Glossary
to accompany
Thermodynamics: An Engineering Approach, 5th edition
by Yunus A. Çengel and Michael A. Boles28Isothermal efficiency of a compressor is defined as the ratio of the work input to a
compressor for the reversible isothermal case and the work input to a compressor for the
actual case.
Isothermal process is a process in which the temperature is maintained constant.
Jet-propulsion cycle is the cycle used in aircraft gas turbines. The ideal jet-propulsion
cycle differs from the simple ideal Brayton cycle in that the gases are not expanded to the
ambient pressure in the turbine. Instead, they are expanded to a pressure such that the
power produced by the turbine is just sufficient to drive the compressor and the auxiliary
equipment. The gases that exit the turbine at a relatively high pressure are subsequently
accelerated in a nozzle to provide the thrust to propel the aircraft.
Joule (J) is a unit of energy and has the unit “newton-meter (N·m).”
Joule-Thomson coefficient μJT is a measure of the change in temperature with pressure
during a constant-enthalpy process.
Kay’s rule, proposed by W. B. Kay in 1936, predicts the P-v-T behavior of a gas mixture
by determining the compressibility factor for a gas mixture at the reduced pressure and
reduced temperature defined in terms of the pseudocritical pressure (the sum of the
products of the mole fraction and critical pressure of each component) and pseudocritical
temperature (the sum of the products of the mole fraction and critical temperature of each
component).
kelvin is the temperature unit of the Kelvin scale in the SI.
Kelvin-Planck statement of the second law of thermodynamics is expressed as
follows: It is impossible for any device that operates on a cycle to receive heat from a
single reservoir and produce a net amount of work. This statement can also be expressed
as no heat engine can have a thermal efficiency of 100 percent, or as for a power plant to
operate, the working fluid must exchange heat with the environment as well as the
furnace.
Kelvin scale is the thermodynamic temperature scale in the SI and is named after Lord
Kelvin (1824–1907). The temperature unit on this scale is the kelvin, which is designated
by K (not °K; the degree symbol was officially dropped from kelvin in 1967). The lowest
temperature on the Kelvin scale is 0 K.
Kilojoule (1 kJ) is 1000 joules.
Kilopascal (kPa) is the unit of pressure equal to 1000 pascal or 1000 N/m
2
.