Search results for "Anti nuclear"
showing 10 items of 415 documents
CFD parametrical study of the spacer geometry for Membrane Distillation
Membrane Distillation (MD) is a thermal process that separates water from aqueous solutions containing non-volatile components such as salt. Water vapor from the hot feed channel permeates through a hydrophobic membrane thanks to a partial pressure gradient, and condenses in the cool channel. One of the main advantages of MD is the easy coupling with renewable resources, as the solar thermal energy. In the various MD configurations developed, net spacers are used in order to support the membrane, thus creating the channels; moreover, they can counteract the side effects of temperature polarization by promoting mixing. However, the presence of the spacer involves an increase of pressure drop…
CFD analysis of mass transfer in spacer-filled channels for reverse electrodialysis
2014
Reverse electrodialysis (RE) is a promising technology for electric power generation by converting the chemical potential difference of a salinity gradient, within a stack equipped by selective ion-exchange membranes. Concentration polarization phenomena and pressure drop affect strongly the power output obtainable; therefore the channel geometry is a fundamental operating parameter for the optimization of the system. In this work, Computational Fluid Dynamic simulations were performed to predict fluid flow and mass transfer in spacer-filled channels for RE applications. A parametric analysis for different spacer geometries was carried out; in particular, woven and non woven spacers were si…
Fluid-structure interaction and flow redistribution in membrane-bounded channels
2019
The hydrodynamics of electrodialysis and reverse electrodialysis is commonly studied by neglecting membrane deformation caused by transmembrane pressure (TMP). However, large frictional pressure drops and differences in fluid velocity or physical properties in adjacent channels may lead to significant TMP values. In previous works, we conducted one-way coupled structural-CFD simulations at the scale of one periodic unit of a profiled membrane/channel assembly and computed its deformation and frictional characteristics as functions of TMP. In this work, a novel fluid&ndash
Modelling and cost analysis of hybrid systems for seawater desalination: Electromembrane pre-treatments for Reverse Osmosis
2019
Abstract The need to reduce energy consumption in seawater Reverse Osmosis (RO) process has pushed research towards the development of new hybrid systems in which, for example, other membrane processes can be used to pre-treat seawater. Electrodialysis (ED) and Reverse Electrodialysis (RED) can act as a pre-desalting step before seawater enters the RO unit, thus leading to an important energy saving in RO. In this work, two coupled models are proposed for the RED-RO and ED-RO systems. Each process model was validated. Then a sensitivity analysis was performed to assess the effect of the integration on the overall process cost saving. The analysis was performed by changing ED or RED voltage …
Experiments and modelling for determining the Limiting Current Density in Electrodialysis units
2018
In the present work, in order to explore such issues on the LCD identification, we performed in-situ measurements with ED units, assessing the influence of operating conditions and validating a purposely implemented process simulator, which was then used for further investigation
Numerical prediction of flow fields in baffled stirred vessels: A comparison of alternative modelling approaches
1998
Abstract Numerical simulations of the flow field in baffled mixing tanks, based on three alternative methods, are presented and discussed. In the first method, the impeller is not explicitly simulated, and its effects are modelled by imposing suitable, empirically derived, boundary conditions to the external flow. In the second method, the whole vessel volume is divided into two concentric, partially overlapping, regions. In the inner region, containing the impeller, the flow field is simulated in the rotating reference frame of the latter, while in the outer region simulations are conducted in the reference frame of the laboratory. Information is iteratively exchanged between the two regio…
CFD analysis of concentration polarization phenomena in spacer-filled channels for Reverse Electro-Dialysis
2012
In this work, carried out within the EU-FP7 funded REAPower project, CFD simulations were carried out in order to study the fluid flow behaviour and mass transport phenomena within spacer-filled channels.
On some issues in the computational modelling of spacer-filled channels for membrane distillation
2017
Abstract This study addresses issues which arise in the computational and experimental modelling of flow and heat/mass transfer in membrane distillation and other processes adopting spacer-filled channels (either planar or spiral wound), but have not been sufficiently clarified in the literature so far. Most of the argumentations presented are based on original computational results obtained by the authors by finite volume simulations; some literature results are also considered. The questions addressed regard the choice of scales for the reduction of data and the definition of dimensionless numbers ( Re , f , Nu , Sh ); the definition of average heat or mass transfer coefficients; the comb…
Effect of membrane profiles on the limiting current density in electrodialysis
2019
In the present work, we experimenrtally investigated the effect of different membrane profiles on the LCD, testing also different operating conditions.
A novel colorimetric experimental technique for the characterisation of metal hydroxides reactive crystallization phenomena
2021
The reactive crystallization of metal hydroxides constitutes a field of raising interest driven by the importance of metals recovery and the wide industrial applications of their hydroxides. A popular example is related to the case of magnesium hydroxide (Mg(OH)2), which is widely employed in the fields of water treatment, desulphurization of fuel gases, pharmaceutical industry, refractory field and flame retardants