Fluid dynamic analysis of a Ranque-Hilsch vortex tube

Fluid dynamic analysis of a commercial, counter-flow Ranque-Hilsch Vortex Tube (RHVT), Exair 25 scfm, has been performed in this work both experimentally and numerically; in particular RHVT cooling power and temperature separation performances have been tested in both direct cooling employment (jet impingement) and indirect cooling employment (supplying cold plates). Experimental techniques, used in this work, revealed several difficulties to produce detailed information about velocity and temperature fields inside the tube and at both the exits. Hence numerical simulation of the flow inside the tube has been conducted using the commercial CFD code FLUENT 6.3.26. Compressible, turbulent, high swirling flow inside RHVT has been simulated by using both RANS and LES approaches. In particular several turbulence closures have been used in the RANS simulations and results have been compared with LES ones. Large Eddy Simulations have been performed by using Smagorinsky sub-grid model

THERMOGRAPHIC ANALYSIS OF ACOUSTIC DISTOURBANCE EFFECTS ON LAMINAR SEPARATION BUBBLE

Abstract This research is aimed to evaluate the possibility to destabilize the boundary layer in order to reduce the Laminar Bubble phenomenon; this is carried out by means of acoustic or mechanical perturbations of the flow field. The analyses are performed in a low speed wind tunnel for an Eppler 205 airfoil typically subjected to the laminar separation bubble phenomenon at low Reynolds. The effects of the acoustic perturbations on the flow pattern are revealed by means of an infrared camera and the heated thin foil technique; instead, at the present work stage, the results of the mechanical perturbations are observed by using the pressure distribution analysis. The experimental results show, as expected, a frequency and amplitude influence on the bubble reduction. These effects are not constant varying the angle of attack for the tested airfoil neither modifying the chord based Reynolds number

Exploring the Low Voltage Behavior of V2O5Aerogel as Intercalation Host for Sodium Ion Battery

Boosted by costs benefits, the development of room temperature Na-ion batteries is strongly desired for stationary applications. In this study we explore the possible use of V2O5 aerogel as anode material for sodium ion batteries. The aerogel is able to reversibly insert more than 3 Eq. of sodium in the voltage range 0.1 V–4 V vs. Na/Na+ demonstrating to possess additional capacity when cycled to lower voltage. The anode delivers about 200 mAh g−1 in the voltage range 0.01 V–1.5 V vs. Na/Na+. The preliminary characterization of a full Na-ion cell made coupling the V2O5 aerogel anode with carbon-coated Na3V2(PO4)3 cathode is also reported. The cell, showing an average voltage of 2.5 V, performed 200 cycles with good efficiency and a maximum specific capacity of 113 mAh per gram of anode material

The use of protic ionic liquids with cathodes for sodium-ion batteries

Herein, we report for the first time the use of a protic ionic liquid as a component of a new Na-ion battery electrolyte. The protic ionic liquid has been tested in combination with two different types of sodium-ion cathode materials, polyanionic Na3V2(PO4)3 and layered Na0.67Mn0.89Mg0.11O2, in order to reveal its impact on the electrode material electrochemical performance. The results evidence that this novel electrolyte performs very well in combination with a polyanionic electrode material, while it shows poor performance with a layered oxide material

Wells turbine for wave energy conversion : a review

In the past twenty years, the use of wave energy systems has significantly increased, generally depending on the oscillating water column (OWC) concept. Wells turbine is one of the most efficient OWC technologies. This article provides an updated and a comprehensive account of the state of the art research on Wells turbine. Hence, it draws a roadmap for the contemporary challenges which may hinder future reliance on such systems in the renewable energy sector. In particular, the article is concerned with the research directions and methodologies which aim at enhancing the performance and efficiency of Wells turbine. The article also provides a thorough discussion of the use of computational fluid dynamics (CFD) for performance modeling and design optimization of Wells turbine. It is found that a numerical model using the CFD code can be employed successfully to calculate the performance characteristics of W-T as well as other experimental and analytical methods. The increase of research papers about CFD, especially in the last five years, indicates that there is a trend that considerably depends on the CFD method

Antitrust in the Digital Economy: Big Tech as an Impetus for a Renewal in American Antitrust

The research presented in this report presents the development of antitrust law in the United States from its very beginning and attempts to trace the political and economic narratives that have contributed to antitrust thinking in the United States. In order grapple with the new data-driven economy, it is important to first look at the different eras of big business -- the path that several big businesses took to rise from humble beginnings, to then-dominant pre-existing markets, and subsequently face regulatory scrutiny seems to be a key aspect in the story of Big Tech. In other words, the story of big business in America runs virtually parallel to the development of different schools of antitrust thought. Furthermore, it is helpful to assess how different eras of big business have provoked conflicting notions about how the government should handle antitrust enforcement. The success of potentially harmful corporations has historically sparked antitrust debate in four distinct eras -- this history serves as the foundation which current regulators must work from. What remains unclear is whether there is an existing, comprehensive method of assessing the behavior of big tech or if some new way of thinking about consumers, the competitive process, and market structure must be developed

Documentación e investigación sobre Migraciones: interdisciplinariedad, multiplicidad de fuentes de información y su reflejo en un portal de Internet.

Título del Simposio : "Los que van, los que vienen y los que regresan. Los movimientos migratorios en el siglo XX y XXI : Fondos documentales e investigaciones" Título del Congreso: “Memoria Presente y Porvenir en América Latina”: (7º Congreso de CEISAL) Celebrado los días 12 al 15 de junio en OportoEl interés creciente que investigadores y estudiosos vienen manifestando a la hora de elaborar sus investigaciones sobre los movimientos migratorios desde un punto de vista multidisciplinar así como la utilización de nuevas fuentes de información como herramientas interesantes para su elaboración académica, nos ha conducido a este portal temático para dar a conocer, a través de las bbdd ya establecidas, el estado de la cuestión en esta materia, reseñando y difundiendo los eventos producidos sobre este tema en Europa y referidos al fenómeno migratorio entre este continente y Latinoamérica , tales como : Noticias; Artículos y libros publicados; Congresos/Jornadas celebrados; Tesis/Enlaces; etc. Por otro, ofrecer una recopilación de las nuevas fuentes documentales, testimonios transmitidos por medio de: Cine/documentales; Entrevistas; Fotografías; Páginas webs; Blogs, etcPeer reviewe