Work done in Brayton cycle

Question

I am studying Brayton cycle. In Brayton cycle, heat addition and exhaust is carried out at constant pressure. Now, the efficiency is $$eta=frac {w_{net}}{q_{in}}$$
My book, while calculating $w_{net}$ for efficiency takes into account only the compressor work and the turbine work. My doubt is shouldn't the work in constant pressure heat addition and extraction be also taken into account.

Thanks

I have added the image of book problem. The book is Engineering Thermodynamics by Cengel Boles. It is an example problem. In (c) part I have to calculate efficiency. Just have a look at it.

Bob D · Answer

The Brayton cycle (or Joule cycle) represents the operation of a gas turbine engine.

For the gas turbine operation the constant pressure heat addition process is an idealization of the combustion process. No pressure volume work is involved

The constant pressure heat extraction process simply cools the air to its original state. Its basically a condenser. Again no pressure volume work is involved.

Bottom line, the constant pressure processes are basically heat exchange processes where

$$Q=C_{p}Delta T$$

Here is another resource for the Brayton Cycle

http://web.mit.edu/16.unified/www/SPRING/propulsion/notes/node27.html

Hope this helps.

Work done in Brayton cycle

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