This diploma thesis discusses fouling processes and mechanisms of industrial heat exchangers, with focus on shell side fouling of heat transfer area by flue gases, and eventually taking fouling into account, or more precisely its modeling and predicting by calculation. Thermal-hydraulic design of heat exchanger is focused mainly on shell side, as flue gases are dominant process medium in terms of fouling and heat transfer. Based on available operational data of evaluated industrial heat exchanger, specific process has been developed to determine by calculation, or more precisely predict change of fouling factor throughout operational period of heat exchanger. Usage and various options of this specific calculation technique are being discussed in conclusion, whether there is a potential to use this technique regarding more complex operational inputs or prediction of fouling process for different operational regime of heat exchanger.

V súčasnosti sa kladie veľký dôraz na znižovanie produkcie emisií, čistotu a kvalitu životného prostredia. Tieto trendy sa týkajú všetkých odvetví, tak isto aj stavebného priemyslu a vykurovania budov. Doposiaľ bolo najrozšírenejším typom vykurovania spaľovanie fosílnych palív. Do popredia sa však dostávajú tepelné čerpadlá a začínajú zaberať výrazný podiel trhu. Kvôli dopytu po tepelných čerpadlách vzrastá počet výrobcov a konkurencia. Cieľom výrobcov je zvyšovanie účinnosti tepelných čerpadiel a zároveň znižovanie výrobných nákladov na dosiahnutie lepšej pozície na trhu. Predložená práca sa zaoberá procesmi prebiehajúcimi v chladivovom okruhu tepelného čerpadla. Skúma správanie chladiva počas kondenzácie a možnosti zvýšenia účinnosti tepelného čerpadla. Zvýšenie účinnosti je dosiahnuté podchladením chladiva počas kondenzácie na zvýšenie tepelných ziskov. To je dosiahnuté zaradením druhého elektronického expanzného ventilu za kondenzátorom. Táto technológia je však finančne náročná. Práca sa zaoberá výpočtom kapiláry na základe praktických meraní, ktorá bude zadržiavať chladivo v kondenzátore a bude plniť podobnú úlohu ako expanzný ventil. Následne sú porovnané výsledky jednotlivých meraní. Výsledky sú porovnané voči jednoduchému systému, kde nedochádza k podchladeniu chladiva. V závere práce je analýza výsledkov jednotlivých systémov.

The cooling systems in a gas turbine are especially important as the turbine blades and vanes are exposed to extreme temperatures. The relatively cool air is extracted from the compressors and fed to the turbines to cool the turbine blades. The manufacturing of these blades and channels used to cool is especially complicated using conventional manufacturing techniques. Additive Manufacturing (AM) gives the designer much more freedom to design core components. The AM technique currently explored is the Selective Laser Melting process (SLM). The surface area is exposed to the cooling airflow by using lattice structures which can be manufactured at relative ease using AM. This thesis will provide some insights into using AM parts for the cooling, by analyzing the pressure drop that could be expected from superalloys that are manufactured using AM. The surface roughness is an inherent property of the AM components therefore it would be interesting to analyze a turbulent flow through AM channels (CM247LC and INCONEL 939). The thesis deals with turbulent flows as the airflow used for cooling in the gas turbine is most likely turbulent.  The friction factor (Darcy–Weisbach friction factor) is used to relate the impact of the surface roughness to the pressure drop. The results from the previous experiments are contrasted as the flow in the previous experiments was assumed to be fully developed but in reality, it was not. And the accuracy of the previous results to the actual fully developed flow will shed some light on the feasibility of the flow analysis techniques used in the previous experiments. It is found that the previous experimental results for the CM247LC TPs have good agreement with current experimental results but INCONEL 939 exhibits significant deviation. The possible reasons for the deviations are directly linked to the assumptions made to calculate the minor losses. The Test Pieces (TP) analyzed in this thesis have varying length to diameter (L/D) ratios and the impact of the variation of different L/D ratios is analyzed along with varying pressure ratios. Where the flow resistance increases with an increase in L/D and pressure ratio. The technique to accommodate the compressibility of the airflow is also explored in this thesis. Finally, reasons for the manifestation of anomalies are discussed. The probability of the compressibility effects of the airflow on the anomalies was found to be quite high, and concluding remarks are provided.

This doctoral thesis deals with potentials of methods for cleaning of flue gas from pollutants such as acidic components. Wet method of flue gas cleaning is analysed in detail with special focus on elimination of sulphur dioxide (SO2). Introduction presents advantages and disadvantages of thermal processing of waste and production of undesired pollutants. Following parts comprise facts about main pollutants produced from incineration. Legislation providing for emission of gaseous pollutants from incinerators is also given. Chapter concerning methods of pollutants elimination is mostly focused on absorption (wet and/or semidry scrubber) and adsorption methods. Several up-to-date technological procedures are mentioned; they have a multifunctional effect such as elimination of acidic components, heavy metals, polychlorinated dibenzo-p-dioxines and dibenzo-furanes from flue gas using single injection of suspense. Elimination of mercury (Hg) is among the technologies for heavy metal elimination which is described in detail. Main part of the thesis is related to experiments at two-stage flue gas cleaning equipment. Function of this experimental unit is described along with methods for measurement of individual quantities and detailed description of all the equipment and its components. Experimental measurements carried out at this equipment are explicated and assessed. Along with experimental work, the author has created a simulation model of wet flue gas cleaning in ChemCad programme. Particular operational parameters were tested on this model. This thesis contains results of the measurement which provide background for verification of the mathematical model. Further, the balance of heavy metals conducted on the basis of measurements in waste incinerator is displayed. Main contribution of the thesis may be summed up as follows: ­ Author has designed and constructed experimental equipment for two stage flue gas cleaning. ­ He also formed calculation for pressure drop of O-element prototype equipment and for packing column with FLEXIPAC structured packing. ­ He created data file with measurements at the experimental unit. ­ He determined temperature at outlet of a random device where liquid is injected into stream of hot flue gas. ­ He designed a simulation model which is identical with experimental equipment and which usage enabled comparison of measured and calculated data; it also serves as a basis for industrial applications. ­ Last part deals with creation off heavy metals balance in a case industrial waste incinerator.

No description available.

Carbon dioxide capture, transportation, and storage has been identified as the most promising way to reduce anthropogenic carbon dioxide (CO2) released into the atmosphere. Efforts made to achieve this purpose include the Paris (Climate) Accord. This agreement seeks to encourage countries to take the issue of rising global temperatures seriously. With nearly all countries signing this agreement, many CCTS projects are expected. Pipelines are employed in the transportation of CO2. CO2 fluids contain impurities that affect the fluid properties and flow dynamics, but pipelines are mostly designed assuming that the CO2 fluid is pure. CO2 pipeline fluids contain at least 90 % CO2 with the balance made up of impurities. The impurities include nitrogen, methane, oxygen, hydrogen, sulphur dioxide, hydrogen sulphide, carbon monoxide, ammonia, argon, etc. The effects of the impurities are studied using simulation software; Aspen HYSYS, gPROMS and HydraFlash. The results show that all impurities impacted negatively on transportation. At equal concentrations, hydrogen had the greatest effect on fluid properties and hydrogen sulphide the least impact. At the specified allowable concentration, nitrogen had the worst effect on pressure loss (32.1 %) in horizontal pipeline, density, and critical pressure. Carbon monoxide (with only 0.2-mol %) had the smallest effect in pressure drop (0.3 %). Analysis of supercritical and subcritical (or liquid) CO2 fluid transportation shows that subcritical fluids have higher densities (more volume transported) and lower pressure losses than supercritical fluids. Subcritical fluid transportation would therefore have lower pipeline transportation costs than supercritical fluids. Also, soil heat conductivity has greater effect than ambient temperature in buried pipelines. Simple equations that approximate binary CO2 fluid properties from pure CO2 properties were developed and presented.

Dans le cadre de la présente thèse, a été étudié l’impact de la texturation par traitement thermo-mécanique DIC (Détente Instantanée Contrôlée) sur le séchage de divers produits alimentaires. Ce prétraitement a induit une amélioration de la cinétique de l’opération de séchage quand elle est limitée par le transfert interne de la matière couplé au rétrécissement du produit. Ainsi, la diminution du temps de séchage a atteint 67% dans le cas de l’oignon et 77% dans le cas du cassis. Quant à la diffusivité effective Deff, elle a augmenté par rapport à la matière première jusqu’à 246% pour les pépins et 795% pour les déchets de canneberge, 336% pour l’oignon et 1223% pour le cassis. Dans le cas des produits étudiés, la pression de vapeur de traitement DIC a généralement un effet significatif positif sur la cinétique de séchage et d’extraction des différentes molécules. Concernant les caractérisatiques des produits, nous constatons l’impact positif du traitement par DIC quant aux principales caractéristiques de la matière. Ainsi, les composés phénoliques apparaissent plus disponibles à la suite du traitement adéquat par DIC. Le contenu en composés phénoliques et la capacité antioxydante étant supérieurs dans les produits traités par DIC, la qualité nutritionnelle s’est ainsi également trouvée améliorée. Avec une dégradation thermique négligeable, le traitement DIC implique un effet mécanique dû à la détente instantanée, ce qui permet la rupture de certaines structures cellulaires de la matière et l’augmentation de la quantité maximale extractible. Les caractéristiques physiques diverses (masse volumique apparente et taux relatif d’expansion), les caractéristiques microstructurelles (mesurées par microscopie électronique à balayage) et fonctionnelles d’interaction avec l’eau (réhydratation, teneur en eau, isotherme de sorption, microbiologie et contenu nutritionnel...) peuvent être optimisées en fonction des conditions opératoires DIC, selon les besoins du consommateur. / The present PhD work concerns the effect of thermo-mechanical texturing by DIC (Instantaneous Controlled Pressure-Drop) on fruit and vegetable drying. This pretreatment dramatically improves drying kinetics when the internal mass transfer coupled to the shrinkage of the product, is the limiting process. Indeed, the drying time decreased by 67% in the case of onion and 77% for blackcurrants, while the effective diffusivity Deff increased up to 246%, 795%, 336%, and 1223% for cranberry seed and waste, onion and blackcurrants, respectively. With these products, the saturated steam pressure generally has a significant positive effect on the drying kinetics.DIC treatment significantly improves the main nutritional and functional characteristics of the fruits and vegetables, with more available phenols and higher antioxidant activity. As thermal degradation is negligible, the DIC treatment involves micromechanical effect linked to the instant pressure drop, which allows cell to break and structure to be more porous such increasing the maximum extractable amount. Various physical, microstructural and functional characteristics of new textured material allow water interaction to be completely modified in terms of rehydration kinetics and capacity, sorption isotherm, microbiological and nutritional content... depending on operating DIC conditions, which can be optimized according to the consumer needs.

Durant les dernières années, les études des procédés de trituration ou d’extraction des huiles végétales à partir des graines oléagineuses se sont concentrées sur les impacts environnementaux, la consommation énergétique et les qualités nutritionnelles. Les travaux de recherche ont donc visé l’étude de l’intensification des procédés d’extraction des huiles et de leur raffinage à travers leur décontamination phytosanitaire, grâce à la texturation par Détente Instantanée Contrôlée DIC et à la technologie d’autovaporisation multi-flash (MFA), respectivement. D’une part, ces travaux de recherche ont porté sur l’impact d’une texturation par la technologie de DIC, qui est à l’origine d’une modification de l’aptitude technologique des graines, vis-à-vis de l’extraction et de la préservation de la qualité nutritionnelle des huiles extraites. Appliquée sur des graines oléagineuses (graines de colza et de soja) et sur la base d’un bilan quantitatif (rendements en huile), cette étude met en évidence l’impact de la technologie DIC comparée à des prétraitements conventionnels tels que la cuisson, le concassage, l’aplatissage et le traitement par expandeur. D’autre part, sur la base d’une modélisation phénoménologique, les cinétiques d'extraction ont aussi été étudiées en vue de comparer les paramètres cinétiques d'extraction d'huiles végétales, cités plus haut, tels que la diffusivité effective et l’accessibilité initiale, par rapport aux systèmes conventionnels. Les résultats indiquent l’amélioration de la cinétique d'extraction des matières traitées par DIC d'une part, et la préservation de la qualité nutritionnelle des composés extraits, d'autre part. Enfin, les travaux fondés sur la technologie d’autovaporisation multi-flash (MFA) ont porté sur le raffinage des huiles extraites principalement au plan de son contenu phytosanitaire. L’efficacité de cette technologie a été prouvée dans l’objectif d’une décontamination des résidus de pesticides (organochlorés) dans le cas de l’huile de colza brute. / Recently, studies of structural pretreatment and improvement of the sector of vegetal oil extraction from oilseeds have focused on the intensification of the concerned processes in both aspects of performance (environmental impacts, energy consumption, and kinetics) and quality (nutritional content, sensorial attributes…). Therefore, this research aimed to study the improvement of oil extraction processes and their phytosanitary decontamination, based on DIC texturing and multi-flash autovaporization (MFA), respectively. First, the effect DIC texturing technology was studied as structural pretreatments in improving the technological aptitudes of processing seeds such as rapeseed and soybean, regarding the extraction kinetics and yields, and the preservation of the nutritional composition of the extracted oils. DIC was studied based on quantitative assessments of oil (yields, composition…), highlighting its impact following the conventional pretreatments such as cooking, crushing, flattening, and expanding. Furthermore, founded on the Coupled Washing Diffusion CWD phenomenological model, in the specific cases of Negligible External Resistance NER extraction kinetics were also conducted to determine the fundamental extraction parameters of solvent vegetal oil extraction kinetics, such as the effective diffusivity and the starting accessibility, compared to conventional systems. The results denoted the improvement of extraction kinetics of the materials treated with DIC, on the one hand, and the preservation of the nutritional quality of the extracted compounds, on the other hand. Finally, this work focused on the study of multi-flash autovaporization (MFA) technology and its effect on the phytosanitary aspect of the extracted oils. The effectiveness of this technology has been proven for pesticide residue decontamination (organochlorine) of crude rapeseed oil.

La valorisation de l'énergie thermique contenue dans des gaz chauds pour produire de l'électricité est possible grâce à l'utilisation de cycles thermodynamiques, parmi lesquels le cycle de Rankine mérite d'être considéré. Cependant, l'industrialisation d'un tel système passe par une connaissance approfondie du comportement thermohydraulique du fluide actif. Ceci permettra d'améliorer le design des principaux composants du système, spécialement les échangeurs de chaleur. Dans le cas du cycle organique de Rankine, les conditions thermodynamiques du fluide sont éloignées des conditions usuelles rencontrées dans les domaines de la climatisation ou de la réfrigération. En effet, le fluide est mis en œuvre dans des conditions proches de son point critique. La température des gaz d'échappement varie entre 400°C et 900°C et l'évaporation se produit à une température de saturation supérieure à 100°C. En ce qui concerne les caractéristiques des écoulements diphasiques (chute de pression, coefficient de transferts thermiques, régimes d'écoulement), la quasi-totalité des méthodes de prédiction a été développée pour des températures comprises entre -20°C et 40°C correspondantes aux domaines de la climatisation ou de la réfrigération. C'est pourquoi la fiabilité de ces modèles reste incertaine dans les conditions d'évaporation du cycle de Rankine, car leur utilisation est limitée par la base de données à partir de laquelle ils ont été établis et ne peuvent être extrapolés avec précision. Cette thèse vise à étudier les caractéristiques thermohydrauliques du R-245fa en ébullition convective dans les conditions du cycle de Rankine. Dans un premier temps, un banc expérimental a été conçu et construit afin de réaliser des tests en ébullition convective dans un minicanal de 3.00 mm de diamètre. Ce banc expérimental permet de faire des mesures sur les régimes d'écoulement, les coefficients de transfert de chaleur et les pertes de charge par frottement. Dans un second temps, une méthode de traitement d'image a été développée afin de caractériser différents régimes d'écoulement. Cette méthode couplée à une analyse des transferts thermiques a permis d'identifier quatre principaux régimes d'écoulement. L'influence de la température de saturation sur les régimes d'écoulement et leurs transitions a été soulignée et discutée. Les caractéristiques des bulles ont également été étudiées à l'aide de cette méthode. Dans un troisième temps, une base de données expérimentale sur les coefficients de transfert de chaleur a été créée. L'influence de la température de saturation sur les mécanismes de transfert thermique a été étudiée dans ces conditions originales. Afin de tester la fiabilité des méthodes de prédiction, les résultats expérimentaux ont été confrontés à différentes méthodes. Finalement, les chutes de pressions ont été mesurées et une analyse paramétrique a été menée. Les mesures ont été confrontées aux principales méthodes disponibles dans la littérature. / Because of current environmental issues, some technologies are being developed to reduce the fuel consumption and to reduce the emissions of CO2. Energy recovery by means of Organic Rankine Cycles or Hirn Cycles recovery is one investigated track to answer these issues. At present, some systems based on Organic Rankine Cycle (ORC) are available in industry but advanced studies are needed to allow their application in the road transport industry. A better understanding of the two-phase fluid behaviour is necessary to optimize the design models of the components containing a two-phase refrigerant. For the Organic Rankine Cycle system, the thermodynamic conditions are different to standards relevant to refrigeration or air-conditioning systems. Indeed, the key characteristic of the ORC system is the evaporation saturation temperature. Exhaust gases temperature ranges from 400°C to 900°C and the refrigerant evaporation occurs at temperatures higher than 100°C. Almost all the flow boiling heat transfer models or correlations have been obtained for saturation temperatures ranging from -20°C to 40°C which correspond to standards relevant to refrigeration or air conditioning systems. The empirical models for boiling in such conditions are limited by the experimental data on which they are based, whereas analytical and theoretical approaches are needed to advanced knowledge on the behaviour of thermohydraulic two-phase refrigerant. This PhD thesis aims at studying the flow boiling characteristics of R-245fa in a 3.00 inner diameter channel in the thermodynamic conditions of the ORC system. Therefore, the saturation temperature ranged from 60°C to 120°C. To achieve this goal, an experimental test facility was designed and built to conduct refrigerant evaporation experiments. This test facility allowed to perform flow regime visualizations, pressure drop and heat transfer measurements in minichannel. First, an image processing method for two phase flow pattern characterization was developed. Based on this method and with the help of an adequate analysis of the heat transfer coefficient, the main flow regimes have been identified. The influence of saturation temperature on the flow patterns and their transitions has been highlighted. The second objective was to provide new experimental data concerning flow boiling heat transfer in minichannel. Flow boiling heat transfer coefficients at such high temperature have, so to say, almost never been reported in the open literature so far. The influence of saturation temperature on the heat transfer mechanisms has been discussed. In order to evaluate the capability of the current flow boiling prediction methods to predict the heat transfer coefficient, the comparison between experimental results and theoretical results predicted with the commonly used correlations and models were made. Lastly, pressure drop databases are presented. Experimental values of pressure drops were compared against several methods.

Questions that were answered in the dissertation: Which process is suitable to desulphurize biogas knowing that chemical absorption will be used to separate CO2? Which absorption solvent is suitable to separate CO2 from concentrated gases such as biogas at atmospheric pressure? What properties of the selected solvent, namely aqueous diglycolamine (DGA), are already known? How to determine solvent properties such as equilibrium CO2 solubility under absorption and desorption conditions using simple, but robust apparatuses? What values do solvent properties such as density, viscosity and surface tension take at various DGA contents and CO2 loadings? How do primary alkanolamine content and CO2 loading influence solvent properties? What is the optimal DGA content in the solvent? What is the optimal desorption temperature at atmospheric pressure? How can equilibrium CO2 solubility in aqueous DGA solvents be simulated? What is the uncertainty in the results? How to debottleneck an absorber and increase its gas-treating capacity? How to determine the optimal lean loading of the absorption solvent? What are the characteristics of the absorption process that uses aqueous DGA as the solvent to separate CO2 from biogas and is more energy efficient and safer than the state-of-the-art processes? How to quantitatively compare the hazards of absorption solvents? What is the disposition of the German population towards hazards from biogas plants? What are the favourable and adverse environmental impacts of biomethane? / Fragen, die in der Dissertation beantwortet wurden: Welches Verfahren ist zur Entschwefelung von Biogas geeignet, wenn die chemische Absorption zur CO2-Abtrennung genutzt wird? Welches Absorptionsmittel ist geeignet, um CO2 aus konzentrierten Gasen, wie Biogas, bei atmosphärischem Druck abzutrennen? Welche Eigenschaften des ausgewählten Absorptionsmittels, wässriges Diglykolamin (DGA), sind bereits bekannt? Wie wird die CO2-Gleichgewichtsbeladung unter Absorptions- und Desorptionsbedingungen mit einfachen und robusten Laborapparaten bestimmt? Welche Werte nehmen die Absorptionsmitteleigenschaften wie Dichte, Viskosität und Oberflächenspannung bei verschiedenen DGA-Gehalten und CO2-Beladungen? Wie werden die Absorptionsmitteleigenschaften durch den Primäramin-Gehalt und die CO2-Beladung beeinflusst? Was ist der optimale DGA-Gehalt im Absorptionsmittel? Was ist die optimale Desorptionstemperatur bei atmosphärischem Druck? Wie wird die CO2-Gleichgewichtsbeladung im wässrigen DGA simuliert? Welche Ungenauigkeit ist zu erwarten? Wie wird eine Absorptionskolonne umgerüstet, um die Kapazität zu erweitern? Wie wird die optimale CO2-Beladung des Absorptionsmittels am Absorbereintritt (im unbeladenen Absorptionsmittel) bestimmt? Was sind die Prozesseigenschaften eines Absorptionsverfahrens, das wässriges DGA als Absorptionsmittel nutzt sowie energieeffizienter und sicherer als Verfahren auf dem Stand der Technik ist? Wie kann das Gefahrenpotenzial von Absorptionsmittel quantitativ verglichen werden? Wie werden Gefahren aus einer Biogasanlage durch die deutsche Bevölkerung wahrgenommen? Welche positive und negative Umweltauswirkung hat Biomethan?