Glossary
to accompany
Thermodynamics: An Engineering Approach, 5th edition
by Yunus A. Çengel and Michael A. Boles46Stagnation properties are the properties of a fluid at the stagnation state. These
properties are called stagnation temperature, stagnation pressure, stagnation density, etc.
The stagnation state and the stagnation properties are indicated by the subscript 0.
Stagnation temperature (total temperature) is the temperature an ideal gas will attain
when it is brought to rest adiabatically.
Standard reference state for the properties of chemical components is chosen as 25°C
(77°F) and 1 atm. Property values at the standard reference state are indicated by a
superscript (°) (such as h°and u°).
Standard-state Gibbs function change is the difference between the sum products of
the stoichiometric coefficients and the Gibbs function of a component at 1 atm pressure
and temperature T for the products and reactants in the stoichiometric reaction.
State is the condition of a system not undergoing any change gives a set of properties that
completely describes the condition of that system. At this point, all the properties can be
measured or calculated throughout the entire system.
State postulate specifies the number of properties required to fix the state of a system:
The state of a simple compressible system is completely specified by two independent,
intensive properties.
Static enthalpy is the ordinary enthalpy of the flow measured at the fluid state.
Stationary systems are closed systems whose velocity and elevation of the center of
gravity remain constant during a process.
Statistical thermodynamics, an approach to thermodynamics more elaborate than
classical thermodynamics, is based on the average behavior of large groups of individual
particles.
Steady implies no change with time. The opposite of steady is unsteady, or transient.
Steady-flow conservation of mass states that the total rate of mass entering a control
volume is equal to the total rate of mass leaving it.
Steady-flow devices operate for long periods of time under the same conditions.
Steady-flow process is a process during which a fluid flows through a control volume
steadily. That is, the fluid properties can change from point to point within the control
volume, but at any point, they remain constant during the entire process. During a
steady-flow process, no intensive or extensive properties within the control volume
change with time.