Search results for "Spacer"

Computational Fluid Dynamics of Reverse Electrodialysis Systems

Investigation of Reverse ElectroDialysis Units by Multi-Physical Modelling

2016

Reverse electrodialysis (RED) is an electrochemical membrane process that converts the salinity gradient energy between two solutions into electric current, by using ion exchange membranes. A novel multi-physical approach for RED modelling is proposed. 2-D simulations of one cell pair with tertiary current distribution (Nernst–Plank equation and local electroneutrality) were performed. Moreover, the Donnan exclusion theory was implemented for simulating double layer phenomena. Transport phenomena and electrochemical behavior were well described. The influence of membrane/channel configuration, dilute concentration and feeds velocity on the process performance was assessed. For a dilute conc…

Flow and mass transfer in spacer-filled channels for reverse electrodialysis: a CFD parametrical study

2016

Abstract In reverse electrodialysis (RED) concentration polarization phenomena and pressure drop affect strongly the power output obtainable; therefore the channel geometry has a crucial impact on the system optimization. Both overlapped and woven spacers are commonly commercialised and adopted for RED experiments; the latter exhibit some potential advantages, such as better mixing and lower shadow effect, but they have been poorly investigated in the literature so far. In this work, computational fluid dynamics was used to predict fluid flow and mass transfer in spacer-filled channels for RED applications. A parametric analysis for different spacer geometries was carried out: woven (w) and…

CFD analysis of the fluid flow behavior in a reverse electrodialysis stack

2012

Salinity Gradient Power by Reverse Electrodialysis (SGP-RE) technology allows the production of electricity from the different chemical potentials of two differently concentrated salty solutions flowing in alternate channels suitably separated by selective ion exchange membranes. In SGP-RE, as well as in conventional ElectroDialysis (ED) technology, the process performance dramatically depends on the stack geometry and the internal fluid dynamics conditions: optimizing the system geometry in order to guarantee lower pressure drops (DP) and uniform flow rates distribution within the channels is a topic of primary importance. Although literature studies on Computational Fluid Dynamics (CFD) a…

Characterization of membrane-spacer industrial distillers using thermochromic liquid crystals

2011

Pressure drop in woven-spacer-filled channels for reverse electrodialysis: CFD prediction and experimental validation

2015

Reverse electrodialysis (RED) is a promising technology for electric power generation by the chemical potential difference of two salt solutions within a stack equipped by selective ionexchange membranes (salinity gradient energy). Mechanical energy is required for pumping the feed solutions, which can reduce dramatically the net power output. In this work Computational Fluid Dynamics (CFD) simulations of spacer-filled channels for RED were carried out in parallel with an experimental campaign focused on the collection of data for model validation.

CFD prediction of scalar transport in thin channels for reverse electrodialysis

2014

Reverse ElectroDialysis (RED) is a very promising technology allowing the electrochemical potential difference of a salinity gradient to be directly converted into electric energy. The fluid dynamics optimization of the thin channels used in RED is still an open problem. The present preliminary work focuses on the Computational Fluid Dynamics (CFD) simulation of the flow and concentration fields in these channels. In particular three different configurations were investigated: a channel unprovided with a spacer (empty channel) and two channels filled with spacers, one made of overlapped filaments the other of woven filaments. The transport of two passive scalars, representative of the ions …

Cover Crop Impact on Soil Organic Carbon, Nitrogen Dynamics and Microbial Diversity in a Mediterranean Semiarid Vineyard

2020

Cover crop (CC) management in vineyards increases sustainability by improving soil chemical and biological fertility, but knowledge on its effects in semiarid soils is lacking. This study evaluated the effect of leguminous CC management on soil organic carbon (SOC) sequestration, soil nitrate content and microbial diversity in a semiarid vineyard, in comparison to conventional tillage (CT). SOC and nitrate were monitored during vine-growing season

Studies on the response of soil microflora to the application of the fungicide fenhexamid

2007

The aim of this work was to evaluate the impact of the fungicide fenhexamid (FEX) on the genetic structure of soil bacterial communities using the Ribosomal Intergenic Spacer Analysis molecular technique. Using real-time PCR, we also tried to quantify the pcaH sequences which encode the dioxygenases involved in the degradation process of a variety of aromatic compounds. Soil taken from a vineyard in the Etna Park (Sicily, Italy) was treated with FEX in the ratio 2 µg g-1 soil every 7 days, the process being repeated four times. The analyses were carried out before treatment and 7 days after each further application of FEX. At the same time, the degradation rate was evaluated. The use of FEX…

Sampling strategy in molecular microbial ecology: influence of soil sample size on DNA fingerprinting analysis of fungal and bacterial communities.

2003

Assessing soil microbial community structure by the use of molecular techniques requires a satisfactory sampling strategy that takes into account the high microbial diversity and the heterogeneous distribution of microorganisms in the soil matrix. The influence of the sample size of three different soil types (sand, silt and clay soils) on the DNA yield and analysis of bacterial and fungal community structure were investigated. Six sample sizes from 0.125 g to 4 g were evaluated. The genetic community structure was assessed by automated ribosomal intergenic spacer analysis (A-RISA fingerprint). Variations between bacterial (B-ARISA) and fungal (F-ARISA) community structure were quantified b…