SECOND LAW OF THERMODYNAMICS
With the practice of using reversible processes, Sadi Carnot in 1824 advanced the study of the
second law by disclosing a principle consisting of the following propositions.
No engine can be more efficient than a reversible engine operating between the
same high temperature and low temperature reservoirs. Here the term heat
reservoir is taken to mean either a heat source or a heat sink.
The efficiencies of all reversible engines operating between the same constant
temperature reservoirs are the same.
The efficiency of a reversible engine depends only upon the temperatures of the
heat source and heat receiver.
The above principle is best demonstrated with a simple cycle (shown in Figure 21) and an
example of a proposed heat power cycle. The cycle consists of the following reversible
adiabatic compression from TC to TH due to work performed on fluid.
isothermal expansion as fluid expands when heat is added to the fluid at
adiabatic expansion as the fluid performs work during the expansion process and
temperature drops from TH to TC.
isothermal compression as the fluid contracts when heat is removed from the fluid
at temperature TC.