Reversible Heat Transfer?

I read in a textbook that heat transfer is not a reversible process. So how come for cases like the Carnot cycle, there were series of heat transfer and the process was still called a reversible process
- Dare (age 18)
Nigeria

Great question!

Heat transfer only is reversible in the limit where the temperatures of the two regions are the same. In that limit, the rate of heat transfer goes to zero! The Carnot  engine is revsible because it assumes that the heat transfer is "isothermal", which means between regions at the same T. An ideal Carnot engine would take forever to cycle. Real ones have to sacrifice some efficiency to run at reasonable rates.

Mike W.

p.s. We love it when people pay close enough attention to school lessons to notice when things sound inconsistent. If the pandemic and poliical situations clear up enough to allow travel, perhaps you could think about UIUC as a destination.

(published on 09/04/2020)