The JEREMI-project on thermocapillary convection in liquid bridges. Part B : Overview on impact of co-axial gas flow

Pure surface-tension-driven flow is a unique type of flow that can be controlled through external manipulation of thermal and/or mechanical boundary conditions at the free liquid surface where the entire driving force for the convection is generated. This unique feature has been exploited in recent studies for the active control of the flow instability. The use of forced coaxial gas streams has been proposed as a way to stabilize the Marangoni convection in liquid bridges in the planned space experiment JEREMI (Japanese and European Research Experiment on Marangoni Instabilities). It is aimed at understanding the mechanism of the instability and the role of the surface heat transfer and surface shear stresses. This overview presents corresponding preparatory experimental and numerical studies

Diffusion in liquid mixtures

The understanding of transport and mixing in fluids in the presence and in the absence of external fields and reactions represents a challenging topic of strategic relevance for space exploration. Indeed, mixing and transport of components in a fluid are especially important during long-term space missions where fuels, food and other materials, needed for the sustainability of long space travels, must be processed under microgravity conditions. So far, the processes of transport and mixing have been investigated mainly at the macroscopic and microscopic scale. Their investigation at the mesoscopic scale is becoming increasingly important for the understanding of mass transfer in confined systems, such as porous media, biological systems and microfluidic systems. Microgravity conditions will provide the opportunity to analyze the effect of external fields and reactions on optimizing mixing and transport in the absence of the convective flows induced by buoyancy on Earth. This would be of great practical applicative relevance to handle complex fluids under microgravity conditions for the processing of materials in space

European Space Agency experiments on thermodiffusion of fluid mixtures in space

Abstract.: This paper describes the European Space Agency (ESA) experiments devoted to study thermodiffusion of fluid mixtures in microgravity environment, where sedimentation and convection do not affect the mass flow induced by the Soret effect. First, the experiments performed on binary mixtures in the IVIDIL and GRADFLEX experiments are described. Then, further experiments on ternary mixtures and complex fluids performed in DCMIX and planned to be performed in the context of the NEUF-DIX project are presented. Finally, multi-component mixtures studied in the SCCO project are detailed

Diffusion and Soret in Ternary Mixtures: Preparation of the DCMIX2 Experiment on the ISS

We report on ground-based studies in course of preparation of the experiment DCMIX2 (Diffusion coefficient in mixtures) to be performed on the International Space Station (ISS). In microgravity experiment the diffusion and thermodiffusion coefficients will be measured at six points with different compositions of the ternary mixture Toluene-Methanol-Cyclohexane. This mixture attracts attention of the researchers, as it has a miscibility gap and presumably large region with negative Soret coefficients. By using Optical Digital Interferometry we have measured the variations of refractive index Δn in the full parameter space of concentrations. The regions of stable and unstable behavior of system were determined from the time-dependent behavior of Δn. The system is hydrodynamically unstable in a wide region of compositions where Soret measurement should be done in microgravity. We present the results of the study of the compatibility of this mixture with often used sealing materials:Viton (R), Chemraz (R) and different types of Kalrez. To facilitate the expected theoretical studies we have measured density and thermal expansion in the points of the interest. © 2013 Springer Science+Business Media Dordrecht.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Impacto de las asociaciones público privadas del sector transporte en el producto bruto interno del Perú durante el período 1980-2017

El objetivo de tesis fue analizar el impacto de las Asociaciones Publico Privadas del sector transporte en el Producto Interno Bruto para Perú con data trimestral. Para el período 1980-2017, se examinó la cartera de proyectos del sector transporte (carreteras, ferrocarriles, puertos y aeropuertos) y como la inversión privada mediante este mecanismo fortalece y disminuye la brecha de infraestructura de este sector generando crecimiento y desarrollo económico para el país. Se utilizó el modelo de Mínimos Cuadrados Ordinarios (MCO), porque permiten realizar las mejores estimaciones sobre la Inversión Privada y la Inversión Pública y el efecto que estas tienen en el crecimiento del producto. Por consiguiente, se recurrió al análisis de estadística descriptiva, puesto que se partió de supuestos (Países con ingresos medios y altos, Instituciones fuertes, respecto a los derechos de propiedad privada) en los cuales las Asociaciones Publico Privadas son más eficientes en la economía. Los resultados muestran que la infraestructura del sector transporte es más eficiente el mecanismo de las Asociaciones Publico Privadas, por tres razones: Primero, los proyectos buscan resolver limitaciones o falta de infraestructura evidentes y que tengan altas tasas de rentabilidad económica y por ello resultan atractivas al sector privado. Segundo, con las APP se obtienen ganancias de eficiencia bajo ciertas condiciones. Tercero, se obtiene un filtro eficiente de elefantes blancos (obras ineficientes) y una mejor construcción, operación y mantenimiento en el tiempo que la provisión pública