What factors or parameters prevent us from creating a reversible heat engine? Is it simply due to the micro/macroscopic work done between surfaces and heat generated from friction (with the latter creating a net positive entropy generation from dS=dQ/T)?

Question

What factors or parameters prevent us from creating a reversible heat engine?  Is it simply due to the micro/macroscopic work done between surfaces and heat generated from friction (with the latter creating a net positive entropy generation from dS=dQ/T)?

ybarrap · Answer

You got it! This is why perpetual motion machines are impossible - friction. The lost energy due to friction can not be recovered without some external work done TO the engine.