ES184
-‐
Mechanics,
Structures
&
Thermodynamics
01
-‐
Intro
to
Thermodynamics
(Heat
&
Work)
1. Introduction
Microscopic:
Start
with
equations
of
motion
of
the
gas
molecules,
consider
these
statistically,
and
derive
large-‐scale
properties.
This
is
the
view
of
Statistical
Mechanics.
Macroscopic:
Deal
with
large-‐scale
properties
(e.g.
volume
of
gas,
pressure
etc.)
without
considering
microscopic
nature.
This
is
the
view
of
Thermodynamics.
Laws
Of
Thermodynamics
There
are
four
commonly
accepted
laws
of
thermodynamics
(in
this
course
we
use
three
of
these;
zeroth,
first,
and
second.
They
are
postulates,
and
not
laws
that
can
be
derived
analytically.
Yet,
they
have
stood
the
test
of
time
and
cannot
be
disproved
by
example
The
laws
of
thermodynamics
are
very
general:
• Not
just
gases,
chemical
reactions,
electrical
power,
but
the
whole
Universe
obeys
the
laws
of
thermodynamics
Applications
Of
Thermodynamics
• Helps
us
design
engines,
refrigeration,
air
conditioning,
chemical
plants
etc
• Underpins
materials
science
(growth,
processing
etc)
and
phase
transformations
• Underpins
climate
change
and
even
the
fate
of
the
universe
Thermodynamic
Terminology
System:
The
portion
of
the
universe
we
select
for
investigation
Surroundings:
Everything
outside
the
system
Boundary:
What
separates
the
system
from
the
surroundings
Steam
Turbine
Power
Plant
Boiler:
for
raising
steam
to
higher
than
atmospheric
pressure
Turbine:
where
steam
expands
(i.e.
p
drops)
produce
work
Condenser:
where
steam
is
cooled,
rejects
heat
to
environment
and
returns
to
liquid
state
Feed
Pump:
to
return
water
to
boiler
at
high
pressure
1
,
ES184
-‐
Mechanics,
Structures
&
Thermodynamics
2. Thermodynamic
Systems
Types
of
Systems
Open
Systems:
Allows
mass
in
or
out
(or
both),
as
well
as
energy
in,
out
or
both.
Closed
Systems:
Does
not
allow
mass
in
or
out,
but
does
allow
energy
in,
out
or
both.
Walls
in
Thermodynamic
Systems
Adiabatic
(adiathermal)
walls:
walls
that
prevent
thermal
interaction.
Diathermal
walls:
walls
that
allow
thermal
interaction.
Two
systems
separated
by
a
diathermal
wall
are
in
thermal
contact.
Types
of
Thermodynamic
Variables
Intensive
• Variables
that
are
essentially
local
in
character
• E.g.
pressure,
electric
field,
force
density,
temperature
Extensive
• Variables
that
correspond
to
some
measure
of
the
system
as
a
whole
• E.g.
mass,
volume,
internal
energy,
length
• Extensive
variables
are
proportional
to
the
mass
of
the
system
(if
the
intensive
variables
remain
constant)
2
-‐
Mechanics,
Structures
&
Thermodynamics
01
-‐
Intro
to
Thermodynamics
(Heat
&
Work)
1. Introduction
Microscopic:
Start
with
equations
of
motion
of
the
gas
molecules,
consider
these
statistically,
and
derive
large-‐scale
properties.
This
is
the
view
of
Statistical
Mechanics.
Macroscopic:
Deal
with
large-‐scale
properties
(e.g.
volume
of
gas,
pressure
etc.)
without
considering
microscopic
nature.
This
is
the
view
of
Thermodynamics.
Laws
Of
Thermodynamics
There
are
four
commonly
accepted
laws
of
thermodynamics
(in
this
course
we
use
three
of
these;
zeroth,
first,
and
second.
They
are
postulates,
and
not
laws
that
can
be
derived
analytically.
Yet,
they
have
stood
the
test
of
time
and
cannot
be
disproved
by
example
The
laws
of
thermodynamics
are
very
general:
• Not
just
gases,
chemical
reactions,
electrical
power,
but
the
whole
Universe
obeys
the
laws
of
thermodynamics
Applications
Of
Thermodynamics
• Helps
us
design
engines,
refrigeration,
air
conditioning,
chemical
plants
etc
• Underpins
materials
science
(growth,
processing
etc)
and
phase
transformations
• Underpins
climate
change
and
even
the
fate
of
the
universe
Thermodynamic
Terminology
System:
The
portion
of
the
universe
we
select
for
investigation
Surroundings:
Everything
outside
the
system
Boundary:
What
separates
the
system
from
the
surroundings
Steam
Turbine
Power
Plant
Boiler:
for
raising
steam
to
higher
than
atmospheric
pressure
Turbine:
where
steam
expands
(i.e.
p
drops)
produce
work
Condenser:
where
steam
is
cooled,
rejects
heat
to
environment
and
returns
to
liquid
state
Feed
Pump:
to
return
water
to
boiler
at
high
pressure
1
,
ES184
-‐
Mechanics,
Structures
&
Thermodynamics
2. Thermodynamic
Systems
Types
of
Systems
Open
Systems:
Allows
mass
in
or
out
(or
both),
as
well
as
energy
in,
out
or
both.
Closed
Systems:
Does
not
allow
mass
in
or
out,
but
does
allow
energy
in,
out
or
both.
Walls
in
Thermodynamic
Systems
Adiabatic
(adiathermal)
walls:
walls
that
prevent
thermal
interaction.
Diathermal
walls:
walls
that
allow
thermal
interaction.
Two
systems
separated
by
a
diathermal
wall
are
in
thermal
contact.
Types
of
Thermodynamic
Variables
Intensive
• Variables
that
are
essentially
local
in
character
• E.g.
pressure,
electric
field,
force
density,
temperature
Extensive
• Variables
that
correspond
to
some
measure
of
the
system
as
a
whole
• E.g.
mass,
volume,
internal
energy,
length
• Extensive
variables
are
proportional
to
the
mass
of
the
system
(if
the
intensive
variables
remain
constant)
2
