Una panorámica de la superdotación para el siglo XXI

APORTACIONES:Una panorámica de la superdotación para el siglo XXI. Mª José Iglesias Cortizas,C. Jiménez Fernández, J.E Ferro Fontenla, E. Oliveria, C. Palhares, C. y A.MPorto CastroAPORTACIONES:Una panorámica de la superdotación para el siglo XXI. Mª José Iglesias Cortizas,C. Jiménez Fernández, J.E Ferro Fontenla, E. Oliveria, C. Palhares, C. y A.MPorto Castr

Experimental and Computational Studies of Gas Mixing in Conical Spouted Beds

The residence time distribution data in a conical spouted bed, obtained both from the bed bottom and the bed surface at different radial positions, were analyzed to obtain the mean residence time and the Peclet number. In parallel, local flow structures of a bed with the same dimensions and operating conditions as in the experiment were generated from the computational fluid dynamics (CFD) simulation using the FLUENT codes, and then were used for the simulation of gas dispersion. The results show that CFD simulations agree reasonably well with experiments. The radial distribution of the Peclet number is quite complex, with a maximum value at r=0.135 m under three operating conditions investigated

Fluidized Bed Membrane Reactor for Steam Reforming of Higher Hydrocarbons: Model Sensitivity

A fluidized bed membrane reactor (FBMR) was built and operated at temperatures \u3c600°C to reform higher hydrocarbons like propane and heptane. A two-phase reactor model is utilized to simulate the FBMR with hydrogen withdrawn from both phases. The superficial gas velocities in the reactor change because of variations in molar flow due to reaction and hydrogen withdrawal through the membranes, as well as variations in temperature, pressure and cross-sectional area. Sensitivity studies show that the FBMR performance is primarily controlled by chemical equilibrium and hydrogen permeation through the membranes, while being insensitive to errors in accurately characterizing the chemical kinetics and hydrodynamics

The future of evapotranspiration : global requirements for ecosystem functioning, carbon and climate feedbacks, agricultural management, and water resources

The fate of the terrestrial biosphere is highly uncertain given recent and projected changes in climate. This is especially acute for impacts associated with changes in drought frequency and intensity on the distribution and timing of water availability. The development of effective adaptation strategies for these emerging threats to food and water security are compromised by limitations in our understanding of how natural and managed ecosystems are responding to changing hydrological and climatological regimes. This information gap is exacerbated by insufficient monitoring capabilities from local to global scales. Here, we describe how evapotranspiration (ET) represents the key variable in linking ecosystem functioning, carbon and climate feedbacks, agricultural management, and water resources, and highlight both the outstanding science and applications questions and the actions, especially from a space-based perspective, necessary to advance them

Modeling of an Interconnected Fluidized Bed Reactor for Chemical Looping Combustion

Chemical Looping Combustion (CLC) is comprised of two reactors, in which direct contact between air and fuel is avoided. A metal oxide, as oxygen carrier, transports oxygen from the air reactor to the fuel reactor while circulating between them. Based on the hydrodynamics coupled with reaction kinetics of oxygen carrier from the literature, a model for an interconnected fluidized bed reactor has been developed to optimize the design and operation of the reactor system. The model considers the chemical reaction of a single particle and a particle population balance for the calculation of bed particle conversion. The core-annulus and two-phase hydrodynamic models are assumed for the air and fuel reactors, respectively. Predictions of the oxygen emission, particle conversion and fuel conversion efficiency under different operating conditions are presented for a pilot scale CLC reactor system

Cold Modelling of an Internally Circulating Fluidized Bed Membrane Reactor

A novel fluidized bed membrane reactor with internal catalyst circulation is being developed for the production of high-purity H2 from an autothermal reformer. In order to provide guidance to pilot reactor testing, a cold model was built to study the influence of reactor configuration on hydrodynamics and catalyst circulation. It was found that catalyst circulation was reproducible, but that parallel non-communicating flow channels could lead to flow instability. Solids circulation was found to be adequate for design of the autothermal reformer

Improved gas-solid mixing and mass transfer in a pulsed fluidized bed of biomass with tapered bottom

To improve fluidization quality and mass transfer rate of biomass fluidized beds with pulsed gas flow, an existing fluidized bed with rectangular cross-section area was modified with the insertion of a tapered bottom section such that dead zones observed in the original design could be eliminated. Batch drying tests were performed as an indirect indicator of gas-solid contact efficiency and mass transfer performance. Compared to the original design, biomass particles could be fluidized at a wider range of gas pulsation frequencies with significantly reduced channeling and gas bypassing in the new tapered design. Faster drying and thus improved mass transfer were also observed in the tapered bed, as reflected by both the instantaneous drying rate and final moisture content of the sample. A simple particle drying model was applied to fit measured drying curve, and the results showed that under the same operating condition fluidized bed with a tapered bottom had a higher effective vapor diffusion coefficient compared to the original design