Search results for "IMPIANTI"
showing 10 items of 797 documents
Membrane Deformation and Its Effects on Flow and Mass Transfer in the Electromembrane Processes
2019
In the membrane processes, a trans-membrane pressure (TMP) may arise due to design features or operating conditions. In most applications, stacks for electrodialysis (ED) or reverse electrodialysis (RED) operate at low TMP (<
Optimization of the first wall for the DEMO water cooled lithium lead blanket
2015
The maximum heat load capacity of a DEMO First Wall (FW) of reasonable cost may impact the decision of the implementation of limiters in DEMO. An estimate of the engineering limit of the FW heat load capacity is an essential input for this decision. This paper describes the work performed to optimize the FW of the Water Cooled Lithium-Lead (WCLL) blanket concept for DEMO fusion reactor in order to increase its maximum heat load capacity. The optimization is based on the use of water at typical Pressurised Water Reactors conditions as coolant. The present WCLL FW with a waved plasma-faced surface and with circular channels was studied and the heat load limit has been predicted with FEM analy…
A probabilistic approach to radiant field modeling in dense particulate systems
2016
Radiant field distribution is an important modeling issue in many systems of practical interest, such as photo-bioreactors for algae growth and heterogeneous photo-catalytic reactors for water detoxification.In this work, a simple radiant field model suitable for dispersed systems showing particle size distributions, is proposed for both dilute and dense two-phase systems. Its main features are: (i) only physical, independently assessable parameters are involved and (ii) its simplicity allows a closed form solution, which makes it suitable for inclusion in a complete photo-reactor model, where also kinetic and fluid dynamic sub-models play a role. A similar model can be derived by making us…
Multi-physical modelling of reverse electrodialysis
2017
Abstract Reverse electrodialysis (RED) is an electrochemical membrane process that directly converts the energy associated with the concentration difference between two salt solutions into electrical energy by means of a selective controlled mixing. The physics of RED involves the interaction of several phenomena of different nature and space-time scales. Therefore, mathematical modelling and numerical simulation tools are crucial for performance prediction. In this work, a multi-physical modelling approach for the simulation of RED units was developed. A periodic portion of a single cell pair was simulated in two dimensions. Fluid dynamics was simulated by the Navier-Stokes and continuity …
On the measurement of local gas hold-up, interfacial area and bubble size distribution in gas–liquid contactors via light sheet and image analysis: I…
2013
Abstract In this work a novel experimental technique for measuring local gas hold-up, interfacial area and bubble size distribution, in gas–liquid systems is proposed. The technique is based on advanced Image Processing coupled with experimental set-ups typically available for Particle Image Velocimetry. A fluorescent dye dissolved in the liquid phase allows to identify in-plane bubbles among all visible bubbles in the images. To this end, a suitable algorithm is proposed. The raw data so obtained are processed by previously developed statistical methods that result in a reliable reconstruction of actual dispersion properties. The technique is applied to the case of a gas-dispersed mechanic…
Experiments and predictions of the transition of the flow pattern with impeller clearance in stirred tanks
2001
In the present work, the double- to single-loop flow pattern transition in a stirred vessel equipped with a Rushton turbine is investigated by Laser Doppler anemometry (LDA). In particular, the clearance at which such transition occurs is assessed by comparing axial velocity profiles underneath the impeller. Computational fluid dynamics (CFD) simulations of the same system are carried out, by employing the 'inner-outer' fully predictive computation strategy. The comparison of predicted results with the experimental data collected shows that the transition is well reproduced by simulations. A good agreement on the mean velocities is also observed but for the impeller discharge stream angle t…
A reaction engineering approach to kinetic analysis of photocatalytic reactions in slurry systems
2016
Abstract The knowledge of the rate equation is fundamental for the assessment of the activity of the photocatalytic material and for the study, design and optimization of photocatalytic reactors. In the case of photocatalytic reactions, the local volumetric rate of photon absorption (LVRPA) affects the reaction rate and its inherently uneven distribution within a “slurry” reactor makes complex a correct kinetic analysis. In the present work it is shown which are the critical aspects of the kinetic analysis in slurry reactors and how to carry out photocatalytic experiments to minimize the misinterpretations of the experimental results. In particular, the influence of the type of illumination…
Quasi-isoactinic reactor for photocatalytic kinetics studies
2007
Photochemical reactors characterized by almost uniform values of the local volumetric rate of photon absorption (LVRPA), i.e., quasi-isoactinic photoreactors, are particularly suitable for assessing the influence of radiant field intensity in kinetic studies. In this work, Monte Carlo simulations have been performed to obtain LVRPA values in a flat photoreactor irradiated on both sides. This configuration appears to be particularly suitable for obtaining quasi-isoactinic conditions. The influence of catalyst albedo and scattering phase function is assessed, and the conditions for obtaining iso-actinicity are discussed. Finally, these conditions are related to an easy-to-measure parameter, n…
Solid–Liquid Suspensions in Top-Covered Unbaffled Vessels: Influence of Particle Size, Liquid Viscosity, Impeller Size, and Clearance
2014
Particle suspension in liquids is a unit operation commonly encountered in the process industry. Although it is usually carried out in baffled stirred tanks, there are some specific applications where the presence of baffles may be undesirable. In the present work solid-liquid suspensions are investigated in a radially stirred unbaffled tank provided with a top cover. The minimum impeller speed at which all solid particles get suspended (Njs) and the relevant power requirements (Pjs) are assessed. The dependence of these two parameters on physical properties (liquid viscosity, particle concentration, and size) and system geometrical configurations (impeller diameter and clearance) is invest…
Determination of limiting current density and current efficiency in electrodialysis units
2018
Abstract A crucial parameter for the design and operation of electrodialysis (ED) units is the limiting current density (LCD). This is often identified with the diffusion-limited current density, which corresponds to the complete solute depletion in the layer adjacent to the membrane. Current-voltage curves obtained from measurements with electrodes in contact with the solution (i.e. without membranes) are consistent with this interpretation and exhibit a horizontal plateau identifying LCD. However, real ED systems show more complex behaviours, with a reduced-slope tract instead of a plateau and a third region in which the current increases more markedly (overlimiting current). The phenomen…