Wet Gas Metering is becoming increasingly important to the Oil and Gas Industry. In this research a wet gas flow is defined as a liquid / gas two-phase flow that has a gas mass content greater then 50 %. The Venturi Meter is a favoured wet gas meter in the Oil and Gas Industry. However, industry's understanding of wet gas flow phenomena in such a meter is limited and is therefore forced to accept large metering errors when existing correlations are used to take account of the liquid presence. Furthermore, these correlations all require an input value for the liquid flowrate. This information is not readily available to natural gas production engineers. This research extensively discusses the current wet gas metering situation and then uses new independent data from the NEL Wet Gas Loop to compare the performance of existing correlations when used with a Venturi Meter. This new data is examined to determine parameters that effect the meter reading and then new correlations are presented. One new correlation offered uses the additional information from a downstream pressure tapping in conjunction with the traditional upstream pressure reading and the Venturi pressure differential to predict the gas flowrate without knowledge of the liquid flowrate.

Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Currently the three main algae strains that are manufactured commercially are Chlorella, Spirulina and Dunaliela salina, which are produced for biomass and bioproducts. Photobioreactors (PBR) allow the exploitation of over 50 000 known microalgae species with over 15 000 novel compounds having been chemically identified to date. Many of these algae could be sources of high-value products which are produced using a method that delivers them from renewable resources. Designing an optimal photobioreactor is a complex process because a large array of variables is included in the design, with several of the variables interacting with each other directly. The interactions of most of these variables have not been established. The initial information that is available is inadequate because most photobioreactors have been tested on a laboratory scale and the information given does not include the manufacturing materials, the size of tubing used and other design variables. Before designing a photobioreactor, it is important to understand the best conditions for the production of algae because these have a direct influence on the requirements. In order to produce algae biomass under the specific conditions, one has to investigate current photobioreactors that have been designed in order to establish whether they are capable of optimum production under the production conditions; determine possible factors that could influence the production negatively and how they could be prevented; and undertake a cost analysis to determine whether the production of algae is an economically viable process using the specific reactor. All of these criteria have to be met for a photobioreactor to be viable in the production of algae biomass. Currently a Bubble column reactor is considered to be the best design for a photobioreactor and also the most scalable. Due to the limited information available, testing was conducted to determine the effect of: 1) different manufacturing materials, 2) the gas dispersion unit, 3) the diameters of the tubing and 4) the density. Bubble column reactors were used to test the effects of the four variables and were considered to be the most important aspects in the design. For testing these variables and their interaction, Chlorella Vulgaris was used because it is one of the most popular algae species used for production currently. As temperature and the availability of light play a large role in the production of algae, all testing was done in a laboratory environment to ensure small temperature changes and the constant availability of light. The reactors that were tested were made of PVC couplings, with the clear tubing used being made of either PVC or acrylic tubing. Enriched air was supplied at a 5% volume per volume ratio of CO2, with a flow rate of 0.02 volume per volume per minute (vvm) for the 50 mm diameter reactors and 0.36 vvm for the 90 and 110 mm diameter reactors. Two gas dispersion units were used to determine whether they would have any effect on the production. The gas dispersion units create small bubbles to ensure a high surface area to volume ratio and thereby they allow for maximum CO2 and O2 mass transfer. A growth rate of 0.14 gram per litre per day was found to yield the best production of all the reactors and configurations that were tested. The 50 mm diameter reactors showed the best growth followed by the 110 mm diameter reactors. The 90 mm diameter reactors all had a negative growth rate which appeared to be due to an insufficient gas flow rate. The 50 mm reactors had the best growth rate of 0.14 and 0.10 grams per litre per day for the acrylic tubing, while 0.08 grams per litre per day was achieved with PVC tubing. The 110 mm reactors had a highest growth rate of 0.05 grams per litre per day with PVC tubing. It was found that the 50 mm and 90 mm reactors showed a better performance with acrylic tubing while the 110 mm reactors showed a better performance with PVC tubing. The gas dispersion unit is affected by the gas flow rate, the density, the diameter of the tubing and the material that is used. The gas dispersion units’ effect is dependent on the diameter of the reactor seeing that the 50 mm reactor shows better performance with the small unit, while the 110 mm reactor shows better performance with the large unit, due to the gas flow rate that is required in the reactors. Because the gas flow rate and gas dispersion unit directly affect the agitation, the optimal density is affected directly due to the availability of light and therefore the tubing material. The gas dispersion units should fit properly into the reactor and be capable of handling the gas flow rate that is required. The diameter of the tubing does not show any effect but could have an effect under different testing conditions and could not be conclusively eliminated. The density of algae does have an effect, although most reactors showed a better production rate at a higher culture density. The scale up of the bubble column reactor creates a dead zone when a module is constructed. The scale up of a bubble column reactor could range from increasing the vertical tubing length, increasing the diameter of the tubing to adding vertical tubing to a module. The dead zone is formed at the bottom of the reactor where the module interconnects the vertical growth tubes, because these fittings are not constructed from a clear material, due to cost of such a construction. The dead zone that is created causes a large portion of algae to form a sediment, which directly affects the production of the system because it is in a dark zone of the reactor. Improved results would be obtained if the algae were kept at a homogeneous density that would ensure maximum expose to light. The ratio of gas flow rate to reactor volume and diameter of the tubing was found to be crucial. It is suspected that the 90 mm tubing reactor had a negative growth rate as this ratio was not correct. The 50 mm reactors had to be run at a much lower reactor volume per volume gas flow rate which could consist of air, carbon dioxide enriched air or other gases as required. The inclusion of the tubing diameter in the ratio is of vital importance and should be studied further. A cost analysis shows that the bubble column reactors under the tested conditions are not financially viable. A large component of the cost is carbon dioxide and medium, which is a composition of nutrients. This could be removed if a free source were obtained, which would make the system financially viable. These sources could include waste water and flue gas from industrial processes. It is recommended that a gas dispersion tube be positioned at the bottom of the reactor to ensure that no sedimentation occurs and that there is a homogeneous culture, and to maximise the production capabilities of a bubble column reactor. It is also recommended that the gas flow rate inside the reactor be studied to obtain a ratio where the volume of the reactor, the height of the reactor and the diameter of the tubing are included to obtain a sufficient rate of flow. / AFRIKAANSE OPSOMMING: Tans is daar drie belangrike alg stamme wat kommersieel geproduseer word, Chlorella, Spirulina en Dunaliela salina. Fotobioreaktors het meegebring dat meer as 50 000 bekende alg spesies met meer as 15 000 komponente tot op datum chemies geïdentifiseer is. Baie van hierdie alge kan hoë waarde produkte wees, wat met behulp van hernubare metodes geproduseer kan word. Die ontwerp van 'n optimale fotobioreaktor is 'n komplekse proses aangesien 'n groot verskeidenheid veranderlikes ingesluit moet word wat ‘n invloed op mekaar kan hê. Die interaksie van meeste van hierdie veranderlikes is nog nie vasgestel nie. Die inligting oor hierdie onderwerp is beperk aangesien die meeste fotobioreaktors in 'n laboratorium getoets is en dus nie die vervaardigingsmateriale, die grootte van buise en ander ontwerp veranderlikes insluit nie. Voordat 'n fotobioreaktor ontwerp kan word, moet die ideale alg produksie toestande verstaan word, aangesien dit 'n direkte impak op die produksie vereistes kan hê. Om alg biomassa onder spesifieke omstandighede te produseer, moet die bestaande fotobioreaktor ontwerpe ondersoek word. Daar moet vasgestel word of die bepaalde ontwerp oor die kapasiteit beskik om optimale produksie te lewer; identifisering van faktore wat produksie negatief kan beïnvloed en hoe dit voorkom kan word; en 'n koste ontleding moet gedoen word om te bereken of die produksie van alge met die geidentifiseerde ontwerp 'n ekonomies lewensvatbare proses is. Daar moet aan al die vereistes voldoen word om te bepaal of 'n fotobioreaktor lewensvatbaar is vir die produksie van alg biomassa. 'n Borrel-kolom reaktor ontwerp word tans as die beste ontwerp vir 'n fotobioreaktor geag, asook die mees aanpasbare ontwerp. As gevolg van die beperkte inligting wat beskikbaar is, is navorsing gedoen om die invloed van verskillende faktore te bepaal, naamlik: vervaardigingsmateriaal, gasverspreidingseenheid, buisdeursnee en digtheid. Borrel-kolom reaktors is gebruik om die vier belangrikste veranderlikes in die ontwerp te toets. Om die veranderlikes en hul interaksie te toets, is Chlorella vulgaris gebruik, aangesien dit een van die gewildste alg spesies is vir die produksie van biomassa. As gevolg van die belangrike rol wat temperatuur en lig beskikbaarheid in die produksie van alge speel, is al die toetse in 'n laboratorium-omgewing gedoen om temperatuur wisseling te beperk en konstante lig beskikbaarheid te verseker. Die reaktors wat getoets is, is vervaardig uit PVC koppelstukke, met die deurskynende buise wat uit PVC of akriel vervaardig is. Verrykte lug is verskaf op 'n 5% volume per volume verhouding CO2, met 'n vloei tempo van 0,02 volume per volume per minuut (vvm) vir die 50 mm deursnee reaktors en 0,36 vvm vir die 90 mm en 110 mm reaktors. Twee gasverspreidingseenhede is gebruik om hulle invloed op die produksie te bepaal. Die gasverspreidingseenhede skep kleiner borrels, om 'n hoë oppervlak area tot volume verhouding te skep en daardeur 'n maksimum CO2 en O2 massa-oordrag te verseker. 'n Groeikoers van 0,14 gram per liter per dag is gevind as die beste produksie van al die reaktors en konfigurasies wat getoets is. Die 50 mm deursnee reaktors het die beste groei getoon, gevolg deur die 110 mm deursnee reaktors. Die 90 mm deursnee reaktors het 'n negatiewe groeikoers getoon, wat moontlik toegeskryf kan word aan onvoldoende gas vloei tempo. Die 50 mm reaktors het die beste groeikoers van 0,14 en 0,10 gram per liter per dag vir die akriel buise getoon, terwyl ‘n 0,08 gram per liter per dag behaal is met 'n PVC buis. Die 110 mm reaktors het die hoogste groeikoers aangedui van 0,05 gram per liter per dag met 'n PVC buis. Daar is bevind dat die 50 mm en 90mm reaktors 'n beter prestasie met akriel buise gehad het, terwyl die 110 mm reaktors 'n beter prestasie met 'n PVC buis gehad het. Die gasverspreidingseenheid word beinvloed deur die gas vloei tempo, digtheid, buisdeursnee en die vervaardigingsmateriaal wat gebruik word. Die gasverspreidingseenhede word verder beinvloed deur die reaktor se buisdeursnee aangesien die 50 mm reaktor ‘n beter prestasie getoon het met die kleiner gas eenheid, terwyl die 110 mm reaktor ‘n beter prestasie getoon het met die groter gas eenheid, as gevolg van die gas vloei tempo wat vereis is. Die gas vloei tempo en gasverspreidingseenheid het ‘n direkte invloed op die groei van die kultuur, dus is die optimale digtheid afhanklik van die lig beskikbaarheid en dus die vervaardigingsmateriaal van die buise. Die gasverspreidingseenhede moet stewig in die reaktor pas en in staat wees om die gas vloei tempo wat vereis word te kan hanteer. Hoewel die deursnee van die buise nie 'n invloed getoon nie, kan dit 'n invloed onder verskillende toets omstandighede toon en kon nie finaal uitgeskakel word. Die digtheid van die alge het wel 'n effek, hoewel die meeste reaktors ‘n beter produksie tempo op 'n hoër kultuur digtheid toon. Die groter skaal borrel-kolom reaktor ontwikkel 'n dooie sone indien ‘n module saamgestel word. Die groter skaal borrel-kolom reaktor kan insluit: die verhoging van die vertikale buis lengte, 'n toename in deursnee van die buise en toevoeging van vertikale buise in die module. Die dooie sone het gevorm aan die onderkant van die reaktor waar die module se vertikale groei buise met mekaar verbind is. Hierdie area is uit nie-deurskynende materiaal vervaardig as gevolg van die konstruksie koste. Die dooie sone het veroorsaak dat groot hoeveelhede van die alge ‘n sediment gevorm het en ‘n direkte invloed op die produksie van die stelsel gehad het aangesien dit 'n donker sone in die reaktor gevorm het. Beter resultate kan verwag word indien die alge op 'n homogeniese digtheid gehou kan word om maksimum lig blootstelling te verseker. Daar is bevind dat die verhouding van gas vloei tempo tot reaktor volume en buisdeursnee deurslaggewend is. Die negatiewe groeikoers in die 90 mm reaktor word toegeskryf daaraan dat hierdie verhouding nie korrek was nie. Die 50 mm reaktors het op 'n laer reaktor volume per volume gas vloei tempo gefunksioneer wat kan bestaan uit die lug, verrykte lug of ander gasse soos benodig. Dit dui daarop dat die insluiting van die buis deursnee in hierdie verhouding van kardinale belang is en verder bestudeer moet word. 'n Koste ontleding toon dat die borrel-kolom reaktors onder hierdie getoets omstandighede nie finansieel lewensvatbaar is nie. 'n Groot deel van die koste is die medium, wat 'n samestelling van voedingstowwe is, en koolstofdioksied koste. Om finansieel lewensvatbaar te raak, moet hierdie kostes deur 'n gratis bron vervang word. Die bronne kan bestaan uit afval water en oortolige CO2 uit industrie. Daar word aanbeveel dat 'n gasverspreidingsbuisie aan die onderkant van die reaktor geplaas word. Dit sal verseker dat geen sediment vorm nie en 'n homogeniese kultuur gehandhaaf kan word om maksimum produksie in 'n borrel-kolom reaktor te handhaaf. Verder word aanbeveel dat die gas vloei tempo binne die reaktor verder bestudeer word om 'n verhouding tussen die volume van die reaktor, die hoogte van die reaktor en die deursnee van die buise te bepaal deur sodoende 'n voldoende tempo van vloei te verkry.

<p>The reduction of iron oxide from slag is involved in many processes, such as, bath smelting, EAF steelmaking and copper slag cleaning processes, and it is known to occur via gaseous intermediates. Four possible rate determining steps are involved during the reduction. Among them, these two interfacial chemical reactions, gas slag and gas carbon could ultimately limit the enhancement of these processes.</p><p>In this work, the gas slag reaction kinetics in slag cleaning of copper slags has been studied. The dissociation rate of CO2 on the surface of liquid copper slags is measured using an isotope exchange method, where the mass transfer in the gas phase was eliminated by using a sufficiently high gas flowrate.</p><p>It is found that, for slag of the FexO-SiO2-Al2O3-Cu2O system, the apparent rate constant remains fixed with Cu2O content from 1-10 wt pct at higher oxygen potentials. The rate constant becomes approximately 2 times higher after metallic copper is reduced from the slag, this is due to the suspension of small metal drops on the slag surface.</p><p>The effect of temperature in the range from 1200-1450°C on the rate constants was also studied. The activation energy was 190 kJ/mole for slag of composition 60FexO30SiO2-1 0Al2O3. In the presence of Cu metal~10%, the activation energy was reduced to 122 kJ/mole.</p> / Thesis / Master of Engineering (MEngr)

Thesis (MEng (Chemical Engineering))--Cape Peninsula University of Technology, 2020 / Continuous growth in the world population has raised significant fears with regards to the sustainability of energy and water resources. Globally, water is an indispensable resource as it is essential for the sustenance of human, animal and plant life. Water is essential for all forms of life and plays a pivotal role in economic growth. The textile industry is one of the greatest consumers of water, it is, therefore, necessary to effectively treat the large amounts of wastewater before discharge to the environment. It is estimated that annually, more than 700,000-tonnes of textile wastewater is produced by the dyeing industry. Textile wastewater is generally characterised by electrolytes, suspended solids, mineral oils and multiple textile dyes, and has therefore been classified as one of the most polluting wastewaters. These dyes are toxic and, in most cases, are not biodegradable. The presence of very small amounts (i.e. < 1 ppm) of dyes in water has aesthetic impacts and is thus undesirable. It is, therefore, necessary to treat textile wastewater before discharging. Currently, membrane technology is widely used for wastewater treatment, as well as water purification. Forward osmosis (FO) is a promising technology for both these applications. FO is characterised by the flow of water through a semipermeable membrane from a feed solution (FS) characterised by the low solute concentration or low osmotic pressure (OP) to a draw solution (DS) characterised by the high solute concentration or high OP, due to the OP gradient across the membrane. The FO process eliminates the need for high hydraulic pressure, as required in traditional membrane technologies, and also has low fouling tendencies. Furthermore, FO has the advantage of lower energy requirements and membrane replacement costs. However, there are still many disadvantages such as reverse solute flux (RSF), membrane fouling, and concentration polarisation (CP) amongst others that still need to be addressed. Therefore, more research needs to be done in light of these limitations to better understand and mitigate these limitations to increase the effectiveness and efficiency of the FO process. This study aimed to evaluate a dye-driven FO system for the reclamation of water from textile wastewater and synthetic brackish water (BW5) by investigating the effects of membrane orientation, system flowrate, change in DS, and membrane fouling on the FO systems performance and energy consumption. The FS used was BW5 with sodium chloride (NaCl) content of 5 g/L whereas Reactive Black 5 (i.e. a reactive dye) and Maxilon Blue GRL (i.e. a basic dye) dyes were used as a DS, respectively. The membrane utilised was a cellulose triacetate (CTA) membrane and was tested in FO mode and pressure retarded osmosis (PRO) mode whilst the system flowrate was adjusted to 400, 500 and 600 mL/min, respectively. Experiments were performed using a bench-scale FO setup which comprised of an FO membrane cell, a double-head variable speed peristaltic pump, a digital scale, two reservoirs for the FS and DS, respectively, a digital multiparameter meter and a digital electrical multimeter to measure system energy consumption. Each experiment comprised of six steps: baseline 1 (membrane control), main experiment (dye-driven FO experiment), baseline 2 (membrane control repeat), membrane cleaning, membrane integrity (membrane damage dye identification) and membrane cleaning (preparation for next experiment). The baseline 1 and baseline 2 experiments operated for 3 h whilst each membrane cleaning procedure operated for 30 min. The main experiments operated for 5 h in the FO mode and 4 h in PRO mode whilst the membrane integrity experiments operated until a minimum of 10 mL water was recovered. Results showed that the PRO mode achieved both higher forward flux (𝐽𝑤) (i.e. 8.87, 8.71 and 9.13 L/m2.h for flowrates of 400, 500 and 600 ml/min) and water recovery (𝑅𝑒) rates compared to FO mode (i.e. 6.60, 6.88 and 7.58 L/m2.h for flowrates of 400, 500 and 600 ml/min). The variation of flowrates had little to no influence on the 𝐽𝑤, 𝐽𝑠 and 𝑅𝑒 of the system. The system consumed less energy in PRO mode (i.e. 381 kWh/m3 average consumption for all three flowrates) than FO mode (i.e. 417 kWh/m3 average consumption for all three flowrates). It was also observed that at a higher DS 𝑂𝑃, the system consumed less energy. Therefore, selecting an optimum initial 𝑂𝑃 is essential for a FO process to minimise the pumping energy. Furthermore, a change in DS from Reactive Black 5 dye to Maxilon Blue GRL dye had no significant impact on the system performance and energy consumption. In this study, no significant membrane fouling was observed, however, minute traces of fouling in the form of foreign functional groups could be observed in the attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) spectrums of the used membranes. Additionally, the observation of negligible changes in baseline 2 (membrane control) Re and Jw results suggested the possible occurrence of membrane fouling during the main experiment (dye-driven FO system).

Above 90% of the current installed concentrating solar power plants are based on conventional steam-turbine cycles. The operation of steam turbines in these plants is distinctive when compared to traditional base-load power plants. The reason goes back to the intermittent nature of solar power which, in the absence of thermal energy storage or a back-up combustion boiler, forces plant operators to shut down the turbines during night time or at times of low solar radiation. Furthermore, such intermittency often leads to undesirable off-design turbine operating circumstances, either by load variations or changes on live-steam conditions.The present study examines the influence of implementing two operating strategies dealing with steam flow control as a function of incoming solar power for enhancing the thermo-economic performance of a direct steam generation solar tower power plant. The first one consists of a simultaneous high pressure turbine stage- and feed-water preheater bypass. This strategy is used during periods in which the solar radiation is higher than nominal. On these occasions, the plant is capable of generating a larger flow of steam, which allows for an increase in the power production when inserting the additional steam in the turbine bypass. On the other hand, the second operating strategy consists of using an additional feed-water preheater when the power from the field is lower than nominal. In this way, the feed water can reach a higher temperature prior entering the boiler, which is not only beneficial during times of cloud-passages, but also during the start-up process.A dynamic model of a direct steam generation solar tower power plant has been developed following design and operation specifications of an existing reference plant. The two proposed strategies were implemented to the reference model, then a whole year worth simulation was performed for both the reference and the modified models. Lastly, the thermodynamic and economic performance of both systems was measured for the purpose of comparison, by means of using KTH in-house tool DYESOPT. Results show that the implementation of the proposed strategies can enhance the economic viability of the systems by yielding a reduction of 8.7% on the levelized cost of electricity, mainly due to allowing achieving a 12% increase in the net electricity production.

For over 30 years research has been done concerning the solidification and quenching of light metal alloys for the purpose of improving material properties. This thesis is concerned with an interesting new process for casting metals, by spraying water onto a sand mould, removing the sand and the directly quenching the part. This process is challenging since the component during solidification is extremely fragile, and the rate of cooling that is needed could seriously damage it. The water flow rate to the component needs to be quickly and precisely controlled. Additionally as this a new method there is very little prior art. The purpose of this thesis to develop a control system for the water sprayers flow rates. With this system the flow rate through the nozzles will be controlled indirectly using pressure feedback. The material properties and casting process, and how they influenced the design and construction of the spraying apparatus, are explained first. The hydraulic plant being controlled consists of three proportional valves connected to six spray nozzles. Based on experiments, the plant is extremely nonlinear making it difficult to control. Several controllers were developed and compared experimentally. The best performance was produced by extending a proportional plus integral plus derivative controller by adding an empirical nonlinear feedforward component; smoothing the setpoint; bounding the integration term; adding one bias at time zero and a 2nd bias for the remaining time (to mitigate valve stiction and to prime the hoses). This extended PID controller produced a 0.7% mean error and 1.9% mean absolute error for a multi-step setpoint covering a range of 0 to 80 PSI. Its performance was also highly repeatable. The standard deviations of the mean error, mean absolute error and maximum absolute error were less than 0.2 PSI over five runs. / Thesis / Master of Applied Science (MASc) / During the sand casting of aluminium and magnesium rapid cooling will greatly improve the material properties. By containing the liquid metal in a water soluble sand mould, and spraying it with water; the desired part shape and rapid cooling can be achieved. Removing the mould requires a powerful high flow rate jet. During the solidification of the metal, the flow rate must be reduced or the part would be demolished. This necessitated the development of a high speed, high flow rate controller to adjust the flow rate to remove the sand but not damage the part, and to maintain a smooth continuous cooling rate. The hydraulic system being controlled consists of three electronic valves connected to six spray nozzles. Several controllers are developed and compared experimentally. The best controller is shown to provide a quick and precise response.

[pt] A medição de gás natural pelo princípio do ultrassom se mostra competitiva, sob diversos aspectos, quando comparada com medidores deprimogênios, em especial a placa de orifício. O presente trabalho apresenta uma avaliação técnica da utilização de medidores ultrassônicos de múltiplos feixes em sistemas fiscais e para transferência de custódia. Uma avaliação de conformidade em relação às principais normas internacionais relativas à medição de vazão de gás natural pelo princípio do ultrassom é realizada através de dados coletados, para um mesmo medidor, durante sua calibração em laboratório e durante sua operação no campo. Apresenta também uma análise das ferramentas de diagnósticos disponíveis pelo medidor, comparando os resultados obtidos em laboratório e no campo. Foi proposta uma metodologia para a determinação das estimativas de incerteza da medição da vazão instantânea e do volume de gás em determinado intervalo de tempo. As avaliações de conformidade com as normas e as análises das ferramentas de diagnósticos disponíveis mostram que a utilização de medidores ultrassônicos na medição fiscal de gás natural é tecnicamente viável; além disto, considerando um intervalo de tempo conveniente para a totalização dos volumes medidos, a incerteza de medição pode ser bastante reduzida. / [en] The measurement of natural gas by the ultrasonic principle is shown to be competitive in several aspects when compared with orifice plate meters. This paper presents a technical evaluation of the use of multipath ultrasonic meters for custody transfer. The analysis of the meter performance matching with the requirements of principal international standards for measuring of natural gas flowrate by the ultrasonic principle is made using data collected for the same meter during the calibration in laboratory and during operation in the field. It also presents an analysis of the diagnostic tools available by the meter, comparing the results obtained in laboratory and field. A methodology for determining estimates of measurement uncertainty of flow rate and totalize gas in a given time interval is proposed. Evaluations of compliance with the standards and the analysis of the diagnostic tools available show that the use of ultrasonic meters in the fiscal measurement of natural gas is technically feasible, and that, by varying the time for measuring volumes, the uncertainty of measurement can be quite reduced.

No description available.

Lobjet du présent travail est létude expérimentale et théorique de lhydrodynamique des écoulements dans des colonnes à garnissage et, plus particulièrement, lanalyse par tomographie à rayons X de la distribution spatiale des phases liquide et solide dans des lits fixes parcourus par un écoulement de liquide. La distribution des phases est observée à différents niveaux, depuis léchelle locale jusquà léchelle de la colonne dans son ensemble. Lintroduction permet tout dabord de rappeler les principales applications industrielles des colonnes à garnissage, ainsi que les caractéristiques particulières associées à chacune dentre elles. Lhydrodynamique des écoulements dans ce type dappareils résulte de phénomènes extrêmement complexes, intervenant à une échelle très petite. Cet état de choses a poussé les chercheurs à développer des modèles de plus en plus détaillés, dont la validation requiert une connaissance de plus en plus fine de la répartition des phases au sein des lits fixes. Lobtention de mesures à une échelle très locale savère donc indispensable. Après un bref rappel des différentes techniques de mesure plus ou moins locales qui ont été appliquées, dans le passé, à létude des écoulements dans des colonnes à garnissage, lensemble des techniques tomographiques, ainsi que leurs principaux champs dapplication sont présentés. Parmi ces applications, la tomographie à rayons X semble particulièrement bien adaptée, car elle permet daccéder à une cartographie complète de la distribution spatiale des différentes phases présentes dans une colonne à garnissage de relativement grandes dimensions. Le chapitre I présente en détail les bases de la technique expérimentale utilisée. La tomographie consiste à reconstruire limage dune section droite dun objet à partir de données de transmission, obtenues en illuminant cet objet sous un grand nombre dangles différents. Lalgorithme permettant de reconstruire les images à partir des données de projection est lalgorithme de rétro-projection filtrée, adapté à la géométrie du dispositif de radiographie (faisceau plan angulaire et détecteurs colinéaires équidistants). Cet algorithme, qui est le plus utilisé en pratique, a dû être modifié pour tenir compte dimperfections géométriques existant au niveau du dispositif de mesure. Le chapitre II décrit linstallation expérimentale, qui comprend le tomographe à rayons X, la colonne à garnissage et leurs éléments périphériques respectifs. Le tomographe consiste en un dispositif de radiographie (source de rayons X et détecteur linéaire) fixé sur un manipulateur. Le pilotage de linstallation, ainsi que lacquisition des données expérimentales sont réalisés grâce à un pupitre de commande et à un P.C. Le dispositif de tomographie permet de réaliser des images de sections droites dune colonne à garnissage, irriguée grâce à un dispositif dalimentation et dévacuation des fluides. Après une description relativement détaillée de tous ces éléments, le mode opératoire suivi pour la réalisation des différentes mesures expérimentales est présenté. Dans les chapitres III à V sont regroupés les différents résultats expérimentaux, ainsi que les discussions et commentaires sy rapportant. Le chapitre III présente les différents essais réalisés en vue de valider le dispositif de tomographie. Dans ce but, des objets de forme et de taille connues ont été radiographiés. La confrontation des images reconstruites et des objets originaux permet deffectuer cette validation, mais également dapprécier la résolution de la technique tomographique de mesure. Le chapitre IV expose les résultats obtenus sur base des images de sections droites de la colonne sèche. Dans un premier temps, les différentes opérations effectuées sur les images, après leur reconstruction, sont décrites. Ces opérations ont pour but de donner une signification physique réelle aux valeurs des pixels composant les images, mais également daméliorer la représentation graphique de ces dernières. Une des premières grandeurs calculées sur les sections reconstruites est la fraction de vide de lempilage. Les valeurs de porosité ainsi calculées sont comparées à dautres valeurs obtenues expérimentalement, ainsi quaux valeurs annoncées par les fabricants dempilages. Une dimension caractéristique, propre à chacun des types dempilage, est ensuite calculée grâce à lapplication de différentes méthodes comme lanalyse de lentropie de configuration, lanalyse de la distribution de la fraction de solide ou encore lanalyse de la fonction dautocorrélation. La dimension caractéristique ainsi déterminée permet daccéder à la taille des cellules élémentaires susceptibles de représenter la morphologie de la phase solide dans le cadre dune modélisation des phénomènes hydrodynamiques intervenant au sein du lit fixe. Après une brève conclusion récapitulative, la dernière partie du chapitre IV est consacrée à la visualisation des différentes échelles caractéristiques présentes dans les images analysées. Le chapitre V décrit les résultats obtenus sur base des images de sections droites de la colonne irriguée. Dans un premier temps, les images obtenues sur des sections irriguées font lobjet dune analyse purement qualitative. Cette analyse permet dobserver linfluence exercée par le distributeur de liquide sur la distribution du liquide au sein de sections droites situées à différentes hauteurs au sein de la colonne, pour différentes valeurs du débit de liquide. Elle permet également dobserver la corrélation existant entre les distributions des phases liquide et solide au sein de la colonne. Ensuite, les valeurs globales de la rétention de liquide calculées sur base des valeurs des pixels composant les images reconstruites sont confrontées à des valeurs de rétention obtenues par dautres méthodes, expérimentales ou théoriques, afin de valider les résultats obtenus par tomographie. Dans ce but, des comparaisons sont effectuées avec des résultats expérimentaux présentés dans la littérature, avec des valeurs de rétentions mesurées par essais de traceur, ainsi quavec des valeurs calculées grâce à des corrélations proposées dans la littérature et plus particulièrement grâce à la corrélation issue dun modèle découlement en canaux. Un modèle hydrodynamique basé sur une approche probabiliste est ensuite utilisé pour modéliser lhydrodynamique au sein de la colonne à garnissage. Cette approche permet non seulement de rendre compte de lévolution des valeurs globales de la rétention de liquide, mais également de modéliser la distribution des valeurs locales de la vitesse du liquide dans les différentes sections de la colonne à garnissage. Pour terminer, la conclusion résume lensemble des résultats issus de la présente étude, avant de lancer quelques pistes pour des travaux de recherche à venir.

Fjärrvärmen utgör omkring hälften av all uppvärmning som sker i Sverige idag och har utöver det en viktig roll då den tar vara på mycket energi som annars hade gått till spillo. Att kunna vara ekonomiskt konkurrenskraftig gentemot andra uppvärmningsalternativ är en viktig del för fjärrvärmens fortsatta utveckling. Det finns flera alternativ och möjligheter att göra detta, ett av dem är att hålla nere driftkostnaderna. Det kan bland annat göras genom att minska tryckfallen i näten, som även kan ge en ökad expansionsmöjlighet. Idag används främst avstängningsventiler med reducerande genomlopp i näten, främst på grund av den billigare investeringen. Trots detta saknas en kunskap om hur dessa ventiler påverkar näten sett till tryckfall, drift- och investeringskostnader jämfört med ventiler med fullt genomlopp. För att undersöka detta har två metoder använts för att komplettera varandra och öka förståelsen för ventilerna. Den första metoden beräknade det generella fallet teoretiskt för att se vid vilka flöden som ventiler med fullt genomlopp är mer gynnsamma. Den andra metoden beräknade ett specifikt fall med simuleringar i ett verkligt nät med de olika ventilerna och beräkna vilken som är den mest ekonomiskt gynnsamma. Resultaten av det generella fallet visar att ventiler med fullt genomlopp blir mer gynnsamma när flödeshastigheten överstiger omkring 1 m/s, oavsett dimension, beräknat på under 30 år med ett elpris på 1,50 kr/kWh. Vid dimensionering av nät är det vanligt att använda 1,5 - 2,0 m/s, detta utgör ofta en liten del av nätets drifttid och är ofta lägre. Beräkning av det specifika fallet visade att ventiler med reducerande genomlopp är det ekonomiska alternativet då återbetalningstiden för ventiler med fullt genomlopp var över 600 år vid 1,50 kr/kWh. Utifrån detta kan slutsatsen dras att ventiler med fullt genomlopp inte bör ersätta reducerande genomlopp, utan att det i stället handlar om att identifiera de delar i nätet som utgör, eller kan komma att utgöra, en strypning eller förträngning i nätet där höga flödeshastigheter kan förekomma och möjligtvis byta till fullt genomlopp. / District heating makes up about half of all heating that takes place in Sweden today and, in addition to that, has an important role as it makes use of a lot of energy that would otherwise have been wasted. Being able to be economically competitive against other heating alternatives is an important part of the continued development of district heating. There are several options to do this, one of which is to keep operating costs down. This can be done by reducing the pressure drops in the networks, which can also provide an increased possibility of expansion. Today, shut-off valves with reducing throughput are mainly used in networks, often because of the cheaper investment. Despite this, there is a lack of knowledge about how these valves affect the networks, which is attributed to pressure drop, operating and investment costs compared to valves with full flow. To investigate this, two methods have been used to complement each other and increase the understanding of the valves. In the first method, the general case is calculated theoretically to see at which flows valves with full flow are advantageous. The second method calculates a specific case with simulations in a real network with the different valves and calculates which one is the most economically advantageous. The results of the general case show that valves with full flow become more advantageous when the flow rate exceeds about 1 m/s, regardless of dimension, calculated over 30 years with an electricity price of SEK 1.50 /kWh. When dimensioning networks, 1.5 - 2.0 m/s is a common value, this often constitutes a small part of the network's operating time and is often lower. Calculation of the specific case showed that valves with reducing throughput are the economic alternative as the payback period for valves with full throughput was over 600 years at SEK 1.50/kWh. Based on this, the conclusion can be drawn that valves with full throughput should not replace reducing throughput, but that it is instead a question of identifying the parts of the network that constitute a throttling or constriction in the network where high flow rates can occur and possibly switch to valves with full throughput.