Thermo & Stat Mech - Spring 2006 Class 4 1 Thermodynamics and Statistical Mechanics Does the...
-
Upload
jewel-weatherly -
Category
Documents
-
view
217 -
download
2
Transcript of Thermo & Stat Mech - Spring 2006 Class 4 1 Thermodynamics and Statistical Mechanics Does the...
Thermo & Stat Mech - Spring 2006 Class 4
1
Thermodynamics and Statistical Mechanics
Does the Internal Energy of a Real Gas Depend Only on Temperature?
Thermo & Stat Mech - Spring 2006 Class 4
2
Change of Phase
First Law is: du = đq – Pdv
For a finite change at constant temperature
u = q – Pv
At transition, u2 – u1 = l12 – P(v2 – v1)
l12 = (u2 + Pv2) – (u1 + P v1)
l12 = h2 – h1
Thermo & Stat Mech - Spring 2006 Class 4
3
Enthalpy and Latent Heat
on)(sublimati vapor tosolid
ion)(vaporizat vapor toliquid
(fusion) liquid tosolid
13
23
12
hh
hh
hh
Enthalpy is defined as: h = u + Pv
Thermo & Stat Mech - Spring 2006 Class 4
4
Enthalpy is a State Function
Thermo & Stat Mech - Spring 2006 Class 4
5
Does u depend on Volume?
If u = u(T, v), then,
dvvu
dTTu
duTv
Thermo & Stat Mech - Spring 2006 Class 4
6
From Cyclical Relation
uv
T
v
T
v
T
u
vT
cvu
cvu
Tuvu
vT
Thermo & Stat Mech - Spring 2006 Class 4
7
Gay-Lussac–Joule Experiment
Thermo & Stat Mech - Spring 2006 Class 4
8
Gay-Lussac–Joule Results
3-m kilomoleK 001.0
0
u
u
vT
vT
Thermo & Stat Mech - Spring 2006 Class 4
9
Joule-Thompson Throttling Process
A gas passes through a constriction from a region where it is at high pressure to a region where it is at lower pressure. The gas expands, and the temperature of the gas can be lowered. This is an important tool in low temperature physics.
Thermo & Stat Mech - Spring 2006 Class 4
10
Joule-Thompson Throttling Process
Thermo & Stat Mech - Spring 2006 Class 4
11
Joule-Thompson Throttling Process
On high pressure side: Wi = – PiVi
On low pressure side: Wf = + PfVf
Total work: W = PfVf – PiVi
Q = 0 = U + W0 = Uf – Ui + PfVf – PiVi
0 = (Uf + PfVf ) – (Ui + PiVi )
Thermo & Stat Mech - Spring 2006 Class 4
12
Enthalpy
vdPdhqd
VdPQddH
QdPdVdU
PdVQddU
VdPPdVdUdH
PVUH
so
law)(First
Thermo & Stat Mech - Spring 2006 Class 4
13
Enthalpy
PPP
cdTdh
dTqd
vdPdhqd
Thermo & Stat Mech - Spring 2006 Class 4
14
Enthalpy
hP
TThP
TP
TP
dPdT
cPh
Ph
dPdT
c
dh
dPPh
dTcdPPh
dTTh
dh
PThh
or 0
,0For
),(For
Thermo & Stat Mech - Spring 2006 Class 4
15
Enthalpy
)( 0, If
t coefficienThomson -Joule
Phh
cPh
dPdT
PT
h
True for ideal gas.
Thermo & Stat Mech - Spring 2006 Class 4
16
Ideal Gas
dTdu
c
dTdh
dTdh
c
V
PP
Thermo & Stat Mech - Spring 2006 Class 4
17
Joule-Thompson Throttling Process