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 -dl -Pdv du nCvdT P system X Presisting PV=ART Pav +Vap nrdT 绝热压缩和膨胀 SJTU Thermodynamics of Materials Spring2006©X.J.Jin Lecture 3 Second law IPhase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2006 © 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 δ +δ = dUWQ =− = V dTnCdUPdV nRdTVdPPdV nRTPV =+ = 绝热压缩和膨胀