If you read my previous post on perfect engines, then you might have thought a heat engine that did not discharge any heat would be more efficient. However, this would contravene the second law of thermodynamics, which requires that every real process must generate an increase in disorder, in this case by the discharge of waste heat. Thermodynamicists like to call this increase in disorder, an increase in ‘entropy’.
A consequence of the second law of thermodynamics is that the entropy, or disorder, of the universe is always increasing; but now I have strayed from engineering to physics. Together with Bob Handscombe, I wrote a book on this topic called the ‘Entropy Vector: Connecting science and business’. It was not a best-seller but it got some good reviews, see http://www.worldscientific.com/worldscibooks/10.1142/5365#t=reviews.