Review Key points S.J.T.U. Phase Transformation and Applications Systems can be classified as open,close and isolated systems 0th law 1st law energy conservation ·Heat/work Internal energy enthalpy heat capacity State function Mechanical energy Equilibrium/steady state SJTU Thermodynamics of Materials Fall 2012 ©X.J.Jin Lecture 2 First Law ll
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Fall 2012 © X. J. Jin Lecture 2 First Law II Review / Key points • Systems can be classified as open, close and isolated systems • 0th law • 1st law / energy conservation • Heat / work • Internal energy / enthalpy / heat capacity • State function Mechanical energy Equilibrium / steady state
1.14 Adiabatic flow through a valve: S.J.T.U. Joule-Thomson expansion Phase Transformation and Applications Adiabatic:no heat is added or removed from the system. Adiabatic fluid flow through a valve:insulated or the flow is so fast System:valve at steady state H.om,-H.om +0+W=du Steady state 8W=0 System boundary Adiabatic 80=0 δm im=im。 H,=H Adiabatic process Isenthalpic expansion 绝热过程 SJTU Thermodynamics of Materials Fall 2012 ©X.J.Jin Lecture 2 First Law ll
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Fall 2012 © X. J. Jin Lecture 2 First Law II 1.14 Adiabatic flow through a valve: Joule-Thomson expansion Adiabatic: no heat is added or removed from the system. Adiabatic fluid flow through a valve: insulated or the flow is so fast System boundary mi mo System: valve at steady state Hi mi Ho mo Q W dU Adiabatic Q 0 W 0 Steady state mi mo Hi Ho Adiabatic process Isenthalpic expansion 绝热过程
1.14 Joule-Thomson Coefficient S.J.T.U. Phase Transformation and Applications Joule-Thomson Coefficient defined as the change of temperature with pressure at constant enthalpy. at System boundary H δm δmo 温度计 77777 Adiabatic process SJTU Thermodynamics of Materials Fall 2012 ©X.J.Jin Lecture 2 First Law ll
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Fall 2012 © X. J. Jin Lecture 2 First Law II 1.14 Joule-Thomson Coefficient Joule-Thomson Coefficient : defined as the change of temperature with pressure at constant enthalpy. System boundary mi mo H JT P T Adiabatic process
1.15 Equations of State (1) S.J.T.U. Phase Transformation and Applications Equations of state the relationship among the physical variables that describe the condition of a material. For gases the relationship between pressure(P),volume (V), temperature (T)and number of moles(n). PV=ART PV-RT R:the universal gas constant:8.314 J/(mol.K) One mole of gas at 273.15 K and one atmosphere V=22.4L/mol 状态方程 理想气体的状态方程 SJTU Thermodynamics of Materials Fall 2012 ©X.J.Jin Lecture 2 First Law ll
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Fall 2012 © X. J. Jin Lecture 2 First Law II 1.15 Equations of State (1) Equations of state : the relationship among the physical variables that describe the condition of a material. For gases : the relationship between pressure (P), volume (V), temperature (T) and number of moles (n). PV nRT PV RT R : the universal gas constant: 8.314 J/(molK). V 22.4L/ mol One mole of gas at 273.15 K and one atmosphere 状态方程 理想气体的状态方程
P-V-T surface of ideal gas S.J.T.U. Phase Transformation and Applications ·Single value of specific volume for every pressure and temperature ·No discontinuities ·A smooth surface ·No phase change Volume- Temperature 等容线 等温线 SJTU Thermodynamics of Materials Fall 2012 ©X.J.Jin Lecture 2 First Law ll
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Fall 2012 © X. J. Jin Lecture 2 First Law II P-V-T surface of ideal gas • Single value of specific volume for every pressure and temperature • No discontinuities • A smooth surface • No phase change 等容线 等温线