This report considers different energy solutions for a floating LNG production vessel. The two alternatives analyzed are gas turbine and steam turbine. In addition to being stand-alone alternatives they are the basis for other alternatives, such as electric drive and combined cycle. Light side studies have been performed on the two latter ones. A LNG process model has been built in Aspen HYSYS, and from this several cases has been run. There are 3 levels of different parameters that have been run: 1) Energy system, 2) Feed Gas Composition, and 3) Liquefaction process. As mentioned the two energy systems are GT and ST. Three different feed gas compositions have been analyzed: 1) Low content of both CO2 and N2 (0.5 % and 1 % respectively), 2) High content of CO2 (9.5 %), and 3) High content of both CO2 and N2 (9.5 % and 3 %). The liquefaction processes analyzed are two of the most promising for a floating LNG application: Dual mixed refrigerant and dual N2 expander.The feed gas compositions was chosen to give a wide area of applications for the results, and to give illustration on how the two different energy solution would respond to changing feed gas composition. The DMR liquefaction process was chosen mainly because this is the one being implemented in Shell Prelude FLNG. Being the most proposed solution for offshore application the dual N2 expander was a natural alternative to the DMR.The analysis show a clear advantage for gas turbine and DMR process, when exclusively looking at efficiency. However; as the objective of the study states, important factors such as safety, vessel motion sensitivity, reliability, availability is also to be considered. The results show 245 kWh/ton LNG energy consumption with the DMR liquefaction process, whereas the dual N2 expander requires 424 kWh/ton LNG; over 70 % increase. However; the side- cases run in this report show advantages to the N2 dual expander in safety, weight/space requirements and ease of start-up and shut down.The ST/N2 has fuel gas consumption 4% higher than the GT/N2. On the basis of the results in this report and other studies performed on FLNG a selection of the ST/N2 setup will be favorable as long as there is a high CO2 content in the feed. With low CO2 content, hence heat demand, the advantage of the ST is smaller thanks to lower heat recovery demand.

This objective of this thesis has been to development and analysis a measurement apparatus designed to determine thermal conductivity of porous materials. A literature survey concerning available experimental techniques for thermal conductivity measurements was conducted. A steady state radial heat transfer method with cylindrical geometry and a centered heating element was found to be most suited technique for achieving accurate and reliable results. A side wall cooling arrangement was used to achieve desired cooling temperatures. To restrict the extent of the work, it was decided to only investigate heat transfer behavior at cryogenic temperatures. Test specimen with a thermal conductivity of 0.05 W/(m*K), (assumed to be the thermal conductivity of the materials to be tested in the apparatus) and a thermal conductivity of 0.01 W/(m*K) for the insulation components, were the ones chosen for investigations. The design process of the new apparatus, using the software COMSOL Multiphysics 4.2, was initiated by evaluating heat transfer behavior in a simple cylinder, containing a hollow heating element and the test specimen. Radial heat transfer was verified, hence, the design process proceeded. Extensive, step-wise analyses were conducted to evaluate heat transfer behavior as the complexity of the apparatus increased. Implemented elements such as insulation blocks, a heater support and three thermocouples proved to cause heat losses in the test section, which resulted in errors in the calculated thermal conductivities. Furthermore, an electric wire, supplying the heating element with current, was included in the model. In addition, the hollow heater was replaced by an aluminum oxide heater since such an element is to be used when building the apparatus. Unexpected results revealed critical heat transfer into the test section from the wire. This led to an investigation of the wire length to reduce such effects. Lastly, as a result of the analyses carried out, the overall error of the thermal conductivity measurements due to heat losses was determined. Dimensional drawings of the characteristic dimensions, as well as practical solutions for the final compilation of the apparatus, were suggested as the last step of the design process. It was of interest to estimate the overall uncertainty of the apparatus when all parameters effecting the measurements, were included. For this, a comprehensive uncertainty analysis was conducted and compared to previous work. Results showed that temperature recordings from the thermocouples placed in the mid-section of the test cylinder would provide the most reliable results for the determination of thermal conductivity in the test apparatus.

The main objective of this thesis is to describe the transient thermodynamics during physisorption of hydrogen gas using a commercial numerical software.Simulations of thermal effects during adsorption are valuable tools for the efficient design of hydrogen adsorption storage systems. Transient mass and energy equations are used for describing the adsorption process. For this purpose, experimental adsorption data has to be presented analytically. Several models have been developed for this objective.The thesis consists of two parts. In the first, a literature study on adsorption theories and thermodynamic assumptions for development of transient mass and energy balances is conducted. The models are discussed, and from this, the Langmuir approach is selected to be used for numerical calculations. The model is implemented into a lumped-parameter analysis describing an infinitesimal element within an adsorbent bed, allowing for neglecting heat leaks into the system as well as the structural steel mass. The second part describes the simulations conducted in the study. The numerical software COMSOL Multiphysics 4.2.a is used for numerical calculations. Modules for implementation of the transient mass and energy balances are considered, before Heat Transfer in Porous Media and Brinkman Equations are applied, for heat transfer, pressure- and velocity calculations, respectively. The simulations are run for different initial and boundary conditions. The porous material is defined with Fe-btc properties. The simulation model is built step by step, and problems encountered are analyzed continuously in the process towards a complete model. After completion, the model geometry is adjusted and the porous material is changed to MOF-5 properties, to resemble a selected published paper. Numerical results are compared and discussed. Modeling restrictions for the present study is accounted for, and all choices made when considering the assigned task are justified. The report is completed by listing the conclusions drawn from the present study, and concrete suggestions for further work are given.Simulation results found in the present study differs slightly from the published research work. Instabilities in the solver results in a temperature dip in the simulated domain. This leads to an increased adsorption rate. Furthermore, it appears that mass is not conserved, which means that the inlet velocity of the feed gas does not change as expected when the adsorption is disabled from the model.

A Pelton design software is currently being developed at the Waterpower laboratory at NTNU. The motivation behind this software is to streamline the parametric design process for Pelton turbines. A numerical flow model is a cornerstone in this application, but the lack of a bucket geometry and model runner has prevented the development of such a model. DynaVec, a turbine producer who specializes on sediment erosion and corrosion problems, offered to help by providing a bucket geometry and a model runner.The objective of this Master's thesis was to develop and validate a CFD model that predicts the torque applied to a non-stationary Pelton bucket, subject to a high-speed water jet. The numerical model was based on a method proposed by DynaVec, and the bucket geometry used in the simulations was identical (1:1) to the model runner.Numerous simulations were conducted, testing mesh dependency and different operational points (e.g. head). Mesh independence occurred at approximately 4.5 million elements. Furthermore, simulations of varying heads showed that the model may be independent of the head (40-80m), but this was not verified properly.Experiments showed that the numerical prediction was fairly accurate. A comparison of the numerical and experimental measurements showed that the CFD model over-predicts the torque by approximately 1.5%. This prediction was validated for the specific geometry used in the simulations, and a head of 75m.Overall, the results suggest that the numerical model is promising as a parametric design tool, but further development is required to obtain a true validation of the model.Task three and four were changed in agreement with Ole Gunnar Dahlhaug, because Solemslie's design program was delayed. In essence, the parametric study proceeded in favor of the development of a CFD model. To ensure that this work would benefit future research, especially students at the Waterpower laboratory, a detailed procedure for the CAD modeling, meshing and physical setup was included in the Appendix.

The incentive to reduce energy consumption in the industry is big, especiallyin high temperature systems. Heat pipes are of great interest for this purposedue to their favorable thermomechanical properties. This master thesis is apart of the ongoing study of Ph.D. candidate Geir Hansen, who is currentlydeveloping a rectangular heat pipe with potassium as working fluid at NTNU.The rectangular heat pipe is intended to be implemented in the walls ofelectrolysis cells as a part of a heat recovery system.The present work reports results of theoretical calculations of two importantheat transfer limitations, the incipience of boiling and the capillarylimitation for two types of nickel foam wicks. Results of experimental testscarried out on the cooling circuit for the proposed rectangular heat pipe arealso reported. The foam porosity, permeability and effective pore radius forwick 1 is 0.797, 31·10−12m2 and 62·10−6m, respectively, and for wick 2; 0.886,205·10−12m2 and 126·10−6m.A literature survey showed that porous coated surfaces improves the heattransfer and requires less superheat for boiling to commence. Calculationsperformed showed no danger of homogeneous nucleation in the proposed heatpipe. Boiling inside the nickel foam wick(s) were found to only be of concernfor wick 2 at high heat fluxes and a operating temperature of 600C.Calculations of the capillary limit showed that wick 2 is the best choicefor sustaining high heat fluxes. Increasing the wick length to 20cm madewick 2 not suitable for usage, and wick 1 was the best choice for increasedwick length. Combination of the two wick types showed to be very effectiveand significantly (factor of almost 4) improved the performance. An unevenheat flux distribution where a lower heat flux is at the bottom region of theevaporator is found to lower the performance, while a higher heat flux at thebottom region increases the performance.Early tests revealed that the PID controller was marginally stable, so thecontroller was tuned and stable operating conditions were achieved. Experimentsshowed that in order to get an accurate heat balance for the test rig,knowledge about the exact position of the thermocouples is needed.

Over the last few years Norway has seen an increasing number of hours where the grid frequency exceeds the required limits (49.9-50.1Hz). To improve this situation one alternative is to implement hydropower governing with quicker response time. However, long conduits and oscillatory flow set strict requirements to the hydropower system stability and turbo set governing. This thesis establishes a simulation program based on the structure matrix method for stability analysis of hydropower systems. The method is implemented in a Matlab program to study the oscillatory flow in the frequency domain. Implementation of frictional influence, turbine characteristics, and alternative governing has been given special attention. The program is validated through comparison with measurements and previous analysis at Kongsvinger and Tafjord power plants. The program simulations generally compare well with physical dynamics of the two systems. Further a stability analysis of speed governing at Aldal power plant has been performed. Finally some alternative control systems are discussed.

The purpose of this thesis is to highlight some of the areas of interest when it comes to wind tunnel experimenting of offshore platforms regarding stability concerns such as critical angles and wind overturning moment. Some important factors include design of tower geometry, the effect of surface roughness on drag, methods of calculating blockage corrections of wall interference and the generation of an atmospheric boundary layer to resemble full-scale conditions. Data obtained from wind tunnel experiments with two different models have been compared and discussed according to the areas of interest as mentioned above. Testing of platforms was done at NTNU with a six-component balance, measuring forces of drag, side and lift and moment of pitch, roll and yaw with increments of 10° the whole 360° to account for wind coming from all directions. Two geometries were tested for the tower members, one with a circular cross-section which was smaller than scale and another with a square cross-section in correct scale. There was noticeable change in both global forces and moments. Blockage corrections caused by wall interference were researched from different sources and reviewed, and it was apparent that it is still an area with lots of uncertainty. Consensus was that and area ratio of maximum 0.10 should be abided in any case and that the simplified method of Pope is widely used. An atmospheric boundary layer was simulated at NTNU using trial-and-error and the validity of this was confirmed by comparing experimental data with theoretical data regarding the velocity profile, turbulence intensity and energy spectrum. For the experiments of surface roughness on an individual circular cylinder and the corresponding change in drag, a simple three-component balance was used. The cylinder represents the platform legs. Two types of surface roughness were tested, first a plain wooden surface and then with a layer of coarse sand applied to the whole surface. It was seen that the rougher surface provoked an earlier transition to a turbulent boundary layer, causing an earlier drop in drag which is a better fit to estimated full-scale characteristics.Finally, the element that contributes most to the inaccuracy of the experiments is shown to be the difficulty of geometric similarity. Further investigation is needed.

Reduction of the energy used to acclimatise buildings is a huge challenge simultaneously with the implementation of air tight low energy buildings. In residential buildings with several living units centralised air handling units are the most energy efficient system. However, in a centralised system there is important to avoid leakages of pollutions between the exhaust air and the supply air. This leads to that flat plate heat exchangers are used instead of the more energy efficient rotary heat exchanger in these types of buildings. Flat plate heat exchangers will have problems concerning water condensation and frost formation in the exhaust air channels at low supply inlet temperatures. In this thesis a membrane based heat exchanger, which also was able to transfer moisture, was compared to a plastic based heat exchanger to see if the membrane based exchanger had less problems concerning condensation and freezing. In addition a mathematical method was derived to predict the heat and moisture transfer effectiveness in a membrane based heat exchanger.To compare the different heat exchanger plate materials a test rig was built in the laboratory at the Department of Energy and Process Engineering at NTNU. The experiments showed that the plastic based heat exchangers had problems with condensation and freezing in the tested conditions. The membrane based exchanger did not experience the same problems. However, additional problems with expansion of the membrane in high humidity showed that the tested membrane had drawbacks and was not really suitable.The derived mathematical method to predict the moisture transfer effectiveness was shown to correlate very well with the experimental results. The derived method and the developed Microsoft Excel tool called HXcalc may then be used to investigate other membranes moisture transfer effectiveness.

I denne hovedoppgaven har slippstrømninger generert av sirkulære sylindre og to typer elliptiske varmeveksler - rør blitt undersøkt. Målet med arbeidet har vært å beskrive virvelavløsningsfenomener på elliptiske varmeveksler - rør i håp om å kunne belyse innvirkningene dette fenomenet har i forbindelse med støy-, og vibrasjonsproblematikk i en varmeveksler utviklet ved NTNU i samarbeid med Norsk Hydro. Studiet har blitt gjort gjennom eksperimenter i vindtunnel ved Strømningsteknisk laboratorium ved Institutt for energi-, og prosessteknikk under veiledning av Professor Lars Roar Sætran. Forsøkene som har blitt gjennomført innbefatter målinger av turbulente hastighetsfelt og virvelavløsningsfrekvenser med hetetrådsanemometer. Måling av gjennomsnittshastigheter med pitotrør har også blitt gjennomført. Resultater fra målingene har vist at Strouhal - tallet for den ene typen elliptiske varmeveksler -rør har en verdi på 0.2 for Reynolds - tall i området $3.8 cdot 10^3$ til $2.38 cdot 10^4$, hvor den karakteristiske lengden i Strouhal - tallet og Reynolds - tallet er definert som to ganger den lille halvaksen til det elliptiske røret. Ingen periodiske virvelavløsninger ble detektert for den andre typen varmeveksler - rør. Det ble konkludert med at virvelavløsningene fra den ene typen elliptiske varmeveksler - rør genererer dynamiske krefter som har samme frekvens som de observerte vibrasjonene fra varmeveksleren der rør av denne typen er installert. Dette tilsier at virvelinduserte krefter er involvert i dannelsen av vibrasjoner og støy i varmeveksleren.

Komponenter innen smelteverksindustrien utsettes for ekstreme varmeflukser og temperaturforhold, og må derfor kjøles for å unngå nedsmelting av konstruksjonsmaterialet. I forbindelse med kjøling av overflater er det vanlig og benytte serpentinmønster for å effektivt kjøle hele overflaten. Serpentinmønsteret er oppbygd av en rette kanaler og tilhørende skarpe 180° bend for å snu vannstrømmen. I disse 180° bendene oppstår ett strømningsmønster som er særs lite jevnfordelt, både med hensyn på strømningshastigheter og varmeovergang. Variasjonene i varmeovergangen skaper temperaturgradienter i konstruksjonsmaterialet og disse kan over tid skape skjørhet i materialet og brudd i konstruksjonen.På bakgrunn av dette er det i denne oppgaven utført numeriske simuleringer av strømnings, varmeovergangs og temperaturforhold i skarpe 180° bend. De numeriske beregningene er utført med programvaren COMSOL Multiphysics som benytter seg av Finite Element Method. Beregningene er gjort med RANS likningene og k-ω turbulensmodellen for strømning, og energilikningen og Kays-Crawford modellen for varme. Innledningsvis er den numeriske modellen validert opp mot publiserte målte resultater. Valideringen består av både en sammenligning av hastighetsprofiler i utløpskanalen og en sammenligning av strømningsmønsteret generelt i bendet. Sammenligningen av hastighetsprofilene ga ingen absolutt overenstemmelse, trolig på bakgrunn av for unøyaktige turbulensmodeller. Derimot ga simuleringene meget god resultater ved sammenligningen av strømningsmønsteret og det ble besluttet av simuleringene skulle videreføres. Oppgavens formål er å utjevne strømningshastigheter og varmeovergangen i de skarpe bendene, og tiltakene som ble foreslått i forprosjektet er simulert numeriske her. Tiltakene omfatter flere typer av ledeplater i bendet i tillegg til lekkasjespalter mellom tilstøtende bend. Ledeplatene ble vurdert fra de simulerte strømningsresultatene, og de viste seg her at de forlengede ledeplatene ga både minst separasjonssone og en hastighetsøkning i bendet hjørner. En ledeplate med rett forlengelse nedover utløpskanalen ble utvalgt som den beste og tatt videre til også å inkludere lekkasjespalter. Det ble sett på strømningsresultatene for tre forskjellige plasseringer av ledeplaten i samhandling med lekkasjespaltene. Videre ble det simulert varmeovergang og temperaturforhold for ett skarpt bend uten tiltak, med ledeplate og med ledeplate og lekkasjespalter. Fra disse simuleringene ble det beregnet lokale fluidtemperaturer, temperaturer i konstruksjonsmaterialet og varmeovergangskoeffisient. Resultatene viser tydelige områder med høyere temperatur både i bendets hjørner og i separasjonssonen for basecaset. Ved bruk av ledeplate er disse sonene mye bedre kjølt, men en temperaturøkning registreres på ledeplatens innside. Med ledeplate og lekkasjespalter i bendet er temperaturforholdene enda mer jevnfordelt. Som en absolutt sikkerhet mot koking inne i elektrodeskjoldet er det beregnet nødvendig massestrøm for å kjøle veggtemperaturen under fluidets metningstemperatur for de tre overnevnte casene. Denne modellen er basert på det laveste varmeovergangstallet i bendet og gir en reduksjon av nødvendig massestrøm på 29 % for ledeplate jamfør ingen tiltak. Med lekkasjespalter og ledeplate kan massestrømmen reduseres med 31 %. Det er anbefalt ledeplaten alene som tiltak på bakgrunn av det høye trykktapet skapt av lekkasjespaltene.