Search results for "Membrane distillation"
showing 10 items of 53 documents
A tool for modelling spacer-filled MD channels based on open source CFD code
2011
ASSESMENT OF TEMPERATURE POLARIZATION IN MEMBRANE DISTILLATION CHANNELS BY LIQUID CRYSTAL THERMOGRAPHY
2014
AbstractThe measurement of local temperature distributions within a membrane distillation (MD) channel is a crucial step for the optimization of the channel and spacer geometry. This information allows the estimation of temperature polarization phenomena, which can dramatically influence the thermal efficiency of the process and the optimal choice of the geometric configuration (net spacer features, channel size, etc.). In the present work, a recently presented experimental technique, based on the use of thermochromic liquid crystals and digital image analysis, has been employed in order to assess the temperature polarization phenomena. The local heat transfer coefficient distribution on th…
A neural network-based optimizing control system for a seawater-desalination solar-powered membrane distillation unit
2013
Abstract Several schemes have been proposed so far for coupling desalination processes with the use of renewable energy. One of their main drawbacks, however, is the nature of the energy source that requires a discontinuous and non-stationary operation, with some control and optimization problems. In the present work, a solar powered membrane distillation system has been used for developing an optimizing control strategy. A neural network (NN) model of the system has been trained and tested using experimental data purposely collected. Afterwards, the NN model has been used for the analysis of the process performance under various operating conditions, namely distillate production versus fee…
Membrane distillation: Solar and waste heat driven demonstration plants for desalination
2013
Abstract The development of small to medium size, autonomous and robust desalination units is needed to establish an independent water supply in remote areas. This is the motivation for research on alternative desalination processes. Membrane distillation (MD) seems to meet the specific requirements very well. This work is focused on experimental studies on full scale demonstration systems, utilizing a parallel multi MD-module setup. Three different plant concepts are introduced, one of them is waste heat driven and two of them are powered by solar thermal collectors. Design parameters and system design are presented. After the analysis of plant operation a comparison among the plants as we…
Development of a Membrane Distillation module for solar energy seawater desalination
2012
Abstract Membrane Distillation (MD) processes are gaining growing interest among novel desalination technologies, in particular for small scale applications also coupled with non-conventional energy sources. In the present work an original laboratory scale planar geometry Membrane Distillation unit was designed, built and tested for future coupling with solar energy. Though conceptually simple, the original geometry was developed in order to allow for multi-stage arrangement, compactness, internal heat recovery and possible integration with a polymeric heat exchanger for final brine heating by means of solar energy or waste heat. The laboratory scale unit was tested in order to investigate …
Evaluation of vapor mass transfer in various membrane distillation configurations: an experimental study
2011
Vapor mass transfer phenomena in four different membrane distillation (MD) configurations were examined through a self-built laboratory scale experimen- tal apparatus: Air Gap MD, Sweeping Gas MD, Vacuum Sweeping Gas MD and Vacuum MD. Vapor fluxes were measured and compared with those predicted by various models, showing that MD performance under usual processing conditions is severely controlled by the permeate side resistance to mass transfer.
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-Ï 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 â¼200 to â¼2000, an interval of great interest in practical MD applications. For both values of θ, CFD predicted steady-state flow for Re up to â¼300, and chaotic flow …
Experimental investigation of two-side heat transfer in spacer-filled channels
2020
Abstract In Membrane Distillation (MD), spacers support the membranes and promote mixing, thus reducing temperature polarization. Their efficient design requires a knowledge of the distribution of the local heat transfer coefficient h and of its dependence on Reynolds number, spacer geometry and flow-spacer relative orientation. In previous work, we applied Thermochromic Liquid Crystals (TLC) and digital image processing to the measurement of h distributions for different spacer configurations; data were used to validate CFD simulations and select turbulence models. For constructive reasons, the test section allowed only one-side heat transfer, while in most MD configurations (e.g. spiral-w…
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…