等V过程： W=0,0y=dU=CydT=80 dS 7 T T 或 Cr T AS Cy =nCv, 2020 等 V 过程： W`=0， QV  = dU = CV dT = QR  dS = T QR = T QV = dT T CV 或 T C T S V V =   ( ) ΔS = dT T T C T V  2 1 = CV Ln 1 2 T T CV = nCV，m