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Areas on TS Diagrams for Open Systems

SISO, Internally Reversible, Steady-State Processes

Internally Reversible

System at uniform temperature

Differential form:

Integral form:

Area =

Heat Tranfer per unit mass of the flowing fluid

Isothermal
Processes:

Lesson
8B Blog

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Lesson 8B: page 7 of 23

Let’s begin with the 1st Law for a SS, SISO process. Nothing new about that, right ?
It is convenient to solve this equation for WS,dot over mdot.
This ratio is the amount of work done by the process per unit mass of flowing fluid.
But, what kind of work is this ?
Well, you remember that the PV work is included in the ΔH term, right.
Well, this term is all the other forms of work.
The cool part is that, for the systems we will analyze in this course, the only other type of work is SHAFT work.
And shaft work is one of the two quantities that we are most interested in for open systems. The other one is the heat transfer rate.
OK, now, the big question is, how does the fact that the process is internally reversible affect the 1st Law ?
Well, on the previous page, we just showed that Qdot over mdot is equal to the integral of T dS.
We can make this substitution, but that seems to make the equation MORE complicated, rather than simpler as we would like.
Bear with me. On the next page, Gibbs will save us.

Areas on TS Diagrams for Open Systems

SISO, Internally Reversible, Steady-State Processes

Ch 8, Lesson B, Page 7 - Areas on TS Diagrams for Open Systems