THERMODYNAMIC SYSTEMS AND PROCESSES
Thermodynamics
The theory also states W = 0. Our observations again confirm this to be true as clearly no
"work" has been done by the throttling process. Finally, the theory states that an ideal throttling
process is adiabatic. This cannot clearly be proven by observation since a "real" throttling
process is not ideal and will have some heat transfer.
Summary
The important information from this chapter is summarized below.
Thermodynamic Systems and Processes Summary
•
A thermodynamic system is a collection of matter and space with its boundaries
defined in such a way that the energy transfer across the boundaries can be best
understood.
•
Surroundings are everything not in the system being studied.
•
Systems are classified into one of three groups:
Isolated system -
neither mass nor energy can cross the
boundaries
Closed system
-
only energy can cross the boundaries
Open system
-
both mass and energy can cross the
boundaries
•
A control volume is a fixed region of space that is studied as a thermodynamic
system.
•
Steady state refers to a condition where the properties at any given point within the
system are constant over time. Neither mass nor energy are accumulating within the
system.
•
A thermodynamic process is the succession of states that a system passes through.
Processes can be described by any of the following terms:
Cyclic process
- a series of processes that results in the system
returning to its original state
Reversible process - a process that can be reversed resulting in no change
in the system or surroundings
Irreversible process - a process that, if reversed, would result in a change to
the system or surroundings
Adiabatic process
- a process in which there is no heat transfer across the
system boundaries
Isentropic process - a process in which the entropy of the system remains
unchanged
Polytropic process - the plot of Log P vs. Log V is a straight line, PVn =
constant
Throttling process - a process in which enthalpy is constant h1 = h2, work
= 0, and which is adiabatic, Q=0.
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