Experimental study of concentration polarization in a crossflow reverse osmosis system using Digital Holographic Interferometry

Digital Holographic Interferometry (DHI) has been used to visualize the polarization concentration layer during crossflow RO. This technique is based on the fact that changes in the concentration of the solution produce changes in its refractive index. Therefore, the concentration profile formed due to the polarization phenomenon can be visualized as interference fringes. Experiments with Na2SO4 and NaCl solutions have been carried out. Three variables of the process were studied: crossflow velocity, initial concentration and pressure applied. In each experiment, crossflow velocity was changed every 30min, in an increasing or decreasing sequence. Few minutes after changing the crossflow velocity the steady-state was reached. Interference fringe patterns of the polarization layer and their corresponding concentration profiles, as well as the permeate flux in different experimental conditions, are presented. The major experimental result is the visualization for the first time in situ and in real-time of the polarization layer in a process of crossflow by a non-invasive method. Experimental results show a close relationship among crossflow velocity, permeate flux and polarization layer. Furthermore, experimental maximum concentration values reached at the membrane surface were compared with values calculated by using the film theory approach and a good agreement was obtained.This research has been sponsored by the Plan Nacional de I+D+I CTQ2006-14904 (Ministerio de Ciencia e Innovación) and Generalitat Valenciana, Consellería de Educación (ACOMP/2009/366)

Uso de Google Calendar para la coordinación entre asignaturas del Grado en Ingeniería Química

Uno de los aspectos peor valorados por los estudiantes de las nuevas titulaciones de grado es la coordinación entre asignaturas del mismo curso en cuanto a la distribución de controles y otro tipo de pruebas objetivas a lo largo del cuatrimestre, que afecta a la carga de trabajo no presencial en determinados momentos. En la guía docente de cada asignatura aparece la información sobre las pruebas a realizar dentro de un cronograma aproximado por semanas, y está disponible antes del comienzo del curso. Sin embargo, esa distribución puede variar ligeramente una vez empezado el curso debido a diversos motivos, y no se dispone de la información para todas las asignaturas del cuatrimestre en un mismo documento, lo que facilitaría su visualización. En este trabajo se propone el uso de la herramienta Google Calendar con el objetivo de tener un mayor control de este aspecto y poder detectar y corregir conflictos que puedan surgir, aplicándolo al Grado en Ingeniería Química

Coordinación para la planificación de la próxima acreditación del Grado en Ingeniería Química

El Grado en Ingeniería Química de la Universidad de Alicante, como muchas otras titulaciones, se encuentra en proceso de renovación de la acreditación nacional. La preparación para ello ha requerido un gran esfuerzo y coordinación de los profesores de la titulación, y el presente trabajo se ha desarrollado especialmente para afrontar el último tramo previo a la presentación de la documentación. Para ello, se han identificado los puntos fuertes de la titulación y los puntos con posibilidad de mejora en base a los criterios de ANECA, y se han realizado propuestas de mejora de los últimos mediante la coordinación de profesores y alumnos. Entre estas propuestas, se encuentra el uso de la herramienta Google Calendar con el objetivo de tener un mayor control de la carga de trabajo no presencial del alumnado, puesto que este aspecto es uno de los valorados con puntuación más baja en las encuestas realizadas por la Unidad Técnica de Calidad

Google Calendar vs Google Drive para la coordinación de asignaturas del Grado en Ingeniería Química

Uno de los aspectos peor valorados por los estudiantes en las nuevas titulaciones con evaluación continua suele ser la distribución de controles y otro tipo de pruebas objetivas a lo largo del cuatrimestre. En la guía docente de cada asignatura aparece la información sobre las pruebas a realizar dentro de un cronograma aproximado, y está disponible antes del comienzo del curso. Sin embargo, esa distribución puede variar ligeramente una vez empezado el curso debido a diversos motivos, y no se dispone de la información para todas las asignaturas del cuatrimestre en un mismo documento, lo que facilitaría su visualización. Para el Grado en Ingeniería Química se comenzó a utilizar la herramienta Google Calendar con el objetivo de tener un mayor control de este aspecto y poder detectar y corregir conflictos que pudieran surgir. Sin embargo, se encontraron ciertas limitaciones y por ello se decidió probar otra opción distinta, un documento Excel compartido en Google Drive. En este trabajo se compara la experiencia con ambas herramientas

Red de coordinación del Grado en Ingeniería Química para el curso 15-16

Una vez renovada la acreditación nacional de la ANECA y obtenido el sello internacional EUR-ACE® para ingenierías, en el Grado en Ingeniería Química de la Universidad de Alicante existen algunos aspectos que se pueden mejorar, siendo el principal la coordinación entre asignaturas. Para lograr la calidad en cualquier ámbito siempre es fundamental la mejora continua. En relación con la coordinación, en este trabajo se propone la elaboración de un calendario de actividades de evaluación mediante una herramienta sencilla con el objetivo de tener un mayor control de la carga de trabajo no presencial del alumnado, puesto que este aspecto es uno de los valorados con puntuación más baja en las encuestas realizadas por la Unidad Técnica de Calidad. Por otra parte, se propone también la realización de reuniones de coordinación con los profesores de la titulación para tratar otros aspectos además de la carga de trabajo, poder detectar posibles problemas o dificultades e intentar resolverlos. Por último, se propone la realización de encuestas propias de la titulación para conocer la opinión del alumnado sobre las asignaturas de forma detallada

Diffusion/dilution of desalination discharges into seawater

Póster presentado en 7th ANQUE International Congress "Integral water cycle: present and future. A shared Commitment", Oviedo, June 13-16, 2010.Holographic interferometry (HI) is an optical technique, by means of which changes in the refractive index can be visualized as interference fringes. The technique has been used to study the behavior of brine discharges from desalination plants into the sea. When the brine discharges in the sea, the diffusion/dilution of the salts in the seawater begins thus causing concentration changes associated to changes in the refractive index. This variation of the refractive index can be visualized as an interference fringe pattern by means of HI. In the present work, the first aim has been to determine the diffusion coefficient of brine in seawater. Diffusion experiments, consisting on slowly introducing brine in spectrophotometric cell containing seawater, have been carried out. When both solutions get in contact, the diffusion of solute starts and interference fringes (interferogram) begin to appear. The diffusion coefficient of brine in sea water has been calculated using these interferograms and a value of 1.27•10-5 cm2/s has been obtained. Dynamic experiments have also been carried out, introducing a flow of brine into a transparent container with seawater. Several characteristics of the brine discharge (flow rate, concentration, depth at which is poured and angle of discharge) have been studied. Using the interferometric fringe patterns obtained, concentration profiles in the container have been calculated. The results obtained show a better diffusion/dilution of the brine when the discharge is not horizontal and a moderate flow rate is used

Experiment V. Ultrafiltration of PEG10000 with initial concentration = 5 kg/m3 and the module in 180º orientation

Video 7 from paper "BUOYANCY EFFECT ON THE ULTRAFILTRATION OF PEG10000. VISUALIZATION BY DIGITAL HOLOGRAPHIC INTERFEROMETRY", submitted to AIChe Journal, 2011. Video shows the first 3 min at the beginning of experiment and the first 6 min after the pressure ceased. The speed is increased three times during the UF process, whereas after the pressure ceases the speed is increased 6 times

Digital holographic interferometry experimental setup to study mass transfer processes

Póster presentado en 11th Mediterranean Congress of Chemical Engineering, Barcelona, October 21-24, 2008.For many years, holographic interferometry (HI) has been an optical method widely used to study mass transfer processes in liquids and in transparent gels. During an experiment, changes in the refractive index distribution, and therefore in the concentration distribution, are visualized as an interference fringe pattern. In real-time HI, the first step is to obtain the hologram (an image of the object at a certain time, holographically stored), which is usually recorded on a holographic plate by a photographic method. This hologram represents the object at its reference state. The second step is to obtain an interferogram at different times. The interferogram allows changes in the object to be visualized by combining the current object wave with the reference object wave stored in the hologram. A major drawback of classical HI is not so much the cost of the holographic plates but the difficulty in developing the film. Moreover, all interferograms are obtained by comparing the current state of the object with the only hologram taken. Therefore, the temporal states that are compared cannot be freely chosen. These problems were overcome with digital holographic interferometry (DHI) (Marquadt and Richter). Digital holography (DH) is the digital recording and numerical reconstruction of numerous holograms and it offers the possibility of combining the current object wave with reference waves captured at different times. The use of DH has been possible due to the tremendous development in data processing and in opto-electronics. Digital CCD (Charged Coupled Device) cameras, that digitize the hologram, have continuously increased their resolution in the past years and they are now applicable for optical measurements. Adjustments in the classical HI setup previously used to study mass transfer processes have been made to adapt it to the DHI. The main change has been the use of a CCD camera instead of the holographic plates to record the holograms. Furthermore, a MATLAB program has been developed in order to capture and reconstruct the holograms numerically. In this work it was checked that the new DHI technique worked correctly by comparing the new interferograms with those obtained with optical HI in studies about diffusion and polarized reverse osmosis processes

Experiment IV. Ultrafiltration of PEG10000 with initial concentration = 12.5 kg/m3 and the module in 90º orientation

Video 3 from paper "BUOYANCY EFFECT ON THE ULTRAFILTRATION OF PEG10000. VISUALIZATION BY DIGITAL HOLOGRAPHIC INTERFEROMETRY", submitted to AIChe Journal, 2011. Video shows the first 3 min at the beginning of experiment but it reproduces the images at three times the speed of the real process (as a consequence, the video is 60 seconds long)

Visualization by digital holographic interferometry of flux velocity effect in cross-flow reverse osmosis

Póster presentado en 11th Mediterranean Congress of Chemical Engineering, Barcelona, October 21-24, 2008.Digital holographic interferometry (DHI) allows interferometric fringe patterns to be obtained, that are indicative of changes in the optical path followed by the light, and are related to changes in the refractive index. In the case of the appearance of the polarization concentration layer during the reverse osmosis process, changes in the concentration distribution, and therefore in the refractive index distribution, can be visualized as an interference fringe pattern. The phenomenon called concentration polarization occurs as filtration proceeds and the solute rejected by the membrane builds up a layer of high concentration near the membrane surface. The formation and development of the concentration polarization layer in the RO process will decrease the effective water filtration driving force and therefore, will decrease the permeate flux. To reduce or control concentration polarization many possible methods have been considered, one of them is the increase of shear at the membrane surface using a greater cross-flow velocity. In this work, DHI has been used to visualize the effect of cross-flow velocity during reverse osmosis of salts. All the experiments were carried out at a constant pressure of 6 bar, using a special module designed with transparent windows to observe the membrane surface. In all experiments a thin film reverse osmosis membrane was used. Two solutes (NaCl and Na2SO4), with different feed concentration (3.5 - 8.5 kg/m3) and different cross-flow velocities (0.002 - 0.017 m/s) (Re = 10 - 77) were used. In every run, the module was filled with the salt solution. The reference state (recorded by a CCD camera) was obtained with the salt solution flowing at the initial cross-flow velocity without pressure. During the reverse osmosis process, different fringe patterns were digitally reconstructed. In all runs, the higher the cross-flow velocity, the lesser the number of interference fringes that appears, showing that the concentration polarization has a minor effect. When higher cross-flow velocities (which reduce the concentration polarization layer) were used, the permeate flux increased