No description available.

Continental rifting is an important geodynamic process during which the Earth's outer-most rigid shell undergoes continuous stretching resulting in continental break-up and theformation of new oceanic basins. The East African Rift System, which has two continentalsegments comprising largely of the East African Rift (EAR) to the West and the easternmostsegment Madagascar, is the largest narrow rift on Earth. However, the driving mechanismsof continental rifting remain poorly understood due to a lack of numerical infrastructure tosimulate rifting, the lack of knowledge of the underlying mantle dynamics, and poor knowl-edge of mantle rheology. Here, we use state-of-art computational modeling of the upper660 km of the Earth to: 1) provide a better understanding of mantle flow patterns and themantle rheology beneath Madagascar, 2) to elucidate the main driving forces of observedpresent-day∼E-W opening in the EAR, and 3) to investigate the role of multiple plumesor a superplume in driving surface deformation in the EAR. In chapter 1, we simulate EdgeDriven convection (EDC), constrained by a lithospheric thickness model beneath Madagas-car. The mantle flow associated with the EDC is used to calculate induced olivine aggregates'Lattice Preferred Orientation (LPO), known as seismic anisotropy. The predicted LPO isthen used to calculate synthetic seismic anisotropy, which were compared with observationsacross the island. Through a series of comparisons, we found that asthenospheric flow result-ing from undulations in lithospheric thickness variations is the dominant source of the seismicanisotropy, but fossilized structures from an ancient shear zone may play a role in southern Madagascar. Our results suggest that the rheological conditions needed for the formationof seismic anisotropy, dislocation creep, dominates the upper asthenosphere beneath Mada-gascar and likely other continental regions. In chapter 2, we use a 3D numerical model ofthe lithosphere-asthenosphere system to simulate instantaneous lithospheric deformation inthe EAR and surroundings. We test the hypothesis that the∼E-W extension of the EAR isdriven by large scale forces arising from topography and internal density gradients, known aslithospheric buoyancy forces. We calculate surface deformation solely driven by lithosphericbuoyancy forces and compare them with surface velocity observations. The lithosphericbuoyancy forces are implemented by imposing observed topography at the model surfaceand lateral density variations in the crust and mantle down to a compensation depth of 100km. Our results indicate that the large-scale∼E-W extension across East Africa is driven bylithospheric buoyancy forces, but not along-rift surface motions in deforming zones. In chap-ter 3, we test the hypothesis that the anomalous northward rift-parallel deformation observedin the deforming zones of the EAR is driven by viscous coupling between the lithosphereand deep upwelling mantle material, known as a superplume, flowing northward. We testtwo end-member plume models including a multiple plumes model simulated using high res-olution shear wave tomography-derived thermal anomaly and a superplume model (Africansuperplume) simulated by imposing a northward mantle-wind on the multiple plumes model.Our results suggest that the horizontal tractions from northward mantle flow associated withthe African Superplume is needed to explain observations of rift-parallel surface motions indeforming zones from GNSS/GPS data and northward oriented seismic anisotropy beneaththe EAR. Overall, this work yields a better understanding of the geodynamics of Africa. / Doctor of Philosophy / Continental rifting is an important geodynamic process during which the Earth's outer-most rigid shell undergoes continuous stretching resulting in continental break-up and theformation of new oceanic basins. The East African Rift System, which has two continentalsegments comprising largely of the East African Rift (EAR) to the West and the easternmostsegment Madagascar, is the largest narrow rift on Earth. However, the driving mechanismsof continental rifting remain poorly understood due to a lack of numerical infrastructure tosimulate rifting, the lack of knowledge of the underlying mantle dynamics, and poor knowl-edge of mantle rheology. Here, we use state-of-art computational modeling of the upper660 km of the Earth to: 1) provide a better understanding of mantle flow patterns and themantle rheology beneath Madagascar, 2) to elucidate the main driving forces of observedpresent-day∼E-W opening in the EAR, and 3) to investigate the role of multiple plumesor a superplume in driving surface deformation in the EAR. In chapter 1, we simulate EdgeDriven convection (EDC), constrained by a lithospheric thickness model beneath Madagas-car. The mantle flow associated with the EDC is used to calculate induced olivine aggregates'Lattice Preferred Orientation (LPO), known as seismic anisotropy. The predicted LPO isthen used to calculate synthetic seismic anisotropy, which were compared with observationsacross the island. Through a series of comparisons, we found that asthenospheric flow result-ing from undulations in lithospheric thickness variations is the dominant source of the seismicanisotropy, but fossilized structures from an ancient shear zone may play a role in southern Madagascar. Our results suggest that the rheological conditions needed for the formationof seismic anisotropy, dislocation creep, dominates the upper asthenosphere beneath Mada-gascar and likely other continental regions. In chapter 2, we use a 3D numerical model ofthe lithosphere-asthenosphere system to simulate instantaneous lithospheric deformation inthe EAR and surroundings. We test the hypothesis that the∼E-W extension of the EAR isdriven by large scale forces arising from topography and internal density gradients, known aslithospheric buoyancy forces. We calculate surface deformation solely driven by lithosphericbuoyancy forces and compare them with surface velocity observations. The lithosphericbuoyancy forces are implemented by imposing observed topography at the model surfaceand lateral density variations in the crust and mantle down to a compensation depth of 100km. Our results indicate that the large-scale∼E-W extension across East Africa is driven bylithospheric buoyancy forces, but not along-rift surface motions in deforming zones. In chap-ter 3, we test the hypothesis that the anomalous northward rift-parallel deformation observedin the deforming zones of the EAR is driven by viscous coupling between the lithosphereand deep upwelling mantle material, known as a superplume, flowing northward. We testtwo end-member plume models including a multiple plumes model simulated using high res-olution shear wave tomography-derived thermal anomaly and a superplume model (Africansuperplume) simulated by imposing a northward mantle-wind on the multiple plumes model.Our results suggest that the horizontal tractions from northward mantle flow associated withthe African Superplume is needed to explain observations of rift-parallel surface motions indeforming zones from GNSS/GPS data and northward oriented seismic anisotropy beneaththe EAR. Overall, this work yields a better understanding of the geodynamics of Africa.

In the modern practice, a sustainable development strategy in a domain of wasteutilization is shifting its focus from a general completeness of recycling to a morespecific attention to efficiently utilize elements in the wastes. This is well-illustrated bythe steelmaking slag industries. The major waste product from the steelmaking practiceis slag and its main constituents are: CaO, SiO2, Al2O3, MnO, FeO and so on. The mainfield of application for the steelmaking slags is civil engineering, especially for road andwaterway construction. However, a significant amount of the slag remains in the dumps,damaging the environment as well as requiring a land for secure storage. Efficientrecycling of these materials is of increasing interest worldwide as a result of increasingsustainability in processes with respect to increasing raw material costs and wastereduction.In order to find a practical solution, joint efforts are currently made at the RoyalInstitute of Technology, Sweden and National Metallurgical Academy of Ukraine. Theconcept is based on transformation of non-magnetic wüstite (FeO) to magneticmagnetite (Fe3O4) using an oxidizing atmosphere was proposed.In order to verify the feasibility of the proposed way of slag utilization, experiments onthe ternary CaO-FeO-SiO2 and quaternary CaO-FeO-SiO2-MnO slags systems,accompanied by thermodynamic and kinetic modelling, were performed. The crystalprecipitation during synthetic slag oxidation was observed by Confocal Scanning LaserMicroscopy (CSLM). Precipitated phases were found to be magnetite and manganeseferrite in the spinel form.Obtained magnetite and manganese ferrite can be separated from the slag by magneticseparation.The formation of nanosize manganese ferrite from the CaO-FeO-SiO2-MnO slag systemduring oxidation was investigated. Experiments were conducted in a horizontalresistance furnace in an oxidizing atmosphere (air). The final product was analysed by Xraydiffraction (XRD). The particles size of the manganese ferrite was estimated by theScherrer formula and was found to be of the order of 23-25 nm. In order to get anunderstanding of the magnetic properties of the manganese ferrite recovered from slagtreatment, it was necessary to synthesize a reference compound from pure precursors.The MnFe2O4 nanopowder was synthesized by the oxalate route. The size effects on themagnetic properties of manganese ferrite particles were investigated.IIThe potential way of the magnetite particles separation from liquid slags was investigatedby cold model studies. The experimental technique of mobilising non-conducting,nonmagnetic particles in conducting liquid in crossed electric and magnetic fields wasinvestigated in order to find the way of the particle separation from the liquidsteelmaking slags. The effects of the current density, magnetic field, size and shape ofthe particle on the particle velocity under action of the electromagnetic buoyancy force(EBF) in the electrolyte were analyzed. / QC 20100916

No description available.

Motivated by the existence of complex behaviors arising from interactions between chemistry and fluid dynamics in numerous research problems and every-day life situations, we theoretically investigate the dynamics resulting from the interplay between chemistry, diffusion, and fluid motions in a reactive aqueous solution. As a chemical reaction induces changes in the temperature and in the composition of the reactive medium, such a reaction can modify the properties of the solution (density, viscosity, surface tension,…) and thereby trigger convective motions, which in turn affect the reaction. Two classes of convective flows are commonly occurring in solutions open to air, namely Marangoni flows arising from surface tension gradients and buoyancy flows driven by density gradients. As both flows can be induced by compositional changes as well as thermal changes and in turn modify them, the resulting experimental dynamics are often complex. The purpose of our thesis is to gain insight into these intricate dynamics thanks to the theoretical analysis of model systems where only one type of convective flow is present. In particular, we numerically study the spatio-temporal evolution of model chemical fronts resulting from the coupling between reactions, diffusion, and convection. Such fronts correspond to self-organized interfaces between the products and the reactants, which typically have different density and surface tension. Fluid motions are therefore spontaneously induced due to these differences across the front.<p><p>In this context, we first address the propagation of a model autocatalytic front in a horizontal solution layer, in the presence of pure Marangoni convection on the one hand and of pure buoyancy convection on the other hand. We evidence that, in both cases, the system attains an asymptotic dynamics characterized by a steady fluid vortex traveling with the front at a constant speed. The presence of convection results in a deformation and acceleration of the chemical front compared to the reaction-diffusion situation. However we note important differences between the Marangoni and buoyancy cases that could help differentiate experimentally between the influence of each hydrodynamic effect arising in solutions open to the air. We also consider how the kinetics and the exothermicity of the reaction influence the dynamics of the system. The propagation of an isothermal front occurring when two diffusive reactants are initially separated and react according to a simple bimolecular reaction is next studied in the presence of chemically-induced buoyancy convection. We show that the reaction-diffusion predictions established for convection-free systems are modified in the presence of fluid motions and propose a new way to classify the various possible reaction-diffusion-convection dynamics./En induisant des changements de composition et de température, une réaction chimique peut modifier les propriétés physiques (densité, viscosité, tension superficielle,…) de la solution dans laquelle elle se déroule et ainsi générer des mouvements de convection qui, à leur tour, peuvent affecter la réaction. Les deux sources de convection les plus courantes en solution ouverte à l’air sont les gradients de tension superficielle, ou effets Marangoni, et les gradients de densité. Comme ces deux sources sont en compétition et peuvent toutes deux résulter de différences de concentration ou de température, les dynamiques observées expérimentalement sont souvent complexes. Le but de notre thèse est de contribuer à la compréhension de telles dynamiques par une étude théorique analysant des modèles réaction-diffusion-convection simples. En particulier, nous étudions numériquement l’évolution spatio-temporelle de fronts chimiques résultant du couplage entre chimie non-linéaire, diffusion et hydrodynamique. Ces fronts constituent l’interface auto-organisée entre les produits et les réactifs qui typiquement ont des densités et tensions superficielles différentes. Des mouvements du fluide peuvent dès lors être spontanément initiés dus à ces différences au travers du front.<p> <p>Dans ce contexte, nous étudions la propagation d’un front chimique autocatalytique se propageant dans une solution aqueuse horizontale, d’une part en la seule présence d’effets Marangoni, et d’autre part en présence uniquement d’effets de densité. Nous avons montré que dans les deux cas, le système atteint une dynamique asymptotique caractérisée par la présence d’un rouleau de convection stationnaire se propageant à vitesse constante avec le front. Ce front est à la fois déformé et accéléré par les mouvements convectifs par rapport à la situation réaction-diffusion. Nous avons mis en évidence d’importantes différences entre les deux régimes hydrodynamiques qui pourraient aider les expérimentateurs à différencier les effets de tension superficielle de ceux de densité générés par la propagation de fronts chimiques en solution. Nous avons également considéré l’influence de la cinétique de réaction ainsi que de l’exothermicité sur la dynamique de ces fronts. Enfin, nous avons étudié la propagation en présence de convection d’un front de réaction impliquant deux espèces de densités différentes, initialement séparées et réagissant selon une cinétique bimoléculaire. Nous avons montré que la convection modifie les propriétés réaction-diffusion du système et nous proposons de nouveaux critères pour classifier les dynamiques réaction-diffusion-convection.<p><p><p> / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

The subject of this thesis is the evaluation of hydrodinamic load on a physical model of a bridge deck, especially to find the relation between the median and extreme quantiles of each hydrodanamic load part and to evaluate the influence, which has the shape of the bridge deck on the size of this load. Relations, that was found may be used to determine characteristic values of loads, caused by water flow, for example, when designing the bridge bearings.

The diploma thesis deals with experimental determination of hydrodynamic load on the overflowed bridge deck model. In the first part of the thesis the author describes the analysis of the problem together with the basic physical laws and principles that are used or assumed in the measurement itself. In the second part the author describes the measurements in the laboratory of the Faculty of Civil Engineering and its gradual processing. At the end of the work are described the results of measurement, their comparison with numerical modeling, other authors and their possible use in practice.

<p>This is a thesis work proposed by Sweco System in order to carry out a study related to the heating system of a circular fuel oil storage tank or cistern. The study tank is a 23m diameter and 18m height with a storage capacity of around 7500m3 of Eo5 heavy fuel oil. The content ought to be at a minimum storage temperature of 50ºC so that the fuel oil is fluid enough and operation labors can be adequately performed. In fact, these types of heavy fuel oils have fairly high viscosities at lower temperatures and the heating and pumping system can be compromised at temperatures below the pour point. For this purpose a heating system is installed to maintain the fluid warm. So far the system was operated by an oil burner but there are plans to its replacement by a District Heating-heat exchanger combo. Thereby, tank heating needs, flow and thermal patterns and heat transfer within it are principally studied.</p><p> </p><p>Tank boundaries are studied and their thermal resistances are calculated in order to dimension heat supply capacity. The study implies Finite Elements (Comsol Multiphysics) and Finite Volume (Fluent) analysis to work out some stationary heat transfer by conduction cases on some parts and thermal bridges present on these boundaries. Afterwards both cooling and heating processes of the fuel oil are studied using several strategies: basic models and Computational Fluid Dynamics (CFD). CFD work with Fluent is focused on optimizing inlet and outlet topologies. Understanding the cooling process is sought as well; Fluent CFD transient models are simulated in this way as well. Additionally the effect of filling levels is taken into account leading to a multiphase (fuel oil and air) flow cases where especially heating coupling of both phases is analyzed.</p><p> </p><p>Results show that maximum heat supply needs are around 80kW when the tank temperature is around 60ºC and 70kW when it is around 50ºC. Expectedly the main characteristic of the flow turns out to be the buoyancy driven convective pattern. K-ε turbulence viscous models are applied to both heating and cooling processes showing thermal stratification, especially at the bottom of the tank. Hotter fluid above follows very complex flow patterns. During the heating processes models used predict fairly well mixed and homogenous temperature distribution regardless small stratification at the bottom of the tank. In this way no concrete inlet-outlet configuration shows clear advantages over the rest. Due to the insulation of the tank, low thermal conductivity of the fluid and vast amount of mass present in the tank, the cooling process is slow (fluid average temperature drops around 5.7 ºC from 60ºC in 15 days when the tank is full and ambient temperature is considered to be at -20ºC) and lies somewhere in the middle between the solid rigid and perfect mixture cooling processes. However, due to stratification some parts of the fluid reach minimum admissible temperatures much faster than average temperature does. On the other hand, as expected, air phase acts as an additional thermal resistance; anyhow the cooling process is still faster for lower filling levels than the full one.</p> / <p>El presente proyecto fue propuesto por Sweco Systems para llevar a cabo un estudio relacionado con el sistema de calefacción de una cisterna o tanque de almacenamiento de fuel oil circular. Dicho tanque tiene 23 m de diámetro  y 18 m de altura con una capacidad de almacenamiento de alrededor de 7500 m³ de Eo5 fuel oil pesado. El contenido mantenerse a una temperatura mínima de 50 ºC de manera que el fuel oil es suficientemente fluido para que las labores de operación puedan ser ejecutadas adecuadamente. De hecho, estos tipos de fuel oil pesado tienen altas viscosidades a bajas temperaturas y, por tanto, tanto los sistemas de calefacción y como el de bombeo pueden verse comprometidosr a temperaturas por debajo del pour point. Con este fin un sistema de calefacción es instalado para mantener el fluido suficientemente caliente. Hasta el momento, el sistema era operado por un quemador de fuel, sin embargo, hay planes que éste sea sustituido por un combo intercambiador de calor-District Heating. Por lo tanto, principalmente son estudiadas las necesidades de calefacción así como los flujos térmicos y fluidos.</p><p>Se estudian las fronteras del tanque, y sus respectivas resistencias térmicas son calculadas con el fin de dimensionar la capacidad necesaria de suministro de calor. El estudio implica Elementos Finitos (Comsol Multiphysics) y Volúmenes Finitos (Fluent) para elaborar análisis estacionarios de transferencia de calor por conducción en algunos casos. Existen puentes térmicos en las paredes y su importancia es también anallizada. Posteriormente se estudian tanto los procesos de calentamiento y enfriamiento del fuel oil utilizando diversas estrategias: modelos básicos y Dinámica de Fluidos Computacional (CFD). El trabajo con CFD se centra en la optimización de topologías de entradas y salidas del sistema. También es solicitado entender el proceso de enfriamiento; En este sentido, se simulan modelos CFD transitorios de Fluent. Además, el efecto de los niveles de llenado se tiene en cuenta dando lugar a estudios de flujo multifase (fuel oil y aire), haciendo hincapié en el análisis de acoplamiento de transferencia de calor entre las dos fases.</p><p>Los resultados muestran que las necesidades de calefacción máximas son de alrededor de 80kW cuando la temperatura del tanque es de alrededor de 60 º C y 70kW cuando está alrededor de 50 ºC. Como era de esperar, la principal característica de este tipo de flujos es la convección natural resultante de las fuerzas de flotabilidad. Se aplican modelos turbulentos k-ε a los procesos de calentamiento y enfriamiento, mostrando estratificación térmica, sobre todo en la parte inferior de la cisterna. El líquido más caliente que se sitúa encima muestra complejos patrones de flujo. Durante los procesos de calentamiento, los modelos utilizados predicen un buen mezclado y distribución homogénea de la temperatura independientemente de esta pequeña estratificación en la parte inferior de la cisterna. De esta manera, ninguna concreta configuración de entradas-salidas simuladas muestra claras ventajas sobre el resto. Debido al aislamiento de la cisterna, la baja conductividad térmica del fluido y la gran cantidad de masa presente en el tanque el proceso de enfriamiento es lento (la temperatura media del fluido desciende 5.7 º C desde 60 º C en 15 días cuando el tanque está lleno y la temperatura ambiente es de -20 º C) y se encuentra en algún lugar en medio de los procesos de enfriamiento del sólido rígido y perfecta mezcla. Sin embargo, debido a la estratificación, algunas partes el líquido alcanzan la temperatura mínima admisible mucho más rápido que la media de temperatura. Por otra parte, como se esperaba, la fase de aire actúa como una resistencia térmica adicional, de todos modos, el proceso de enfriamiento es aún más rápido para niveles de llenado más bajos que el lleno.</p>

This is a thesis work proposed by Sweco System in order to carry out a study related to the heating system of a circular fuel oil storage tank or cistern. The study tank is a 23m diameter and 18m height with a storage capacity of around 7500m3 of Eo5 heavy fuel oil. The content ought to be at a minimum storage temperature of 50ºC so that the fuel oil is fluid enough and operation labors can be adequately performed. In fact, these types of heavy fuel oils have fairly high viscosities at lower temperatures and the heating and pumping system can be compromised at temperatures below the pour point. For this purpose a heating system is installed to maintain the fluid warm. So far the system was operated by an oil burner but there are plans to its replacement by a District Heating-heat exchanger combo. Thereby, tank heating needs, flow and thermal patterns and heat transfer within it are principally studied.   Tank boundaries are studied and their thermal resistances are calculated in order to dimension heat supply capacity. The study implies Finite Elements (Comsol Multiphysics) and Finite Volume (Fluent) analysis to work out some stationary heat transfer by conduction cases on some parts and thermal bridges present on these boundaries. Afterwards both cooling and heating processes of the fuel oil are studied using several strategies: basic models and Computational Fluid Dynamics (CFD). CFD work with Fluent is focused on optimizing inlet and outlet topologies. Understanding the cooling process is sought as well; Fluent CFD transient models are simulated in this way as well. Additionally the effect of filling levels is taken into account leading to a multiphase (fuel oil and air) flow cases where especially heating coupling of both phases is analyzed.   Results show that maximum heat supply needs are around 80kW when the tank temperature is around 60ºC and 70kW when it is around 50ºC. Expectedly the main characteristic of the flow turns out to be the buoyancy driven convective pattern. K-ε turbulence viscous models are applied to both heating and cooling processes showing thermal stratification, especially at the bottom of the tank. Hotter fluid above follows very complex flow patterns. During the heating processes models used predict fairly well mixed and homogenous temperature distribution regardless small stratification at the bottom of the tank. In this way no concrete inlet-outlet configuration shows clear advantages over the rest. Due to the insulation of the tank, low thermal conductivity of the fluid and vast amount of mass present in the tank, the cooling process is slow (fluid average temperature drops around 5.7 ºC from 60ºC in 15 days when the tank is full and ambient temperature is considered to be at -20ºC) and lies somewhere in the middle between the solid rigid and perfect mixture cooling processes. However, due to stratification some parts of the fluid reach minimum admissible temperatures much faster than average temperature does. On the other hand, as expected, air phase acts as an additional thermal resistance; anyhow the cooling process is still faster for lower filling levels than the full one. / El presente proyecto fue propuesto por Sweco Systems para llevar a cabo un estudio relacionado con el sistema de calefacción de una cisterna o tanque de almacenamiento de fuel oil circular. Dicho tanque tiene 23 m de diámetro  y 18 m de altura con una capacidad de almacenamiento de alrededor de 7500 m3 de Eo5 fuel oil pesado. El contenido mantenerse a una temperatura mínima de 50 ºC de manera que el fuel oil es suficientemente fluido para que las labores de operación puedan ser ejecutadas adecuadamente. De hecho, estos tipos de fuel oil pesado tienen altas viscosidades a bajas temperaturas y, por tanto, tanto los sistemas de calefacción y como el de bombeo pueden verse comprometidosr a temperaturas por debajo del pour point. Con este fin un sistema de calefacción es instalado para mantener el fluido suficientemente caliente. Hasta el momento, el sistema era operado por un quemador de fuel, sin embargo, hay planes que éste sea sustituido por un combo intercambiador de calor-District Heating. Por lo tanto, principalmente son estudiadas las necesidades de calefacción así como los flujos térmicos y fluidos. Se estudian las fronteras del tanque, y sus respectivas resistencias térmicas son calculadas con el fin de dimensionar la capacidad necesaria de suministro de calor. El estudio implica Elementos Finitos (Comsol Multiphysics) y Volúmenes Finitos (Fluent) para elaborar análisis estacionarios de transferencia de calor por conducción en algunos casos. Existen puentes térmicos en las paredes y su importancia es también anallizada. Posteriormente se estudian tanto los procesos de calentamiento y enfriamiento del fuel oil utilizando diversas estrategias: modelos básicos y Dinámica de Fluidos Computacional (CFD). El trabajo con CFD se centra en la optimización de topologías de entradas y salidas del sistema. También es solicitado entender el proceso de enfriamiento; En este sentido, se simulan modelos CFD transitorios de Fluent. Además, el efecto de los niveles de llenado se tiene en cuenta dando lugar a estudios de flujo multifase (fuel oil y aire), haciendo hincapié en el análisis de acoplamiento de transferencia de calor entre las dos fases. Los resultados muestran que las necesidades de calefacción máximas son de alrededor de 80kW cuando la temperatura del tanque es de alrededor de 60 º C y 70kW cuando está alrededor de 50 ºC. Como era de esperar, la principal característica de este tipo de flujos es la convección natural resultante de las fuerzas de flotabilidad. Se aplican modelos turbulentos k-ε a los procesos de calentamiento y enfriamiento, mostrando estratificación térmica, sobre todo en la parte inferior de la cisterna. El líquido más caliente que se sitúa encima muestra complejos patrones de flujo. Durante los procesos de calentamiento, los modelos utilizados predicen un buen mezclado y distribución homogénea de la temperatura independientemente de esta pequeña estratificación en la parte inferior de la cisterna. De esta manera, ninguna concreta configuración de entradas-salidas simuladas muestra claras ventajas sobre el resto. Debido al aislamiento de la cisterna, la baja conductividad térmica del fluido y la gran cantidad de masa presente en el tanque el proceso de enfriamiento es lento (la temperatura media del fluido desciende 5.7 º C desde 60 º C en 15 días cuando el tanque está lleno y la temperatura ambiente es de -20 º C) y se encuentra en algún lugar en medio de los procesos de enfriamiento del sólido rígido y perfecta mezcla. Sin embargo, debido a la estratificación, algunas partes el líquido alcanzan la temperatura mínima admisible mucho más rápido que la media de temperatura. Por otra parte, como se esperaba, la fase de aire actúa como una resistencia térmica adicional, de todos modos, el proceso de enfriamiento es aún más rápido para niveles de llenado más bajos que el lleno.