States and Equilibrium State:"condition"of a system as described by its properties -How many properties do we need to fix the state of a given system? For a single component system (e.g.,gases),we need two independent intensive property values For a two-component system (e.g.,a mixture of water and steam), we need three independent intensive property values. Mass 300°C250°C Steady state in Control volume During a steady-flow process,fluid 225C properties within the control volume Mass may change with position but not with 200°C 150°C out m=2 kg time m=2kg T2=20℃ Time:1 PM T1=20°C 4=2.5m3 Mass V=1.5m3 Mass 300°C 250C in Control volume Control volume (a)State 1 (b)State 2 mcy const. 225C Mass Mass Ecy=const. out Two different states 200C 150C out Time:3 PM 上降文通大学 February 28,2019 25 SHANGHAI JIAO TONG UNIVERSITYFebruary 28, 2019 25 States and Equilibrium State: “condition” of a system as described by its properties –How many properties do we need to fix the state of a given system? • For a single component system (e.g., gases), we need two independent intensive property values • For a two-component system (e.g., a mixture of water and steam) , we need three independent intensive property values. Two different states During a steady-flow process, fluid properties within the control volume may change with position but not with time Steady state