Glossary
to accompany
Thermodynamics: An Engineering Approach, 5th edition
by Yunus A. Çengel and Michael A. Boles54Vapor implies a gas that is not far from a state of condensation.
Vapor-compression refrigeration cycle is the most frequently used refrigeration cycle
and involves four main components: a compressor, a condenser, an expansion valve, and
an evaporator.
Vapor pressure is usually considered to be the partial pressure of water vapor in
atmospheric air.
Vaporization line separates the liquid and vapor regions on the phase diagram.
Venturi nozzle is a duct in which the flow area first decreases and then increases in the
direction of the flow and is used strictly for incompressible flow.
Virial equations of state is an equation of state of a substance expressed in a series form
as
P = RT/v + a(T)/v^2 + b(T)/v^3 + c(T)/v^4 + d(T)/v^5 +...
where the coefficients a(T ), b(T ), c(T ), and so on, are functions of temperature alone
and are called virial coefficients.
Volume expansivity (also called the coefficient of volumetric expansion) relates how
volume changes when temperature changes when pressure is held constant.
Volume flow rate is the volume of the fluid flowing through a cross section per unit of
time.
Volume fraction of a gas component in a gas mixture is the ratio of the component
volume to the mixture volume. Note that for an ideal-gas mixture, the mole fraction, the
pressure fraction, and the volume fraction of a component are identical.
Waste heat is energy that must be dissipated to the atmosphere from a process such as
the heat transferred from condensing steam in the condenser of a steam power plant.
Wasted work potential represents irreversibility as the energy that could have been
converted to work but was not and is the lost opportunity to do work.
Water heater efficiency is defined as the ratio of the energy delivered to a house by hot
water to the energy supplied to the water heater.
Wave angle (see shock angle)
Weak oblique shocks are straight oblique shocks that have the smaller of the possible
values of the shock angles for deflection angles less than the maximum deflection angle.