2019 NCEES Problem #73

[Minipett]

Could someone help clarify why the thermal efficiency equation within the reference manual is not the correct equation to use.

 

[Slay the P.E.]

...because that equation in the manual is valid only when the regenerator has 100% effectiveness.

 

[Slay the P.E.]

So, I assume that we have to memorize the second equation since its not provided in the Mechanical Reference Handbook?

Probably a good idea to memorize that the thermal efficiency of any heat engine is the ratio of the net power produced by the heat input, yes.

This is in the reference handbook in a couple of places (poorly organized, IMO). Referring to version 1.3: First, you see it in page 266 under the diagrams for the Otto cycle. Then you also see it in page 270 under the diagram for the Rankine Cycle with Regeneration.