Publications related to Rayleigh number

Multi-Scale Study of High-Temperature Latent Heat Storage With Metallic Phase Change Materials

Energy storage is a central issue in the green economy with half the global end energy usage being heat. Latent heat thermal energy storage (LHTES) provides an energy dense heat storage solution with a well-defined discharge temperature. Utilizing low-cost ...

EPFL2022

Evaluation Criterion of Proton Exchange Membrane (ECPEM) fuel cells considering inserted porous media inside the gas flow channel

Jan Van Herle, Hossein Pourrahmani

The focus of this study is to evaluate the effects of porous media inside the gas flow channel of Proton Exchange Membrane Fuel Cells (PEMFC) on four different output parameters of voltage, power density, pressure drop, and Nusselt number (Nu) considering ...

PERGAMON-ELSEVIER SCIENCE LTD2022

Convection of water vapour in snowpacks

Varun Sharma, Michael Lehning, Mahdi Jafari

This paper studies numerically the convection of water vapour in snowpacks using an Eulerian-Eulerian two-phase approach. The convective water vapour transport in snow and its effects on snow density are often invoked to explain observed density profiles, ...

Cambridge University Press2022

Convective regimes induced by surface cooling and topography in stratified waterbodies

Damien Bouffard, Tomy Doda, Hugo Nicolás Ulloa Sánchez, Cintia Luz Ramon Casanas

Gravitational convection plays a significant role in the ventilation, heat and mass distribution of aquatic systems. This study investigates thermally driven convection resulting from heat loss at the air-water interface during cooling periods in freshwate ...

Iahr-Int Assoc Hydro-Environment Engineering Research2022

Buoyancy-driven convection of droplets on hot nonwetting surfaces

François Gallaire, Eunok Yim

The global linear stability of a water drop on hot nonwetting surfaces is studied. The droplet is assumed to have a static shape and the surface tension gradient is neglected. First, the nonlinear steady Boussinesq equation is solved to obtain the axisymme ...

AMER PHYSICAL SOC2021

Energetics and mixing of thermally driven flows in Hele-Shaw cells

Hugo Nicolás Ulloa Sánchez

Thermally driven flows in fractures play a key role in enhancing the heat transfer and fluid mixing across the Earth’s lithosphere. Yet the energy pathways in such confined environments have not been characterised. Building on Letelier et al. (J. Fluid Mec ...

Cambridge University Press2021

Data-Driven Reduced-Order Modeling of Convective Heat Transfer in Porous Media

Carlo Fiorina

This work presents a data-driven Reduced-Order Model (ROM) for parametric convective heat transfer problems in porous media. The intrusive Proper Orthogonal Decomposition aided Reduced-Basis (POD-RB) technique is employed to reduce the porous medium formul ...

MDPI2021

Buoyancy-driven melting and solidification heat transfer analysis in encapsulated phase change materials

Sophia Haussener, Nithin Mallya

Controlled melting and solidification in encapsulated phase change materials (PCMs) is of practical interest, for example, in latent heat storage applications. The choice of PCMs and the dynamic heat transfer characteristics during phase change - affecting ...

2021

Shape optimization of segmental porous baffles for enhanced thermo-hydraulic performance of shell-and-tube heat exchanger

Hossein Pourrahmani

This study presents the development and evaluation of a novel shell-and-tube heat exchanger (STHX) design with segmental porous baffles. Computational fluid dynamics (CFD) in combination with machine learning tools are utilized to investigate the thermo-hy ...

PERGAMON-ELSEVIER SCIENCE LTD2020

Turbulent patterns in wall-bounded shear flows: invariant solutions and their bifurcations

Florian Reetz

When laminar shear flows in large wall-bounded domains transition to turbulence, the flow exhibits spatio-temporally chaotic dynamics. Despite its chaotic dynamics, the flow may self-organize into characteristic spatially periodic patterns of unknown origi ...

EPFL2019

Cfd-Based Correlation For Forced Convection Heat Transfer In Circular Ducts Of Internally Heated Molten Salts

Carlo Fiorina

Heat transfer phenomena involving internally heated fluid flows are of particular interest in several industrial applications, in chemical plants as in the nuclear field. This topic is relevant for the development of the Molten Salt Reactors (MSRs) since i ...

AMER SOC MECHANICAL ENGINEERS2018

Direct numberical simulation of turbulent slope flows up to Grash of number Gr=2.1 x 10(11)

Jiannong Fang, Marc Parlange, Marco Giovanni Giometto, Gabriel George Katul

Stably stratified turbulent flows over an unbounded, smooth, planar sloping surface at high Grashof numbers are examined using direct numerical simulations ( DNS). Four sloping angles ( alpha = 15 degrees; 30 degrees; 60 degrees and 90 degrees) and three G ...

Cambridge University Press2017

Spatio-temporal patterns in inclined layer convection

Tobias Schneider

This paper reports on a theoretical analysis of the rich variety of spatio-temporal patterns observed recently in inclined layer convection at medium Prandtl number when varying the inclination angle gamma and the Rayleigh number R. The present numerical i ...

Cambridge University Press2016

High resolution infrared measurements of single-phase flow of R245fa and R236fa within a compact plate heat exchanger, Part 2: Heat transfer results

John Richard Thome, Raffaele Luca Amalfi

In the second article of the present two-part paper, upward single-phase heat transfer within a compact plate heat exchanger was investigated experimentally. The experimental setup, the data reduction technique and pressure drop results were presented in P ...

Pergamon-Elsevier Science Ltd2016

High resolution infrared measurements of single-phase flow of R245fa and R236fa within a compact plate heat exchanger, Part 1: Experimental setup and pressure drop results

John Richard Thome, Raffaele Luca Amalfi

This two-part paper presents experimental work to characterize thermal and hydraulic performances of a compact plate heat exchanger. Upward single-phase heat transfer and pressure drop of low pressure, liquid refrigerants R245fa and R236fa was investigated ...

Pergamon-Elsevier Science Ltd2016

The effect of rounding corners or cutting edges on the absolute/convective instability properties of mixing layers

François Gallaire

We revisit the inviscid spatio-temporal stability properties of mixing layers. Earlier comparisons of the dispersion relations pertaining to the broken line model and the hyperbolic tangent profile have shown that the temporal stability properties are main ...

Elsevier2015

Particle-size and -density segregation in granular free-surface flows

Christophe Ancey

When a mixture of particles, which differ in both their size and their density, avalanches downslope, the grains can either segregate into layers or remain mixed, dependent on the balance between particle-size and particle-density segregation. In this pape ...

Cambridge University Press2015

Interface structure and flux laws in a natural double-diffusive layering

Alfred Johny Wüest, Martin Schmid

The diffusive regime of double-diffusive convection generates staircases consisting of thin high-gradient interfaces sandwiched between convectively mixed layers. Simultaneous microstructure measurements of both temperature and conductivity from the stairc ...

Amer Geophysical Union2013

Stability of a Double-Diffusive Interface in the Diffusive Convection Regime

Alfred Johny Wüest

In this paper, the authors explore the conditions under which a double-diffusive interface may become unstable. Focus is placed on the case of a cold, freshwater layer above a warm, salty layer [i.e., the diffusive convection (DC) regime]. The "diffusive i ...

Amer Meteorological Soc2012

Experimental investigation into segregating granular flows down chutes

Christophe Ancey, Nicolas Andreini, Gaël Epely Chauvin, Sébastien Wiederseiner, Gaudenz Moser

We experimentally investigated how a binary granular mixture made up of spherical glass beads size ratio of 2 behaved when flowing down a chute. Initially, the mixture was normally graded, with all the small particles on top of the coarse grains. Segregati ...

2011