Glossary
to accompany
Thermodynamics: An Engineering Approach, 5th edition
by Yunus A. Çengel and Michael A. Boles13Dew-point temperature is defined as the temperature at which condensation begins
when the air is cooled at constant pressure.
Diesel cycle is the ideal cycle for compress-ignition reciprocating engines, and was first
proposed by Rudolf Diesel in the 1890s. Using the air-standard assumptions, the cycle
consists of four internally reversible processes:
1-2 Isentropic compression,
2-3 Constant pressure heat addition,
3-4 Isentropic expansion,
4-1 Constant volume heat rejection.Diffuser is a device that increases the pressure of a fluid by decreasing the fluid velocity.
Dimensionally homogeneous means that every term in an equation must have the same
unit. To make sure that all terms in an engineering equation have the same units is the
simplest error check one can perform.
Dimensions are any physical characterizations of a quantity.
Direct-contact feedwater heater ( see open feedwater heater)
Displacement volume is the volume displaced by the piston as it moves between top
dead center and bottom dead center.
Dodecane, C 12 H 26 , is a common liquid fuel that approximates diesel fuel.
Dome is the saturation states located beneath the joined saturated liquid line and
saturated vapor line.
Dry air is air that contains no water vapor.
Dry-bulb temperature is the ordinary temperature of atmospheric air.
Dual cycle is the ideal cycle which models the combustion process in both gasoline and
diesel engines as a combination of two heat-transfer processes, one at constant
volume and the other at constant pressure.
Dynamic temperature is the kinetic energy per unit mass divided by the constant
pressure specific heat and corresponds to the temperature rise during the stagnation
process.
Efficiency is defined as the ratio of desired result for an event to the input required to
accomplish the event. Efficiency is one of the most frequently used terms in