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Partager le résultat de cette recherche Interroger des sources externesContribution à l’étude de la convection naturelle dans des enceintes à parois courbées remplies de nanofluides. / Abdelaziz Yahiaoui
Titre : Contribution à l’étude de la convection naturelle dans des enceintes à parois courbées remplies de nanofluides. Type de document : texte imprimé Auteurs : Abdelaziz Yahiaoui, Auteur ; Mahfoud Djezzar, Directeur de thèse Editeur : جامعة الإخوة منتوري قسنطينة Année de publication : 2019 Importance : 147 f. Format : 30 cm. Note générale : 2 copies imprimées disponibles
Langues : Français (fre) Catégories : Français - Anglais
PhysiqueTags : Physique Energétique: Photothermique convection naturelle nanofluides enceintes à parois courbées vorticité-fonction
de courant simulation numérique Natural convection Nanofluids enclosures with curved walls vorticity-Streamlines Numerical simulation الحمل الطبيعي النانوفلويد تجويف بجدران منحنية التدويم-دوال التيارات المحاكات العدديةIndex. décimale : 540 Chimie et sciences connexes Résumé :
In our investigation we have studied and compared the laminar and permanent natural convection in two-dimensional enclosures (square enclosure, enclosures with curved walls) filled with nanofluid (water-Cu) and subject to three different types of boundary conditions that are: first case (horizontal walls of enclosure are adiabatic, and vertical walls are isothermal maintained at cold temperature Tc and hot temperature Th), second case (vertical walls of enclosures are maintained isothermal at a cold temperature Tc, horizontal top walls are considered adiabatic and bottom walls are maintained isothermal at a constant hot temperature Th), third case (vertical walls of the enclosures are maintained isothermal at a cold temperature Tc, horizontal top walls are considered adiabatic and bottom walls are maintained at a sinusoidal hot temperature). We considered a Newtonian fluid and the flow is incompressible. The values of Rayleigh number are: 103, 104, 105 and 106, the Prandtl number is fixed to 6.2 and the volume fraction ϕ is taken equal to: 0, 0.1 and 0.2. The method used in this study is the finite volume method. The numerical results obtained show that the heat transfer rate increases both with increasing the volume fraction and the Rayleigh number, and that the average Nusselt number and therefore the heat transfer increases with the increase of the volume fraction of the nanoparticles for the full range of Rayleigh numbers, and that the effect of the nanofluid on natural convection is much more manifest for higher values of Rayleigh number.Note de contenu :
Annexes.
Diplôme : Doctorat en sciences En ligne : ../theses/physique/YAH7521.pdf Format de la ressource électronique : Permalink : https://bu.umc.edu.dz/md/index.php?lvl=notice_display&id=11360 Contribution à l’étude de la convection naturelle dans des enceintes à parois courbées remplies de nanofluides. [texte imprimé] / Abdelaziz Yahiaoui, Auteur ; Mahfoud Djezzar, Directeur de thèse . - جامعة الإخوة منتوري قسنطينة, 2019 . - 147 f. ; 30 cm.
2 copies imprimées disponibles
Langues : Français (fre)
Catégories : Français - Anglais
PhysiqueTags : Physique Energétique: Photothermique convection naturelle nanofluides enceintes à parois courbées vorticité-fonction
de courant simulation numérique Natural convection Nanofluids enclosures with curved walls vorticity-Streamlines Numerical simulation الحمل الطبيعي النانوفلويد تجويف بجدران منحنية التدويم-دوال التيارات المحاكات العدديةIndex. décimale : 540 Chimie et sciences connexes Résumé :
In our investigation we have studied and compared the laminar and permanent natural convection in two-dimensional enclosures (square enclosure, enclosures with curved walls) filled with nanofluid (water-Cu) and subject to three different types of boundary conditions that are: first case (horizontal walls of enclosure are adiabatic, and vertical walls are isothermal maintained at cold temperature Tc and hot temperature Th), second case (vertical walls of enclosures are maintained isothermal at a cold temperature Tc, horizontal top walls are considered adiabatic and bottom walls are maintained isothermal at a constant hot temperature Th), third case (vertical walls of the enclosures are maintained isothermal at a cold temperature Tc, horizontal top walls are considered adiabatic and bottom walls are maintained at a sinusoidal hot temperature). We considered a Newtonian fluid and the flow is incompressible. The values of Rayleigh number are: 103, 104, 105 and 106, the Prandtl number is fixed to 6.2 and the volume fraction ϕ is taken equal to: 0, 0.1 and 0.2. The method used in this study is the finite volume method. The numerical results obtained show that the heat transfer rate increases both with increasing the volume fraction and the Rayleigh number, and that the average Nusselt number and therefore the heat transfer increases with the increase of the volume fraction of the nanoparticles for the full range of Rayleigh numbers, and that the effect of the nanofluid on natural convection is much more manifest for higher values of Rayleigh number.Note de contenu :
Annexes.
Diplôme : Doctorat en sciences En ligne : ../theses/physique/YAH7521.pdf Format de la ressource électronique : Permalink : https://bu.umc.edu.dz/md/index.php?lvl=notice_display&id=11360 Exemplaires (1)
Code-barres Cote Support Localisation Section Disponibilité YAH/7521 YAH/7521 Thèse Bibliothèque principale Thèses Disponible
Titre : Contribution à l’étude des transferts thermiques dans les nanofluides. Type de document : texte imprimé Auteurs : Ahlam Ghennai, Auteur ; Rachid Bessaih, Directeur de thèse Mention d'édition : 07/06/2021 Editeur : جامعة الإخوة منتوري قسنطينة Année de publication : 2021 Importance : 136 f. Format : 30 cm. Note générale : Doctorat 3éme CYCLE LMD.
1 copies imprimées disponibles
Langues : Français (fre) Catégories : Français - Anglais
Génie MécaniqueTags : G.Mécanique: Energétique Transfert thermique simulation numérique cavité canal nanofluides génération d’entropie modèle de mélange
Heat transfer numerical simulation cavity channel nanofluids entropy generation mixture model الحمل الحراري المحاكاة العددية التجويف القناة الموائع النانوية توليد الإنتروبيا نموذج الخليطIndex. décimale : 620 Génie Mécanique Résumé :
This thesis deals with the numerical modelling of laminar natural and mixed convection flows of different anofluids types. Numerical simulations were performed using Ansysfluent software, considering three configurations: the square cavity, the cubic cavity, and the inclined channel. The numerical results obtained were validated with those found in the literature. A good agreement was obtained. We present three parts grouping the treated configurations: The first part concerns the study of 2-D natural convection in a square cavity equipped with a pentagonal obstacle, filled with a nanofluid (Cu/Water). The effects of the Rayleigh number Ra, the volumetric concentration of nanoparticles , the aspect ratio r and the orientation of the block were discussed The second part examines the 3-D mixed convection inside a cubic cavity with a heated square-section obstacle. This study compares the single carbon nanotube CNT/water nanofluid and the hybrid CNT-Copper/water nanofluid with different concentration ratios, Richardson number Ri, Reynolds number Re, and block aspect ratio r. In this case, three correlations have been developed to predict the average Nusselt number Nu's variation as a function of the chosen parameters. The third part deals with the numerical study of laminar mixed convection with entropy generation in an inclined channel with four heated blocks, traversed by a hybrid Al2O3- Cu/water nanofluid. In this part, the use of a two-phase mixing model approach was considered to demonstrate the effects of several parameters such as Ri, Re, , θ (the channel tilt), and the position of the block on Nusselt number, entropy generations, and Bejan number. Two different correlations were also determined to express Nu's average values for the position of aligned and non-aligned blocks.
Diplôme : Doctorat En ligne : ../theses/gmecanique/GHE7758.pdf Format de la ressource électronique : Permalink : https://bu.umc.edu.dz/md/index.php?lvl=notice_display&id=11591 Contribution à l’étude des transferts thermiques dans les nanofluides. [texte imprimé] / Ahlam Ghennai, Auteur ; Rachid Bessaih, Directeur de thèse . - 07/06/2021 . - جامعة الإخوة منتوري قسنطينة, 2021 . - 136 f. ; 30 cm.
Doctorat 3éme CYCLE LMD.
1 copies imprimées disponibles
Langues : Français (fre)
Catégories : Français - Anglais
Génie MécaniqueTags : G.Mécanique: Energétique Transfert thermique simulation numérique cavité canal nanofluides génération d’entropie modèle de mélange
Heat transfer numerical simulation cavity channel nanofluids entropy generation mixture model الحمل الحراري المحاكاة العددية التجويف القناة الموائع النانوية توليد الإنتروبيا نموذج الخليطIndex. décimale : 620 Génie Mécanique Résumé :
This thesis deals with the numerical modelling of laminar natural and mixed convection flows of different anofluids types. Numerical simulations were performed using Ansysfluent software, considering three configurations: the square cavity, the cubic cavity, and the inclined channel. The numerical results obtained were validated with those found in the literature. A good agreement was obtained. We present three parts grouping the treated configurations: The first part concerns the study of 2-D natural convection in a square cavity equipped with a pentagonal obstacle, filled with a nanofluid (Cu/Water). The effects of the Rayleigh number Ra, the volumetric concentration of nanoparticles , the aspect ratio r and the orientation of the block were discussed The second part examines the 3-D mixed convection inside a cubic cavity with a heated square-section obstacle. This study compares the single carbon nanotube CNT/water nanofluid and the hybrid CNT-Copper/water nanofluid with different concentration ratios, Richardson number Ri, Reynolds number Re, and block aspect ratio r. In this case, three correlations have been developed to predict the average Nusselt number Nu's variation as a function of the chosen parameters. The third part deals with the numerical study of laminar mixed convection with entropy generation in an inclined channel with four heated blocks, traversed by a hybrid Al2O3- Cu/water nanofluid. In this part, the use of a two-phase mixing model approach was considered to demonstrate the effects of several parameters such as Ri, Re, , θ (the channel tilt), and the position of the block on Nusselt number, entropy generations, and Bejan number. Two different correlations were also determined to express Nu's average values for the position of aligned and non-aligned blocks.
Diplôme : Doctorat En ligne : ../theses/gmecanique/GHE7758.pdf Format de la ressource électronique : Permalink : https://bu.umc.edu.dz/md/index.php?lvl=notice_display&id=11591 Exemplaires (1)
Code-barres Cote Support Localisation Section Disponibilité GHE/7758 GHE/7758 Thèse Bibliothèque principale Thèses Disponible
Titre : Investigation des échanges convectifs dans diverses configurations Type de document : texte imprimé Auteurs : Issam Rezaiguia, Auteur ; Mahfoud Kadja, Directeur de thèse Editeur : constantine [Algérie] : Université Constantine 1 Année de publication : 2014 Importance : 142 f. Format : 30 cm. Note générale : 2 copies imprimées disponibles
Langues : Français (fre) Catégories : Français - Anglais
Génie MécaniqueTags : convection naturelle nanofluides cavité triangulaire angle d'inclinaison simulation numérique microcanaux chute de pression transfert thermique conjugué fraction solide comportement non-Newtonien natural convection nanofluids triangular cavity inclination angle numerical simulation microchannels pressure drop conjugate heat transfer solid fraction non-Newtonian behavior الحمل الحراري الطبيعي مائع نانوي تجويف ثلاثي الشكل زاوية الميل محاكاة العددية قنوات ميكروية هبوط الضغط نقل الحرارة نسب الحيود للذرات الصلبة سلوك غير نيوتوني Index. décimale : 620 Génie Mécanique Résumé : This thesis reports the results of two studies: the first one concerns natural convection in isosceles triangular cavities with a partially active base while the second one concerns heat transfer in microchannels.
The first study considers natural convection cooling of a heat source located on the bottom wall of an inclined isosceles triangular enclosure filled with a Cu water-nanofluid. The right and left walls of the enclosure are both maintained cold at constant equal temperatures, while the remaining parts of the bottom wall are insulated. The study has been carried out for a Rayleigh number in the range 104 ≤ Ra ≤ 106, for a heat source length in the range 0.2 ≤ ε ≤ 0.8, for a solid volume fraction in the range 0.0 ≤ � ≤ 06 and for an inclination angle in the range 00 ≤ δ ≤ 450. Results are presented in the form of streamline contours, isotherms, maximum temperature at the heat source surface and average Nusselt number. It is noticed that the addition of Cu nanoparticles enhances the heat transfer rate and therefore cooling effectiveness for all values of Rayleigh number, especially at low values of Ra. The effect of the inclination angle becomes more noticeable as one increases the value of Ra. For high Rayleigh numbers, a critical value for the inclination angle of δ = 150 is found for which the heat source maximum temperature is highest.
The second study investigates heat transfer in microchannels machined in heat dissipating sinks. The fluid used is a nanofluid whose properties are temperature dependent. The energy dissipation is evaluated for various solid fraction contents along with the cooling effectiveness of this modern type of heat exchangers. The shape of the channels is also investigated. The evaluation parameter used for thermal energy dissipation is the Nusselt number while that used for cooling effectiveness is the static pressure drop between the inlet and the outlet of the microchannel. Conjugate convection-conduction energy conservation equations have been solved along with mass and momentum conservation equations in order to determine these parameters.
The results obtained showed important heat transfer augmentation with solid fraction at the expense of an increased pressure drop, i.e high pumping cost (therefore low cooling effectiveness). The microchannel inlet section geometry was also found to contribute to the values of the Nusselt number and pressure drop. Among the tested geometries (elliptical, rectangular, trapezoidal) the rectangular section provided the best compromise between heat transfer augmentation and pumping cost. At the end of the study, a comparison was made between the results obtained by assuming Newtonian rheology and those obtained with non-Newtonian rheological behavior of the same nanofluid sample. It was found that the assumption of non-Newtonian rheological behavior of nanofluids gives higher Nusselt number values and much lower pressure drops.
Diplôme : Doctorat en sciences En ligne : ../theses/gmecanique/REZ6773.pdf Format de la ressource électronique : Permalink : https://bu.umc.edu.dz/md/index.php?lvl=notice_display&id=9837 Investigation des échanges convectifs dans diverses configurations [texte imprimé] / Issam Rezaiguia, Auteur ; Mahfoud Kadja, Directeur de thèse . - constantine [Algérie] : Université Constantine 1, 2014 . - 142 f. ; 30 cm.
2 copies imprimées disponibles
Langues : Français (fre)
Catégories : Français - Anglais
Génie MécaniqueTags : convection naturelle nanofluides cavité triangulaire angle d'inclinaison simulation numérique microcanaux chute de pression transfert thermique conjugué fraction solide comportement non-Newtonien natural convection nanofluids triangular cavity inclination angle numerical simulation microchannels pressure drop conjugate heat transfer solid fraction non-Newtonian behavior الحمل الحراري الطبيعي مائع نانوي تجويف ثلاثي الشكل زاوية الميل محاكاة العددية قنوات ميكروية هبوط الضغط نقل الحرارة نسب الحيود للذرات الصلبة سلوك غير نيوتوني Index. décimale : 620 Génie Mécanique Résumé : This thesis reports the results of two studies: the first one concerns natural convection in isosceles triangular cavities with a partially active base while the second one concerns heat transfer in microchannels.
The first study considers natural convection cooling of a heat source located on the bottom wall of an inclined isosceles triangular enclosure filled with a Cu water-nanofluid. The right and left walls of the enclosure are both maintained cold at constant equal temperatures, while the remaining parts of the bottom wall are insulated. The study has been carried out for a Rayleigh number in the range 104 ≤ Ra ≤ 106, for a heat source length in the range 0.2 ≤ ε ≤ 0.8, for a solid volume fraction in the range 0.0 ≤ � ≤ 06 and for an inclination angle in the range 00 ≤ δ ≤ 450. Results are presented in the form of streamline contours, isotherms, maximum temperature at the heat source surface and average Nusselt number. It is noticed that the addition of Cu nanoparticles enhances the heat transfer rate and therefore cooling effectiveness for all values of Rayleigh number, especially at low values of Ra. The effect of the inclination angle becomes more noticeable as one increases the value of Ra. For high Rayleigh numbers, a critical value for the inclination angle of δ = 150 is found for which the heat source maximum temperature is highest.
The second study investigates heat transfer in microchannels machined in heat dissipating sinks. The fluid used is a nanofluid whose properties are temperature dependent. The energy dissipation is evaluated for various solid fraction contents along with the cooling effectiveness of this modern type of heat exchangers. The shape of the channels is also investigated. The evaluation parameter used for thermal energy dissipation is the Nusselt number while that used for cooling effectiveness is the static pressure drop between the inlet and the outlet of the microchannel. Conjugate convection-conduction energy conservation equations have been solved along with mass and momentum conservation equations in order to determine these parameters.
The results obtained showed important heat transfer augmentation with solid fraction at the expense of an increased pressure drop, i.e high pumping cost (therefore low cooling effectiveness). The microchannel inlet section geometry was also found to contribute to the values of the Nusselt number and pressure drop. Among the tested geometries (elliptical, rectangular, trapezoidal) the rectangular section provided the best compromise between heat transfer augmentation and pumping cost. At the end of the study, a comparison was made between the results obtained by assuming Newtonian rheology and those obtained with non-Newtonian rheological behavior of the same nanofluid sample. It was found that the assumption of non-Newtonian rheological behavior of nanofluids gives higher Nusselt number values and much lower pressure drops.
Diplôme : Doctorat en sciences En ligne : ../theses/gmecanique/REZ6773.pdf Format de la ressource électronique : Permalink : https://bu.umc.edu.dz/md/index.php?lvl=notice_display&id=9837 Exemplaires (1)
Code-barres Cote Support Localisation Section Disponibilité REZ/6773 REZ/6773 Thèse Bibliothèque principale Thèses Disponible
Titre : Modelisation et optimisation des capteurs solaires hybrides. Type de document : texte imprimé Auteurs : Amel Ghellab, Auteur ; Abdennacer Kabi, Directeur de thèse Editeur : جامعة الإخوة منتوري قسنطينة Année de publication : 2018 Importance : 120 f. Format : 30 cm. Note générale : 2 copies imprimées disponibles. Langues : Français (fre) Catégories : Français - Anglais
Génie ClimatiqueTags : Cellule PV capteur solaire verre PMMA air eau nanofluides modélisation simulation performances PV cell solar collector glass water nanofluids modeling الخلايا الكهروضوئية تجميع الطاقة الشمسية الزجاج الهواء الماء الناتو المانع النمذجة المحاكاة الأداء Index. décimale : 626 Génie Climatique Résumé : The growing in demand of energy risks exhausting totally different conventional fields, so in order to mitigate many states turn to deal with it and in the same time they wanted to maximize performance with less costs.
Thus we have developed a study highlighting the use of solar by introducing the hybrid photovoltaic / thermal collector consisting of a PV module under which a heat exchanger is provided to ensure the cooling of the cells.
The energy produced will be used to generate electricity and heat. At this stage we have studied the feasibility by taking two elements that are plastics as cover and nanofluids as cooling fluid.
Regarding plastics, these have proved to be the most widely used materials for the manufacture of various components, in particular those of solar heating ... etc.
As for nanofluids, it is a new technology that has revolutionized all those that have preceded it because they have high thermo physical properties.
At this stage, the study proposes the simulation of two different systems in forced convection inside the fluid channel, both for plastics and for nanofluids, the two systems proposed were based on the development of an energy balance between the different nodes of the system.
Hence the equations will be discretized and then introduced into a program written in Matlab for the purpose of calculating the unknowns and also being able to validate our results.
The results show that the use of PMMA is beneficial for transmitting more radiation compared to the glass and as for the nanofluids, the extraction of the heat under the panel proved to be better compared to the conventional fluids.
Diplôme : Doctorat en sciences En ligne : ../theses/gclim/GHE7207.pdf Format de la ressource électronique : Permalink : https://bu.umc.edu.dz/md/index.php?lvl=notice_display&id=10756 Modelisation et optimisation des capteurs solaires hybrides. [texte imprimé] / Amel Ghellab, Auteur ; Abdennacer Kabi, Directeur de thèse . - جامعة الإخوة منتوري قسنطينة, 2018 . - 120 f. ; 30 cm.
2 copies imprimées disponibles.
Langues : Français (fre)
Catégories : Français - Anglais
Génie ClimatiqueTags : Cellule PV capteur solaire verre PMMA air eau nanofluides modélisation simulation performances PV cell solar collector glass water nanofluids modeling الخلايا الكهروضوئية تجميع الطاقة الشمسية الزجاج الهواء الماء الناتو المانع النمذجة المحاكاة الأداء Index. décimale : 626 Génie Climatique Résumé : The growing in demand of energy risks exhausting totally different conventional fields, so in order to mitigate many states turn to deal with it and in the same time they wanted to maximize performance with less costs.
Thus we have developed a study highlighting the use of solar by introducing the hybrid photovoltaic / thermal collector consisting of a PV module under which a heat exchanger is provided to ensure the cooling of the cells.
The energy produced will be used to generate electricity and heat. At this stage we have studied the feasibility by taking two elements that are plastics as cover and nanofluids as cooling fluid.
Regarding plastics, these have proved to be the most widely used materials for the manufacture of various components, in particular those of solar heating ... etc.
As for nanofluids, it is a new technology that has revolutionized all those that have preceded it because they have high thermo physical properties.
At this stage, the study proposes the simulation of two different systems in forced convection inside the fluid channel, both for plastics and for nanofluids, the two systems proposed were based on the development of an energy balance between the different nodes of the system.
Hence the equations will be discretized and then introduced into a program written in Matlab for the purpose of calculating the unknowns and also being able to validate our results.
The results show that the use of PMMA is beneficial for transmitting more radiation compared to the glass and as for the nanofluids, the extraction of the heat under the panel proved to be better compared to the conventional fluids.
Diplôme : Doctorat en sciences En ligne : ../theses/gclim/GHE7207.pdf Format de la ressource électronique : Permalink : https://bu.umc.edu.dz/md/index.php?lvl=notice_display&id=10756 Exemplaires (1)
Code-barres Cote Support Localisation Section Disponibilité GHE/7207 GHE/7207 Thèse Bibliothèque principale Thèses Disponible
