Power cycles

move clockwise around the process path and

refrigeration

and

heat pump cycles

move couterclockwise around the path.

We also found that the area enclosed by the process path of a Carnot Cycle on a TS Diagram is equal to the net work for the cycle.

We learned that the area under the process path for each reversible step in the cycle represents the heat transfer associated with that step. Reversible, adiabatic steps must be vertical lines so that the area beneath them is zero. A vertical line on a TS Diagram is a path of

constant entropy

. A process that follows a path of constant entropy is called an isentropic process.

Chapter 7, Lesson B - Entropy: A New Property

In this lesson, defined a new property called

entropy

, S.

= Extensive Property (kJ/K)

Because S is a

state variable

:

For reversible, isothermal processes
(reversible heat exchange with a reservoir):

We found that, just like U and H, we need a

reference state

for S. For example, the

NIST WebBook

uses the liquid at triple point as the reference state for water.

Next, we introduced

TS Phase Diagrams

and demonstrated how to use them to analyze

Carnot Cycles

.

 

We closed with a brief discussion of

HS Diagrams

. We will use these diagrams more in Chapter 8.

Lesson
7B Blog

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