815.6 A new concept: entropy 2. The calculation of the entropy do For a reversible processes: pdS 0 4s=ds=rrde 0dQ>0 ∠AS= <0dQ<0 =0 d@=0 Isentropic process 0 cvcle 15.6 A new concept: entropy For irreversible processes: Since the entropy is a state variable, the entropy change between two equilibrium state is the same regardless of how the change is executed 3. Entropy changes in various thermodynamic processes (a)Ideal gas in a quasi-static reversible process dQr∫dU+Pdv 4S T dT d nR 1616 For a reversible processes: ∫ ∫ = = rev rev 0 d d T Q S ∫ ∫ = = f i f i T Q S S d ∆ d ⎪ ⎪ ⎩ ⎪ ⎪ ⎨ ⎧ = = = < < > > = 0 cycle 0 d 0 0 d 0 0 d 0 Q Q Q ∆S Isentropic process 2. The calculation of the entropy §15.6 A new concept: entropy For irreversible processes: Since the entropy is a state variable, the entropy change between two equilibrium state is the same regardless of how the change is executed. 3. Entropy changes in various thermodynamic processes (a) Ideal gas in a quasi-static reversible process ∫ ∫ ∫ ∫ = + + = = f i f i V V T T V f i f i V V nR T T nc T U P V T Q S d d d d d ∆ §15.6 A new concept: entropy