Compact device for mass transfer between liquid films and vapour or gas

University Carlos III of Madrid (Spain) offers a method and device for mass transfer between liquid and vapour or gas. Applications to absorbers and desorbers in absorption chiller technology, evaporators, condensers and chemical reactors. The research group is trying to find companies for further development, commercial viability assessment and commercial exploitation

Dispositivo compacto de aplicación en tecnología frigorífica de absorción, evaporadores, condensadores y reactores químicos

La Universidad Carlos III de Madrid ofrece un dispositivo de transferencia de masa entre fases gaseosa y líquida, para tecnología frigorífica de absorción. La tecnología mejora la eficiencia y reduce significativamente el volumen de elementos como los absorbedores y desorbedores de máquinas frigoríficas de absorción, y otros dispositivos de transferencia de masa. Se solicita colaboración para profundizar en el desarrollo, realizar un estudio de viabilidad técnico-económica para su explotación comercial

Approximate analytic temperature distribution and efficiency for annular fins of uniform thickness

The salient feature in the quasi one-dimensional differential equation for annular fins of uniform thickness is without question the presence of the variable coefficient 1/r multiplying the first order derivative, dT /dr. A good-natured manipulation of the variable coefficient 1/r is the principal objective of the present work. Specifically, the manipulation applies the mean value theorem for integration to 1/r in the proper fin domain extending from the inner radius r¹ to the outer radius r². It is demonstrated that approximate analytic temperature profiles and heat transfer rates of good quality are easily obtainable without resorting to the exact analytic temperature distribution and heat transfer rate embodying modified Bessel functions. For enhanced visualization, the computed temperature profiles, tip temperatures and fin efficiencies of approximate nature are graphed and tabulated for realistic combinations of the normalized radii ratio c and the thermo-geometric fin parameter ξ of interest in thermal engineering applicationsPublicad

4th International Workshop on Hydrogen Infrastructure and Transportation

The 4th International Workshop on Hydrogen Infrastructure and Transportation took place in Egmond aan Zee (The Netherlands) on 24-25 May 2016. The workshop was conducted by the European Commission's Joint Research Centre and supported by US DOE, NOW from Germany and NEDO from Japan. The International Workshops on Hydrogen Infrastructure and Transportation aim at guiding and supporting industry to accelerate and facilitate the roll-out and commercialization of hydrogen refuelling stations. The 4th International Workshop has offered a forum for exchange of information through sharing experiences, best practices and progress on key and relevant issues facing hydrogen infrastructure deployment for fuel cell electric vehicles. Discussion topics included fuelling, H2 quality and metering, as well as utilization experiences of hydrogen refuelling stations. The series of international workshops is recognised by the main hydrogen infrastructure stakeholders as an interesting initiative because it brings together policy makers, and technical experts from industry and research organisations. While participation to the workshop is upon invitation and distribution of the material presented is limited to the attendants; it is nevertheless important to make the most relevant information publicly available. Therefore this JRC Report contains a compilation of the main information shared at the 4th International Workshop on Hydrogen Infrastructure and Transportation so that it can be used as reference material. The workshop was divided into topical sessions. The first session covered General Country/Region Overviews on policy initiatives, R&D, demonstration and deployment, investments and funding, etc. regarding hydrogen and fuel cell infrastructure. The other sessions aimed at discussing technical topics considered critical for the hydrogen infrastructure. In this report the most relevant information of each of the countries' overviews and the outcomes the four technical sessions are summarised.JRC.C.1-Energy Storag

La hipoxia induce la activación de los macrófagos potenciando la fagocitosis y la presentación antigénica, a través de la producción de IFN- gamma, mediada por el factor de transcripción HIF-1 alfa

Tesis doctoral inédita. Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Biología Molecular. Fecha de lectura: 29-06-0

Desarrollo y validación de una nueva técnica de ensayo no destructivo basada en el potencial termoeléctrico para el conocimiento del envejecimiento de los aceros de vasija de reactores nucleares

La vasija de presión del reactor (RPV) en los reactores de agua ligera (LWR) es un componente clave para la operación segura de una central nuclear. La vasija de presión forma parte de la contención del reactor y su vida delimita, en gran medida, la vida de la planta. En los materiales de la PRV el efecto más importante de deterioro por la radiación es la disminución de la ductilidad de los aspectos que la forma. Los métodos tradicionales para determinar el comportamiento mecánico de la RPV son el ensayo de tracción y el d eimpacto Charpy, a partir de los qué puede calcularse la temperatura de transición de dúctil a frágil (DBTT). En los aceros ferríticos utilizados en las vasijas de las centrales nucleares, la DBTT aumenta con la fluencia neutrónica. Los ensayos Charpy y de tracción son destructivos; en cambio la posibilidad de utilizar ensayos no destructivos facilitaría la vigilancia de los materiales que forman la vasija del reactor; por una parte haciendo posible inspección in-situ, y por otra beneficiando a aquellos programas de vigilancia que cuentan con una cantidad insuficiente de manterial. En el marco de esta Tesis Doctoral se ha desarrollado un equipo, llamado STEAM (Seebeck and Thomson Effects on Aged Material), para evaluar de una forma no destructiva el estado de fragilización de aceros ferríticos. Esta técnica se basa en la medida del potecial termoeléctrico, el cual es una característica del material y cambia cuando el acero se deteriora. El objetivo fundamental del estudio llevado a cabo en esta tesis es correlacionar los resultados de los ensayos mecánicos convencionales y STEAM con el cambio en las propiedades mecáncias debido a la irradiación neutrónica. Con este fin, se han utilizado diferentes grupos de aleaciones que cubren un amplio espectro de aceros ferríticos. Dichas aleacciones se caracterizan por una variación paramétrica en el contenido de impurezas tales como fósforo, cobre, y níquel, elementos que se sabe desempeñan un papel significativo en las propiedades y la degradación de los materiales. La técnica STEAM se ha aplicado con éxito para la determinación del daño neutrónico en aceros y aleacciones irradiados en el Reactor de Alto Flujo de Petten (Países Bajos). Los resultados de este análisis permitirán una mejor comprensión del papel y la influencia del cobre, níquel y fósforo en las propiedades mecánicas de los aceros. Además hará posible el desarrollo de la técnica STEAM para su aplicación en la evaluación del daño por irradiación

Compressible-gas two-fluid modeling of isolated bubbles in a vertically vibrated fluidized bed and comparison with experiments

In this work the size and motion of isolated bubbles in a vertically vibrated fluidized bed are numerically investigated by means of two-fluid model simulations. The oscillations of the bed bulk and the bubble diameter and velocity are compared with experimental results of a pseudo-2D bed using an averaging of cycles method to account for the intrinsic unsteadiness caused by vibration. The effects of gas compressibility and the air plenum of the vibrated bed are also numerically investigated. The results show that the two-fluid model simulations resorting to a compressible gas model are able to reproduce both the cyclic compression and expansion of the bed bulk and the bubble oscillations observed in the experiments. In contrast, the simulations with the incompressible gas model fail to reproduce these effects. The presence of the air plenum in the numerical model diminishes the amplitude of the bed and bubble oscillations and improves their resemblance to the experiments. In the simulations with compressible gas, a phase delay is found between the bed displacement and the oscillation of bubble characteristics. In harmony with experiments, the phase delay is smaller in the lower half of the bed (i.e. close to the distributor) than in the upper half. This effect is not reproduced by the simulations with incompressible gas-phase. These results suggest that the phase delay in vibrated beds is caused by the compression of the gas phase, which leads to compression-expansion waves traveling through the bed. The simulations also confirm that the amplitude of vibration influences the magnitude of the bubble diameter and velocity oscillations, whereas the delay of the bubble characteristics is mainly affected by the bed vibration frequency.This work has been partially funded by the Spanish Government (Project DPI2009-10518) and the Autonomous Community of Madrid (Project S2009/ENE-1660).Publicad

Bulk oscillation and velocity wave propagation in a vibrated fluidized bed at minimum fluidization conditions

The present work experimentally characterizes the behavior of the bed bulk and the solids velocity in a vertically vibrated pseudo-2D fluidized bed operated at minimum fluidization conditions. Measurements are undertaken combining Digital Image Analysis (DIA) and Particle Image Velocimetry (PIV). Vibration at different amplitudes and frequencies is applied to the bed by the use of two vibro-motors symmetrically disposed at both sides of the bed vessel. The results show that both the center of mass of the bed and the bed surface oscillate with a frequency equal to that of the bed vessel. The bed surface oscillates in opposition of phase with the bed vessel, which reflects a cyclic compression and expansion of the bed bulk. The average solids velocity at each oscillation phase clearly shows that there exists a compression wave, produced by the impact of the bed bulk with the gas distributor, and an expansion wave, produced by the expansion of the bed bulk. Both waves travel upwards the bed bulk perturbing the velocity of particles along the bed height The waves span all the bed width and separate the bed bulk into two clearly distinguishable regions with different relative velocities. When the particles belonging to the region under the wave move upwards, the particles in the region above the wave move downwards and vice versa. The results also reveal that the compression wave generated at the bottom of the bed propagates at a velocity similar to the reported velocity of sound inside a fluidized bed. Far from the distributor, this wave velocity resulted to be nearly independent of the vibration amplitude and frequency for the range of conditions tested. These results can be useful for the understanding of the behavior of particles and bubbles in vibrated fluidized beds

MULTIPLE ORIFICE BUBBLE GENERATION IN GAS-SOLID FLUIDIZED BEDS: THE ACTIVATION REGION APPROACH

This work addresses the bubble generation mechanism at multi-orifice distributors in gas-solid fluidized beds (FB). Different measurements techniques such as high speed video camera and Kistler pressure transducers were applied to obtain information from both local, and global bed dynamics. Pressure fluctuation time series are used for dynamic diagnosis of the 2-D facility used during the study. The bed was operated with different distributor plates at several bubbling conditions leading to different bubble flow patterns characterized by digital image analysis of both the dense and the bubble phases. In order to explain the bubble pattern developed within the bed and the measured bubble dynamics, a phenomenological discrete bubble model is used. This model proposes an activation region (AR) mechanism for multi-orifice bubble generation. The underlying hypothesis is that the bubble formation can be placed in a region above the distributor plate where the initial bubble size is the result of the dynamical interaction of neighbour orifices. From the analysis of the experimental results, it is observed how for two different uniform gas distribution across the distributor plate, bubble dynamics interactions play the main role as the driver of the resulting bubble flow pattern developed within the bed. Moreover, when the activation region hypothesis is used as a bubble generation mechanism in a phenomenological discrete bubble model, it is seen that the proposed activation region mechanism, explains the observed bubble generation phenomena at multi-orifice distributors, and leads to a substantial decrease of the computational cost to simulate bubbling FB dynamics

Thermal and mechanical stresses in bayonet tubes of solar central receivers working with molten salt and liquid sodium

One of the most promising technologies for solar thermal power are solar power towers (SPTs), in which direct solar radiation is redirected by heliostats to a receiver located on top of a tower. The technology used by SPT allows obtaining high thermal efficiencies as well as a high number of hours of operation thanks to thermal storage. However, the high thermal gradients to which the receiver is subjected, in addition to the corrosion of the molten solar salt, can cause the rupture of the receiver and this limits the maximum irradiation the receiver can withstand. To overcome this problem there are different strategies, such as the use of working fluids that are less corrosive than molten salts or the development of new designs of the receiver to avoid overheating of the pipes. In this work we analyze the thermal and structural behavior of a new design of SPT receiver in which bayonet tubes are used instead of simple tubes. A bayonet tube consists of a tube inside another one. In the bayonet tube the working fluid first circulates through the inner tube and then through the annular section between the tubes. An eccentric bayonet tube, created by displacing the inner tube with regards the outer tube, reduces the overheating of the fluid and the outer tube wall as will be shown later. Besides, this work also assesses the effect of using either molten salt or liquid sodium as a working fluid on the thermal and structural behavior of the absorber tube. Since the extreme thermal conditions of central receivers preclude a detailed experimental analysis, the analyses of the present work are performed through multi-physics (CFD – FEM) simulations of the working fluid flow in the annular section and the stresses in the outer wall of the bayonet tube, which are the most critical elements of the receiver. In particular, to perform the hydrodynamic and thermal analysis of the fluid section and the outer wall of the tube, the RANS equations of the fluid together with the turbulent RSM model and the head diffusion equation of the wall were solved using ANSYS Fluent v18 CFD code. Boundary conditions of temperature and non-uniform irradiation were selected to represent typical operative conditions of receivers. Subsequently, using the temperature profiles obtained from the CFD simulations for each working fluid, ANSYS Workbench v18 was employed to obtain the thermal and mechanical stresses in the outer tube as a function of its different constraints, including the attachment of the tube. The results obtained with the CFD – FEM simulations show that, regardless of the working fluid, the eccentricity of the bayonet tube decreases local peaks of temperature in the flow and temperature gradients in the outer tube wall, which leads to a reduction of the wall stresses of the SPT receiver. Furthermore, thanks to its high conductivity, liquid sodium is able to yield lower temperature gradients and stresses in the wall, independently of the kind of tube, compared to molten salt