Department of MECH
exists within the system. Energy transfers across the system disturb the equilibrium state
of the system but may not shift the system significantly from its equilibrium state if
carried out at low rates of change. I mentioned earlier that to define the properties of a
system, they have to be uniform throughout the system.
Therefore to define the state of system, the system must be in equilibrium.
(Inequilibrium of course implies non-uniformity of one or more properties).
A process is the description of what happens when a system changes its state by going
through a succession of equilibrium states.
A cyclic process is one for which the initial and final states of the system are identical.
11. Isentropic process:
is one in which for purposes of engineering analysis and calculation, one may assume
that the process takes place from initiation to completion without an increase or decrease
in the entropy of the system, i.e., the entropy of the system remains constant.
12. Isentropic flow:
An isentropic flow is a flow that is both adiabatic and reversible. That is, no heat is
added to the flow, and no energy transformations occur due to friction or dissipative
effects. For an isentropic flow of a perfect gas, several relations can be derived to define
the pressure, density and temperature along a streamline.
13. Adiabatic heating
Adiabatic heating occurs when the pressure of a gas is increased from work done on it
by its surroundings, e.g. a piston. Diesel engines rely on adiabatic heating during their