الأيام الوطنية للبحث العلمي والتجديد التكنولوجي تونس 19-20 نوفمبر2007 Ministère de l'Enseignement Supérieur, de la Recherche Scientifique et de la Technologie. الأيام الوطنية للبحث العلمي والتجديد التكنولوجي تونس 19-20 نوفمبر2007 Assises Nationales de la Recherche Scientifique et de l’Innovation Technologique Tunis 19-20 Novembre 2007 وزارة التعليم العالي و البحث العلمي و التكنولوجيا Unité de recherche Thermodynamique Appliquée جامعة قابس المدرسة الوطنية للمهندسين بقابس Code : 99/UR/11-21 Résumés des Principaux Articles parus en 2006 et 2007 Unité de Recherche : Thermodynamique Appliquée وحدة البحث : ديناميكا حرارية مطبقة Research Unit : Applied Thermodynamics Code :99/UR/11-21الرمز : Abstract for principal article appeared in 2006 and 2007 المسؤول : عمار بن ابرهيم Responsable : Ben Brahim Ammar ملخص لأهم منشورات سنتي 2006 و2007 E-mail : ammar.benbrahim@enig.rnu.tn Far East J. Appl. Math. 25(2) (2006), 179-197 Influence of thermodiffusion effect on entropy generation in thermosolutal convection Abstract : The physical problem studied in this paper is the influence of thermodiffusion effect on the entropy generation in steady state of thermosolutal convection in a square cavity filled with a binary gas mixture with one vertical wall heated and the other vertical wall is cooled, the remaining two walls are insulated. The analysis deals with a numerical determination of the entropy generation on 2D approximation using the finite volume method adapted to the staggered grid. In this study, the total entropy generation is treated a function of : (1) the buoyancy forces by report to the thermal buoyancy, (2) the thermal diffusion ratio KT, a parameter characterizing the importance of thermodiffusion effect phenomenon and (3) the well know thermal buoyancy forces dominate the solutal buoyancy forces, values are not sensible for the variation of KT. In this case, thermodiffusion effect has no influence on the entropy production. When the solutal buoyancy forces dominate, thermodiffusion effect leads to an increase of the entropy generation in both cases of opposite and cooperative buoyancy forces. It has been found also, that the total entropy generation takes a minimum value found also, that the total entropy generation takes a minimum value found also, that the total entropy generation takes a minimum ratio for higher values of the thermal Grashof number. This minimum is found for N=-1 and GrT=105 and is minimum for KT=0.3. More details of the investigation is focused for the special case when N=-1. Keywords : Soret effect, heat and mass transfer, entropy generation, numerical methods, cavity Int. J. Exergy, Vol. 4, No. 3, 2007 Journal de la Société Chimique de Tunisie, 2006, 8, 237-250 N. HIDOURI, H. ABBASSI*, M. MAGHERBI+ and A. Ben Brahim Performances des mélanges LiBr-H2O, LiCl-CaCl2 et LiCl-MgCl2-H2O en pompe à chaleur et en réfrigération Influence of Dufour effect on entropy generation in double diffusive convection Department of Chemical and Process Engineering National School of Engineers, Applied Thermodynamics Unity Avenue of Omar Ibn El Khattab, 6029 Gabes, Tunisia e-mail: n_hidouri@yahoo.com ammar.benbrahim@enig.rnu.tn * Departement of Physics, Sciences Faculty P. B. 802, 3018 Sfax, Tunisia e-mail: hassen.abbassi@fss.rnu.tn + Civil Engineering Department High Institute of Applied Sciences and Technology e-mail: magherbim@yahoo.fr B. Chaouachi *, S. Gabsi, A. Ben Brahim École Nationale d'Ingénieurs de Gabès, Rue Omar Ibn El Khattab, 6029 Gabès, Tunisie M. Magherbi* Civil Engineering Department, High Institute of Applied Sciences and Technology, Avenue of Omar Ibn El Khattab, Gabès 6029, Tunisia Fax: +216-753-92-190 E-mail: magherbim@yahoo.fr *Corresponding author N. Hidouri Chemical and Process Engineering Department, Engineers National School of Gabès, Avenue of Omar Ibn El Khattab, Gabès 6029, Tunisia E-mail: n_hidouri@yahoo.com Abstract : Les cycles à absorption mettent en jeu au moins deux fluides: un solvant et un soluté. Bien que d'autres couples soient étudiés, les seuls qui soient utilisés en pratique pour la quasi-totalité des applications sont les deux couples LiBr-H2O et NH3-H20. Ces mélanges présentent quelques inconvénients tels que les niveaux de pression, la corrosion, la toxicité, le prix élevé, le risque de cristallisation pour le cas du binaire LiBr-H2O. L'objectif de ce travail est d'analyser les deux mélanges LiCl-MgCl2-H2O et LiCl-CaCl2-H2O. Il s'agit d'étudier l'effet des divers variables opératoires sur le coefficient de performance, la puissance dégagée, la dépense d'énergie et la densité de stockage en mode de fonctionnement en pompe à chaleur et en réfrigération. Les résultats obtenus montrent que le mélange LiCl-MgCl2-H2O présente des caractéristiques intéressantes telles qu'un coefficient de performance qui peut atteindre 1,95 en pompe à chaleur et 0,9 en réfrigération, un effet de pompe à chaleur qui peut dépasser de 100 % celui du LiBr-H2O et un prix de revient plus bas que ce dernier. Quant à la densité de stockage, qui traduit le volume efficace de la machine, est favorable au mélange conventionnel LiBr-H2O en pompe à chaleur et au mélange LiCl-MgCl2-H2O en réfrigération ce qui nécessite une étude technico-économique pour décider de la possibilité de remplacement du système LiBr-eau par l'un des deux autres systèmes le moins coûteux. Keywords : absorption, pompe à chaleur, réfrigération, performances. A. Ben Brahim Chemical and Process Engineering Department, Engineers National School of Gabès, Avenue of Omar Ibn El Khattab, Gabès 6029, Tunisia E-mail: Ammar.BenBrahim@enig.rnu.tn H. Abbassi Sciences Faculty of Sfax, Department of Physics, P.B. 802, Sfax 3018, Tunisia E-mail: Hassen.Abbassi@fss.rnu.tn Abstract: The influence of Dufour effect on entropy generation in double diffusive convection is numerically investigated in this paper. The dimensionless total entropy generation is evaluated as a function of : - The buoyancy ratio N, a parameter characterising the solutal buoyancy forces by report to the thermal ones ; - The Dufour Parameter KF, a parameter characterising the influence of the diffision-thermo effect ; - The thermal Grashof number. More details of the investigation is focused for the special case when N = -1. Advances and Applications in Fluid Mechanics Volume 1, Issue 2, 2007 Pages 181-205 Entropy generation optimization in double diffusive convection considering Soret effect Abstract : Optimization of entropy generation in an inclined square cavity filled with a fluid and submitted to thermal and concentration gradients in presence of the Soret effect is numerically analysed by solving the mass, the momentum, the energy and the species conservation equations. Entropy generation is evaluated as a function of: (1) the inclination angle of the cavity β, ranging between 0° and 180°, (2) the thermal diffusion ratio KT, a parameter characterizing the Soret effect phenomenon and ranging between 0 and 0.5, (3) the buoyancy ratio N, a parameter measuring the intensity of the solutal buoyancy forces by report to the thermal buoyancy forces and (4) the well known thermal Grashof number. Entropy generation takes a constant minimum value for all KT values at β = 0° and 180° for respectively, opposite, and cooperative buoyancy forces. The inclination angle for which entropy generation is maximum, is constant for all KT values. For a fixed inclination angle, Soret effect tends always to increase the entropy generation. More details of the influence of Soret effect on entropy generation for the special case when N = -1 is discussed. Keywords : double diffusive convection, entropy generation, inclined enclosure, Soret effect thermodynamics of irreversible processes. M. Maghrebi*, N. Hidouri and A. Ben Brahim * Civil Engineering Department High Institute of Applied Sciences and Technology Gabes University Avenue of Omar Ibn El Khattab, 6029 Gabes, Tunisia e-mail: magherbim@yahoo.fr Unit of Applied Thermodynamics Chemical and Process Engineering Department Engineers National School, Gabes University Omar Ibn El Khattab, 6029 Gabes, Tunisia e-mail: n_hidouri@yahoo.com ammar.benbrahim@enig.rnu.tn Progress in Computational Fluid Dynamics, Vol. 7, No. 5, 2007 Entropy generation in double diffusive convection in presence of the Soret effect M. Magherbi* High Institute of Applied Sciences and Technology, Gabès University, Avenue of Omar Ibn El Khattab, 6029 Gabès, Tunisia Fax: +216 75 392 190 E-mail: magherbim@yahoo.fr *Corresponding author Int. J. Exergy, Vol. 3, No. 4, 2006 Cooling loads analysis of an endoreversible solar absorption refrigerator cycle N. Hidouri Engineers National School of Gabès, Gabès University, Avenue of Omar Ibn El Khattab, 6029 Gabès, Tunisia Fax: +216 75 392 190 E-mail: njiidouri@yahoo.com A. Ben Brahim Engineers National School of Gabès, Gabès University, Avenue of Omar Ibn El Khattab, 6029 Gabès, Tunisia Fax: +216 75 392 190 E-mail: Ammar.BenBrahim@enig.mu.tn A. Fellah* and A. Ben Brahim Applied Thermodynamics Research Unit, National Engineers School of Gabes, Omar Ibn Elkhattab Street, 6029 Gabes, Tunisia Fax: +216- 75 392 190 E-mail: ali.fellah@laposte.net E-mail : ammar.benbrahim@enig.rnu.tn *Corresponding author M. Bourouis and A. Coronas Centro de Innovacion Tecnolôgica en Revalorizaciôn Energética y Refrigeraciôn (CREVER), Univ. Rovira i Virgili Autovi'a de Salou, s/n, 43006, Tarragona, Spain Fax: +977 54 22 72 E-mail: mahmoud.bourouis@urv.net E-mail: Alberto.coronas@urv.net Entropy 2006, 8[1], 1-17 H. Abbassi Faculty of Sciences, Sfax University, 3018 Sfax, Tunisia E-mail: Hassen.Abbassi@fss.mu.tn Second law analysis in convective heat and mass transfer Magherbi Mourad1, Abbassi Hassen2, Hidouri Nejib3, Ben Brahim Ammar4 Abstract: Influence of the Soret effect on entropy generation in a square cavity filled with a binary gas mixture in double diffusive convection is numerically studied. It was found that entropy generation increases with the increase of thermal diffusion and buoyancy ratios for fixed thermal Grashof number. Total irreversibility takes a minimum value at a special buoyancy ratio ranging between -1 and 0. Soret effect causes the increase of total irreversibility by more than 50 % at higher values of thermal Grashof number and buoyancy ratio. More details of the irreversibility localisation are discussed. Keywords : cavity; heat and mass transfer; entropy generation ; irreversible processes; numerical methods; Soret effect. High Institute of Applied Sciences and Technology. Civil Engineering Department, Avenue Omar Ibn El Khattab. 6029 Gabes-Tunisia. Tél.: +21675392100, Fax: +21675392190, e-maii : magherbim@yahoo.fr Sfax Faculty of Sciences, Department of physics. P. B. 802. 3018 Sfax-Tunisia. Fax : + 216 4 274 437. e-mail : Hassen.Abbassi@fss.rnu.tn Engineers National School of Gabes, Chemical and Processes Engineering Departement, Avenue Omar Ibn El Khattab, 6029 Gabes-Tunisia, Tél. : +21675392100, Fax: +21675392190. e-mail :n_hidouri@yahoo.com Engineers National School of Gabes, Chemical and Processes Engineering Departement, Avenue Omar Ibn El Khattab, 6029 Gabes-Tunisia, Tél.: +21675392100, Fax: +21675392190, e-mail : Ammar.BenBrahim@enig.rnu.tn Abstract : This paper deals with the analysis of the Cooling Loads (CL) of a solar absorption refrigerator. For this purpose, a new Process Conceptual Design (PCD) approach based on equivalent endoreversible model and hierarchical decomposition is developed. The influences of many cooling load aspects on the model performances are investigated. A sensitive study is made : performance coefficient (i.e., its inverse) vs, different cooling load aspects. New relationships between technical and economical criteria and optimal parameters stand out. An endoreversible new bound for the Inverse Specific Cooling Load (ISCL) is achieved. For every case, functional and practical domains are defined. Academic interest domains are also notified. Keywords : absorption cycle; conceptual design; cooling load; endoreversible; hierarchical decomposition. Abstract : This paper reports the numerical determination of the entropy generation due to heat transfer. mass transfer and fluid friction in steady state for laminar double diffusive convection. In an inclined enclosure with heat and mass diffusive walls. by solving numerically the mass, momentum. species conservation and energy balance equations, using a Control Volume Finite-Element Method. The influences of the inclination angle, die thermal Grashof number and the buoyancy ratio on total entropy generation were investigated. The irreversibilities localization due to heat transfer, mass transfer and fluid friction is discussed for three inclination angles at a fixed thermal Grashof number. Keywords : Heat transfer. Mass transfer. Cavity. Entropy generation École Nationale d'Ingénieurs de Gabès, Rue Omar Ibn El Khattab, 6029 Gabès, Tunisie