A l'heure actuelle le stockage de l'hydrogène sous forme gazeuse, comprimée à haute pression, apparaît comme la solution le plus mature présentant le meilleur compromis en termes de masse, de pression de service mais aussi de volume des réservoirs. Cependant pour un développement plus large et sécurisé, l'amélioration des performances et la réduction des coûts des réservoirs restent des enjeux prioritaires. C'est dans ce contexte que nous avons étudié le stockage de l'hydrogène dans des réservoirs de type IV, en composites fibres de carbone/époxy. Ce travail a eu pour objectif d'accroitre la fiabilité du dimensionnement. Dans un premier temps, une étude expérimentale de caractérisation des matériaux constitutifs du réservoir a été réalisée. Pour améliorer la fiabilité des calculs, un modèle probabiliste a été proposé pour décrire le comportement de la partie composite du réservoir, principalement la rupture des fibres. Des calculs multiéchelles ont été mis en place basés sur les propriétés mécaniques et physiques des fibres. Les autres modes de dégradations, décollement entre plis, liaison embase-liner ont aussi été pris en compte dans les calculs de comportement du réservoir jusqu'à son éclatement. Enfin des recommandations de dimensionnement du réservoir ont été proposées afin d'améliorer les performances tout en minimisant la masse de composite dans un objectif de réduction des coûts. / Presently, the compressed hydrogen storage under high pressure appears to be the most sophisticated solution regarding to a compromise of mass, service pressure and also volume of pressure vessels. However, the challenges of pressure vessels nowadays are their performance improvement as well as their cost reduction. In this context, we studied the type IV hydrogen storage pressure vessel in carbon fibre/epoxy composites. This work aims to obtain a reliable pressure vessel design. Firstly, an experimental study of associated materials and pressure vessel characterisation has been carried out. Then, we proposed a probabilistic model for a composite which is dedicated in particular to fibre breakage using multi-scale simulations in accordance with its mechanical and physical properties. Once this model joined with damage criteria dedicated separately to the others damage mechanisms are integrated into the pressure vessel simulations. Finally, recommendations on composite pressure vessels have been proposed in order to improve their performances and to decrease the mass of composite directly corresponding to the reduction of composite pressure vessels cost.

The test facility ROCOM (Rossendorf Coolant Mixing Model) has been built for the investigation of coolant mixing processes in the reactor pressure vessel of pressurised water reactors (PWR). ROCOM is a 1:5 model of the German PWR KONVOI and has been designed for a wide range of different mixing scenarios. ROCOM disposes of four loops with fully controllable coolant pumps. The test facility is operated with demineralised water. For the investigation of mixing, tracer solution (water labelled with salt) is injected into the facility. The transient distribution of the electrical conductivity is is measured at different positions of the flow path by means of wire-mesh sensor technique with high resolution in space and time. The measured conductivity is transformed into a dimensionless mixing scalar. The mixing at quasi-stationary conditions (constant loop mass flow rates) has been investigated in the presented experiments. That concerned nominal operation conditions, the operation with a reduced number of loops and the investigation of cold-water transients with running pumps and conditions of developed natural circulation. In special experimental series, the reproducibility of the results at identicla boundary conditions within the confidence intervalls has been shown. Further, the influence of various factors on the mixing has been investigated. This included the pressure losses at the core bottom plate, the global coolant flow level and the influence of the loop flow rate on the perturbed sector at the core inlet. An analysis of the measurement error of the used measurement technique completes the report.

Ziel des BMWi-Fördervorhabens 1501393 ist es, durch den Einsatz von Untersuchungsmethoden auf der nm-Skala einen Beitrag zur Aufklärung von Flusseffekten und von Late-Blooming-Effekten in bestrahlten RDB-Stählen zu leisten. Zur Untersuchung dieser Effekte wurde auf RDB-Stähle deutscher Reaktoren aus zwei bei der AREVA GmbH abgeschlossenen Vorhaben zurückgegriffen. Die Auswahl der Grundwerkstoffe und Schweißgüter erfolgte so, dass sich optimale Voraussetzungen für das Erreichen des Gesamtziels des Vorhabens ergeben. Die ausgewählten Untersuchungsmethoden umfassen mit der Neutronenkleinwinkelstreuung, der Atomsondentomographie und der Positronen-annihilationsspektroskopie solche Techniken, die die nm-skaligen bestrahlungsinduzierten Defekt-Fremdatom-Cluster bestmöglich und in komplementärer Weise zu detektieren und zu charakterisieren gestatten. Es wurde ein Flusseffekt auf die Größe der bestrahlungsinduzierten Fremdatomcluster, jedoch nicht auf den Volumenanteil und die mechanischen Eigenschaften gefunden. In einem Cu-armen RDB-Schweißgut wurde ein Late-Blooming-Effekt nachgewiesen, der sich in einem steilen Anstieg des Clustervolumenanteils und der Übergangstemperaturverschiebung nach einer Phase schwacher oder fehlender Zunahme niederschlägt. The BMWi project 1501393 aimed at contributing to the clarification of flux effects and late blooming effects in irradiated RPV steels by means of experimental techniques of sensitivity at the nm scale. The investigation of these effects was focussed on RPV steels, both base metal and weld of German reactors selected according to the objectives of the present project from two previous projects performed at AREVA GmbH. The complementary techniques of small-angle neutron scattering, atom probe tomography and positron annihilation spectroscopy were applied to detect and characterize the irradiation-induced nm-scale defect-solute clusters. A flux effect on the size of the irradiation-induced clusters but no flux effect on both cluster volume fraction and mechanical properties was found. For a low-Cu RPV weld, a late blooming effect was observed, which results in a steep slope of both cluster volume fraction and transition temperature shift after an initial stage of small or no change.

The aim of this study is to develop an explicit analytical formulation based on the anisotropic elasticity theory that determines the behavior of fiber reinforced composite vessel under hygrothermal loading. The loading is studied for three cases separately, which are plane strain case, free ends and pressure vessel cases. For free-end and pressure vessel cases, the vessel is free to expand, on the other hand for plane strain case, the vessel is prevented to expand. Throughout the study, constant, linear and parabolic temperature distributions are investigated and for each distribution, separate equations are developed. Then, a suitable failure theory is applied to investigate the behavior of fiber reinforced composite vessels under the thermal and moisture effects. Throughout the study, two computer programs are developed which makes possible to investigate the behavior of both symmetrically and antisymmetrically oriented layers. The first program is developed for plane strain case, where the second one is for pressure vessel and free-end cases. Finally, several thermal loading conditions have been carried out by changing the moisture concentration and temperature distributions and the results are tabulated for comparison purposes.

This study is conducted for the design and analysis of pressure vessels and associated pressurized equipment using various codes and methods. A computer software is developed as the main outcome of this study, which provides a quick and comprehensive analysis by using various methods utilized in codes and standards together with theoretical and empirical methods which are widely accepted throughout the world. Pressure vessels are analyzed using ASME Boiler and Pressure Vessel Code, whereas auxiliary codes, especially ASCE and AISC codes are utilized for structural analyses of these equipment. Effect of wind, seismic, and other types of loadings are also taken into consideration in detail, with dynamic analyses. Support structures and their auxiliary components are also items of analysis. Apart from pressure vessels, many pressurized process equipments that are commonly used in the industy are also included in the scope of the study. They include safety valves which are an integral part of those kinds of pressurized or enclosed systems, two of the heat exchanger components with great importance -tubesheets and expansion joints-, and API 650 tanks for oil or water storage. The computer software called as VESSELAID is written in Microsoft Visual Basic 6.0 using SI units. Design and analysis methods of VESSELAID are based on various code rules, recommended design practices and alternative approaches.

Ce travail a pour but de proposer une nouvelle approche du dimensionnement optimisé des réservoirs de stockage d’hydrogène de type IV visant à mieux répondre aux enjeux industriels. Les objectifs scientifiques et techniques consistent à disposer de modèles qualifiés pour la simulation du comportement de ces réservoirs, associés à des méthodologies de dimensionnement et d’optimisation fiables. La démarche s’appuie sur trois axes principaux :– proposer une démarche de conception prédictive en intégrant (i) un premier aspect lié à la ruine de la structure qui est la conséquence de mécanismes complexes et multiples d’endommagement s’initiant, s’accumulant et se développant dans un milieu anisotrope et (ii) des modèles de simulation de la structuration composite spécifique au procédé d’enroulement filamentaire, technologie employée largement dans la fabrication des réservoirs de stockage à haute pression. Leurs implémentations constituent une première avancée face à l’existant ;– choisir et évaluer les paramètres structuraux par une démarche d’optimisation où nous sommes amenés à utiliser (i) des méthodes de métamodélisation permettant de répondre aux contraintes de coûts, (ii) des méthodes spécifiques de tri et (iii) des méthodes à spectres larges qui recherchent des solutions sur une large population telles que des méthodes génétiques ;– qualifier la démarche dans sa globalité par une comparaison entre calculs et essais. Ainsi, la finalité de ce travail est de développer et valider des modèles et méthodes pour permettre de mieux concevoir, tester et fabriquer à moindre coût un réservoir avec une structure calculée optimisée. / The purpose of this study is to suggest a new way to design type IV high pressure hydrogen composite vessels to better fulfil industrial requirements. Developing suitable models for the comportment’s simulation of these vessels in relation with a reliable design method is the main scientific and technical aim. This approach relies on the three following lines :– perform a predictive design method using the most recent theoretical and numerical works investigated on composite materials and more specifically in taking into account (i) an essential aspect linked to the structural failure which is the consequence of the initiation, accumulation and propagation of complex damage mechanisms and (ii) the use of specific composite lay-up models related to the filament winding process, used for pressure vessels manufacturing. These approaches are significant breakthroughs compared with previous studies ;– choose and assess structural parameters with an optimisation approach where we use (i) surrogate methods to meet economic requirements, (ii) specific sorting methods and (iii) broad-spectrum methods such as genetic algorithm methods ;– approve of the whole approach by theoretical and experimental comparisons.The goal of the project will be to develop, provide and approve models to enable a better conception and industrialisation of an optimal high pressure vessel in relations with costs.

Large air-cooled heat exchangers (ACHEs) are most popularly implemented in the petrochemical and power industries at arid locations. They operate on a simple concept of convective heat transfer, whereby air in the surrounding atmosphere is caused to flow across a tube bundle, which in turn transports a process fluid. The distribution and direction of the process fluid flow may furthermore be guided via a set of appropriately located header boxes, which essentially consist of a collection of welded flat plates and nozzle attachments. Perforations on one of the faces of these boxes serve as an interface to the tube bundle. The overall design and construction of an ACHE is commonly regulated by an American Petroleum Institute (API) standard, which is required to be used in conjunction with acceptable design codes. In spite of this, the design of certain header box configurations remains of prominent concern. It is the focus of the present study to investigate the approach adopted for a header box variant labelled as the removable cover type. In this configuration, one of the plates used to construct the header box is fastened and sealed by a collection of bolted joints and a gasket, allowing it to be removed. One appropriate design code for the header box equipment is the ASME (American Society of Mechanical Engineers) boiler and pressure vessel code. However, it provides no specific approach pertaining to the removable cover design. Instead it has been commonplace in industry for a number of aspects from this code to be synthesized, together with a collection of assumptions surrounding the header box behaviour, into an all encompassing design by rule approach. In this approach, the header box behaviour is accepted as being planar, whilst circumstances such as nozzle attachments and associated loading would suggest that a more comprehensive approach should be undertaken. The aim of the present study is therefore to critically evaluate the current practice, and establish its adequacy. To do so, a detailed three-dimensional finite element model (FEM) of an example header box design is developed. Subsequent comparisons with the stress distribution predicted via current practice show that the existing analytical model gives inaccurate and, in cases, overly conservative results. A new analytical approach developed from rigid frame theory is demonstrated to provide improved correlation with FEM. The linear elastic design by analysis approach, presented in the ASME code, is also utilised as a method for establishing design adequacy. Results obtained via design by analysis incorporating the finite element method are shown to be less conservative than those arising from design by rule methods. The design by analysis approach is also used to conduct a more detailed investigation of nozzle placement and external loading. In general, the effect of including a nozzle did not result in a significant increase in side plate stress, with failure more likely to occur within the nozzle wall. / Dissertation (MEng)--University of Pretoria, 2011. / Mechanical and Aeronautical Engineering / unrestricted

This diploma thesis deals with a practical comparison of pressure vessels design approaches within ČSN EN 13445. The thesis aimed to design the device using various approaches described in the European Standard and compare them. For the design was chosen a liquid filter, which works as the first stage of the filtration system in a waste-to-energy plant. In the first part of the thesis is introduced to different routes of design by analysis (DBA), including a description of plasticity conditions and finite element types. These theoretical knowledge are applied in the practical part. The practical part consists of designs of the pressure vessel according to different approaches and methods. The first approach is a design by formulae (DBF), which was done in software Visual Vessel Design. The second approach is DBA. This method of design can be realized according to the European Standard by two routes, either by Method base on the stress categories or so-called Direct Route. Both routes were performed in this work. Stress analyzes were made in programs ANSYS Workbench and NozzlePRO. At the end of the thesis, there is a comparison of used approaches and the resulting values of the design.

The test facility ROCOM (Rossendorf Coolant Mixing Model) has been built for the investigation of coolant mixing processes in the reactor pressure vessel of pressurised water reactors (PWR). ROCOM is a 1:5 model of the German PWR KONVOI and has been designed for a wide range of different mixing scenarios. ROCOM disposes of four loops with fully controllable coolant pumps. The test facility is operated with demineralised water. For the investigation of mixing, tracer solution (water labelled with salt) is injected into the facility. The transient distribution of the electrical conductivity is is measured at different positions of the flow path by means of wire-mesh sensor technique with high resolution in space and time. The measured conductivity is transformed into a dimensionless mixing scalar. The mixing at quasi-stationary conditions (constant loop mass flow rates) has been investigated in the presented experiments. That concerned nominal operation conditions, the operation with a reduced number of loops and the investigation of cold-water transients with running pumps and conditions of developed natural circulation. In special experimental series, the reproducibility of the results at identicla boundary conditions within the confidence intervalls has been shown. Further, the influence of various factors on the mixing has been investigated. This included the pressure losses at the core bottom plate, the global coolant flow level and the influence of the loop flow rate on the perturbed sector at the core inlet. An analysis of the measurement error of the used measurement technique completes the report.

Ziel des BMWi-Fördervorhabens 1501393 ist es, durch den Einsatz von Untersuchungsmethoden auf der nm-Skala einen Beitrag zur Aufklärung von Flusseffekten und von Late-Blooming-Effekten in bestrahlten RDB-Stählen zu leisten. Zur Untersuchung dieser Effekte wurde auf RDB-Stähle deutscher Reaktoren aus zwei bei der AREVA GmbH abgeschlossenen Vorhaben zurückgegriffen. Die Auswahl der Grundwerkstoffe und Schweißgüter erfolgte so, dass sich optimale Voraussetzungen für das Erreichen des Gesamtziels des Vorhabens ergeben. Die ausgewählten Untersuchungsmethoden umfassen mit der Neutronenkleinwinkelstreuung, der Atomsondentomographie und der Positronen-annihilationsspektroskopie solche Techniken, die die nm-skaligen bestrahlungsinduzierten Defekt-Fremdatom-Cluster bestmöglich und in komplementärer Weise zu detektieren und zu charakterisieren gestatten. Es wurde ein Flusseffekt auf die Größe der bestrahlungsinduzierten Fremdatomcluster, jedoch nicht auf den Volumenanteil und die mechanischen Eigenschaften gefunden. In einem Cu-armen RDB-Schweißgut wurde ein Late-Blooming-Effekt nachgewiesen, der sich in einem steilen Anstieg des Clustervolumenanteils und der Übergangstemperaturverschiebung nach einer Phase schwacher oder fehlender Zunahme niederschlägt. The BMWi project 1501393 aimed at contributing to the clarification of flux effects and late blooming effects in irradiated RPV steels by means of experimental techniques of sensitivity at the nm scale. The investigation of these effects was focussed on RPV steels, both base metal and weld of German reactors selected according to the objectives of the present project from two previous projects performed at AREVA GmbH. The complementary techniques of small-angle neutron scattering, atom probe tomography and positron annihilation spectroscopy were applied to detect and characterize the irradiation-induced nm-scale defect-solute clusters. A flux effect on the size of the irradiation-induced clusters but no flux effect on both cluster volume fraction and mechanical properties was found. For a low-Cu RPV weld, a late blooming effect was observed, which results in a steep slope of both cluster volume fraction and transition temperature shift after an initial stage of small or no change.