This thesis embraces simulations of NOx emissions from a partially premixed 20 kW swirl burner. The simulations were carried out in the commercial computational fluid dynamics software FLUENT. The concept of partial premixing air and fuel before adding additional air for complete combustion has proven promising with a view on the NOx emissions. However, little research has been done on reach premixing of fuel and air and therefore further investigation of this topic is of interest. In most experiments in the literature methane is used as fuel, but due to problems with stability and blow off in the 20 kW swirl burner propane were chosen as fuel.Simulations of eight different air-fuel ratios have been performed, ranging from diffusion flame to a mass based air-fuel ratio of four. The results from these simulations proved satisfactory when comparing with previous experimental and simulated work, except from the calculations of the exact NOx concentration. This difference in the concentration was one the other hand expected since the power of FLUENT and similar software is to predict variation trends and not the exact value itself.The simulations showed that the NOx concentration increased with increasing premixing, reaching a local peak at an air-fuel ratio of two. After this a local minimum in the NOx concentration was observed before a strong increase when further raising the air-fuel ratio. This is the same trends that are observed in the literature when using methane as fuel, but for propane there is no global reduction in the NOx emissions when applying premixing. This increase in the NOx emission was found to be due to an expansion of the high temperature flame zone with increasing premixing, which benefits the thermal NOx formation mechanism. The NOx reducing effect of swirl generation observed to decrease when the air-fuel ratio was increased. For subsequent experimental work it is recommended to perform a high amount of experiments at different air-fuel ratios, especially in the ratio range where the NOx concentrations starts to fluctuate.

Litteraturstudien viste at tørkehastigheter i klippfiskproduksjon påvirkes av forholdene i tørkeluften; relativ fuktighet, temperatur og lufthastighet. Det er to typer tørker som er utbredt, nemlig langsblåste tørker med kontinuerlig drift og tverrblåste tørker med batchdrift. Den langsblåste er vesentlig mer energieffektiv enn den tverrblåste. I et typisk anlegg står flere tunneler i serie, med hvert sitt avvanningsaggregat. Det ble kjørt forsøk på en tørkerigg på kuldeteknisk lab på Gløshaugen. Her ble det logget temperatur og luftfuktighet før og etter tørkekammeret, hensikten var å holde disse parameterne konstante i hvert forsøk. Tørkekammeret var delt i to slik at det var forskjellige lufthastigheter i hver del, 1 m/s i det ene kammeret og 3 m/s i det andre. Vekten av hver fisk ble logget gjennom tørkeforløpet. Dette ble for alle unntatt en utført manuelt. Den siste ble satt opp slik at vekten ble logget hvert femte minutt. Dessverre ble disse målingene påvirket av friksjon langs stagene som forbandt fisken med vekten.Basert på målingene ble det satt opp kurvetilpassninger for å finne kurver for tørkehastighet. Det ble funnet at tørkehastighetene ble påvirket av hvordan tørkeprosessen har forløpt forut for det aktuelle punktet.Med utgangspunkt i en tverrblåst batchtørke med tre tunneler i parallell ble det gjennomført casestudie hvor tørkeforløpet ble modellert i Excel ved hjelp av rnlib og hxsim. Tabeller for tørkehastigheter ble tatt fra forsøkene. Siden det ble observert at disse påvirkes av tørkeforløpet forut fører dette til vesentlig unøyaktighet, og det er ønskelig at det på et senere tidspunkt blir utarbeidet en modell som beskriver tørkehastighetenes utvikling mer nøyaktig.Med dette forbeholdet ble det utviklet tre case. Case1 viser en prosess uten regulering av ytelsen med tre tunneler i parallell, case 2 viser en prosess med ytelsesregulering med tre tunneler i parallell, og case 3 har ytelsesregulering og tre tunneler i serie, drevet av et indirekte varmepumpesystem.Det ble funnet at det for slike anlegg er vesentlig potensial for forbedring både på nødvendig installert effekt og energiforbruk totalt ved å benytte case 3 istedenfor case 1. Case 3 oppnådde mer enn dobbelt så høy SMER (kg vann fjernet per kWh) med 20 % lavere effektbehov.

Institutt for Energi- og Prosessteknikk ved NTNU gikk, for en tid tilbake, til innkjøp av en fullskala ventilator av typen som Vegdirektoratet i Norge benytter til ventilering i tunneler. Motivasjonen bak innkjøpet var et ønske om å drive utviklingsarbeid rundt impellerdesign, da Vegdirektoratet ved flere anledninger opplevde at innkjøpte ventilatorer ikke overholdt produsentens egne spesifikasjoner. Denne oppgaven er et ledd i dette arbeidet, og har som målsetning å utvikle bladgeometri spesielt for denne typen applikasjon, for en fembladet impeller som kan tilpasses på det originale navet, og med bedret ytelse sett i forhold til den originale impelleren. Geometridesignet tar utgangspunkt i et løfteprofil utviklet på instituttet noen år tilbake med spesielt godt løft-per-motstandsforhold, men såkalt skarpe steilingsegenskaper. Bestemmelse av fordeling av kordelengde og geometrisk vridning langs bladets radius, er gjort ved hjelp av bladelementmetoden programmert i matrisebehandlingsprogrammet . Geometrien er meshet i MatLab og etterprøvet i CFD-programmet Fluent for konstant rotasjonshastighet og varierende volumstrøm, og resultatene er sammenliknet med testdata fra den originale impelleren. Sammenligningsprosessen er vanskeliggjort av at mengden av tilgjengelig testdata fra den originale impelleren, eller liknende impellere, er svært begrenset. Sammenligningen som er gjort, indikerer imidlertid at det nye impellerdesignet har høyere virkningsgrad og høyere spesifikk skyvkraft over hele arbeidsområde enn den originale. I bladelementprogrammet ble ett blad delt inn i 20 elementer. Geometrien er lagret som 21 .dat-filer med profilkoordinater i alle tre romlige retninger for de 21 profilveggene som skiller disse 20 elementene.

Målet med denne oppgaven er å måle pumpevirkningsgrad ved hjelp av termodynamisk metode. Termodynamisk metode måler strømningstapene over en hydraulisk strømningsmaskin. For strømningsmaskiner med løftehøyde over 100 m ligger usikkerheten mellom 0,5-1,0 % i følge ISO 5198. Pumpen målingene er utført på er en neddykket elektrisk sjøvannsløftepumpe, fra Frank Mohn Flatøy AS. Dette er en sentrifugalpumpe med et kort aksielt innløp. Målingene er utført ved Frank Mohn Flatøy AS sin prøvestand. To utfordringer er knyttet til plassering av målepunkt på leveringssiden til denne pumpen. Pumpen er neddykket i en testtank under test, og den drives av en oljefylt elektromotor som er integrert i pumpekonstruksjonen. Som en følge av disse utfordringene er det valgt å benytte flere målepunkter enn det som er vanlig for termodynamisk metode.Pumpens virkningsgrad er også målt med konvensjonell metode hvor tilført elektrisk effekt og avgitt hydraulisk effekt måles. Instrumentering til konvensjonell målemetode er standard instrumentering for testriggen som er brukt. Logging av måledata ble gjennomført i 8 driftspunkt med to logginger i designpunktet.Resultatene fra den termodynamiske målemetoden sammenlignes med resultatene fra konvensjonell målemetode. Måleusikkerheten i den termodynamiske metoden er beregnet.Forventet virkningsgrad er 87 % ut fra tidligere tester med konvensjonell metode på samme pumpe. Den konvensjonelle metoden gir en virkningsgrad på η=87,2 % i beste punkt, mens virkningsgraden fra den termodynamiske metoden er η=77,5 % i beste punkt. Dette er et avvik på 9,7 %. Måleusikkerheten for den termodynamiske metoden er innenfor kravene fra ISO 5198. Ved beste virkningsgradspunkt er måleusikkerheten 0,88 %. Dette tyder på at det er en systematisk feil i den termodynamiske metoden. Den systematiske feilen er antakelig i testoppsettet for temperaturmålepunktet på leveringssiden av pumpen. Entalpien holdes ikke konstant ved trykkreduksjon i målepunktet.

Moderne, godt isolerte bustadar med ventilasjon og varmegjenvinning, har lågt energibehov til oppvarming. Dette har ført til at behovet for energi til oppvarming av tappevatn er den dominerande energiposten, spesielt i lågenergi- og passivhus.Noreg har gjennom Kyoto-avtalen forplikta seg til å redusere utsleppa av klimagassar til 1% over 1990 nivå. For å nå dette målet er det nødvendig å redusere energiforbruket vårt. Auka bruk av solfangarar i Noreg vil kunne bidra positivt til reduksjon av klimagassar som følgje av redusert energibruk. Oppgåva gjennomgår grunnleggjande prinsipp for utnytting av solenergi til romoppvarming og oppvarming av tappevatn, samt aktuelle system og bruksområde. For å gjere ei vurdering av nytteverdien av solfangarar i lågenergihus er det i denne oppgåva laga ein modell som reknar ut energiutbytte frå sola for fire leilegheiter med ulike varmebehov. Modellen tar utgangspunkt i solstrålingsdata og oppvarmingsbehov for ei leilegheit i Oslo. Ein lågenergibustad med solvarmeanlegg har stort potensiale til å redusere det årlege elektriske energiforbruket sitt. Antar ein at dette fører til tilsvarande reduksjon i energiproduksjon ved forureinande kolkraftverk i Europa, er potensialet for reduksjon av CO2-utslepp også stort.Ein investeringsanalyse basert på data frå modellen viser at det vil lønne seg å installere solfangaranlegg for varming av tappevatn. Det kan derimot ut frå privatøkonomiske synspunkt vere vanskelegare å forsvare ei større investering i solvarmeanlegg for romoppvarming i lågenergihus.

The motivation of the work is to increase the knowledge about thermodynamic modeling of freezeouts in natural gas systems and a deeper understanding of the phase behavior of natural gasmixtures, due to the problems experienced in cryogenic natural gas process-plants. Criticalcomponents in natural gas mixtures introduce a risk of forming a solid coating and plugging theprocess equipment. Hence, it is relevant to examine methane rich binary mixtures containingcomponents with high risk of freezing. Due to their high triple point temperatures, carbon dioxide,benzene and cyclohexane are regarded as the most critical components.The preferred thermodynamic method for modeling the solid – fluid system is by describing the fluidphases with a traditionally equation of state in combination with an expression for the solid phasebased on melting and triple point properties. This method is based on the assumption of a purecomponent solid phase, which does not always represent the precipitated substances in natural gassystems. However, it is the situation which represents the highest risk of crystallization at a giventemperature.This study was carried out by applying a simulation tool called NeqSim, where the equation of statemethod is implemented based on the computational algorithms provided by Michelsen andMollerup. To investigate the reliability and accuracy of the equation of state method, it is usedexperimental data from the literature as a foundation and further compared against two existingsimulation tools for freezing point predictions of natural gas mixtures, GPA and HYSYS.The Soave-Redlich-Kwong equation was selected together with classical mixing rules and the use ofbinary interaction parameters. The binary interaction parameters were discovered to be of crucialimportance to the accuracy of the predictions, both for the binary mixtures containing carbondioxide and the heavy hydrocarbons. The model showed promising results for carbon dioxide inmethane rich binary mixtures, after the binary interaction parameter had been optimized. However,the interaction parameter dependency for solid-vapor equilibrium systems was discovered to be lessthan in solid-liquid equilibrium systems. Predictions of freeze outs of heavy hydrocarbons werediscovered to be more challenging, due to numerical problems and a scarce experimental database.One of the main issues concerning the development of reliable thermodynamic models for solid-fluidsystems is the lack of experimental data, which prevents extensive validation of the proposedmodels. The experimental work related to the freeze out rig has mainly involved trouble-shootingand experiments for determining the behavior of the rig. Hence, the experimental focuses were onthe gathering operational experience by running these experiments, and identify the main challengesand the potential areas for improvement. Including a phase study of pure carbon dioxide where thesolid-liquid equilibrium and three-phase point was determined.In order to investigate the binary mixtures of interest, where the composition and the componentexposed to freeze outs is known, the heat loss from the Dewar container and the temperaturedifference between the air bath and the fluid has to be reduced. Hence, the solids will form in thesapphire cell, where the freeze outs can be visually detected. Further, for studying multi-componentmixtures similar to real natural gas mixtures where the composition of the precipitating substance isunknown; a solution for the sampling of the different phases has to be developed, includingextensively testing and validation.

Turbulent jet diffusion flames and flame lift-off have been the topic of a great deal of research due to its complexity in combining both turbulent flow and combustion. The mechanisms controlling flame lift-off however, are not yet properly understood and is still an active field of research. In this report, experimental studies of lift-off characteristics for oxy-fuel combustion with methane have been conducted for oxygen concentrations ranging from 34% to 50%. Three different fuel nozzles were used, with diameters of of 2mm, 4mm and 5mm. In addition to oxy-fuel combustion, experiments were carried out in air, and oxygen enriched air, as a reference case.The goal has been to observe how oxy-fuel flames differ from regular diffusion flames burning in air with regards to lift-off. Lift-off heights and velocities were found to be strongly dependent on oxygen concentration, with increasing concentration causing shorter lift-off heights and higher lift-off velocities. It was also discovered that the combustion chamber wall temperature seemed to have a great impact on flame stability. Higher wall temperatures had a stabilizing effect on the flame, probably due to lower heat loss and higher burning velocities.Results from the air cases were compared to data from other studies, and were found to deviate some, most likely due to the presence of co-flow.

The main objective in this thesis was to investigate a potential increase of power output from the existing turbines at Ruacana Hydropower Station. This was restricted to only consider a runner replacement, and only technical aspects of a rehabilitation project has been evaluated. This involved an investigation of hydraulic condtions, limited to surge oscilliation and water hammer calculations. The results was thereafter used in a calculation model to estimate potential increase in power output. Vital information about the plant and the condition of the waterway was obtained from a study trip to Ruacana. An increase in power output in a turbine can be obtained by increasing the volume flow and/or efficiency. The first criteria can be achieved through expanding the outlet diameter of the runner, and/or altering the flow angles. Therefore has the hydraulic conditions also been analysed with the aim of increasing volume flow. It was found that it can be increased to a maximum nominal volume flow of one unit to 85 m3/s. It was limited by the maximum upsurge in the Surge Headbay with the intake level at highest flood level. The restrictions are altered for the minimum water levels in the intake and maximum levels in the tailrace when operating 1 to 4 units. The advances in Francis runner design over the last deacades makes an increase in efficiency feasible. Finally a calculation method for estimating a potential increase in power output was developed. This was based on traditional turbine theory, and the aim was to find the maximum increase starting from the existing degree of submergence. In addition were the results compared to values obtained from a calculation method developed by Sintef. From a preliminary study of achievements in refurbishment projects was it found that on average has an increase of 18% been obtained. The method developed in this thesis concluded that an increase of 10 - 14% in nominal power output is possble. Assuming a turbine efficiency of 0.93 and only replacing the runner. Sintef's method estimated a maximum value of 15% for the same conditions. It is also found that the outlet diameter at Ruacana can be increased by 60 mm. The additional increase in power output is only estimated to be 1% from the method developed in this thesis. The Sintef method estimates additional 3% increase for the same scenario.

A literature survey of LNG processes suitable for offshore environment has been evaluated. Thesurvey has been performed with emphasis on space requirements, complexity, efficiency and safety.Thermodynamics theory is described and used in the investigation of the NicheLNG process. Theliquefaction part of the HLNG FPSO-1 has been evaluated with respect to its energy consumption,improvements and the possibility to expand the process to give an indication about improvementpotentials. In addition, one alternative liquefaction process has been compared with the NicheLNGprocess.Dual expander processes based on nitrogen as refrigerant are the most proposed solution suitable foroffshore applications. Therefore it was chosen as an alternative process to NicheLNG. In theinvestigation of the two processes the processes simulated were with equal conditions. The NicheLNGprocess, based on an open methane cycle and a nitrogen cycle, had a significantly lower mass flow rateresulting in 10% lower power consumption. Decision of chosen refrigerant gas (methane or nitrogen)has different specific heat capacity and hence an influence on the flow rate. Methane as refrigerantrequires less mass flow rate than nitrogen for a given duty. In addition, higher pressure levels willcontribute to increased efficiency and reduced unit sizes.In the open refrigeration cycle of the NicheLNG process, methane is cooled down to -1,5°C before itis expanded. If the internal heat exchange is extended to -10°C before expansion is it possible toachieve some efficiency increase for the methane cycle.Comparison criteria are important when the quality of liquefaction processes is to be determined. Feedand product specifications provide some restrictions on obtainable efficiency. With an increasing feedgas pressure, the whole liquefaction process (from feed to LNG) demands less work, but the overallprocess efficiency is reduced due to the high efficiency of the feed gas compressor and the lowefficiency of the liquefaction part. Hence, the efficiency of the liquefaction process should not becalculated from its feed gas pressure but rather the liquefaction pressure. For the NicheLNG process,the exergy efficiency of the liquefaction part was calculated to 26,6%, with a liquefaction pressure at75 bar.An increase of LNG production with emphasis on improvements to keep work consumption down wasalso discussed. The four evaluated solutions were utilization of End Flash Gas, liquid expander,additional compressor and increase of heat exchanger area. The liquid expander was the improvementthat stands out as the highest contribution to the efficiency. With a 25% increase in LNG productionand with new units and modifications of the design resulted in a reduction in the specific workconsumption from 0,5502 kWh/kgLNG to 0,4791 kWh/kgLNG. These efficiency improvements canjustify higher investment costs since the work consumption, with 25% higher LNG production, was12,9% lower than for the original design of the NicheLNG process. Never the less, space and weighton a FPSO are limited and has to be considered when a more efficient process is desired.

Transport of natural gas to continental Europe and UK is a large portion ofNorwegian petroleum industry. The gas is mainly transported undersea inlarge-scale transport pipelines. Amount of transported gas is currently closeto maximum capacity of the pipeline network, and as a consequence the gastransport must be careful planned so that the optimal capacity can be utilized.An important tool in this planning is the use of computational method topredict the flow. Accurate computational tools is therefore of great value whenpredicting the pressures and flow rates in transient cases such as opening of avalve or shut down of a flow. This report is a part of a major research projectinitiated by Gassco, for better flow-predictions models in natural gas pipelines.A computational model based on the method of characteristics has beendeveloped. In this report the main focus is on the solution of the energy equationand introduction of this equation to an already existing code solving for pressureand mass flux. The method is verified using measured values of pressure at theinlet.Since much of the uncertainty is related to the transients, this report focuseson transient cases. The old program solving the characteristic equations using anisothermal assumption actually proves surprisingly accurate, and the additionalsolution of temperature does not significantly improve the results. The methodhowever does not provide satisfactory results at the larger transients.If large temperature gradients are imposed on the solver we see instabilities inthe flow and it affects the solution of the parameters. The Joule Thomson effectthat we have in our solution also results in a much higher drop of temperaturethan what can be measured, in case of pressure drop at the inlet.From the results we also see that the coefficient that is supposed to correctfriction factor for additional drag effects, also should be a function of pressureand/or Reynold number. If such a correlation would provide more accurateresults in the transient has not been debated, but more accurate correlation offriction depending on flow rate would probably give a more accurate result.Also worth noticing is that the method does not have a clear convergence,or reduction of error as the number of calculation points increases. It givessmaller extreme values, but average error is not reduced significantly. This isprobably a result of the reduced effect of missing convective-term as the gridhas a finer resolution and time-step decreases and the effect of loss of velocityin the characteristic becomes small.As a simple tool for calculation of gas transport in pipelines, the isothermalmethod of characteristics proves to give surprisingly accurate results. However,for more complex systems, i.e. including the temperature and variable propertiessuch as compressibility and density, finite difference methods are more versatile.Finite difference methods can be done implicit, giving a more stable solver, andit’s simpler to account for some of the effects such as temperature etc.iv