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Etude paramétrique des échanges convectifs turbulents dans les configurations d’intérêt pratique / Ridha Mebrouk

Titre : Etude paramétrique des échanges convectifs turbulents dans les configurations d’intérêt pratique Type de document : texte imprimé Auteurs : Ridha Mebrouk, Auteur ; Abderrahim Boudenne, Directeur de thèse ; Yassine Kabar, Directeur de thèse Editeur : جامعة الإخوة منتوري قسنطينة Année de publication : 2017 Importance : 139 f. Format : 30 cm. Note générale : 2 copies imprimées disponibles

Langues : Français ( fre)Tags : Convection turbulente Simulation numérique Nanofluide Enceinte chauffée par le bas,

Convection forcée Echanges turbulents Echangeur de chaleur Transfert thermique conjugué Turbulent convection Numerical simulation Nanofluid Enclosure heated from below Forced

convection Turbulent exchanges Heat exchanger Conjugate heat transfer ????? ???????? ???????? ???????? ????????? ??????? ????? ?? ??????? ????? ??????? ??????? ???????? ?????????

???????????? ??????? ?????????Index. décimale : 620 Génie Mécanique Résumé : This thesis presents the results of two studies: the first concerns natural turbulent convection in a

rectangular cavity heated from the bottom wall and filled with a nanofluid and the second relates to the

investigation of conjugate heat transfer in a fin-and-tube heat exchanger.

The cavity of the first study is tall and has a heat source embedded on its bottom wall, while its left, right

and top walls are maintained at a relatively low temperature. The working fluid is a water based nanofluid

having three nanoparticle types: alumina, copper and copper oxide. The influence of pertinent parameters

such as the Rayleigh number, the type of nanofluid and solid volume fraction of nanoparticles on the cooling

performance is studied. Steady forms of two dimensional Reynolds-Averaged-Navier-Stokes equations and

conservation equations of mass and energy, coupled with the Boussinesq approximation, are solved by the

control volume based discretisation method employing the SIMPLE algorithm for pressure-velocity

coupling. Turbulence is modeled using the standard k-ε model. The Rayleigh number, Ra, is varied from

2.49x1009 to 2.49x1011. The volume fractions of nanoparticles were varied in the interval 0≤φ≤ 6% . Stream

lines, isotherms, velocity profiles and Temperature profiles are presented for various combinations of Ra,

the type of nanofluid and solid volume fraction of nanoparticles. The results are reported in the form of

average Nusselt number on the heated wall. It is shown that for all values of Ra, the average heat transfer

rate from the heat source increases almost linearly and monotonically as the solid volume fraction increases.

Finally the average heat transfer rate takes on values that decrease according to the ordering Cu, CuO and

Al2O3.

In the second study we determined the heat transfer and friction characteristics of a realistic fin-andtube heat exchanger . The computations assume steady-state heat transfer and fluid flow. Nusselt number

and friction factor characteristics of the heat exchanger are presented for various values of Reynolds

numbers. The energy conservation and the heat conduction equations in 3 dimensions have been solved

in the fluid and the solid respectivelyalong with the mass and momentum conservation equations in order

to determine these characteristics. Both laminar and turbulent flow regimes are considered. The effect of

turbulence modeling was investigated using three different models (the one equation Spalart-Allmaras

turbulence model, the standard k-ε model and the RSM model). The computations allowed the

determination of the dynamic and thermal fields. Model validation was carried out by comparing the

calculated friction factor f and Colburn j-factor to experimental results found in the literature. The

plotted results showed a qualitatively good agreement between numerical results and experimental data. The

results obtained also showed that the simplest of the three turbulence models tested(i.e. SpalartAllmaras) gives the closest values to the experimental data

Diplôme : Doctorat en sciences En ligne : ../theses/gmecanique/MEB7154.pdf Format de la ressource électronique : Permalink : https://bu.umc.edu.dz/md/index.php?lvl=notice_display&id=10428 Etude paramétrique des échanges convectifs turbulents dans les configurations d’intérêt pratique [texte imprimé] / Ridha Mebrouk, Auteur ; Abderrahim Boudenne, Directeur de thèse ; Yassine Kabar, Directeur de thèse . - [S.l.] : جامعة الإخوة منتوري قسنطينة, 2017 . - 139 f. ; 30 cm.

2 copies imprimées disponibles

Langues : Français (fre)

Tags : Convection turbulente Simulation numérique Nanofluide Enceinte chauffée par le bas,

Convection forcée Echanges turbulents Echangeur de chaleur Transfert thermique conjugué Turbulent convection Numerical simulation Nanofluid Enclosure heated from below Forced

convection Turbulent exchanges Heat exchanger Conjugate heat transfer ????? ???????? ???????? ???????? ????????? ??????? ????? ?? ??????? ????? ??????? ??????? ???????? ?????????

???????????? ??????? ?????????Index. décimale : 620 Génie Mécanique Résumé : This thesis presents the results of two studies: the first concerns natural turbulent convection in a

rectangular cavity heated from the bottom wall and filled with a nanofluid and the second relates to the

investigation of conjugate heat transfer in a fin-and-tube heat exchanger.

The cavity of the first study is tall and has a heat source embedded on its bottom wall, while its left, right

and top walls are maintained at a relatively low temperature. The working fluid is a water based nanofluid

having three nanoparticle types: alumina, copper and copper oxide. The influence of pertinent parameters

such as the Rayleigh number, the type of nanofluid and solid volume fraction of nanoparticles on the cooling

performance is studied. Steady forms of two dimensional Reynolds-Averaged-Navier-Stokes equations and

conservation equations of mass and energy, coupled with the Boussinesq approximation, are solved by the

control volume based discretisation method employing the SIMPLE algorithm for pressure-velocity

coupling. Turbulence is modeled using the standard k-ε model. The Rayleigh number, Ra, is varied from

2.49x1009 to 2.49x1011. The volume fractions of nanoparticles were varied in the interval 0≤φ≤ 6% . Stream

lines, isotherms, velocity profiles and Temperature profiles are presented for various combinations of Ra,

the type of nanofluid and solid volume fraction of nanoparticles. The results are reported in the form of

average Nusselt number on the heated wall. It is shown that for all values of Ra, the average heat transfer

rate from the heat source increases almost linearly and monotonically as the solid volume fraction increases.

Finally the average heat transfer rate takes on values that decrease according to the ordering Cu, CuO and

Al2O3.

In the second study we determined the heat transfer and friction characteristics of a realistic fin-andtube heat exchanger . The computations assume steady-state heat transfer and fluid flow. Nusselt number

and friction factor characteristics of the heat exchanger are presented for various values of Reynolds

numbers. The energy conservation and the heat conduction equations in 3 dimensions have been solved

in the fluid and the solid respectivelyalong with the mass and momentum conservation equations in order

to determine these characteristics. Both laminar and turbulent flow regimes are considered. The effect of

turbulence modeling was investigated using three different models (the one equation Spalart-Allmaras

turbulence model, the standard k-ε model and the RSM model). The computations allowed the

determination of the dynamic and thermal fields. Model validation was carried out by comparing the

calculated friction factor f and Colburn j-factor to experimental results found in the literature. The

plotted results showed a qualitatively good agreement between numerical results and experimental data. The

results obtained also showed that the simplest of the three turbulence models tested(i.e. SpalartAllmaras) gives the closest values to the experimental data

Diplôme : Doctorat en sciences En ligne : ../theses/gmecanique/MEB7154.pdf Format de la ressource électronique : Permalink : https://bu.umc.edu.dz/md/index.php?lvl=notice_display&id=10428 ## Exemplaires

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