Search results for " Membrane Distillation"

A tool for modelling spacer-filled MD channels based on open source CFD code

2011

Unsteadiness and transition to turbulence in woven spacer filled channels for Membrane Distillation

2017

To characterize the performance of Membrane Distillation (MD) modules, channels filled with woven spacers were investigated by Computational Fluid Dynamics (including Direct Numerical Simulations and the use of the SST k-ω turbulence model) and by parallel experiments with Thermochromic Liquid Crystals. The cases considered here regard mutually orthogonal filaments with a spacer pitch to channel height ratio P/H=2, two spacer orientations θ with respect to the main flow (0° and 45°), and bulk Reynolds numbers Re from ∼200 to ∼2000, an interval of great interest in practical MD applications. For both values of θ, CFD predicted steady-state flow for Re up to ∼300, and chaotic flow …

Design, construction and operational results of a pilot plant for the treatment and valorization of pickling waste solutions

2021

An innovative hybrid technology for both minimizing the waste production and optimizing the pickling process through the continuous control of pickling baths composition has been proposed by means of a pilot-plant installed at the Tecnozinco Srl, Carini (PA) hot-dip galvanizing plant. The recovery process has been accomplished by coupling a diffusion dialysis (DD), where HCl is recovered, a membrane distillation (MD), where HCl is concentrated, and a reactive precipitation (RP), where metal ions are recovered as iron hydroxide and ammonium/zinc chloride solution, to be used in the fluxing baths of the plant. The pilot plant was commissioned and operated using synthetic HCl solutions first a…

Effective recovery of HCl and metals from pickling solutions by cutting-edge membrane technologies

2018

The pickling process is an essential step in the hot-dip galvanizing process.It is performed by immersing manufacturedsteel pieces inacid bathsin order todissolve the oxidized layers. During the pickling process, acid attacks metal oxides on the surface, dissolving them in the pickling bath. Thus, the efficiency of the pickling liquor decreases due to the accumulation of metal salts and the consumption of free acid in the solution. When hydrochloric acid is used,ferrous chloride is producedduring the pickling treatment, reaching concentrations up to 250 g/l, while the acid concentration decreases by 75-85%. A pickling bath in this condition is considered spent [1] due to thevery low picklin…

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…

How spacer geometry can affect the Thermo-Fluid Dynamics of a Membrane Distillation module

2009

Membrane Distillation efficiency increase by enhanced heat transfer

2009

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…

Experimental and computational investigation of heat transfer in channels filled by woven spacers

2017

Abstract Models of woven-type spacer-filled channels were investigated by Computational Fluid Dynamics (CFD) and parallel experiments in order to characterize the performance of Membrane Distillation (MD) modules. The case of overlapped spacers was analysed in a companion paper. Experiments were based on a non-intrusive technique using Thermochromic Liquid Crystals (TLC) and digital image processing, and provided the distribution of the local convective heat transfer coefficient on a thermally active wall. CFD simulations ranged from steady-state conditions to unsteady and early turbulent flow, covering a Reynolds number interval of great practical interest in real MD applications. A specif…

Investigation of heat transfer in spacer-filled channels by experiments and direct numerical simulations

2016

Abstract The analysis of flow fields and heat or mass transfer phenomena is of great importance in the optimum design of spacer-filled channel geometries for a variety of membrane-based processes. In the present work, models of spacer-filled channels often adopted in Membrane Distillation are simultaneously investigated by experiments and Computational Fluid Dynamics (CFD). Experiments rely on a non-intrusive technique, based on the use of Thermochromic Liquid Crystals (TLC) and digital image processing, and provide the local distribution of the convective heat transfer coefficient on a thermally active wall. CFD relies on steady-state (laminar flow) simulations in the lower end of the Reyn…