Why should we compare the efficiency of practical heat engine with it's reversible counterparts?

Hi Emilio, I have rephrased the question now. I wanted to ask about second law efficiency.

I am ready to discuss about the 2nd law efficiency, However, you have to guide me through your forum to see where your question is. Can you give me some guidance on where the subject matter begins?

Sure.

I am attaching 2 screenshots here. To find "own posts" and other things on own profile.

Step 1: Go to the home page "Log In" to your account.

Step 2: Once you log in, click on the arrow and a menu will open then click on "Forum Posts" which will show the post you created in the past.