[ Themodynamics
Table of Contents ]
A P-n diagram
is another common
Diagram for Watertype
of property diagram. Figure10
is the P-n diagram
for purewater. A P-n
diagram can beconstructed
for any pure substance.A
P-n diagram
is different from aP-T
diagram in one particularlyimportant
way. There are regionson
a P-n diagram
in which twophases exist
together. In theliquid-vapor
region in Figure 10,water
and steam exist together.For
example, at point A, waterwith
a specific volume (nf),
givenby point B, exists
together withsteam with
a specific volume (ng),given by point C. The dotted
lineson Figure 10 are
lines of constanttemperature.
The quality of themixture
at any point in the liquid-vapor region can be found because
the specific volumes ofwater,
steam, and the mixture are all known. The quality can be
found using the followingrelationship.