Thermodynamics and Propulsion  

However is an exact differential and its integral around a closed contour is zero:
The work done by the cycle, which is represented by the term , is equal to , the area enclosed by the closed contour in the  plane. This area represents the difference between the heat absorbed ( at the high temperature) and the heat rejected ( at the low temperature). Finding the work done through evaluation of is an alternative to computation of the work in a reversible cycle from . Finally, although we have carried out the discussion in terms of the entropy, , all of the arguments carry over to the specific entropy, ; the work of the reversible cycle per unit mass is given by .
Muddy Points
How does one interpret  diagrams? (MP 6.3)
Is it always OK to ``switch''  and  diagram? (MP 6.4)
What is the best way to become comfortable with  diagrams? (MP 6.5)
What is a reversible adiabat physically? (MP 6.6)
UnifiedTP