting and crevice corrosion. This thesis discusses the various operating parameters that affect the susceptibility to pitting and crevice corrosion of AISI 316/316L piping and proposes procedures for identifying piping that are most prone to attack, and calculations of the probability of failure of such piping.In the first part of the thesis, a literature survey of the parameters that affect the pitting and crevice corrosion of AISI 316/316L in an offshore environment is presented. In the second part, a procedure for the identification of piping that is prone to pitting and crevice corrosion is presented. This procedure has been developed taking into consideration the parameters that are assumed to be important and suitable for use in RBI analysis. In the first step, the parameters that affect both pitting and crevice corrosion, that is, the chloride content due to the location of the pipe, coating and temperature, were considered to be the most important ones. In the second step, the possibility of crevice corrosion was assessed. In the third part, a procedure for assessing the possibility of pitting corrosion in the offshore topside environment based on the pitting potential was developed. The temperature of the external pipe surface was used to find the solubility of NaCl in water. The chloride concentration was used to determine the in order to find the possibility of pitting in the topside offshore environment. The last step was to develop a procedure for calculating the probability of failure of a pipe as a function of time. In this step, the functional life of the coating and the rate of pitting corrosion have been considered.

Rock Energy is a Norwegian company with a patented solution for drilling deep geothermal wells, for exploitation of deep geothermal energy from Hot Dry Rocks. The concept involves a drilled sub-surface heat exchanger, referred to as cross wells. The concept is well suited for production of heat for direct heat applications. In this thesis an analysis of the existing district heating plant at Oslo Airport Gardermoen has been conducted, together with examining possibilities of implementing geothermal energy as base load at the plant. A geothermal design that could meet the needs of the district heating plant has been established, and for evaluating the geothermal system in an environmental perspective an analysis based on LCA methodology has been conducted. Hafslund operates two district heating centrals at Gardermoen (Gardermoen heating central and a smaller mobile central) for which both have been analyzed to determine the potential for implementing deep geothermal energy as base load for the systems. Gardermoen heating central is connected to the airport and to the area close to the airport. This central is again connected to the mobile heating central, which is situated near the industrial estate south-east of the airport. Based on Hafslund’s production data from February 2011 to January 2012, a heat load duration curve for the two existing centrals have been established. When adding the two curves together the duration curve show a maximum load of 25,7 MW at present, and a yearly energy production of 74 GWh. The mobile central accounts for only 7,2% of the total load and heat production at present.Future heat demand in the Gardermoen area is expected to increase beyond existing capacity. Hafslund is therefore considering to increase the capacity of both their district heating centrals. The enlargement plans involves that the heating central will be expanded to a design load of 37,4 MW (24 MW at present), while the mobile central need to be increased to a design load of 15,2 MW (1,7 MW at present). Assessment of the geothermal installation showed that it is preferable to include the geothermal system in the base load of the mobile central. The additional geothermal capacity will cover 10 MW, and thus deliver 65% of the required heat load and 90% of the energy production from the mobile central. The geothermal installation was designed using the spreadsheet “Geocalc”. The outputs from Geocalc are used in an analysis of the environmental performance of the designed system through a Life Cycle Assessment (LCA). LCA introduces a technique to assess environmental impacts associated with all stages of a product’s life from “cradle to grave”. The report aims at giving normative results for the environmental impacts of a geothermal installation at Gardermoen. The method provides the ability to quantitatively compare results to other sources of heat provision processes for district heating. It is important to emphasize that the analysis has provided an overview of the potential environmental impact, and not necessarily the actual results of environmental consequences. The system analyzed has a thermal output of 10 MW, lifetime of 30 years, 5000 annual operating hours. The functional unit of district heating produced is kWh. The analysis is based on the main contributing processes to construction, operation and demolition of Rock Energy’s geothermal system. The district heating grid is not included in the analysis, as it is already in place at the site. Each contributing process has been systematically validated. It is however uncertainties associated with the data collection mainly due to contradictory information gathered. The information considered to be mostly uncertain is the energy consumption used for drilling purposes.Possible scenarios for the energy supply to drilling were established. These scenarios were simulated in a system model in Excel. The model is based on data and information gathered from existing literature, the database Ecoinvent, published reports and personal communication with drilling experts and specialists within the relevant fields of study. The results are assessed for the following impact categories: Climate change, metal depletion, fossil depletion, terrestrial acidification and freshwater eutrophication. The evaluated potential energy sources for the drilling operation are electricity from the Norwegian grid, electricity from the European grid, and diesel. The climate change category has especially been in focus when conducting the simulations and this category shows large spread in the results, from 0,9993 g CO2-eq/kWh for the best scenario to 23,6 g CO2-eq/kWh for the worst scenario. As expected, the analysis concludes that electricity from the Norwegian grid for the drilling is preferable. For a geothermal system in Europe, the results show that it would be advantageous to use diesel as energy supply for the drilling operation instead of European electricity mix, for which the emissions are doubled.For the metal depletion impact category, the variation of energy supply to drilling cause the least fluctuation. This is also the only impact category where the Norwegian electricity mix has higher impacts than for the diesel consumption. This can be explained by the infrastructure related to electricity transmission. The results of the study have been compared to other heat sources for district heating (waste incineration, biofuel and solar thermal). The comparison shows that from an LCA perspective geothermal energy based on Rock Energy’s concept is an environmentally friendly energy supplier for district heating. The studies compared are however based on varying assumptions, and thus a generalized conclusion cannot be drawn from this.

Som rassikring langs den svært rasutsatte strekningen av Rv. 70 langs Oppdølsstranda ved Sunndalsøra i Møre og Romsdal skal det bygges en 7,5 km lang vegtunnel. Tunnelen drives gjennom et området med bratt topografi og overdekningen langs deler av tunnelstrekningen vil overstige 500 m. Det er forventet at stabilitetsproblemer kan oppstå i tunnelen på grunn av den steile topografien og høye overdekningen. I denne masteroppgaven er det utført analyser for å vurdere muligheten for bergtrykksproblemer.I løpet av våren 2012 har det i tunnelen blitt utført spenningsmålinger i form av overboring. Målingene viser at det forekommer en betydelig tektonisk spenningskomponent for horisontalspenningene i området og at spenningene er sterkt påvirket av topografien. Største hovedspenning er orientert parallelt fjorden og tunnelens lengderetning. Mellomste og minste hovedspenning er orienter hhv. parallelt og vinkelrett i forhold til topografien.Med utgangspunkt i spenningsdata og bergartens mekaniske egenskaper målt i laboratoriet er det utført ulike analyser for å vurdere muligheten for bergtrykksproblemer. Spenningene ved utvalgte profiler er bestemt ved beregninger og numerisk analyse. Videre er bergtrykksproblemer vurdert ved hjelp av modeller for sammenligning av bergartens styrkeegenskaper og spenningsnivå rundt tunnelen. Analysene viser at det kan forventes svært høye spenninger langs en strekning av tunnelen hvor overdekningen kommer opp mot 575 m. Det er i dette området forventet at det vil oppstå moderate stabilitetsproblemer som følge av de høye spenningene. Problemene vil trolig forekomme i form av sprak og avskalling i heng og vederlag som vender ut mot fjorden. Noe økt oppknusing kan i tillegg forekomme i overgang mellom indre vegg og såle, men antas ikke å utgjøre vesentlige problemer med tanke på stabilitet.Som sikringsmetode ved bergtrykksproblemer er det anbefalt å raskt påføre stålfiberarmert sprøytebetong i minimum 10 – 15 cm tykkelse. Endeforankrede bolter installeres så utenpå sprøytebetongen. Denne sikringsmetoden er i henhold til krav gitt av Statens vegvesen og har gitt gode resultater for lignende prosjekter tidligere.

A multi fuel biogas plant is under planning at Fiborgtangen, Norway. The plant will utilize biogas from several different sources, including fish silage, animal manures, sludge from the paper factory and straw. In order to make good decisions on how to design the plant, characterization of the substrates in regards to biogas potential and nutrient value was done, and laboratory scale models of a possible plant design was established. The characterization showed that a minimum of 42% of the DM should come from manure in order to meet the micro-nutrient demand, it also showed that some nitrogen rich substrates in addition to the manure needed to be present to avoid nitrogen limitation to balance out the high carbon substrates. A biochemical methane potential study was carried out for all substrates and showed promising results, with the exception of the fiber sludge from the paper factory that had a very poor methane potential. The mixed substrate fed to the reactor models gave a methane yield of 300 mL CH4/gVS in the biochemical methane potential study. A mix of all the substrates was fed to 4 semi continuous reactors with a HRT of 25 days and OLR of 3 gVS/L. The reactors performance was unstable, and operating with high propionic acid concentrations. The specific methane yield ranged from 170-230 mL CH4/gVS, but because the reactors did not reach steady state during the experimental period and the propionic acid concentrations were so high, it is not possible to conclude on what yield this design would give. It is recommended that the semi continuous experiments are continued until they reach steady state or collapse because of the high propionic acid concentrations. After this it would be recommended to start experiments with higher proportions of animal manure and to leave the fiber sludge out of the reactor feed as it is has very low methane and nutrient value.

Life cycle assessment (LCA) methodology aims at evaluating the environmental impacts of a product or system from a holistic approach. In this methodology, all life cycle phases of the product are identified and assessed, from the raw material acquisition to the end-of-life phase. This master thesis is dealing with the LCA of a Norwegian bridge. First, a literature review is realized by going through 14 bridge LCA references. Then, a detailed description of bridge LCA methodology is performed. Finally, an LCA study is applied on Tverlandsbrua, a Norwegian bridge project, in order to assess the overall global warming impact of the bridge life cycle.The conclusions of the literature review are very different according to the goals and scopes of the studies. Concrete and timber bridges are often more environmentally performing than steel or composite concrete-steel bridges. Material production is generally the life cycle phase leading to most impacts, followed by the maintenance & repair phase. Improvements in material design and use of recycled materials are important to bring down the overall emissions.The LCA methodology description has been through all elements specified in the ISO standards. The methodology has been adapted to the needs of the case study but the goal and scope definition has been kept wide enough to allow comparisons with future bridge assessments. Input data (energy, material flows, etc.) are as much as possible gathered from the client and subcontractors of the project, but sometimes assumed. Output data (greenhouse gases emissions) are either directly collected from environmental reports or calculated by an LCA software.The overall global warming impact of Tverlandsbrua is 6665 kgCO2-eq per functional unit (FU), all life cycle phases considered. The FU, i.e. the unit to which the emissions are referred, is defined as 1 square meter effective bridge deck area through a lifetime of 100 years. When the operation phase (mainly consisting of traffic-related emissions) is not considered, the emissions are brought down to 1358 kgCO2-eq per FU. Concrete, steel and asphalt life cycles are identified as the main component contributors. Uncertainty and sensitivity analyses, discussions and recommendations for further studies are performed in order to give clues for more environmentally performing solutions.

Det er stadig aukande interesse og fokus på energieffektivitet i byggesektoren, og passivhus er i dag på veg til å verte forskriftskrav i Noreg. Det er likevel stor ueinigheit i om passivhusa er godt nok utreda for konsekvensar i bruk til at dette kan skje i nærmaste framtid. Mykje av kritikken som vert retta mot passivhus er at det vert store problem med overvarme om sommaren.I denne rapporten er det presentert erfaringar frå passivhus i Noreg, Sverige og Danmark og gjennomført simuleringar. Målet er å finne ut om det er eit større problem med overvarme i passivhus enn i andre hus med lågare isolasjonsstandard.Erfaringane og simuleringane presentert i rapporten viser at isolasjonsevna ikkje har betydeleg innverknad på det termiske inneklimaet. Problem med overvarme vil difor oppstå i like stor grad i passivhus og bygg med lågare isolasjonsstandard. Simuleringane viser vidare at både passivhus og hus med lågare isolasjonsstandard vil har store problem med overvarme dersom det ikkje vert iverksatt tiltak for å hindre det. Tre strategiar for å redusere problemet er•Forhindre varmetilskot•Planlegge metode for å fjerne varmeoverskot•Sørgje for tilstrekkeleg varmelagringDersom desse strategiane vert gjennomført, vil den gode isolasjonsevna i passivhus stenge varmen ute og på denne måten sikre eit betre termisk inneklima på varme dagar enn hus med lågare isolasjonsstandard.

In this thesis, a novel open cycle desiccant dehumidification system is experimentally studied. The system is installed and operated at Shanghai Jiao Tong University (SJTU) as part of the Green Energy Laboratory (GEL) initiative. The system uses two-stage desiccant dehumidification as well as regenerative evaporative cooling for chilled water production. The purpose of the thesis is to evaluate the system performance during different ambient and operational conditions. The investigated system has great potential regarding the environmental aspect of HVAC system solutions. The system is more energy efficient compared to conventional air conditioning systems and uses solar thermal power provided by evacuated tube solar air collectors as the main source of energy. Therefore, this type of system can contribute in reducing the use of non-renewable energy sources.A lot of experiments have been performed from June to July 2012 during varying ambient conditions. As a first step, the necessary regeneration temperature level is established. The results show that this temperature should be in the range of 70-75˚C or higher to be able to achieve desired dehumidification effect. Then, experiments regarding the overall system performance during different ambient temperature and humidity conditions are performed and analyzed. The results show that the system excels good performance during periods of high ambient humidity and is capable of achieving average COPth and COPel around 0.8 and 5.7 respectively. The total dehumidification efficiency is approximately 58% and is proven to vary with respect to the regeneration temperature, where increasing regeneration temperature results in higher amount of moisture removed from the processed air. The solar collectors providing heat to the regeneration air has an efficiency of 47-60% depending on the available level of solar radiation intensity. During periods of low intensity it is proven that the heating system needs assistance from an auxiliary device to be able to generate a sufficient temperature level. The evaporative cooler producing chilled water is capable of providing water at a temperature below 21˚C during periods of high ambient temperature, and temperatures below 16˚C if the ambient temperature decreases. The achieved dehumidification and cooling capacity of the desiccant system makes it possible to provide qualified supply air with temperature in the range of 20-26˚C and absolute humidity below 12 g/kg. Also, an experiment with the purpose of investigating the newly installed second desiccant wheel is carried out. The system is operated with only the second wheel running and the results show that the dehumidification performance is very good when the second wheel provides the first stage dehumidification. Lastly, experiments investigating the impact of the pre-cooling heat exchanger is performed and analyzed.

Oppgaven tar for seg opprissing av massive damkonstruksjoner i betong. Utgangspunktet for oppgaven er Skardfossdammen som Skanska skal bygge ved Rjukan i Tinn kommune i Telemark. Her skal Skanska rive den gamle dammen, og bygge en ny betongdam. Den nye dammen blir forholdsvis stor, og er estimert til omtrent 25 000 m3 betong.I massive betongkonstruksjoner med store betongvolum, vil termisk induserte spenninger utgjøre en stor del av spenningsbildet i konstruksjonen. Slike spenninger oppstår på grunn av høye temperaturer i den herdende betongen. Opprissing grunnet ytre fastholding er spesielt interessant. Oppgaven ser på noen tiltak som kan iverksettes for å hindre eller redusere slik opprissing. Målet med oppgaven er å gi svar på hvor mye tiltakene kan endre rissindeksen og betongens maksimaltemperatur. Disse tiltakene er:1.Redusere herdevarme ved å tilsette flyveaske i betong.2.Redusere herdevarme ved å endre sementinnhold og hulrom i tilslag.3.Redusere fersk betongtemperatur ved å benytte knust is under blanding av betong.4.Redusere fastholding ved å legge inn et sjikt mellom konstruksjonen og omkringliggende flater.I tillegg nevner oppgaven tre andre tiltak for å hindre opprissing grunnet termisk induserte spenninger.Effekten av de fire tiltakene er funnet ved å simulere tiltakene i spesielle regneprogrammer. Programmene som er benyttet er CrackTeSt COIN og iDIANA. I tillegg er CrackTeSt COIN sammenliknet med regneprogrammet 4C Temp&Stress. Kostnaden av tiltakene er også anslått der dette har vært mulig.De fire nevnte tiltakene gir en reduksjon i både rissindeks og maksimaltemperatur i konstruksjonen. Ikke alle tiltakene er like enkle å gjennomføre, og det må kanskje brukes en kombinasjon av flere tiltak for å oppnå ønsket resultat.

Nitrogen oxides (NOx) are formed by oxidation of nitrogen during the combustion process, and production rate is highly affected by flame temperature. NOx is regarded as a local pollutant causing smog, acid rain and health complaints, and strictest emission regulations are found in urban areas. Reduction of NOx emissions from gas turbines can be achieved by modifying the combustion process or by exhaust gas clean up. Several technologies are already commercial available, but there are still a great many being developed. Increased focus on the environment also forces manufacturers to improve existing technology. In this report, different NOx abatement technologies are looked into, and an optimal solution for the coming gas turbines on Skarv Idun is presented. Different techniques are compared in terms of thermal efficiency, emissions, maintenance requirements, load acceptance and rejection, engine stability and reliability and availability. Application and suitability of available technologies for reducing NOx from the selected gas turbines is discussed, and user experience for these is collected. It is showed that all technologies influence operation of the gas turbines to some extent, either by increasing/decreasing efficiency or by affecting engine stability. They also differ in their ability to reduce NOx emissions over the entire load range. Due to weight and space restrictions on offshore installations, limited technologies are suitable for platforms and boats. Gas turbines installed offshore are usually aero-derivative engines with high efficiency and relative low emissions of CO2. This year, Norwegian government introduced a NOx tax in order to reduce NOx emissions from the petroleum industry. Operators are forced to use best available technology, and dry low emission control (DLE) is the only one considered qualified as far as NOx is concerned. DLE is also chosen as the optimal solution for the planned gas turbines on Skarv Idun, due to small operational impacts and positive experience from existing fields. It is however recommended to allocate space in case a new and better combustor with lower emission levels is developed. Looking at a longer perspective, Cheng technology including steam injection into the gas turbine combustor seems very promising for NOx abatement.