L21A
         Increasing of entropy principle
         Entropy balance of heat engine cycle

L21B
        Review of example 5.1
        Example 6.5 quenching a hot metal bar
        Statistical interpretation of entropy
        Defining entropy

L21_C
        Statistical interpretation of entropy (cont.)
        Entropy balance of control volume
        Rate balance for control volume at steady state
        One-inlet, one exit control volume at steady state
        Example 6.6 determining entropy production in a steam
        turbine

L21_D
        Example 6.7 evaluating a performance claim
        Example 6.8 determining entropy production in heat
        pump components
        Isentropic process