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 Spring 2006 X.J.Jin Lecture 2 First Law ll
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2006 © 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,oin,-H,i。+dg+δW=dU Steady state w =0 System boundary Adiabatic 89=0 Sm; im,=dim。 H,=H。 Adiabatic process Isenthalpic expansion 绝热过程 SJTU Thermodynamics of Materials Spring 2006 ©X.J.Jin Lecture 2 First Law ll
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2006 © 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 δmi δmo System: valve at steady state Hiδmi − Hoδmo +δQ +δW = dU Adiabatic δQ = 0 Steady state δW = 0 δmi = δmo 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. ot System boundary H 温度计 P:.T 777777777 Adiabatic process SJTU Thermodynamics of Materials Spring2006©X.J.Jin Lecture 2 First Law ll
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2006 © 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 δmi δmo H JT P T ⎟⎠⎞ ⎜⎝⎛ ∂∂ η = 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 Spring 2006 ©X.J.Jin Lecture 2 First Law ll
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2006 © 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). = nRTPV = RTVP R : the universal gas constant: 8.314 J/(mol•K). = /4.22 molLV 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 ·No phase change ·Single value of specific volume for every pressure ·No discontinuities ·A smooth surface Volume- Temperature 等容线 等温线 SJTU Thermodynamics of Materials Spring 2006 ©X.J.Jin Lecture 2 First Law ll
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2006 © X. J. Jin Lecture 2 First Law II P-V-T surface of ideal gas • No phase change • Single value of specific volume for every pressure • No discontinuities • A smooth surface 等容线 等温线