What is the reverse Carnot cycle

to directory mode

Area of ​​Expertise - thermodynamics

The hypothetical process described by the French physicist Sadi Carnot forms the basis of the later formulated 2nd law (2nd law of thermodynamics).

The Carnot cycle consists of two isothermal and two adiabatic changes of state of an ideal gas (ideal gases):

AB: Isothermal expansion at temperature (ideal gas absorbs the amount of heat):

BC: Adiabatic expansion (no heat exchange):

CD: Isothermal compression at temperature (ideal gas gives off the amount of heat):

DA: Adiabatic compression (no heat exchange):

Mechanical energy is generated or consumed in all four phases of the process. The total mechanical energy gained after running through the cycle depends only on the amount of heat supplied and removed or on the temperatures of the heat reservoirs:

At temperatures greater than 0 K, the Carnot efficiency is always below 1. This means that there is no real machine that simply extracts heat from a reservoir during a cycle and converts it completely into work (impossibility of a perpetual motion machine of the second type). The Carnot cycle represents the ideal sequence of a heat engine; run in the opposite direction, it is an ideal heat pump / refrigeration machine:

Learning units in which the term is dealt with

2nd law of thermodynamics - heat engines45 min.

chemistryPhysical chemistrythermodynamics

An important sub-area of ​​thermodynamics deals with the question of how much work can be generated from a given heat. Your answer seems to the chemist far removed from his science. However, in the 19th century it led to the 2nd law of thermodynamics and the extensive state variable entropy, which proved to be fundamental for the theory of chemical equilibrium and which are now a cornerstone of chemical thermodynamics. The learning unit deals with the central point of this development, the Carnot machine. It belongs to the classical educational canon of the natural scientist, since it led to the entropy and the thermodynamic temperature scale.

Thermodynamic machines90 min.

chemistryPhysical chemistrythermodynamics

In the learning unit, the various cycle processes are first shown, e.g. the Carnot process, Stirling process, Joule or Brayton process, Ericson process and Otto and Diesel cycle. The efficiencies of the processes are then calculated in each case. Heat pumps and steam engines are presented and the different types are compared with one another.