<p> Wire-wrapped rod bundles are often used in nuclear reactors operating in a fast neutron spectrum, as designers seek to minimize neutron scattering by packing the fuel pins into a hexagonal lattice. Bundles with many rods have extensively been studied as representative of large fuel assemblies, however far fewer experiments have investigated bundles with 7 rods (7-pin bundles). The large difference in subchannel number between these bundles leads to 7-pin bundles having different pressure drop characteristics. The Versatile Test Reactor (VTR) sodium cartridge loop proposes to use a 7-pin bundle as its experimental core region, highlighting the need for additional data and models. The current work seeks to establish a better understanding of the pressure drop in 7-pin wire-wrapped rod bundles through scaled experiments and a novel pressure drop model. A scaling analysis is first performed to demonstrate the applicability of water experiments to the VTR sodium cartridge loop, before an experimental test facility is designed and constructed. Experiments are then performed at a range of Reynolds numbers to determine the pressure drop. Current models are able to predict the data well, but are complex and can be difficult to use. A comparatively simpler model is developed, based on exact laminar solutions of a simplified rod bundle, which also offers a theoretical lower bound for the pressure drop in wire-wrapped bundles. The proposed model compares well with the existing experimental database, able to predict bundle friction factor with an average absolute percent difference of 10.8%. This accuracy is also similar to existing correlations, while relying on fewer empirical coefficients. The theoretical lower bound is also used to identify several datasets in literature that may feature data that is systemically lower than the true pressure drop, which agrees with previous observations in literature. </p>

<p>In this study, universal databases and semi-empirical correlations are developed for cryogenic two-phase heat transfer and pressure drop in heated tubes undergoing flow boiling.</p>

The increasing highway traffic is leading to higher and higher levels of pollutants in the stormwater, such as suspended solids, metals, oils, nutrients and PAH. This runoff water causes the degradation of water bodies quality, leading to increased interest in the treatment of highway runoff for the removal of contaminants. Traditional treatments mostly consist of sedimentation, aimed primarily at the removal of suspended solids and particlebound contaminants. Recently the concern has shifted to the dissolved and colloidal fractions of contaminants as well, metals in particular, which makes reactive media filters a potentially interesting technology for runoff water treatment. However, very little research has been carried out on this technology so far, mostly in batch laboratory experiments with synthetic runoff water. This study aims at investigating the performance of four reactive media filters (Petrit T, Polonite, D-Rainclean and Filtralite-P) and a defined filter sand used for water processing at removing dissolved and particulate-bound metals. To achieve the goal, a pilot plant has been constructed in Gröndal, south of Stockholm, inside the existing Gröndalsmagasin, a full-scale stormwater treatment plant. The catchment area is located mostly on the E4 and Essingeleden, the highest trafficked motorway in Sweden with an AADT of 140 000 vehicles. A pump feeds the pilot plant from the Gröndalsmagasin outlet, after the stormwater has been treated with flocculation and sedimentation, and collects such water in a collection vessel. The five filter media columns are fed during runoff events with a flow scaled proportionally to the influent in the Gröndalsmagasin to mimic real conditions of flow and pollutant concentrations. Field measurements of pH, turbidity and conductivity, have been carried out during the trial. Samples have also been collected with flow proportional samplers connected to the collection vessel and the outlet of the five columns, as well as in the form of grab samples from sample ports at different depths in the columns. These samples have been sent to ALS Scandinavia AB to perform lab analysis. The pH in the effluent of the reactive filter media increased to values between 10 and 13, and slowly decreased during the trial. No difference was found between the pH in Filtersand outlet and the influent water. All materials showed excellent performance at removal of dissolved and particulate-bound Zn as well as particulate-bound Cu. Dissolved Cu was removed effectively by reactive media, and to a minor extent by Filtersand. Leaching of metals was observed from three materials: Filtersand released Mn during April, Polonite released Cr, with a very good correlation with the Chloride content and Petrit-T released Ba during the entire trials. / Den ökande vägtrafiken leder till allt högre halter av föroreningar i dagvattnet, till exampel suspenderade ämnen, metaller, oljor, närings ämnen och PAH. Detta dagvatten försämrar degradering av vattenförekomsternas kvalitet, vilket har lett till ett ökat intresse för rening av dagvatten fr ̊ån motorvägar för att avlägsna föroreningar. Traditionella behandlingar består oftast av sedimentering, som främst syftar till att reducera suspenderade ämnen och partikelbundna föroreningar. På senaste tiden har intresset förskjutits till att även omfatta lösta och kolloidala fraktioner av föroreningar, speciellt metaller, vilket gör reaktiva filtermaterial till en potentiellt intressant teknik f ̈or behandling av dagvatten. Mycket lite forskning har dock gjorts om denna teknik hittills, då oftast i laboratorieexperiment med syntetiskt dagvatten. Denna studie syftar till att undersöka hur fyra reaktiva mediafilter (Petrit T, Polonite, D-Rainclean och Filtralite-P) och en typ av sandfilter fungerar när det gäller att avlägsna lösta och partikelbundna metaller. F ̈or att uppnå målet har en pilotanläggning byggts i Gröndal, söder om Stockholm, inuti det existerande Gröndalsmagasinet, ett dagvattenreningsverk i full skala. Avrinningsområdet ligger vid E4 och Essingeleden, den mest trafikerade motorvägen i Sverige med en ÅDT på 140 000 fordon. En pump matar pilotanläggningen fr ̊ån Gröndalsmagasinets utlopp, efter att dagvattnet har behandlats med flockning och sedimentering, och samlas upp detta vatten i ett uppsamlingskärl. De fem filtreringskolonnerna matas under avrinningshändelserna med ett flöde som är proportionellt till inflödet till Gröndalsmagasinet för att imitera verkliga förhållanden av flöde och föroreningskoncentrationer. Mätningar av pH, turbiditet och konduktivitet har utförts under försöket. Prover har också samlats in med flödesproportionella provtagare som är kopplade till uppsamlingskärlet och utloppet fr ̊an de fem kolonnerna, samt i form av grabbprover fr ̊an provtagningsöppningar på olika djup i kolonnerna. Dessa prover har skickats till ALS Scandinavia AB för laboratorieanalys. pH-värdet i utflödet fr ̊ån det reaktiva filtermediet ökade till värden mellan 10 och 13 och sjönk långsamt under försöket. Ingen skillnad hittades mellan pH-värdet i filtrets utlopp och inflödesvattnet. Alla material visade mycket goda resultat när det gäller avlägsnande av löst och partikulät bundet Zn samt partikulärt bundet Cu. Lösta Cu avlägsnades mycket effektivt av reaktiva medier och i mindre utsträckning av Filtersand. Läckage av metaller observerades fr ̊ån tre material: Filtersand släppte ut Mn under April, Polonite släppte ut Cr, med en mycket god korrelation med kloridhalten och Petrit-T släppte ut Ba under hela försöket.

<p dir="ltr">Flow patterns in a toroidal-fluidized bed granulator were analyzed using the effects of wall friction on the bed pressure drop. Toroidal flows were generated by directionally inclined jets from a radially-slotted distributor plate. The relatively small open area of the slotted distributor provides significant jet velocities, inducing toroidal flow even at relatively low superficial airflows. In this aspect, the process is of interest to fluidized bed granulation wherein the toroidal flow can assist spray flux without excessive elutriation. The current dissertation explores the effect of toroidal multiphase flow on wall friction and pressure drop. Relevant process parameters include particle size, airflow, temperature, and bed inventory. Particle size growth is especially important in fluidized bed granulation; airflow and temperature parameters must balance with the binder spray enthalpy; and the bed inventory is relevant to capacity and throughput analyses. An empirical process model was developed to guide fluidized bed granulation with a consistent pressure-drop balance across the distributor plate and product bed during the granulation process.</p><p dir="ltr">Fluidized bed granulation integrates several process transformations into a single unit operation. Transformations include powder fluidization, atomization of binder solution and wetting of the fluidized powder, growth and consolidation of granules, drying, and discharge of the fluidized product. The balance of the binder addition and drying rates is used in combination with fluidization (i.e., flow field) parameters to control the process. Balanced control of fluidization can be challenging in the context of micronized powders, prone to elutriation, for example as required in some pharmaceutical formulations. This manuscript explores the effects of thermodynamic and flow field parameters on the size and shape distributions of a challenging pharmaceutical formulation. Pre-wetting the powder mixture prior to fluidization effectively reduces elutriation, stabilizes the fluidization process, and results in narrower granule size distributions. Optimizing blowback pressure can further stabilize the process. These strategies contribute to improved control of fluidized bed granulation, particularly for challenging pharmaceutical formulations, enhancing both product quality and process efficiency.</p><p dir="ltr">A regime map for a challenging pharmaceutical formulation was developed to link operational parameters to granule characteristics, establishing a stable processing space that connects moisture gain with particle size and shape distributions and uniformity. This comprehensive framework supports scale-up and reliable application of fluid bed granulation in pharmaceutical and related industries, contributing to improved process efficiency and product quality. The findings presented here advance the scientific understanding of toroidal fluid bed granulation and offer practical and actionable strategies for controlling this process.</p>

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The aim of this diploma thesis is to get acquainted with modern technological elements currently used in shell-and-tube heat exchanger in the shell-side and tube-side, thermal-hydraulic calculation of selected elements and comparison of thermal-hydraulic properties with classically used competing technological elements. The work deals mainly with EM baffle in the tube-side and tube inserts like the twisted tape type (and its modifications) and coiled wire in the tube-side. The theoretical part is focused on acquaintance with classical technological elements in shell-and-tube heat exchanger and with basic thermal-hydraulic calculations, practical part then on acquaintance with modern elements and thermal-hydraulic calculation of selected elements. These calculations are then compared with the results of the thermo-hydraulic calculation of similar elements.

A compact air separator demonstrator based on centrifugally enhanced distillation has been studied. The full size device is meant to be used on board of a Two Stage To Orbit vehicle launcher. The air separation system must be able to extract oxygen in highly concentrated liquid form (LEA, Liquid Enriched Air) from atmospheric air. The LEA is stored before being used in a subsequent rocket propulsion phase by the second stage of the launcher. Two reference vehicles are defined, one with a subsonic first stage and one with a supersonic first stage. In both cases, oxygen collection is performed during a cruise phase (M 0.7 and M 2.5 respectively). The aim of the project is to demonstrate the feasibility of the air separation system, investigate the separation cycle design, and assess that the separator design selected is suitable for the reference vehicles.<p><p>The project is described from original base ideas to design, construction, extended testing and analysis of experimental results. Preliminary computations for a realistic layout have been performed and the motivations for the choices made during the process are explained. Test rig design, separator design and technical discussion are provided for a subscale pilot unit. Mass transport parameters and flooding limits have been estimated and experimentally measured. Performance has been assessed and shown to be sufficient for the reference Two Stage To Orbit vehicles. The technology developed is found suitable without further optimization, although some volume and mass reduction would be desirable for the supersonic first stage concept. There are many ways of optimisation that can be further investigated. The aim of this program, however, is not to fully optimize the device, but to demonstrate that a device based on a simple, robust, low-risk design is already suitable for the launch vehicles. On top of that analysis, directions for improvements are suggested and their potentials estimated. A complete assessment of those improvements requires further maturation of the technological concept through further testing and practical implementations.<p><p>Directions for future work, general conclusions and a vehicle development roadmap have also been provided.<p> / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

粉体の微粒子化に伴い，固液分離操作の中でも高精度かつ多量処理が可能なろ過の重要性はますます高まっている．しかしながら，微粒子スラリーのろ過抵抗は非常に大きく，所望の処理能力を得られないことが多い．本論文では，ろ過操作設計におけるろ材抵抗，スラリー凝集・分散状態，ケークろ過抵抗の予測に関して数値シミュレーションを利用した検討を行うことで，微粒子スラリーのろ過抵抗の低減に有用な知見を得ることができた． / 著者名の「吉」は「土」の下に「口」の置き換え / 博士(工学) / Doctor of Philosophy in Engineering / 同志社大学 / Doshisha University

Peripheral vascular grafts are used for the treatment of peripheral arterial disease and arteriovenous grafts for vascular access in end stage renal disease. The development of neo-intimal hyperplasia and thrombosis in the distal anastomosis remains the main reason for occlusion in that region. The local haemodynamics produced by a graft in the host vessel is believed to significantly affect endothelial function. Single spiral flow is a normal feature in medium and large sized vessels and it is induced by the anatomical structure and physiological function of the cardiovascular system. Grafts designed to generate a single spiral flow in the distal anastomosis have been introduced in clinical practice and are known as spiral grafts. In this work, spiral peripheral vascular and arteriovenous grafts were compared with conventional grafts using ultrasound and computational methods to identify their haemodynamic differences. Vascular-graft flow phantoms were developed to house the grafts in different surgical configurations. Mimicking components, with appropriate acoustic properties, were chosen to minimise ultrasound beam refraction and distortion. A dual-beam two-dimensional vector Doppler technique was developed to visualise and quantify vortical structures downstream of each graft outflow in the cross-flow direction. Vorticity mapping and measurements of circulation were acquired based on the vector Doppler data. The flow within the vascular-graft models was simulated with computed tomography based image-guided modelling for further understanding of secondary flow motions and comparison with the experimental results. The computational assessments provided a three-dimensional velocity field in the lumen of the models allowing a range of fluid dynamic parameters to be predicted. Single- or double-spiral flow patterns consisting of a dominant and a smaller vortex were detected in the outflow of the spiral grafts. A double- triple- or tetra-spiral flow pattern was found in the outflow of the conventional graft, depending on model configuration and Reynolds number. These multiple-spiral patterns were associated with increased flow stagnation, separation and instability, which are known to be detrimental for endothelial behaviour. Increased in-plane mixing and wall shear stress, which are considered atheroprotective in normal vessels, were found in the outflow of the spiral devices. The results from the experimental approach were in agreement with those from the computational approach. This study applied ultrasound and computational methods to vascular-graft phantoms in order to characterise the flow field induced by spiral and conventional peripheral vascular and arteriovenous grafts. The results suggest that spiral grafts are associated with advanced local haemodynamics that may protect endothelial function and thereby may prevent their outflow anastomosis from neo-intimal hyperplasia and thrombosis. Consequently this work supports the hypothesis that spiral grafts may decrease outflow stenosis and hence improve patency rates in patients.