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Entropy generation during flow boiling of pure refrigerant and refrigerant–oil mixture / R. Revellin in International journal of refrigeration, Vol. 34 N° 4 (Juin 2011) 

Public ISBD [article]  in International journal of refrigeration > Vol. 34 N° 4 (Juin 2011) . - pp. 1040-1047 Titre : Entropy generation during flow boiling of pure refrigerant and refrigerant–oil mixture Titre original : Génération d'entropie lors de l'ébullition en écoulement d'un frigorigène pur et d'un mélange frigorigène-huile Type de document : texte imprimé Auteurs : R. Revellin, Auteur ; J. Bonjour, Auteur Année de publication : 2011 Article en page(s) : pp. 1040-1047 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Thermodynamics  Flow  boiling  Entropy  Refrigerant Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Optimization of evaporators in refrigeration systems, for instance, can be conducted using entropy generation as a criterion. The latter can be used for choosing a technology (smooth tubes, enhanced tubes, tube diameter, etc) or selecting a fluid. Once this optimization is performed, the refrigerant charge can be evaluated. In this paper, different entropy generation expressions are presented for a diabatic two-phase flow of a pure refrigerant and a refrigerant–oil mixture. These expressions are developed based on the separated flow model. Depending on the boundary conditions, the equations are different and the conclusions differ from one to the other. It is shown that for a heat flux condition at the tube wall, the use of enhanced tubes is recommended at low mass velocities whereas, the use of smooth tubes is better at higher mass velocities. On the contrary, for a constant wall temperature, the use of enhanced tubes is always better than smooth tubes. The role of oil is also emphasized. The higher the oil concentration in the refrigerant, the higher the entropy generation. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711000235 [article] Entropy generation during flow boiling of pure refrigerant and refrigerant–oil mixture = Génération d'entropie lors de l'ébullition en écoulement d'un frigorigène pur et d'un mélange frigorigène-huile [texte imprimé] / R. Revellin, Auteur ; J. Bonjour, Auteur . - 2011 . - pp. 1040-1047. Génie Mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 34 N° 4 (Juin 2011) . - pp. 1040-1047 Mots-clés : Thermodynamics  Flow  boiling  Entropy  Refrigerant Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Optimization of evaporators in refrigeration systems, for instance, can be conducted using entropy generation as a criterion. The latter can be used for choosing a technology (smooth tubes, enhanced tubes, tube diameter, etc) or selecting a fluid. Once this optimization is performed, the refrigerant charge can be evaluated. In this paper, different entropy generation expressions are presented for a diabatic two-phase flow of a pure refrigerant and a refrigerant–oil mixture. These expressions are developed based on the separated flow model. Depending on the boundary conditions, the equations are different and the conclusions differ from one to the other. It is shown that for a heat flux condition at the tube wall, the use of enhanced tubes is recommended at low mass velocities whereas, the use of smooth tubes is better at higher mass velocities. On the contrary, for a constant wall temperature, the use of enhanced tubes is always better than smooth tubes. The role of oil is also emphasized. The higher the oil concentration in the refrigerant, the higher the entropy generation. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711000235