S. Moissette

Bio: S. Moissette is an academic researcher. The author has contributed to research in topics: Subcooling & Volume of fluid method. The author has an hindex of 1, co-authored 1 publications receiving 4 citations.

Numerical simulation of subcooled boiling in a turbulent channel flow

Abstract: A numerical study of boiling heat transfer in a turbulent liquid-vapour flow inside a heated channel is carried out for various flow conditions. A Volume Of Fluid model (VOF) is used for liquid-vapour interface tracking coupled with a k-e low Reynolds model to predict the effect of turbulence. Boiling and condensation phenomena are included in the model based on the general laws of phase change. The obtained results are compared with experimental measurements from the literature, and additional results about conjugate heat transfer are presented. The computational predictions are in satisfactory agreement with experimental results.

A novel 1D/2D model for simulating conjugate heat transfer applied to flow boiling in tubes with external fins

Abstract: This study presents a novel, simplified model for the time-efficient simulation of transient conjugate heat transfer in round tubes. The flow domain and the tube wall are modeled in 1D and 2D, respectively and empirical correlations are used to model the flow domain in 1D. The model is particularly useful when dealing with complex physics, such as flow boiling, which is the main focus of this study. The tube wall is assumed to have external fins. The flow is vertical upwards. Note that straightforward computational fluid dynamics (CFD) analysis of conjugate heat transfer in a system of tubes, leads to 3D modeling of fluid and solid domains. Because correlation is used and dimensionality reduced, the model is numerically more stable and computationally more time-efficient compared to the CFD approach. The benefit of the proposed approach is that it can be applied to large systems of tubes as encountered in many practical applications. The modeled equations are discretized in space using the finite volume method, with central differencing for the heat conduction equation in the solid domain, and upwind differencing of the convective term of the enthalpy transport equation in the flow domain. An explicit time discretization with forward differencing was applied to the enthalpy transport equation in the fluid domain. The conduction equation in the solid domain was time discretized using the Crank–Nicholson scheme. The model is applied in different boundary conditions and the predicted boiling patterns and temperature fields are discussed.

Étude des écoulements avec changement de phase : application à l'évaporation directe dans les centrales solaires à concentration

Abstract: Les travaux presentes dans cette these concernent l'etude de l'evolution des regimes d'ecoulements diphasiques lors de l'evaporation progressive dans un canal horizontal. Le but est de mieux comprendre l'ecoulement a l'interieur d'un tube recepteur d'une centrale solaire a concentration a generation directe de vapeur. Cette technologie, presentee comme une amelioration des systemes actuels pouvant permettre une reduction des couts, consiste en la production de vapeur directement sous l'effet du rayonnement solaire concentre. La prevision de l'ecoulement liquide-vapeur alors genere dans le tube est encore de nos jours difficile, c'est pourquoi le recours a la simulation numerique est interessant. Pour cela un modele a ete developpe permettant la simulation de ces ecoulements, depuis le debut de la creation de la vapeur jusqu'a l'existence de larges poches. Base sur le modele diphasique VOF du code Fluent, par l'ajout de fonctions personnalisees et d'une phase dispersee supplementaire, il permet de modeliser differents phenomenes lies au processus d'evaporation : creation en paroi, transport, recondensation et creation de larges structures. Ce developpement a ete mis en oeuvre pour simuler des ecoulements en evaporation, permettant de reproduire l'evolution des regimes d'ecoulement. La validation est faite grâce a une etude experimentale de la litterature, en comparant les regimes d'ecoulements obtenus pour differents debits de liquide et sous l'effet de differents flux de chaleur. Enfin, le modele a ete applique a la simulation de la generation de vapeur dans le tube recepteur d'une centrale solaire, mettant en evidence l'apparition et l'evolution des differents regimes d'ecoulement. Au vu du peu d'installations experimentales trouvees dans la litterature sur le sujet, et afin de valider au mieux les fonctions developpees, une installation experimentale a ete concue et dimensionnee.

Operational management of a centrifugal slurry pump through strategic CFD modelling

Abstract: The objective of this present work is to study the performance characteristics of a centrifugal slurry pump, handling water at different operating speeds using computational fluid dynamics (CFD) code FLUENT. Three-dimensional numerical simulation is carried out to investigate the flow field inside the pump passage at ‘design’ and ‘off-design’ conditions. Turbulence models namely, eddy large simulation, standard k-e and k-? models are being used for simulation of flow through pump. It indicates the accuracy of each model by conducting comparison with experimental values through quantitative tests like ANOVA and generate linear regression line plots for corresponding models for strategic implications. This paper has a limitation that water as a standard fluid has been used as a working fluid instead of direct slurry as it is easy to simulate through CFD. It is rare to see literature regarding statistical comparison of various existing simulating models for slurry pumps at different rpm ranges.

Numerical and experimental investigations of boiling enhancement in buoyancy-driven microchannels

Abstract: In this study, confinement-driven boiling enhancement trends and experimental data from narrow parallel plate channels are presented and analyzed via comparison with numerical simulations of buoyancy-driven boiling and two phase flow using the commercially-available Fluent CFD software package. An Euler-Euler multiphase approach, known as the volume of fluid (VOF) method, is employed, as bubbles sizes are on the order of the channel dimensions. Numerical results suggest that enhanced natural convection already accounts for a large portion of the unconfined pool boiling heat flux. While the increased buoyancy from large vapor fractions in narrow channels may lead to an order of magnitude increase in channel mass flux, confinement-driven convective enhancement is found to increase the unconfined boiling heat flux by less than 10%. Further, simulated convective enhancement is found to be a maximum for intermediate size channels, in direct contrast to experimental data which show maximum enhancement (500%) for the smallest channels investigated. Experimental results for different channel wall materials suggest an enhancement mechanism highly dependent on boiling surface characteristics.