1824 – France
‘The Carnot cycle is the most efficient cycle for operating a reversible heat engine’
It illustrates the principle that the efficiency of a heat engine depends on the temperature range through which it works.
The cycle has a four-stage reversible sequence:
adiabatic compression and isothermal expansion at high temperature; adiabatic expansion and isothermal compression at low temperature.
( ADIABATIC: – no heat flows into or out of a system; ISOTHERMAL: – at a constant temperature )
Carnot suggested that the puissance motrice (motive power, by which he meant work or energy) of a heat engine was derived from the fall of heat from a higher to a lower temperature.
Carnot was the first to grasp the principles that later became known as the second law of thermodynamics.
By the time of Carnot’s death it had become clear there was no such thing as a calorific fluid ; heat is a form of energy, one of many, and the sum of all forms of energy in an isolated system is conserved. This has come to be known as the first law of thermodynamics.
In the case of a steam engine, the heat taken in at the boiler is not equal to the heat removed at the condenser. The work done by the ideal engine is the difference between the two. The first modern experiment proving the first law of thermodynamics was performed by a student of John Dalton’s, JAMES JOULE.