Thermodynamic analysis of a diabatic two-phase flow for a pure refrigerant and a refrigerant/oil mixture under equilibrium conditions Re ´mi Revellin*, Miguel Padilla, Ahmed Bensafi, Philippe Haberschill, Jocelyn Bonjour Universite ´ de Lyon, CNRSINSA-Lyon, CETHIL, UMR5008, F-69621, Villeurbanne, FranceUniversite ´ Lyon 1, F-69622, France article info Article history: Received 9 April 2009 Received in revised form 18 June 2009 Accepted 6 July 2009 Published online 6 August 2009 Keywords: Refrigerant Mixture Oil Calculation Thermodynamics property Two-phase flow Boiling abstract Two different definitions of the vapor quality during a diabatic two-phase flow with and without the presence of oil are presented in this paper: the well-known vapor flow quality and the thermodynamic vapor quality. The vapor flow quality is based on the mass flow rates whereas the thermodynamic vapor quality is based on the mass. Two-phase thermodynamic diagrams for pure R-134a and R-134a/oil mixture are plotted for different slip ratios. It is shown that the iso-flow quality lines are moved to lower enthalpies for larger slip ratios. In addition, the maximum vapor flow quality of a fluid/oil mixture is shown to increase when increasing the slip ratio whereas the maximum thermodynamic vapor quality remains constant. In addition, the correct expression of the elementary derivative of the vapor quality is also proposed, highlighting the role of the heat capacity at constant vapor quality. ª 2009 Elsevier Ltd and IIR. All rights reserved. Analyse thermodynamique de l’e ´ coulement diphasique diabatique d’un frigorige `ne pur et d’un me ´ lange frigorige ` ne/ huile sous des conditions d’e ´ quilibre Mots cle ´s : Frigorige `ne ; Me ´lange ; Huile ; Calcul ; Proprie ´te ´ thermodynamique ; E ´ coulement diphasique ; E ´ bullition 1. Introduction Thermodynamic vapor quality is one of the most important parameter in two-phase systems. It represents the mass of the vapor over the total mass of the system. It dates back to 1869, with the works of Andrews (1869) and the Thomson’s Theory (Thomson, 1871) related to the study of the continuity of liquid and vapor states in multiphase systems, being the first * Corresponding author. Tel.: þ33 472437231; fax: þ33 472438811. E-mail address: remi.revellin@insa-lyon.fr (R. Revellin). www.iifiir.org available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/ijrefrig 0140-7007/$ – see front matter ª 2009 Elsevier Ltd and IIR. All rights reserved. doi:10.1016/j.ijrefrig.2009.07.004 international journal of refrigeration 32 (2009) 1784–1790