Working principle of <a href="https://en.wikipedia.org/wiki/Nicolas_L%C3%A9onard_Sadi_Carnot" class="extiw" title="en:Nicolas Léonard Sadi Carnot">Carnot's</a> heat engine.
Eric Gaba (<a href="//commons.wikimedia.org/wiki/User:Sting" title="User:Sting">Sting</a> - <a href="https://fr.wikipedia.org/wiki/Utilisateur:Sting" class="extiw" title="fr:Utilisateur:Sting">fr:Sting</a>)
Own work<br>Based upon <a href="//commons.wikimedia.org/wiki/File:Carnot-engine.png" title="File:Carnot-engine.png">Image:Carnot-engine.png</a>