Glossary
to accompany
Thermodynamics: An Engineering Approach, 5th edition
by Yunus A. Çengel and Michael A. Boles26differential amount of heat or work is represented by δQ or δW, respectively, instead of
dQ or dW.
Intake valve is an inlet through which the air or air–fuel mixture is drawn into the
cylinder.
Intensive properties are those that are independent of the size of a system, such as
temperature, pressure, and density. Intensive properties of a nonreacting ideal-or real-gas
mixture are obtained by dividing the extensive properties by the mass or the mole number
of the mixture in the gas mixture. The internal energy, enthalpy, and entropy of a gas
mixture per unit mass or per unit mole of the mixture can be determined by summing the
products of the mass fractions and the specific property or summing the products of the
mole fractions and the molar specific property. That is, the intensive properties of a gas
mixture are determined by either a mass weighted or a mole weighted average of the
properties.
Intercooling is a technique used to reduce the compression work for the gas turbine
cycle. The compression process is completed in stages while cooling the working fluid
between stages. Since the steady-flow compression work is proportional to the specific
volume of the flow, the specific volume of the working fluid should be as low as possible
during a compression process.
Internal combustion engines are engines where the energy is provided by burning a fuel
within the system boundaries.
Internal energy U of a system is the sum of all the microscopic forms of energy.
Internal energy change of an ideal gas is given as ΔuCTdTCTT=≅−∫ vv, av21() ( ).
Internally reversible process has no irreversibilities that occur within the boundaries of
the system during the process. During an internally reversible process, a system proceeds
through a series of equilibrium states, and when the process is reversed, the system passes
through exactly the same equilibrium states while returning to its initial state.
Inversion line is the line that passes through the points of zero slope of constant-enthalpy
lines or zero Joule-Thomson coefficient on the T-P diagram. The slopes of the h =
constant lines are negative (μJT < 0) at states to the right of the inversion line and positive
(μJT > 0) to the left of the inversion line.
Inversion temperature is the temperature at a point where a constant-enthalpy line
intersects the inversion line.
Irreversible processes are processes which, once having taken place in a system, cannot
spontaneously reverse themselves and restore the system to its initial state.