Glossary
to accompany
Thermodynamics: An Engineering Approach, 5th edition
by Yunus A. Çengel and Michael A. Boles6Carnot efficiency is the highest efficiency a heat engine can have when operating
between the two thermal energy reservoirs at temperatures TL and TH;
ηth, rev = 1 - TL / TH.
Carnot heat engine is the theoretical heat engine that operates on the Carnot cycle.
Carnot heat pump is a heat pump that operates on the reversed Carnot cycle. When
operating between the two thermal energy reservoirs at temperatures TL and TH, the
Carnot heat pump can have a coefficient of performance of COPHP, rev = 1/ (1- TL / TH) =
TH /( TH - TL).
Carnot principles are two conclusions that pertain to the thermal efficiency of reversible
and irreversible (i.e., actual) heat engines and are expressed as follows:
- The efficiency of an irreversible heat engine is always less than the efficiency of a
reversible one operating between the same two reservoirs. - The efficiencies of all reversible heat engines operating between the same two
reservoirs are the same.
Carnot refrigerator is a refrigerator that operates on the reversed Carnot cycle. When
operating between the two thermal energy reservoirs at temperatures TL and TH the
Carnot refrigerator can have a coefficient of performance of COPR, rev = 1/ (TH / TL - 1) =
TL /( TH - TL).
Cascade refrigeration cycles perform the refrigeration process in stages, that is, to have
two or more refrigeration cycles that operate in series.
Celsius scale (formerly called the centigrade scale; in 1948 it was renamed after the
Swedish astronomer A. Celsius, 1701–1744, who devised it) is the temperature scale used
in the SI system. On the Celsius scale, the ice and steam points are assigned the values of
0 and 100 °C, respectively.
Chemical energy is the internal energy associated with the atomic bonds in a molecule.
Chemical equilibrium is established in a system when its chemical composition does not
change with time.
Chemical equilibrium reactions are chemical reactions in which the reactants are
depleted at exactly the same rate as they are replenished from the products by the reverse
reaction. At equilibrium the reaction proceeds in both directions at the same rate.
Chemical potential is the change in the Gibbs function of the mixture in a specified
phase when a unit amount of a given component of the mixture in the same phase is
added as pressure and temperature and the amounts of all other components are held
constant. The chemical potential of a component of an ideal gas mixture depends on the