ENGR 2213 Thermodynamics
F. C. Lai
School of Aerospace and Mechanical
Engineering
University of Oklahoma
Thermodynamic Properties of Water
Phase Change of Water
T
v
Thermodynamic Properties of Water
Phase Change of Water
T
v
Thermodynamic Properties of Water
Phase Change of Water
T
v
Thermodynamic Properties of Water
Phase Change of Water
T
v
Thermodynamic Properties of Water
Subcooled liquid
T
●
Critical point
Saturated
mixture
Superheated vapor
Phase Change of Water
Saturated vapor
liquid line
line
v
Thermodynamic Properties of Water
Saturation State
A state at which a phase change begins or ends
Critical Point
Intersection of saturated liquid and saturated vapor
Single-Phase Regions
Subcooled liquid (compressed liquid), superheated
vapor
Two-Phase Region
Liquid-vapor mixture
States of Water
Compressed liquid (Subcooled liquid)
● For a given T, P > Psat
● For a given P, T < Tsat
● For a given v, v < vf
compressed liquid
subcooled liquid
Superheated vapor
● For a given P, T > Tsat
● For a given T, P < Psat
● For a given v, v > vg
superheated vapor
States of Water
Saturated mixture
● For a given T, P = Psat
● For a given P, T = Tsat
● For a given v, vf < v < vg
Quality
x
mg
mf  mg
0≤x≤1
Saturated Mixture of Water
V = Vf + Vg
V Vf Vg
v 

m m m
mf v f mgv g


m
m
 (1  x)v f  xv g  v f  x(v g  v f )
Thermodynamic Properties of Water
P-v-T Relations of Water
water
most substances
Thermodynamic Properties of Water
P-T Diagram of Water
liquid
Critical point
●
solid
●
Triple point
vapor
Temperature
Pressure
Pressure
liquid
Critical point
●
solid
●
Triple point
vapor
Temperature
Thermodynamic Property Tables of Water
Simple System
A system for which there is only one way the
system energy can be altered by work as the
system undergoes a quasi-equilibrium process.
Simple Compressible System
The only mode of energy transfer by work is
associated with the volume change (expansion or
compression).
Thermodynamic Property Tables of Water
State Principle (State Postulate)
The number of independent properties required to
specify the state of a system is one plus the number
of relevant work interactions.
Number of independent properties
= 1 + Number of work interactions
The number of independent properties required to
specify the state of a simple compressible system
is two.
Thermodynamic Property Tables of Water
Single-Phase Region (Compressed Liquid,
Superheated Vapor)
● Temperature and Pressure
● Temperature and Specific Volume
● Pressure and Specific Volume
Two-Phase Region (Saturated Mixture)
●
●
●
●
Temperature and Specific Volume
Temperature and Quality
Pressure and Specific Volume
Pressure and Quality
Thermodynamic Property Tables of Water
●
●
●
●
Saturated Water – Temperature Table (A-4)
Saturated Water – Pressure Table (A-5)
Superheated Vapor (A-6)
Compressed Liquid (A-7)
Linear interpolation is required when the states
encountered in problems do not fall exactly on the
values provided by the tables.
Example 1
A rigid tank contains 50 kg of saturated liquid water
at 100 ºC. Determine the pressure in the tank and
the volume of the tank.
Table A-4, Psat = 101.35 kPa,
P = Psat = 101.35 kPa
Table A-4, vf = 0.001044 m3/kg,
V = mvf = 50 (0.001044) = 0.052 m3
Example 2
A piston-cylinder device contains 2 m3 of saturated
water vapor at 100 kPa pressure. Determine the
temperature of the vapor and the mass of the vapor
Inside the cylinder.
inside
Table A-5, Tsat = 99.63 ºC,
T = Tsat = 99.63 ºC
Table A-5, vg = 1.694 m3/kg,
m = V/vg = 2/(1.694) = 1.18 kg
Example 3
A rigid tank contains 10 kg of water at 90 ºC. If 8 kg
of the water is in the liquid form and the rest is in the
vapor form. Determine the pressure in the tank and
the volume of the tank .
Table A-4, Psat = 70.14 kPa,
P = Psat = 70.14 kPa
Table A-4, vf = 0.001036 m3/kg, vg = 2.361 m3/kg
v = vf + x(vgV- =vfV
)=
Vg
+ 0.2(2.361 – 0.001036)
f +0.001036
3/kg
= m=
v
0.473
+
m
v
m
f f
g g
V = mv = 10(0.473)
= 8(0.001036)
= 4.73 m
+32(2.361) = 4.73 m3