Lattice Boltzmann Simulation of Natural Convection in an Annulus between a Hexagonal Cylinder and a Square Enclosure

Laminar natural convection in a water filled square enclosure containing at its center a horizontal hexagonal cylinder is studied by the lattice Boltzmann method. The hexagonal cylinder is heated while the walls of the cavity are maintained at the same cold temperature. Two orientations are treated, corresponding to two opposite sides of the hexagonal cross-section which are horizontal (case I) or vertical (case II). For each case, the results are presented in terms of streamlines, isotherms, local and average convective heat transfers as a function of the dimensionless size of the hexagonal cylinder cross-section (0.1≤B≤0.4), and the Rayleigh number (103≤Ra≤106)

Analysis of Turbulent Natural Convection by an Elliptic Relaxation Model in Tall Vertical Cavities with Linear Temperatures on Sidewalls

Turbulent natural convection of air is studied, by the elliptic-relaxation model v^2-f, in a tall vertical cavity whose hot and cold walls are maintained at linear temperatures of slopes γ_1 and γ_2, respectively. The average temperatures of the active walls are located at mid-height of the cavity. Four situations are analyzed, corresponding to γ_1=γ_2=γ (case I), γ_1=-γ_2=γ (case II), γ_1=0 and γ_2=γ (case III), γ_1=γ and γ_2=0 (case IV). These boundary conditions may be more representative or used to control heat transfer for certain systems. The effects of the slope (-1≤γ≤1), the aspect ratio of the cavity (10≤A≤80) and the average Rayleigh number (5×〖10〗^4≤〖Ra〗_m≤〖10〗^6 ) on the streamlines, isotherms, contours of the turbulent kinetic energy, heatlines, local and average Nusselt numbers are investigated. It is shown that the local and average heat transfers of cases III and IV can be deducted from those of cases I and II. The obtained dynamic and thermal fields as well as local and average heat transfers of the studied cases are quite different of those of the classical case corresponding to γ=0. A simplified procedure for calculating the average Nusselt number is also developed for each case

An Investigation of the Swelling Kinetics of Bentonite Systems Using Particle Size Analysis

Particles size distribution (PSD) is introduced as a tool for analysis of bentonite aggregation and swelling kinetics. Raw Ca-bentonite was purified using a combined wet sieving and sedimentation processes, followed by thermochemical treatment with Na 2 CO 3 to increase its swelling capacity. The detailed analysis of the PSD shows a strong correlation between the PSD and the swelling process. For the chemically treated raw bentonite, PSD revealed two different peaks representing unswelled and swelled particles along with some aggregates. The swelling is shown to be a kinetically controlled process that depends on time, temperature, and bentonite chemical composition. At the beginning of the chemical treatment, the effect of aggregates was more dominant; therefore, the viscosity did not increase much with particle size. However, the combined chemical and thermal treatment has enhanced the Na-activation process and boosted bentonite swelling. The rheological measurements have shown enhancement in the viscosity and confirmed the PSD findings. The same optimal treatment conditions are obtained from both rheological measurements and PSD analysis. A model is developed based on classical reaction rate kinetics and used to describe the conversion from unswelled to swelled particles. The PSD has a strong correlation with the physical properties of the suspension such as the viscosity. The swelling rate fits a second order model with a rate constant, k, in the range 0.002 to 0.124 h 1 and an activation energy, E, of 87 kJ/mol. PSD analysis together with the developed kinetic model are powerful tools for studying the swelling kinetics of bentonites.Scopu

Resonance of Double-Diffusive Convection in a Porous Medium Heated with a Sinusoidal Exciting Temperature

studied numerically. The left vertical wall of the cavity is heated with a temperature varying sinusoidally in time, while the opposite cold wall is maintained at a constant temperature. The same walls of the cavity are salted with constant and different concentrations (the concentration of the heated wall is higher than that of the cooled one). The remaining horizontal walls are considered adiabatic and impermeable. The parameters governing the problem are the amplitude of the variable temperature (0 £ a £ 1), its period (0.0001 £ t £ 10), the buoyancy forces ratio (-5 £ N £ +5), the Lewis number (0.1 £ Le £ 10) and the thermal Darcy-Rayleigh number (RT = 400). Effects of these parameters on fluid flow, temperature and concentration distributions and mean heat and mass transfers within the cavity are analyzed. Results obtained show that both heat and mass transfers could be significantly enhanced or reduced, with respect to those generated in the case of constant heating conditions by proper choice of the parameters related to the periodic temperature

Comparison between direct measurements and indirect estimations of hydraulic conductivity for slope deposits of the North-Western Tuscany, Italy

Hydraulic conductivity (K) is a relevant engineering geology property of deposits that cover the geological bedrock (Slope Deposits – SD). This parameter is useful for many applications fields such as: simulations of both infiltration and runoff processes, hillslope stability numerical analysis, hydrological studies, soil science and environmental problems. A wide range of methods are available in the literature in order to estimate K. Anyhow, they can be divided into direct measurement (field and laboratory test) and indirect estimations (eg. correlation from grain size, pedotransfer functions). However, many factors (eg. SD grain size, bulk density, organic matter, etc.) can affect the K value hence the determination of K within SD is often a challenge. Moreover, the value of K generally shows an high spatial variability requiring a large number of direct measurements to obtain robust spatial estimations. Indirect methods may be used alternatively or in pair with direct methods. However, relations between K and other soil physical properties are generally suitable only for specific type of soils, therefore, the application of those relations are constrained. In this work a wide (about 200) set of field measurements were performed in North-Western Tuscany in order to assess the variability of K in the vadose zone for SD characterized by different grain size composition. Measurements were carried out by means of both constant and falling head permeameters, as well as double ring infiltrometer. In the test sites engineering geology properties of SD such as bulk density and depth have been collected, moreover, samples have been collected for laboratory analysis. A statistical analysis of the K value has been performed for SD characterized by different grain size distribution and geological bedrock. Moreover, a comparison between the field methods have been also performed. Finally, a comparison between measured and estimated values of K has been done in order to assess the reliability of different equations to predict K. The results show that the K value varies across: different geological settings, the SD profile and the geographic neighborhood of the test site. Moreover, the results highlight that the indirect methods used in this work have to be used carefully in our study area

Análisis de la producción central y entrega de hidrógeno, aplicado al Circuito Patagónico Austral

Fil: Medina, M. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Laboratorio de Energías Renovables; Argentina.Fil: Abdelbaki, A. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Laboratorio de Energías Renovables; Argentina.Fil: Lorenzetti, D. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Laboratorio de Energías Renovables; Argentina.Fil: Villarroel Sáez, P. Pontificia Universidad Católica de Valparaíso. Ingeniero investigador; Chile.Fil: Sigal, A. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina.Fil: Rodríguez, C. R. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Matemática; Argentina.El departamento Deseado de la Provincia de Santa Cruz, Argentina, presenta la mayor potencialidad de producción de hidrógeno electrolítico del país, a partir de las tres fuentes de energías primarias sustentables: eólica, solar, biomásica. Allí, la Planta de Hidrógeno de Pico Truncado cuenta con capacidad de producción central de hidrógeno de 100m3 de H2/día (a 18 bar), suficiente para abastecer 318 vehículos con combustible híbrido denominado HGNC, constituido por el corte 20% V/V de hidrógeno en GNC, (in situ) en cada estación. A partir del costo de producción, se analiza el costo de entrega de hidrógeno al circuito Patagónico Austral conformado por: Puerto Deseado, Fitz Roy, Caleta Olivia, Las Heras, Comodoro Rivadavia, Sarmiento y Los Antiguos. Considerando diversos parámetros locales, se determinó como forma de entrega más rentable el gasoducto virtual, con costo total de hidrógeno estimado en 8,46 USD/kg H2 y de HGNC despachado en la estación en 0,537 USD/Nm 3 ($7,82/Nm3).http://www.energiaestrategica.com/concluyo-con-exito-el-congreso-internacional-sobre-ciudades-inteligentes-innovacion-y-sustentabilidad-2/Fil: Medina, M. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Laboratorio de Energías Renovables; Argentina.Fil: Abdelbaki, A. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Laboratorio de Energías Renovables; Argentina.Fil: Lorenzetti, D. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Laboratorio de Energías Renovables; Argentina.Fil: Villarroel Sáez, P. Pontificia Universidad Católica de Valparaíso. Ingeniero investigador; Chile.Fil: Sigal, A. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina.Fil: Rodríguez, C. R. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Matemática; Argentina.Ingeniería del Petróleo, Energía y Combustible

An open-label multi-center phase 1 safety study of BXQ-350 in children and young adults with relapsed solid tumors, including recurrent malignant brain tumors

BACKGROUND: BXQ-350 is a novel anti-neoplastic agent composed of saposin C (SapC) and phospholipid dioleoylphosphatidyl-serine sodium (DOPS) that selectively binds tumor cell phosphatidylserine (PS), inducing apoptosis. BXQ-350 has demonstrated preclinical antitumor effects in high-grade gliomas (HGG) and clinical activity in adult patients with recurrent HGG. METHODS: A phase 1 study was conducted in pediatric patients with relapsed/refractory solid tumors, including recurrent brain tumors. Primary objectives were to characterize safety and determine maximum tolerated dose (MTD) and preliminary antitumor activity. Sequential dose cohorts were assessed up to 3.2 mg/kg using an accelerated titration design. Each cycle was 28 days; dosing occurred on days 1-5, 8, 10, 12, 15, and 22 of cycle 1, and day 1 of subsequent cycles, until disease progression or toxicity. RESULTS: Nine patients, median age 10 years (range: 4-23), were enrolled. Seven patients (78%) had central nervous system (CNS) and two (22%) had non-CNS tumors. Eight patients completed cycle 1. No dose limiting toxicity (DLT) or BXQ-350-related serious adverse events (SAEs) were observed. Six patients experienced at least one adverse event (AE) considered possibly BXQ-350-related, most were grade ≤2. One patient with diffuse intrinsic pontine glioma experienced stable disease for 5 cycles. The study was terminated after part 1 to focus development on the frontline setting. CONCLUSION: No DLTs or BXQ-350-related SAEs were reported, and the maximal planned dose of 3.2 mg/kg IV was tolerable. Limited safety and efficacy data support continued BXQ-350 development in pediatric HGG; however, early discontinuations for progression suggest novel therapies be assessed at earlier disease stages

Análisis de la generación eléctrica distribuida en la localidad de Tres Lagos, provincia de Santa Cruz, Argentina

Fil: Lorenzetti, D. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Laboratorio de Energías Renovables; Argentina.Fil: Moyano, H. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Laboratorio de Energías Renovables; Argentina.Fil: León, H. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Laboratorio de Energías Renovables; Argentina.Fil: Fernández, C. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Laboratorio de Energías Renovables; Argentina.Fil: Abdelbaki, A. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Laboratorio de Energías Renovables; Argentina.Fil: Rodríguez, R. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Matemática; Argentina.Fil: Leiva, E.P.M. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Matemática y Física; Argentina.Fil: Leiva, E.P.M. Universidad Nacional de Córdoba. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Físico-Química de Córdoba; Argentina.Se presenta en este trabajo el diseño de un sistema de generación de energía eléctrica distribuida (GD) para la localidad de Tres Lagos, ubicada en la provincia de Santa Cruz, Argentina. El sistema de GD utiliza en su diseño recursos eólicos, solares y convencional (generador diesel) como fuentes primarias de energía, en una configuración de red eléctrica autónoma.http://www.hyfusen.com/libro.htmlFil: Lorenzetti, D. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Laboratorio de Energías Renovables; Argentina.Fil: Moyano, H. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Laboratorio de Energías Renovables; Argentina.Fil: León, H. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Laboratorio de Energías Renovables; Argentina.Fil: Fernández, C. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Laboratorio de Energías Renovables; Argentina.Fil: Abdelbaki, A. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Laboratorio de Energías Renovables; Argentina.Fil: Rodríguez, R. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Matemática; Argentina.Fil: Leiva, E.P.M. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Matemática y Física; Argentina.Fil: Leiva, E.P.M. Universidad Nacional de Córdoba. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Físico-Química de Córdoba; Argentina.Otras Ingeniería Eléctrica, Ingeniería Electrónica e Ingeniería de la Informació

Análisis de la producción y distribución de hidrógeno en un circuito patagónico

Se presenta en este trabajo un estudio comparativo de la factibilidad técnica y económica de la producción central de hidrógeno mediante fuentes renovables. Dicha comparación se llevó a cabo de manera simulada mediante la utilización de las herramientas de software libre, las cuales funcionan bajo entorno Windows, por una parte y valores reales obtenidos de datos de la Planta Experimental de Hidrógeno de PicoTruncado.http://www.hyfusen.com/libro.htmlFil: MacDonald, E. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Laboratorio de Energías Renovables; Argentina.Fil: Lorenzetti, D. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Laboratorio de Energías Renovables; Argentina.Fil: Moyano, H. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Laboratorio de Energías Renovables; Argentina.Fil: León, H. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Laboratorio de Energías Renovables; Argentina.Fil: Fernández, C. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Laboratorio de Energías Renovables; Argentina.Fil: Abdelbaki, A. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Laboratorio de Energías Renovables; Argentina.Fil: Rodríguez, R. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Matemática; Argentina.Otras Ingeniería de los Materiale

Mechanical Behavior of a Novel Nanocomposite Polysulphone - Carbon Nanotubes Membrane for Water Treatment

Nowadays, global fresh water shortage is becoming the most serious problem affecting the economic and social development. Water treatment including seawater desalination and wastewater treatment is the main technology for producing fresh water. Membrane technology is favored over other approaches for water treatment due to its promising high efficiency, ease of operation, chemicals free, energy and space saving. Membrane filtration for water treatment has increased significantly in the past few decades with the enhanced membrane quality and decreased membrane costs. In addition to high permeate flux and high contaminant rejection, membranes for water treatment require good mechanical durability and good chemical and fouling resistances. Thus, investigation of the mechanical behavior of water treatment membranes with underlying deformation mechanisms is critical not only for membrane structure design but also for their reliability and lifetime prediction. Compared to ceramic and metallic membranes, polymer membranes with smaller pore size and higher efficiency for particle removal are widely used in seawater desalination with a high applied pressure. However, polymer membranes are mechanically weaker and have lower thermal and chemical stability compared to inorganic membranes. Blending of polymers with inorganic fillers is an effective method to introduce advanced properties to polymer based membranes to meet the requirements of many practical applications. The reinforced polymeric membranes with inorganic fillers can provide desirable mechanical strength as well as mechanical stability. Carbon nanotubes (CNTs) have received considerable attention from academic and industries over the last twenty years. In addition to their excellent electrical and thermal properties, CNTs exhibit outstanding mechanical characteristics due to its instinct mechanical strength and high aspect ratio. For the application of water treatment membranes, CNTs could be the excellent channels for water to go through and therefore, CNTs have proven to be excellent fillers in polymer membranes improving the permeability and rejection properties. In literature, it is reported that the mechanical strength of the polymer membranes was improved with the embedding of CNTs due to reinforcement effect of the more rigid CNTs. The mechanical responses of polymer_CNTs composites depended on the interfacial adhesion between the CNTs and the membrane-based polymer as well as the dispersion and distribution of the CNTs within the polymer matrix. In this study, a vertical chemical vapor deposition reactor was designed in order to synthesize CNTs of high aspect ratio using continues injection atomization. Bundles of high purity (99%) and high quality CNTs were produced by this system. The produced CNTs had diameters ranging from 20 to 50 nm and lengths ranging from 300 to 500 micron (corresponded aspect ratios ranging from 6000 to 25000). A novel polysulphone (PSF) based nanocomposite membrane incorporated with the produced high aspect ratio CNTs was then casted via phase inversion method, at a wide range of CNTs loading (0-5 wt. %), in polysulphone-dimethylformamide solutions using the Philos casting system. The poly(vinylpyrrolidone) was used as pore-forming additive. To demonstrate the effect of nanocomposite morphology on the mechanical behavior of the prepared membranes, a set of control samples consisted of PSF membranes embedded with commercial CNTs at the same CNTs loading, were casted at the same conditions. The commercial CNTs had a lengths of 1 ?m to 10 ?m and outer diameters of 10 nm to 20 nm (corresponded aspect ratios ranging from 50 to 1000), with purity >95% and BET surface area of 156 m2/g. The effects of CNTs content and aspect ratio on morphological, water transport and mechanical properties of the prepared PSF-based porous membranes were investigated. The surface and cross-section morphologies of PSF/CNTs porous membranes were examined using scanning electron microscopy (SEM). The orientation, dispersion and distribution of CNTs within polymer membranes were evaluated for the membrane samples with different CNTs content and CNTs aspect ratio. The average membrane pore size was evaluated by using SEM image analysis software. Uniaxial tensile behavior of the membranes was characterized by means of a universal material testing machine under different testing conditions. Wet specimens were carefully cut from the casted membranes by using a razor blade. Elastic, plastic and failure behaviors of the membranes are analyzed with the impacts of CNTs content and aspect ratio. The macroscopic mechanical behaviors of the membranes are correlated with their strain induced microstructure evolution by using SEM. In this, pore shape evolution, pore and CNTs orientations, neighboring pore interaction, interface between the CNTs and PSF matrix and the failure behavior of the deformed porous membranes were analyzed. The macroscopic stress-strain responses of the membranes were correlated with the microstructure of the studied nanocomposites membranes to provide a better understanding of materials' processing-microstructure-properties relationship.qscienc