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System and Boundary in thermodynamic
A thermodynamic systemis defined as a quantity of matter or a
region in space
chosen for analysis,
Surrounding or environment
is can defined as the mass or region outside the system or
everything external to the
system
Boundary
The closed surface that separates the system from its
surroundings, through which
energy and mass may enter or leave the system.
Boundaries can be fixed or movable. Boundaries can be real
(cylinder walls and pistonsurfaces in an internal combustion
engine), in many cases, a thermodynamic analysis
must be made of a device, such as a heat exchanger, that
involves a flow of mass into
and/or out of the device.
Boundaries can also be imaginary (cross sections of pipes at
the
entrance and exit of turbines)t is possible to subdivide a
system into subsystems, or to group several systems
together into a larger system
Thermodynamic System Types
There are three !inds of systems depending on the !inds of
exchanges ta!ing place
between a thermodynamic system and its environment " isolated,
closed and open
system
Isolated systems" is one with rigid walls that has no
communication (i.e., no heat,
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mass, or wor! transfer) with its surroundings. #n example of an
isolated system would
be an insulated container, such as an insulated gas
cylinder.
Closed systems" system is one in which the system mass cannot
cross the boundary,
but energy can (heat or wor!).A greenhouse is an example of a
closed systemexchanging heat but not MASS with its environment.
$hether a system exchanges
heat, wor! or both is usually thought of as a property of its
boundary, which can be
adiabatic boundary" not allowing heat exchange% rigid boundary"
not allowing
exchange of wor! so we can get conclusion the important point of
closed system are "
Consists of a fixed amount of mass
No mass can cross its boundary
No mass can enter or leave a closed system Volume does not have
to be
fixed
But energy, in the form of heat or or! can cross the
boundary
hen the piston rises, the boundary of the system moves "eat and
or!
crosses the boundary of the system during this process but not
mass
#pen systems" system is one in which mass can cross the system
boundary in addition
to energy.A boundary allowing matter exchange is called
permeable.Theocean would be an example of an open system so we can
get conclusion the important
point of closed system are"
The procedure in such an analysis is to specify control volume
that
surrounds the device under consideration
The boundaries of a control volume are called a control
surface
$ass as ell as heat and or! can flo across the control
surface
&rom picture below we can see open system and closed system,
where even energy is
not allowed to cross the boundary in closed system, that system
is called an isolated
system.
