Glossary
to accompany
Thermodynamics: An Engineering Approach, 5th edition
by Yunus A. Çengel and Michael A. Boles33Multistage expansion with reheating requires the expansion process in a turbine be
carried out in stages and reheating the gas between the stages such that the work output of
a turbine operating between two pressure levels can be increased.
Natural convection (see free convection)
Natural-draft cooling tower uses the naturally occurring density gradients between the
inside air-water vapor mixture and the outside air which create an airflow from the
bottom to the top of a wet cooling tower.
Natural gas is produced from gas wells or oil wells rich in natural gas. It is composed
mainly of methane, but it also contains small amounts of ethane, propane, hydrogen,
helium, carbon dioxide, nitrogen, hydrogen sulfate, and water vapor. It is stored either in
the gas phase at pressures of 150 to 250 atm as CNG (compressed natural gas) or in the
liquid phase at 162°C as LNG (liquefied natural gas).
Newton (N), in SI, is the force unit defined as the force required to accelerate a mass of 1
kg at a rate of 1 m/s
2
.Newton’s law of cooling defines the heat transfer by convection as the product of the
convection heat transfer coefficient, heat transfer area, and the difference between the
heat transfer surface temperature and the fluid bulk temperature away from the surface.
Nonflow system exergy (see closed system exergy)
Nonreacting gas mixture is a mixture of gases not undergoing a chemical reaction and
can be treated as a pure substance since it is usually a homogeneous mixture of different
gases.
Normal components are components that are perpendicular to the quantity in question.
Normal shock wave is a shock wave resulting in an abrupt change over a very thin
section normal to the direction of flow.
Nozzle is a device that increases the velocity of a fluid at the expense of decreasing
pressure.
Nuclear energy is the tremendous amount of energy associated with the strong bonds
within the nucleus of the atom itself.
Oblique shock is a complicated shock pattern consisting of inclined shock waves in
which some portions of an oblique shock are curved, while other portions are straight.
Octane, C 8 H 18 , is a common liquid fuel that approximates gasoline.