L20A
        Tds relation
        Entropy change on internally reversible process of
        close system

L20B
        Area representation of heat transfer
        Carrot cycle application
        Example 6.1 evaluating work and heat transfer for an
        internally reversible process of water
        Entropy change for closed system

L20C
         Example 6.2 determining work and entropy
         production for an irreversible process of water

L20D
        Example 6.3 evaluating minimum theoretical
        compression work 
        Closed system entropy rate balance