In this thesis the evaporation from and condensation on a plane liquid surface have been studied by analysis and molecular dynamics simulations. The effect of the condensation coefficient on the inverted temperature gradient for a two-surface evaporation-condensation geometry is investigated by the moment method. The influence of the molecular exchange phenomenon on the gas-kinetic treatment of evaporation and condensation is shown to be neglible under certain assumptions. Methods to simulate half-space steady evaporation or condensation in Direct Simulation Monte Carlo simulations are adapted to Molecular Dynamics (MD). A microscopic definition of evaporation and condensation is introduced and values for the evaporation and condensation coefficients are calculated from MD. The velocity distribution functions for the evaporation and condensation modes have been calculated and compared with the standard assumptions in gas-kinetic calculations.

Soot and radiation play an important role when designing practical combustion devices, and great efforts have been put into developing models which describe soot formation and oxidation. The Eddy Dissipation Concept (EDC) has proven to describe turbulent combustion well, and has the flexibility to describe chemical kinetics in a detailed manner. The aim of this work is to study how the EDC handles soot models based on a detailed representation of the gas-phase chemical kinetics. Two versions of a semi-empirical soot model is used in conjunction with the EDC. Concentrations of various intermediate species are used as input to the soot models. The implementation of the new soot models is discussed in relation to the previous implementation of a less detailed soot model. To assure that the interaction between soot and the gas-phase species is represented correctly, the soot models are implemented with a two-way coupling of soot and gas-phase kinetics. Soot is a good radiator. In a sooting flame a substantial amount of energy will be transferred to the surroundings by thermal radiation. This transfer of energy will alter the temperature field of the flame and the change in temperature will affect the kinetics of soot and gas-phase chemistry. To simulate sooting flames correctly, it was therefore necessary to include a radiation model. To validate the coupled models of turbulence, combustion, soot, and radiation two different turbulent flames were simulated. One turbulent jet flame of methane and one turbulent jet flame of ethylene. For both flames the computed results were compared with measured values. Several aspects of the simulations are studied and discussed, such as the effect of the two-way coupling of soot and gas-phase kinetics on both soot yield and gas-phase composition, and the importance of a suitable radiation model. The two-way coupling of soot and gas phase kinetics is shown to have a positive effect on the computed soot volume fractions, and the results are considered to be encouraging. The work has demonstrated that the EDC has the capacity to handle different types of chemical reaction mechanisms, such as mechanisms for gas-phase combustion and soot kinetics, without modification.

<p>I denne oppgaven skulle jeg kartlegge de tekniske konsekvenser ved endringer i design av rør varmeveksler for varmegjenvinning og de teknisk/økonomiske konsekvenser for eventuell fjernvarmeutbygging ved redusert varmetetthet. Spillvarmen som skulle brukes ble hentet fra elektrolysehallen i et aluminiumsverk. Det var 170 ovner i elektrolysehallen. Varmen fra elektrolysehallen gikk ned i rør i kjelleren under hver ovn. For rør varmevekslere var det 2 alternativer kjølekappe rundt hvert rør til ovn og røykkjel der avgassen fra alle ovnene ble samlet i 4 store varmevekslere. Inntemperaturen til avgassen fra elektrolysehallen til varmeveksler var 400 C, og uttemperaturen til avgassen ut varmevekseleren i det første alternativet var 235 C. Innetemperaturen til avgassen fra elektrolysehallen til varmeveksleren var 400 C mens ute temperatur for røykkjelen var 120 C. I begge tilfellene så skulle vannet bli varme opp fra 50 C til 70 C. Røykkjelen egnet seg best til dette med dimensjonene: lengde 25 meter, diameter 0,1 meter. Antall rør er 10. Energien fra varmevekslere ble brukt videre til å dekke energibehovet til byen, både offentlige og private bygg. Det ble sett på 2 tilfeller energibehovet nå og energibehovet i år 2020. Det ble estimert med at energibehovet til byen blir redusert med 30% fra 2008 til 2020 i følge regjeringens soria moria erklæring angående energibruk. I byen er det også installert et pellets verk. Dette kan utnyttes til å samle rest energi og bruke dette for å dekke topplasten. Det totale energibehovet i 2008 var 21692169.2Kilowatt timer, mens det totale energibehovet i 2020 var 15184518.44 Kilowatt timer. Rørnettet ble distribuert på en total lengde på 8 km. Rørene ble lagt ned i en perfekt grunnforhold i sand og omtrent 1 meter under jorden. Maksimale trykk som er tillat i rørnettet er 16 bar. 10 meter stigning i terrenget tilsvarer 1 bar. Det høyeste toppen i terrenget var 70 meter. Det høyeste trykket blir derved 7 bar. Temperaturen til nettet ble på 70 C Rørnettet hadde en optimal diameter på 240 mm og kostnaden per meter ble i 2008 227 kr, mens i 2020 ble kostnaden 248,84 kr per meter. Den totale distribuerte kostnaden ble i 2008 på 1816071.664 kr, mens den i 2020 ble den totale distribuerte kostnaden på 1990779.649 kr. Kostnaden per Kilowatt timer ble i 2008 på 0,08 kr. Mens den i 2020 ble på 0,13 kr per Kilowatt timer. For selve anleggskostnadene så ble det betraktning til at investeringskostnadene var 1,5 kr per Kilowatt time. Det medførte at anleggsinvester ble 32,538,254 kr. For anleggskostnadene ble det antatt at man fikk 30 % støtte av Enova. Totale Anleggskostnad ble da henholdsvis 14223167.5 kr i 2008 og 12588089 kr i 2020. Dette medførte at i 2008 ble det anleggskostnaden 0,66 kr per Kilowatt time, i 2020 ble anleggskostnaden 0,89 kr per Kilowatt time. Dette medførte at de totale kostnadene per Kilowatt time økte med 30 % når varmebehovet sank med 30 %.</p>

<p>The following paper presents HVAC system commissioning activities, highlighting the most critical techniques and features to consider when commissioning the underfloor air distribution (UFAD) system. UFAD systems are non-standard and unique and therefore a special attention is needed to some issues and situations specific only for UFAD installations, e.g. coordination of the raised access floor, carpet and furnishings, temperature stratification etc. Some of the most important tests to be performed during commissioning of UFAD systems, are the air leakage, air stratification and thermal decay testing. In order to achieve successful operation of UFAD, the active participation of all involved parties, e.g. architects, interior designers, HVAC designers, contractors etc. is needed since the very beginning of the project. Commissioning of UFAD just requires a discipline, structured approach and commitment from all participants involved. The practical study involved assessment of expected UFAD performance at the Sparebank kvartalet office building complex in Trondheim, Norway. The underfloor plenum was not properly sealed, creating a significant risk of future energy waste. The openings in the raised access floor construction also lead to the dust and dirt accumulation in the plenum. This in its turn would not only impair indoor air quality, but could also lead to the malfunction of mechanical equipment installed in the plenum. Trying to seal the plenum after laying down the carpet was found to be difficult, costly and time consuming. Even though relatively good air distribution in the entire floor was achieved, some diffusers (automatically controlled) are located too close to the workstations and it will be probably needed to rearrange their layout in order to avoid draught complaints by occupants. The easier commissioning and better performance of UFAD in Sparebank Kvartalet could actually be achieved in a less time consuming and costly way if the commissioning would start early in the pre-design phase, with a well established commissioning plan.</p>

SammendragAnalyse av konsekvenser ved tiltak for bygging av hus med særlig lavt energiforbrukDenne oppgaven er knyttet til planlegging og utvikling av lavenergi bolighus. Spesielt gjelder dette de nye kravene som ersatt i den norske standarden NS 3700:2010 Kriterier for passivhus og lavenergihus - Boligbygninger. Standarden er utviklet forsertifisering av tre forskjellige klasser med lavenergiboliger for norske forhold. Denne oppgaven omhandler i hovedsakpassivhusspesifikasjonen, som er den strengeste klassifiseringen.Det er blant annet utført beregninger på forholdet mellom energibruk og gulvareal. Disse tyder på at varmetransport vedtransmisjon er den dominerende parameter for energitap i et lavenergibygg, på samme måte som for en normal standard bygning.Dette innebærer at den lineære korreksjon for energibehov som er gjort i NS 3700 vil lette kriteriene for å kvalifisere små bygningermed samme bygningsstandard som større bygninger. Likevel, siden beregningene viser at forholdet mellom gulvflate og spesifikkenergibruk ikke er lineært, vil kravene være strengere for små bygninger.Standarden gjør videre bruk av lokale klimadata for kontrollberegninger mot energikravene. Da det er mangel påstandardiserte timebaserte data for de fleste norske steder, er det i dette arbeidet undersøkt hvordan interpolerte data, generert fraulike klimadatabaser, samsvarer med standardiserte offisielle værdata. Undersøkelsene viser at de interpolerte dataene avviker frastandardiserte måledata, spesielt for dimensjonerende forhold. Dette indikerer at energiberegninger med lokale timebaserteklimadata blant annet kan underestimere bygningens oppvarmingsbehov.For kravene til netto oppvarmingsbehov er det også gitt en klimakorreksjon basert på årsmiddeltemperatur for angittlokalisering. Undersøkelser på ulike klimasteder viser at denne gjennomsnittsbaserte parameteren ikke er den beste indikatoren pågitt varmelast for ulike lokaliseringer. Beregningene viser også at det er mulig å sertifisere en passivkvalifisert bygning for Osloklimaogså i kaldere klima.Det er videre undersøkt varmtvannets andel av varmebehovet i en lavenergibygning og effekten av varmegjenvinning avventilasjonsluft. Disse undersøkelsene viser at varmtvann representerer det dominerende energibehovet i energieffektive boliger,samt viktigheten av fungerende varmegjenvinningssystemer med høy virkningsgrad.Avslutningsvis konkluderes arbeidet med at den nye standarden er mer fokusert på detaljerte spesifikasjoner enn denoriginale standarden og implementeringene i Sverige og Finland. Likevel er de resulterende kravene til oppvarmingsbehov mindrekrevende enn for de andre nordiske standardene med tilsvarende bygningsutforming og klima, og varierer ikke alltid forutsigbart forde ulike forhold.Una Myklebust Halvorsen, Trondheim juni 2010

In a refrigerated seawater (RSW) system using carbon dioxide (CO2) as the refrigerant, a variable bypass valve was installed in front of a suction gas heat exchanger (SGHX). A simulation tool was developed and utilized to optimize the systems transcritical performance (COP) with respect to the gas cooler pressure and choke valve inlet temperature for cooling and combined cooling and water heating. The simulations indicate that the RSW system performance can be increased compared to running a system with a traditional non-variable suction gas heat exchanger, but only when the cooling water temperatures are high (above ~25°C) or where air is used as the cooling medium, for instance commercial or mobile refrigeration. It is strongly recommended that a system to be used for simultaneous cooling and heating should have an improved design compared to the current setup, as this mode of operation shows low cooling capacity and poor energy efficiency.

<p>We live in a world of becoming. The future is not given, but forms continuously in dynamic processes where path dependence plays a major role. There are many different possible futures. What we actually end up with is determined in part by chance and in part by the decisions we make. To make sound decisions we require models that are flexible enough to identify opportunities and to help us choose options that lead to advantageous alternatives. This way of thinking differs from traditional cost-benefit analysis that employs net present value calculations to choose on purely economic grounds, without regard to future consequences.</p><p>Time and dynamic behaviour introduce a separate perspective. There is a focus on change, and decisions acquire windows of opportunity: the right decision at the right time may lead to substantial change, while it will have little effect if too early or too late. Modelling needs to reflect this dynamic behaviour. It is the perspective of time and dynamics that leads to a focus on sustainability, and thereby the role hydrogen might play in a future energy system. The present work develops a particular understanding relevant to energy infrastructures.</p><p>Central elements of this understanding are:</p><p>- Competition</p><p>- Market preference and choice beyond costs</p><p>- Bounded rationality</p><p>- Uncertainty and risk</p><p>- Irreversibility</p><p>- Increasing returns</p><p>- Path dependence</p><p>- Feedback</p><p>- Delay</p><p>- Nonlinear behaviour</p><p>Change towards a “hydrogen economy” will involve far-reaching change away from our existing energy infrastructure. This infrastructure is viewed as a dynamic set of interacting technologies (value sequences) that provide services to end-users and uphold the required supply of energy for this, all the way from primary energy sources. The individual technologies also develop with time.</p><p>Building on this understanding and analysis, an analytical tool has emerged: the Energy Infrastructure Competition (EICOMP) model. In the model each technology is characterised by a capacity, an ordered-, and an actually delivered volume of energy services. It is further characterised through physical description with parameters like efficiency, time required for extending capacity and improvement by learning. Finally, each technology has an attractiveness, composed of costs, quality and availability, that determines the outcome of competition.</p><p>Change away from our present energy infrastructure into a sustainable one based on renewable energy sources, will entail substantial change in most aspects of technology, organisation and ownership. Central results from the overall work are:</p><p>- <i>Change is dynamic and deeply influenced through situations with reinforcing feedback and path dependence. Due to this, there is a need for long-term perspectives in today's decision making: decisions have windows of opportunity and need to be made at the proper time.</i></p><p>- <i>Strategies aimed at achieving change should team up with reinforcing feedback and avoid overwhelming balancing feedback that counteracts change.</i></p><p>- <i>The EICOMP model is now available as a tool for furthe analysis of our existing energy infrastructure and its dynamic development into possible, alternative energy futures. As the model is intended for practical guidance in decisions, a central practical aim has been to allow it to be used close to where decisions are actually made; i.e. decentralised and locally in firms and in public institutions. In this respect much effort has been made in an attempt to make it transparent and easy to communicate.</i></p><p>- <i>The EICOMP model may be used to analyse situations of reinforcing feedback throughout the alternative energy infrastructures that we may come to have in the future.</i></p>

<p>Further development of a two-dimensional thermal analysis code (G2DHeat) to include internal decomposition and charring ablation of insulation materials is presented. An overview of the structural changes made to the program code by implementing an implicit solution routine, including source term is given, before testing and verification of accuracy is performed. A kinetic model for decomposition reactions, as well as routines for handling the generated gas from the decomposition reactions, changes concerning the material properties and erosion of surface material are implemented and explained. Comparisons of results are made with similar results obtained by commercial programs. Possible reasons affecting the results are pointed out, before additional comparisons with experimentally observed measurements are performed. Based on the simulated results it is concluded that a great deal of testing remains for proper validation of the program. How to include better boundary conditions for simulating charring ablation is suggested and recommended for further development of the program.</p>

<p>This paper treats further development of the TEG injection process described in Bråthen (2007). An introduction to separation technology, conventional glycol regeneration and compact mixing is presented, as these are important parts of the alternative dehydration concept. Advantages, disadvantages and operational problems are pointed out, before the problems with the TEG injection process is described. Using hot stripping gas for regeneration of the TEG is one of the suggested improvements, but large glycol losses, large flow rates of stripping gas and oxidizing of glycol are found to be the consequences, thus making the alternative unfeasible. The only improvements used, are to use inline separators for the first separation stages and compact mixers for mixing of TEG and natural gas. A simulation model is developed using the simulation software HYSYS with the CPA EoS as fluid package. Both the absorption and the regeneration part of the process is modeled, and operational data from the Snøhvit LNG facility is used as reference. From simulations it is found that TEG injection requires about 50% more circulated TEG than conventional absorber dehydration to obtain the same water content in the dehydrated gas. The weight and volume of the absorption part of the process is however found to be considerably smaller than the operational process at the Kristin field in the Norwegian North Sea, thus partly compensating for the increased TEG circulation rate. Use of MEG and DEG instead of TEG for the injection concept is also simulated, but it is concluded that TEG is the best suited because of lower regeneration energy, lower absorbent loss and best dehydration performance for low to intermediate flow rates of stripping gas. MEG is found to be unsuited for dehydration because of very large losses of absorbent.</p>

We live in a world of becoming. The future is not given, but forms continuously in dynamic processes where path dependence plays a major role. There are many different possible futures. What we actually end up with is determined in part by chance and in part by the decisions we make. To make sound decisions we require models that are flexible enough to identify opportunities and to help us choose options that lead to advantageous alternatives. This way of thinking differs from traditional cost-benefit analysis that employs net present value calculations to choose on purely economic grounds, without regard to future consequences. Time and dynamic behaviour introduce a separate perspective. There is a focus on change, and decisions acquire windows of opportunity: the right decision at the right time may lead to substantial change, while it will have little effect if too early or too late. Modelling needs to reflect this dynamic behaviour. It is the perspective of time and dynamics that leads to a focus on sustainability, and thereby the role hydrogen might play in a future energy system. The present work develops a particular understanding relevant to energy infrastructures. Central elements of this understanding are: - Competition - Market preference and choice beyond costs - Bounded rationality - Uncertainty and risk - Irreversibility - Increasing returns - Path dependence - Feedback - Delay - Nonlinear behaviour Change towards a “hydrogen economy” will involve far-reaching change away from our existing energy infrastructure. This infrastructure is viewed as a dynamic set of interacting technologies (value sequences) that provide services to end-users and uphold the required supply of energy for this, all the way from primary energy sources. The individual technologies also develop with time. Building on this understanding and analysis, an analytical tool has emerged: the Energy Infrastructure Competition (EICOMP) model. In the model each technology is characterised by a capacity, an ordered-, and an actually delivered volume of energy services. It is further characterised through physical description with parameters like efficiency, time required for extending capacity and improvement by learning. Finally, each technology has an attractiveness, composed of costs, quality and availability, that determines the outcome of competition. Change away from our present energy infrastructure into a sustainable one based on renewable energy sources, will entail substantial change in most aspects of technology, organisation and ownership. Central results from the overall work are: - Change is dynamic and deeply influenced through situations with reinforcing feedback and path dependence. Due to this, there is a need for long-term perspectives in today's decision making: decisions have windows of opportunity and need to be made at the proper time. - Strategies aimed at achieving change should team up with reinforcing feedback and avoid overwhelming balancing feedback that counteracts change. - The EICOMP model is now available as a tool for furthe analysis of our existing energy infrastructure and its dynamic development into possible, alternative energy futures. As the model is intended for practical guidance in decisions, a central practical aim has been to allow it to be used close to where decisions are actually made; i.e. decentralised and locally in firms and in public institutions. In this respect much effort has been made in an attempt to make it transparent and easy to communicate. - The EICOMP model may be used to analyse situations of reinforcing feedback throughout the alternative energy infrastructures that we may come to have in the future.