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[en] The goal of this laboratory/university collaboration of coupled computational and experimental studies is the improvement of predictive methods for supercritical-pressure reactors. The general objective is to develop supporting knowledge needed of advanced computational techniques for the technology development of the concepts and their safety systems.
[en] This review analyzes the studies and developments of technologies based on the use of supercritical fluids for the micronization of polymer particles and the formation of efficient powder polymer coatings. Potential advantages of supercritical fluid technologies which combine different stages of formation of powder coatings in a unified flowsheet are considered. Possible further trends in scientific and engineering research are identified. A growth in the global market of powder coatings by 2020 is forecasted.
[en] This study affords the numerical solution of the mixing of a submerged turbulent jet under supercritical conditions and near-critical conditions. Turbulence plays a very important role in the behaviour of chemical engineering equipment. An accurate prediction of the turbulence at supercritical conditions with low computational cost is crucial in designing new processes such as reactions in supercritical media, high pressure separation processes, nanomaterials processing and heterogeneous catalysis. At high-pressure, the flow cannot be modelled accurately using the ideal-gas assumption. Therefore, the real gas models must be used in order to solve accurately the fluid flow and heat transfer problems where the working fluid behaviour deviate seriously from the ideal-gas assumption. The jet structure has three parts clearly distinguished: the injection, the transition and the fully developed jet. Once the flow is dominated by the turbulent eddies of the shear layer, the flow is fully developed and the radial profiles match a similarity profile. This work reports the state of the project that is not completed and is being processed now. This work is devoted to establish the distance downstream from the injector where the jet become self-preserving and the shape of the similarity profiles. This system is of interest in the design of supercritical reactor inlets, where two streams should be mixed in the shortest length, or mixing conditions strongly affect the behaviour of the processes. The numerical results have been validated with experimental measurements made in the jet mixing region. The radial profiles for average velocity, density and temperature are analyzed. The parameters of the profile that match better the numerical results are summarized in Table 1. The density requires a lower value of n than these for velocity and temperature, which reflect smoother profiles. These conclusions are in good agreement with the results from Oschwald and Schik. (author)
[en] An experimental loop operating with water at supercritical conditions (25MPa, 600 .deg. C in the test section) is designed for operation in the research reactor LVR-15 in UJV Rez, Czech Republic. The loop should serve as an experimental facility for corrosion tests of materials for in-core as well as out-of-core structures, for testing and optimization of suitable water chemistry for a future HPLWR and for studies of radiolysis of water at supercritical conditions, which remains the domain where very few experimental data are available. At present, final necessary calculations (thermalhydraulic, neutronic, strength) are being performed on the irradiation channel, which is the most challenging part of the loop. The concept of the primary and auxiliary circuits has been completed. The design of the loop shall be finished in the course of the year 2007 to start the construction, out-of-pile testing to verify proper functioning of all systems and as such to be ready for in-pile tests by the end of the HPLWR Phase 2 European project by the end of 2009
[en] The thermal and caloric equations of state, composition, and conductivity of a supercritical beryllium vapor are calculated using the earlier proposed “3+” chemical model, which incorporates atoms, electrons, ions, and electron jellium with allowance for interatomic and intercharge interactions. The introduction of an electron jellium makes it possible to describe the pressure-induced ionization and explain the increase in the conductivity of beryllium vapor under compression. The cohesive bond of atoms caused by the electron jellium compensates for interactions when calculating the composition and reduces the effect of intercharge interactions on the equation of state. The parameters of the beryllium critical point and the applicability domain of the model are discussed.
[en] A method is proposed to correlate and to predict the solubilities of pure solids in supercritical gases. The method is based on a very simple thermodynamic model which links the properties of pure components to the enhancement factor E. The only parameters of pure solids required in order to evaluate their solubilities in compressed gases are density, melting point and vapor pressure. According to the proposed method, each supercritical solvent reserves an 'ad hoc' rule. The reliability of the method was tested for several polar and non polar solids in four supercritical solvent (ethane, CO2, CHF3 and CCIF3). Some other equilibrium data pertaining to the solubility of solid hydrocarbons and caffeine in supercritical CO2 are also considered
[it]E' proposto un metodo per correlare e predire la solubilita' dei solidi puri in gas supercritici. Il metodo e' basato su un modello termodinamico che utilizza come dati di ingresso soltanto il punto di fusione ela tensione di vapore del solido. In base al metodo proposto vengono calcolate le solubilita' di alcuni solidi polari e non polari in quattro solventi suopercritici: etano, anidride carbonica CHF3 e CCIF3. Inoltre, una nota formula di letteratura che lega la solubilita' dei solidi alla densita' del solvente supercritico e' giustificata in base al modello termodinamico proposto
[en] A simple model to study thermal-hydraulic stability of a heated cannel under supercritical conditions is presented. Single cannel stability analysis for the SCWR (Supercritical Water Cooled Reactor) design was performed. The drastic change of fluid density in the reactor core of a SCWR may induce DWO (Density Wave Oscillations) similar to those observed in BWRs. Due to the similarities between subcritical and supercritical systems we may treat the supercritical fluid as a pseudo two-phase system. Thus, we may extend the modeling approach often used for boiling flow stability analysis to supercritical pressure operation conditions. The model developed in this work take into account three regions: a heavy fluid region, similar to an incompressible liquid; a zone where a heavy fluid and a light fluid coexist, similar to two-phase mixture; and a light fluid region which behaves like superheated steam. It was used the homogeneous equilibrium model (HEM) for the pseudo boiling zone, and the ideal gas model for the pseudo superheated steam zone. System stability maps were obtained using linear stability analysis in the frequency domain. Two possible instability mechanisms are observed: DWO and excursive Ledinegg instabilities. Also, a sensitivity analysis showed that frictions in pseudo superheated steam zone, together with acceleration effect, are the most destabilizing effects. On the other hand, frictions in pseudo liquid zone are the most important stabilizing effect.
[es]Se presenta un modelo simplificado para el estudio de la estabilidad termohidraulica de un canal uniformemente calefaccionado y refrigerado por un fluido supercritico. Dicho modelo se utilizo para analizar la estabilidad de un canal sujeto a condiciones similares a las encontradas en el nucleo de un reactor refrigerado por agua supercritica. La gran disminucion de la densidad del fluido en el nucleo de este reactor es una fuente potencial para la aparicion de oscilaciones por ondas de densidad, similares a las observadas en BWRs. Debido a la similitud en el comportamiento de ambos sistemas, es posible tratar al fluido supercritico como un pseudo-sistema en ebullicion. Este tratamiento permite extender un modelo ampliamente utilizado en el estudio de inestabilidades de sistemas en ebullicion, a condiciones de operacion supercriticas. El modelo desarrollado en este trabajo contempla entonces tres regiones: una region compuesta por un fluido denso, similar a un liquido incompresible; una zona en la que coexisten un fluido denso y uno liviano, similar a una mezcla de fases; y una region compuesta por un fluido liviano que se comporta como vapor sobrecalentado. Se aplico el modelo homogeneo (HEM- Homogeneous Equilibrium Model) para la zona de pseudo-ebullicion, y el modelo de gas ideal para la zona de pseudo-sobrecalentamiento. Se realizo un analisis de estabilidad lineal en el dominio de la frecuencia que permitio obtener los mapas de estabilidad del sistema. En dichos mapas se observa la posible ocurrencia de dos mecanismos de inestabilidad: oscilaciones por ondas de densidad (o DWO por sus siglas en ingles) e inestabilidades excursivas de Ledinegg. Asimismo, un analisis de sensibilidad muestra que el efecto de las fricciones en la zona de pseudo-vapor sobrecalentado, junto al efecto de la aceleracion, son las contribuciones que mas desestabilizan al sistema. Mientras que las fricciones en la zona de pseudo-liquido subenfriado constituyen el efecto estabilizador mas importante.
[en] The present paper describes the preliminary compilation, assessment and examination of the SuperCritical Heat Transfer (SCHT) database. The availability and reliability of the SCHT data are discussed. Similarities in thermodynamic supercritical properties and SCHT behaviour of water, CO2 and R-134a have been examined and some tentative conclusions are made. Finally, the future experimental and analytical program at the University of Ottawa is described
[en] Supercritical Fluid Extraction (SFE) technique has been widely used for the extraction of metal ions such as lanthanides and actinides. It is a promising and advance method of separation of metal ions from liquid and solid matrices. SFE technology is particularly attractive for the nuclear industry as it minimizes usage of toxic organic solvent and has the potential to reduce liquid secondary waste generation. The extractability and separation of a metal ion into supercritical phase depends on the solubility of the ligand and metal - ligand complex in Supercritical carbon dioxide (SC-CO_2) medium and transportability of metal-ligand complex. Knowledge of solubility of ligand and metal-ligand complex is essential for the design and operation of a SFE based extraction process. Our studies with various trialkyl phosphates have established that tri-isoamyl phosphate (TiAP) as a potential candidate for fast reactor fuel reprocessing. Hence the solubility of TiAP in SC-CO_2 medium was investigated in the present work
[en] A small-volume cyclone separator with changeable extract collection reservoirs for supercritical fluid extraction has been designed. A method for manufacturing the designed separator by 3D-printing from an available polymer is proposed. It is shown that the designed small-volume separator allows a greater extract recovery compared to a standard large volume cyclone separator in supercritical fluid extraction.