SIMULATION STUDY OF THE ADSORPTION DYNAMICS OF CYLINDRICAL SILICA GEL PARTICLES

The paper presents a simulation study of loose cylindrically shaped particles packed within a copper plate and aluminum fins. The model presented solves coupled heat and mass transfer equations using the finite volume method based on ANSY S FLUENT medium. Three different arrangements of cylindrical particles are considered. The model is validated with experimental data. It is found that the arrangements which represented monolayer configurations are only marginally better in heat transfer and uptake efficiency than the tri-layer configuration in the presence of fins. However, there is an appreciable difference in the uptake curve between monoand tri-layer configurations in the absence of fins. Finally, it is found that the fin pitch also plays an important role in determining the time constant for the adsorber design.

Performance evaluation of a two-stage silica gel plus water adsorption based cooling-cum-desalination system

The first objective of this paper is to show that a single-stage adsorption based cooling-cum-desalination system cannot be used if air cooled heat rejection is used under tropical conditions. This objective is achieved by operating a silica gel + water adsorption chiller first in a single-stage mode and then in a 2-stage mode with 2 beds/stage in each case. The second objective is to improve upon the simulation results obtained earlier by way of empirically describing the thermal wave phenomena during switching of operation of beds between adsorption and desorption and vice versa. Performance indicators, namely, cooling capacity, coefficient of performance and desalinated water output are extracted for various evaporator pressures and half cycle times. The improved simulation model is found to interpret experimental results more closely than the earlier one. Reasons for decline in performance indicators between theoretical and actual scenarios are appraised. (C) 2015 Elsevier Ltd and IIR. All rights reserved.

Instrumentation and control of a two-stage 4-bed silica gel plus water adsorption cooling cum desalination system

This paper presents the instrumentation and control architecture for a laboratory based two-stage 4-bed silica gel + water adsorption system. The system consists of primarily two fluids: refrigerant (water vapour) and heat transfer fluid (water) flowing through various components. Heat input to the system is simulated using multiple heaters and ambient air is used as the heat sink. The laboratory setup incorporates a real time National Instruments (NI) controller to control several digital and analog valves, heaters, pumps and fans along with simultaneous data acquisition from various flow, pressure and temperature sensors. The paper also presents in detail the various automated and manual tasks required for successful operation of the system. Finally the system pressure and temperature dynamics are reported and its performance evaluated for various cycle times. (C) 2015 Elsevier Ltd. All rights reserved.

No More HF: Teflon-Assisted Ultrafast Removal of Silica to Generate High-Surface-Area Mesostructured Carbon for Enhanced CO2 Capture and Supercapacitor Performance

An innovative technique to obtain high-surface-area mesostructured carbon (2545m(2)g(-1)) with significant microporosity uses Teflon as the silica template removal agent. This method not only shortens synthesis time by combining silica removal and carbonization in a single step, but also assists in ultrafast removal of the template (in 10min) with complete elimination of toxic HF usage. The obtained carbon material (JNC-1) displays excellent CO2 capture ability (ca. 26.2wt% at 0 degrees C under 0.88bar CO2 pressure), which is twice that of CMK-3 obtained by the HF etching method (13.0wt%). JNC-1 demonstrated higher H-2 adsorption capacity (2.8wt%) compared to CMK-3 (1.2wt%) at -196 degrees C under 1.0bar H-2 pressure. The bimodal pore architecture of JNC-1 led to superior supercapacitor performance, with a specific capacitance of 292Fg(-1) and 182Fg(-1) at a drain rate of 1Ag(-1) and 50Ag(-1), respectively, in 1m H2SO4 compared to CMK-3 and activated carbon.

Scaling analysis and numerical studies on water vapour adsorption in a columnar porous silica gel bed

This article presents a theoretical analysis of heat and mass transfer in a silica gel + water adsorption process using scaling principles. A two-dimensional columnar packed adsorber domain is chosen for the study, with side and bottom walls cooled and vapour inlet from the top. The adsorption process is initiated from the cold walls with a temperature jump of 15 K, whereas the water vapour supply is maintained at a constant inlet pressure of 1 kPa. The first part of the study is dedicated to deriving relevant scales for the adsorption process by an order of magnitude analysis of energy, continuity and momentum equations. In the latter part, the derived scales are compared with the outcome of numerical studies performed for various domain widths and aspect ratio of bed. A good correlation between scaling and simulation results is observed, thereby validating the scaling approach. (C) 2015 Elsevier Ltd. All rights reserved.

No More HF: Teflon-Assisted Ultrafast Removal of Silica to Generate High-Surface-Area Mesostructured Carbon for Enhanced CO2 Capture and Supercapacitor Performance

An innovative technique to obtain high-surface-area mesostructured carbon (2545m(2)g(-1)) with significant microporosity uses Teflon as the silica template removal agent. This method not only shortens synthesis time by combining silica removal and carbonization in a single step, but also assists in ultrafast removal of the template (in 10min) with complete elimination of toxic HF usage. The obtained carbon material (JNC-1) displays excellent CO2 capture ability (ca. 26.2wt% at 0 degrees C under 0.88bar CO2 pressure), which is twice that of CMK-3 obtained by the HF etching method (13.0wt%). JNC-1 demonstrated higher H-2 adsorption capacity (2.8wt%) compared to CMK-3 (1.2wt%) at -196 degrees C under 1.0bar H-2 pressure. The bimodal pore architecture of JNC-1 led to superior supercapacitor performance, with a specific capacitance of 292Fg(-1) and 182Fg(-1) at a drain rate of 1Ag(-1) and 50Ag(-1), respectively, in 1m H2SO4 compared to CMK-3 and activated carbon.

Combined Effects of Silica Filler and Its Interface in Epoxy Resin

In this paper, mechanical properties of silica-filled epoxy resin are tested. The tests show that at elevated temperatures, the material’s properties (e.g. yield stress, flow stress, etc.) vary immonotonically with filler volume fraction. Nanoindentation test results suggest that an interface region, stronger than the matrix, is formed in the materials. The formation of the interface has positive effects on the yield strengths of materials. The addition of particles in the matrix produces a large disturbance in stress distribution, leading to stress concentration in the matrix. The stress concentration has negative effects on the yield strengths of materials. The calculation demonstrates that the maximum stress in samples varies immonotonically with particulate concentration. So, the immonotonic variation of mechanical behavior of materials may be rooted in the contradictory effects of the interface region and the stress concentration caused by particulate addition.

The influence of corrosion on the erosion of aluminium by aqueous silica slurries

The slurry erosion-corrosion behaviour of aluminium in aqueous silica slurries containing 0.5 M NaCl, acetic acid and 0.1 M Na2CO3 at open circuit has been investigated using a modified slurry erosion rig. The erosion rates of aluminium in the NaCl and acetic acid slurries were much higher than those in an aqueous slurry without electrolyte additives even though the pure corrosion component was very small. Eroded specimens were examined by scanning electron and optical microscopy. In pure aqueous slurry erosion, the basic mechanism leading to mass loss was the ductile fracture of flakes formed on the eroded surface. In corrosive slurries, however, the mass loss was enhanced by cracking of the flakes induced by stress and corrosion. © 1995.

La caridad como amor de amistad

Resumen: En este artículo queremos explicar un aspecto de la concepción tomista de la caridad. Verla como amor de amistad. Para ello, primero vamos a investigar la teoría aristotélica de la amistad, como la expone en la Ética a Eudemo y la Ética a Nicómaco. Recurrimos a Aristóteles, ya que es la culminación griega acerca de la reflexión sobre la amistad. Santo Tomás se servirá de la noción aristotélica de la amistad, para explicar la caridad como amor de amistad. Explica que la caridad permite vivir una amistad intensa con Dios y con el prójimo. El acto propio de la caridad, así como sus efectos interiores y exteriores, se entienden más plenamente al captarlos como otros tantos actos de amistad

El viejo, el amor y la hermosa como texto espectacular

Resumen: Inspirada por el Diálogo entre Amor y un viejo, de Rodrigo Cota, Interlocutores senex et amor mulierque pulcra forma es una muy interesante obra concebida para su puesta en escena; sin embargo, no posee acotación autoral alguna, lo que implica que el texto espectacular debe extraerse de la construcción semántica-formal de los signos verbales discursivos en voz de los personajes, que son los que comportan los requisitos necesarios de dramaticidad. A partir de estos signos analizaré varios aspectos contenidos en la estructura, que determino tripartita, de inicio, nudo y desenlace; por ejemplo, la actio (gestus, motus y vultus corporales), la pronuntiatio, la representación de los espacios ficcionales, y elementos obligados de caracterización. Comentaré, también, el espacio para la puesta; habré de aducir condicionantes culturales tanto para la caracterización (corporal y de indumentaria), como para los tipos de gestualidad que deben realizarse en escena (mediante el apoyo de preceptivas retóricas y obras iconográficas). No dejaré del lado la descodificación semántica asociada con todos los elementos referidos.

Del amor en metro y en prosa : lírica amorosa y ficción sentimental en tiempos de los Reyes Católicos

Integran este número de la revista ponencias presentadas en Studia Hispanica Medievalia VIII: Actas de las IX Jornadas Internacionales de Literatura Española Medieval, 2008, y de Homenaje al Quinto Centenario de Amadis de Gaula.

La angustia esencial y la alegría del amor

Esta expresión del Santo Padre Francisco, impactante, es como un centro en el hondo sentido del anuncio del Evangelio: nuestra tristeza se cura con un infinito amor. Es una verdad que no pasa de tiempo, ni manipula ni puede desilusionar, porque la angustia, la experiencia de la finitud y la consiguiente tristeza responden a las más hondas inquietudes del ser humano y por eso el amor puede sostenerla y elevarla. Tanto si se considera la estructura de la subjetividad cuanto el compromiso comunitario y su crisis actual, o si se consideran los desafíos en el ámbito de la familia, la cultura, la educación, etc., la experiencia de la propia finitud natural a partir del trascender y la inquietud ante la exigencia de hacerse cargo de su limitación se iluminan, en la existencia humana, con la alegría y la esperanza del Evangelio que se renueva y se comunica.

Los siete modos de amor de Beatriz de Nazareth : Caleidoscopio estético – místico del deseo de Dios

Los Siete grados de Amor de la poetisa y mística flamenca Beatriz de Nazareth conforma, junto con la obra de sus dos contemporáneas Hadewijch de Amberes y Matilde de Magdeburgo, un coro de voces femeninas que destacan dentro de la teología monástica del siglo XIII, por haber sido escritas en lengua vernácula y haber adoptado de modo creativo las formas poéticas del amor cortés para expresar su experiencia de Dios. En continuidad con la tradición patrística despliega Beatriz la via amoris, centrando su discurso en el deseo de Dios. El objetivo de este trabajo es demostrar la actualidad de esta obra medieval premoderna en el horizonte de una posmodernidad en la que deseo y alteridad se cruzan. La original concepción caleidoscópica del amor que presenta este texto abre horizontes desde los cuales plantear hoy la pregunta por lo absoluto a partir de la experiencia y el lenguaje de los místicos.