Search results for "25"

POWER CONSUMPTION IN UNBAFFLED TANKS: SUB AND SUPER-CRITICAL REGIMES

2013

Unbaffled stirred tanks are increasingly recognized as a viable alternative to common baffled tanks for a range of processes (e.g. crystallization, food and pharmaceutical processes, etc) where the presence of baffles is undesirable for some reason. Also, in the case of bioreactors for animal cell cultivation, where cell damage is mainly related to bubbles bursts at the air –liquid interface, unbaffled tanks have been shown to be able to provide sufficient mass transfer through the free surface vortex. As a consequence bubble formation and subsequent bursting is conveniently avoided (Scargiali et al., 2012). The same feature clearly makes unbaffled vessels potentially advantageous for any f…

ON THE PERFORMANC E OF A TAYLOR-COUETTE REACTOR FOR NANO-PARTICLE PRECIPITATION

2009

Reattore per la precipitazione di micro e nano-particelle

2009

USE OF SUPERCRITICAL CO2 AS DISSOLVED GAS FOR THE ATOMIZATION OF ETHANOL

2011

Supercritical dissolved gas atomization (SDGA) is an atomization process in which carbon dioxide at temperatures and pressures above its critical point is used as atomizing gas. In this work SDGA has been experimentally studied when ethanol is used as the liquid to be atomized. The spray characteristics in terms of droplets size and distribution have been investigated using a droplet size analyzer based on a laser diffraction method. Very narrow droplet size distributions were produced down to 2.5 μm. The main parameter that influences the droplets size is the gas to liquid mass ratio. From the point of view of the atomization mechanism, mean droplet diameter is mainly influenced by the two…

Reverse electrodialysis with saline waters and concentrated brines: A laboratory investigation towards technology scale-up

2015

Abstract The use of concentrated brines and brackish water as feed solutions in reverse electrodialysis represents a valuable alternative to the use of river/sea water, allowing the enhancement of power output through the increase of driving force and reduction of internal stack resistance. Apart from a number of theoretical works, very few experimental investigations have been performed so far to explore this possibility. In the present work, two RED units of different size were tested using artificial saline solutions. The effects of feed concentration, temperature and flowrate on process performance parameters were analysed, adopting two different sets of membranes. These experiments all…

CFD PREDICTION OF SCALAR TRANPORT 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. Fluid dynamics optimization of the thin channels to be devoted for the RED process 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 and two different spacer (made of either overlapped filaments or woven filaments) filled channels. Two passive scalars were transported along with the water in orde…

CFD simulation of radially stirred baffled and unbaffled tanks

2019

Stirred tanks typically employed in process industries are provided with baffles. Although the presence of baffles is known to guarantee good mixing rates, unbaffled vessels may be compulsory in some applications as crystallization, bioremediation, biotechnology and ore industry. A better understanding of unbaffled stirred vessels flow dynamics may allow (i) a proper design to be performed and (i) conditions/processes where baffle presence can be avoided to be recognized. In the present study, the k-ω SST was used to simulate an unbaffled tank from early to fully turbulent regime (Re≈600-33,000). The unbaffled tank simulated has a diameter T=0.19m and is stirred by a standard six-bladed Rus…

Temperature distribution analysis in spacer filled channels for membrane distillation

2012

Particle Suspension in Vortexing Unbaffled Stirred Tanks

2016

Three-phase processes in which particle suspension has to be achieved in conjunction with gas dispersion are traditionally carried out in sparged, baffled stirred tanks. The operation of such tanks can suffer, however, from particles tending to block the sparger holes. A viable alternative might be provided by uncovered unbaffled stirred tanks (UUSTs), where gas self-injection can occur when the free-surface vortex reaches the impeller blades and gas bubbles begin to be ingested by the liquid. In this work, the particle suspension and liquid aeration performances in three-phase UUSTs were experimentally investigated and compared with relevant literature correlations concerning baffled syste…

A Thermochromic Liquid Crystals Image Analysis technique to investigate temperature polarization in spacer-filled channels for Membrane Distillation

2013

The analysis of flow fields and temperature distributions is of paramount importance in the development and optimization of new spacer-filled channel geometries for Membrane Distillation modules. The literature reports only few studies on the experimental characterization of such channels and, to the authors’ knowledge, none of them presents local information concerning the temperature distribution on the membrane surface. In the present work, a non-intrusive experimental technique named TLC-IA-TP is presented: it is based on the use of Thermochromic Liquid Crystals (TLCs) and digital Image Analysis (IA) and it is applied here for the first time to the analysis of Temperature Polarization (…