1.17 Adiabatic Compression or Expansion(1) S.J.T.U. Phase Transformation and Applications Air arises rapidly (adiabatically)up a mountainside. At the higher altitude,the pressure is lower,and the temperature is also lower. Adiabatic Reversible:Presisting=Psystem Ideal gas System boundary ow=dW "pdy dU nCydT Psystem X Presisting PV=ART Pav +Vap nRdT 绝热压缩和膨胀 SJTU Thermodynamics of Materials Spring2010©X.J.Jin Lecture 3 Second law IPhase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2010 © X. J. Jin Lecture 3 Second law I 1.17 Adiabatic Compression or Expansion (1) Air arises rapidly (adiabatically) up a mountainside. At the higher altitude, the pressure is lower, and the temperature is also lower. Presisting System boundary Psystem Adiabatic Reversible: Presisting=Psystem Ideal gas QW  dU  PdV  dU  nCV dT PdV VdP nRdT PV nRT    绝热压缩和膨胀