Search results for "CONVECTION"

Gravity effects on mixing with magnetic micro-convection in microfluidics.

2018

Mixing remains an important problem for development of successful microfluidic and lab-on-a-chip devices, where simple and predictable systems are particularly interesting. One is magnetic micro-convection, an instability happening on the interface of miscible magnetic and non-magnetic fluids in a Hele-Shaw cell under applied field. Previous work proved that Brinkman model quantitatively explains the experiments. However, a gravity caused convective motion complicated the tests. Here we first improve the experimental system to exclude the gravitational convective motion. Afterwards, we observe and quantify how gravity and laminar flow play an important role in stabilizing the perturbations …

Ice Initiation for Various Ice Nuclei Types and its Infl uence on Precipitation Formation in Convective Clouds

2007

Influence of Skin Depth on Convective Heat Transfer in Induction Heating

2017

International audience; We investigate convection driven by induction heating of a horizontal fluid layer using direct numerical simulations (DNS). This problem is of particular interest in the context of nuclear severe accident mastering. In a real severe accident, the molten core is subjected to homogeneous internal sources resulting from nuclear disintegrations. This situation is mimicked in the laboratory using induction heating as the internal source. In induction heating, however, heat sources are localized in the skin layer. Consequently, this concentration of heat may modify the flow and wall heat transfer compared to the case of homogeneous internal sources. DNS are carried out for…

Controlling melt convection—an innovation potential for concerted microstructure evolution of Nd-Fe-B alloys

2005

The solidification process and the resulting microstructure of Nd-Fe-B alloys in consideration of melt convection has been investigated experimentally with a specially designed forced crucible rotation technique. Samples were subjected to well-defined forced rotation and vibration, respectively, during induction heating and solidification. A concerted microstructure evolution is possible by enhancement or suppression of the melt convection. As a result, the microstructure pattern, mainly the volume fraction of the soft magnetic a-Fe phase, vary strongly with the strength of the internal flow motion. A distinct reduction of the a-Fe volume fraction in samples with strong melt rotation was ob…

Variable exponent p(x)-Kirchhoff type problem with convection

2022

Abstract We study a nonlinear p ( x ) -Kirchhoff type problem with Dirichlet boundary condition, in the case of a reaction term depending also on the gradient (convection). Using a topological approach based on the Galerkin method, we discuss the existence of two notions of solutions: strong generalized solution and weak solution. Strengthening the bound on the Kirchhoff type term (positivity condition), we establish existence of weak solution, this time using the theory of operators of monotone type.

On the impact of the heat transfer modelling approach on the prediction of EU-DEMO WCLL breeding blanket thermal performances

2020

Abstract The Water-Cooled Lithium-Lead Breeding Blanket is a key component of a fusion power plant, in charge of ensure Tritium production, shield Vacuum Vessel and magnets and remove the heat power deposited by radiation and particles arising from plasma. The last function is fulfilled by First Wall and Breeding Zone independent cooling systems. Several layouts of BZ coolant system have been investigated in the last years to identify a configuration that might guarantee EUROFER temperature below the limit (550 °C) and good thermal-hydraulic performances (i.e. water outlet temperature of 328 °C). A research activity is conducted to study and compare different modelling approaches to simulat…

Influence of growth parameters and melt convection on the solid-liquid interface during RF-floating zone crystal growth of intermetallic compounds

2001

Abstract The influence of growth parameters and melt convection on the solid–liquid interface of the intermetallic compound Ni3Si grown by the RF-floating zone technique was investigated experimentally as well as numerically. Numerical simulations showed that the heat transfer is strongly influenced by the electromagnetically driven and Marangoni convections whereas both the buoyancy and feed rotation have a negligible effect. It was found experimentally that the inductor design, the rod diameter and the length of the molten zone influence the solid–liquid interface shape significantly. The electromagnetically driven convection increases dramatically with increasing zone length due to the r…

Model emulation to understand the joint effects of ice-nucleating particles and secondary ice production on deep convective anvil cirrus

2021

Abstract. Ice crystal formation in the mixed-phase region of deep convective clouds can affect the properties of climatically important convectively generated anvil clouds. Small ice crystals in the mixed-phase cloud region can be formed by heterogeneous ice nucleation by ice-nucleating particles (INP) and secondary ice production (SIP) by, for example, the Hallett-Mossop process. We quantify the effects of INP number concentration, the temperature dependence of the INP number concentration at mixedphase temperatures, and the Hallett-Mossop splinter production efficiency on the anvil of an idealised deep convective cloud using a Latin hypercube sampling method, which allows optimal coverage…

Heat and mass transfer phenomena in magnetic fluids

2007

In this article the influence of a magnetic field on heat and mass transport phenomena in magnetic fluids (ferrofluids) will be discussed. The first section is dealing with a magnetically driven convection, the so called thermomagnetic convection while in the second section the influence of a temperature gradient on the mass transport, the Soret effect in ferrofluids, is reviewed. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A three-dimensional study of the onset of convection in a horizontal, rectangular porous channel heated from below

2012

Author's version of an article published in the journal: International Journal of Thermal Sciences. Also available from the publisher at: http://dx.doi.org/10.1016/j.ijthermalsci.2011.12.012 The onset of convection is studied in a rectangular channel filled with a fluid saturated porous medium, bounded above and below by impermeable isothermal walls at unequal temperatures and laterally by partially conducting walls. A three-dimensional linear stability analysis is carried out under the assumption of an infinite longitudinal channel length. Then, this assumption is relaxed in order to determine the threshold length for the three-dimensional convection to be the preferred mode at onset. Sens…