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Chapter 1
INTRODUCTION AND
Therm
odynamics: An Engineering Approach, 6thEdition
Yunus A. Cengel, Michael A. Boles
McGraw-Hill, 2008
INTRODUCTION AND
BASIC CONCEPTS
Mehmet Kanoglu
Copyright © The McGraw-Hill Companies, Inc. Perm
ission required for reproduction or display.
Objectives
•Id
entify
the u
niq
ue v
ocabula
ry a
ssocia
ted w
ith
therm
odynam
ics t
hro
ugh t
he p
recis
e d
efinitio
n o
f
basic
concepts
to form
a s
ound f
oundation f
or
the
develo
pm
ent
of th
e p
rincip
les o
f th
erm
odynam
ics.
•R
evie
w t
he m
etr
ic S
I and t
he E
nglis
h u
nit s
yste
ms.
•E
xpla
in t
he b
asic
concepts
of th
erm
odynam
ics s
uch
2
•E
xpla
in t
he b
asic
concepts
of th
erm
odynam
ics s
uch
as s
yste
m, sta
te, sta
te p
ostu
late
, equili
bri
um
,
pro
cess, and c
ycle
.
•R
evie
w c
oncepts
of te
mpera
ture
, te
mpera
ture
scale
s,
pre
ssure
, and a
bsolu
te a
nd g
age p
ressure
.
•In
troduce a
n intu
itiv
e s
yste
matic p
roble
m-s
olv
ing
techniq
ue.
THERMODYNAMICS AND ENERGY
•Therm
odynamics
:T
he
scie
nce
of
energy.
•Energy:
Th
e a
bili
ty t
o c
au
se
ch
an
ge
s.
•T
he
na
me
therm
odynamics
ste
ms fro
m
the
Gre
ek w
ord
s therm
e (
he
at)
an
d
dynamis (
po
we
r).
•Conservation of energy principle
:D
uri
ng
an
in
tera
ctio
n, e
ne
rgy c
an
ch
an
ge
3
Du
rin
g a
n in
tera
ctio
n, e
ne
rgy c
an
ch
an
ge
fr
om
on
e fo
rm to
an
oth
er
bu
t th
e to
tal
am
ou
nt o
f e
ne
rgy r
em
ain
s c
on
sta
nt.
•E
ne
rgy c
an
no
t b
e c
rea
ted
or
de
str
oye
d.
•The first law of therm
odynamics
:A
n
exp
ressio
n o
f th
e c
on
se
rva
tio
n o
f e
ne
rgy
pri
ncip
le.
•T
he
fir
st la
w a
sse
rts th
at energy is a
th
erm
od
yn
am
ic p
rop
ert
y.
Energ
y c
annot
be c
reate
d
or
destr
oyed;
it c
an o
nly
change f
orm
s (
the f
irst la
w).
•The second law of therm
odynamics:
It a
sse
rts th
at e
ne
rgy h
as quality
as
we
ll a
s quantity, a
nd
actu
al p
roce
sse
s
occu
r in
th
e d
ire
ctio
n o
f d
ecre
asin
g
qu
alit
y o
f e
ne
rgy.
•Classical therm
odynamics
:A
m
acro
sco
pic
ap
pro
ach
to th
e s
tud
y o
f th
erm
od
yn
am
ics th
at d
oe
s n
ot re
qu
ire
a
kn
ow
led
ge
of th
e b
eh
avio
r o
f in
div
idu
al p
art
icle
s.
Conserv
ation o
f energ
y
princip
le f
or
the h
um
an b
ody.
4
ind
ivid
ua
l p
art
icle
s.
•It p
rovid
es a
dir
ect a
nd
ea
sy w
ay to
th
e
so
lutio
n o
f e
ng
ine
eri
ng
pro
ble
ms a
nd
it
is u
se
d in
th
is te
xt.
•Statistical therm
odynamics
:A
m
icro
sco
pic
ap
pro
ach
, b
ase
d o
n th
e
ave
rag
e b
eh
avio
r o
f la
rge
gro
up
s o
f in
div
idu
al p
art
icle
s.
•It is u
se
d in
th
is te
xt o
nly
in
th
e
su
pp
ort
ing
ro
le.
Heat flow
s in t
he d
irection o
f
decre
asin
g t
em
pera
ture
.
Application Areas of Therm
odynamics
5
IMPORTANCE OF DIMENSIONS AND UNITS
•A
ny p
hysic
al q
ua
ntity
ca
n b
e c
ha
racte
rize
d b
y
dimensions
.
•T
he
ma
gn
itu
de
s a
ssig
ne
d to
th
e d
ime
nsio
ns
are
ca
lled
units
.
•S
om
e b
asic
dim
en
sio
ns s
uch
as m
ass m
, le
ng
th L
, tim
e t, a
nd
te
mp
era
ture
T a
re
se
lecte
d a
s primary
or fundamental
dimensions
, w
hile
oth
ers
su
ch
as v
elo
city V
, e
ne
rgy E
, a
nd
vo
lum
e V a
re e
xp
resse
d in
6
en
erg
y E
, a
nd
vo
lum
e V a
re e
xp
resse
d in
te
rms o
f th
e p
rim
ary
dim
en
sio
ns a
nd
are
ca
lled
secondary dimensions
, o
r derived
dimensions
.
•Metric SI system
:A
sim
ple
an
d lo
gic
al
syste
m b
ase
d o
n a
de
cim
al re
latio
nsh
ip
be
twe
en
th
e v
ari
ou
s u
nits.
•English system
:It h
as n
o a
pp
are
nt
syste
ma
tic n
um
eri
ca
l b
ase
, a
nd
va
rio
us u
nits
in th
is s
yste
m a
re r
ela
ted
to
ea
ch
oth
er
rath
er
arb
itra
rily
.
Some SI and English Units
Th
e S
I u
nit p
refixe
s a
re u
se
d in
all
bra
nch
es o
f e
ng
ine
eri
ng
.
Wo
rk =
Fo
rce
×D
ista
nce
1 J
= 1
N·m
1 c
al =
4.1
86
8 J
1 B
tu =
1.0
55
1 k
J
7T
he
de
fin
itio
n o
f th
e fo
rce
un
its.
1 B
tu =
1.0
55
1 k
J
A b
ody w
eig
hin
g
60 k
gf
on e
art
h
will
weig
h o
nly
10
kgf on t
he m
oon.
Ww
eig
ht
mm
ass
ggra
vitational
accele
ration
8
The r
ela
tive m
agnitudes o
f th
e f
orc
e
units n
ew
ton (
N),
kilo
gra
m-f
orc
e
(kgf)
, and p
ound-f
orc
e (
lbf)
.
The w
eig
ht
of
a u
nit
mass a
t sea level.
Unity Conversion Ratios
All nonprimary units (secondary units) can be
form
ed by combinations of primary units.
Forc
e u
nits,
for
exam
ple
, can b
e e
xpre
ssed a
s
Dimensional homogeneity
All
equations m
ust
be d
imensio
nally
homogeneous.
9
They c
an a
lso b
e e
xpre
ssed m
ore
convenie
ntly
as unity conversion ratios
as
Unity c
onvers
ion r
atios a
re identically
equal to
1 a
nd
are
unitle
ss,
and t
hus s
uch r
atios (
or
their invers
es)
can b
e insert
ed c
onvenie
ntly into
any c
alc
ula
tion t
o
pro
perly c
onvert
units.
To b
e d
imensio
nally
hom
ogeneous,
all
the
term
s in a
n e
quation
must have t
he s
am
e u
nit.
SYSTEMS AND CONTROL VOLUMES
•System
:A
qu
an
tity
of m
atte
r o
r a
re
gio
n
in s
pa
ce
ch
ose
n fo
r stu
dy.
•Surroundings:T
he
ma
ss o
r re
gio
n
ou
tsid
e th
e s
yste
m
•Boundary
:T
he
re
al o
r im
ag
ina
ry s
urf
ace
th
at se
pa
rate
s th
e s
yste
m fro
m its
su
rro
un
din
gs.
•T
he
bo
un
da
ry o
f a
syste
m c
an
be
fixed o
r movable.
10
movable.
•S
yste
ms m
ay b
e c
on
sid
ere
d to
be
closed
or open.
•Closed system
(Control mass):
A fix
ed
am
ou
nt
of m
ass, a
nd
no
m
ass c
an
cro
ss
its b
ou
nd
ary
.
•Open system
(control volume):
A p
rop
erl
y
se
lecte
d r
eg
ion
in
sp
ace
.
•It u
su
ally
en
clo
se
s a
de
vic
e th
at in
vo
lve
s
ma
ss flo
w s
uch
as a
co
mp
ressor,
tu
rbin
e, o
r n
ozzle
.
•B
oth
ma
ss a
nd
en
erg
y c
an
cro
ss th
e
bo
un
da
ry o
f a
co
ntr
ol vo
lum
e.
•Control surface
:T
he
bo
un
da
rie
s o
f a
co
ntr
ol
vo
lum
e. It c
an
be
re
al o
r im
ag
ina
ry.
11
An o
pen s
yste
m (
a
contr
ol volu
me)
with o
ne
inle
t and o
ne e
xit.
PROPERTIES
OF A SYSTEM
•Property:
An
y c
ha
racte
ristic o
f a
syste
m.
•S
om
e fa
mili
ar
pro
pe
rtie
s a
re
pre
ssu
re P
, te
mp
era
ture
T, vo
lum
e
V, a
nd
ma
ss m
.
•P
rop
ert
ies a
re c
on
sid
ere
d to
be
e
ith
er intensive o
r extensive
.
12
eith
er intensive o
r extensive
.
•Intensive properties:
Th
ose
th
at
are
in
de
pe
nd
en
t o
f th
e m
ass o
f a
syste
m, su
ch
as te
mp
era
ture
, p
ressu
re, a
nd
de
nsity.
•Extensive properties:
Th
ose
w
ho
se
va
lue
s d
ep
en
d o
n th
e s
ize
—o
r e
xte
nt—
of th
e s
yste
m.
•Specific properties:
Exte
nsiv
e
pro
pe
rtie
s p
er
un
it m
ass.
Crite
rion t
o d
iffe
rentiate
inte
nsiv
e
and e
xte
nsiv
e p
ropert
ies.
Continuum
•M
att
er
is m
ade u
p o
f ato
ms t
hat
are
w
idely
spaced in t
he g
as p
hase.
Yet
it is v
ery
convenie
nt
to d
isre
gard
the
ato
mic
natu
re o
f a s
ubsta
nce a
nd
vie
w it as a
continuous,
hom
ogeneous m
att
er
with n
o h
ole
s,
that is
, a continuum
.
•T
he c
ontinuum
idealiz
ation a
llow
s u
s
to tre
at pro
pert
ies a
s p
oin
t fu
nctions
and t
o a
ssum
e t
he p
ropert
ies v
ary
continually
in s
pace w
ith n
o jum
p
13
continually
in s
pace w
ith n
o jum
p
dis
continuitie
s.
•T
his
idealiz
ation is v
alid
as long a
s
the s
ize o
f th
e s
yste
m w
e d
eal w
ith
is larg
e r
ela
tive t
o t
he s
pace
betw
een t
he m
ole
cule
s.
•T
his
is t
he c
ase in p
ractically
all
pro
ble
ms.
•In
this
text
we w
ill lim
it o
ur
consid
era
tion t
o s
ubsta
nces t
hat
can
be m
odele
d a
s a
continuum
.
Despite t
he larg
e g
aps b
etw
een
mole
cule
s,
a s
ubsta
nce c
an b
e t
reate
d a
s
a c
ontinuum
because o
f th
e v
ery
larg
e
num
ber
of
mole
cule
s e
ven in a
n
extr
em
ely
sm
all
volu
me.
DENSITY AND SPECIFIC GRAVITY
Specific gravity:
The r
atio
of th
e d
ensity o
f a
substa
nce t
o t
he d
ensity o
f som
e s
tandard
substa
nce
at a s
pecifie
d t
em
pera
ture
(u
sually
wate
r at 4°C
).
Density
Specific weight:
The
weig
ht
of
a u
nit v
olu
me
of a s
ubsta
nce.
Specific volume
14
Density is
mass p
er
unit
volu
me;
specific
volu
me
is v
olu
me p
er
unit m
ass.
of a s
ubsta
nce.
STATE AND EQUILIBRIUM
•T
herm
odynam
ics d
eals
with
equilibrium s
tate
s.
•Equilibrium
:A
sta
te o
f bala
nce.
•In
an e
quili
brium
sta
te there
are
no
unbala
nced p
ote
ntials
(or
drivin
g
forc
es)
within
the s
yste
m.
•Therm
al equilibrium
:If
the
tem
pera
ture
is t
he s
am
e t
hro
ughout
the e
ntire
syste
m.
A s
yste
m a
t tw
o d
iffe
rent
sta
tes.
15
•Mechanical equilibrium:
If there
is
no c
hange in p
ressure
at
any p
oin
t of th
e s
yste
m w
ith t
ime.
•Phase equilibrium:
If a
syste
m
involv
es t
wo p
hases a
nd w
hen t
he
mass o
f each p
hase r
eaches a
n
equili
brium
level and s
tays t
here
.
•Chemical equilibrium:
If the
chem
ical com
positio
n o
f a s
yste
m
does n
ot
change w
ith t
ime,
that
is,
no c
hem
ical re
actions o
ccur.
A c
losed s
yste
m r
eachin
g t
herm
al
equili
brium
.
A s
yste
m a
t tw
o d
iffe
rent
sta
tes.
The State Postulate
•T
he n
um
ber
of pro
pert
ies
required t
o fix
the s
tate
of a
syste
m is g
iven b
y t
he state
postulate
:
�The state of a sim
ple
compressible system is
completely specified by
16
completely specified by
two independent,
intensive properties.
•Simple compressible
system:
If a
syste
m involv
es
no e
lectr
ical, m
agnetic,
gra
vitational, m
otion, and
surf
ace tensio
n e
ffects
.
Th
e s
tate
of
nitro
ge
n is
fixe
d b
y t
wo
in
de
pe
nd
en
t,
inte
nsiv
e p
rop
ert
ies.
PROCESSES AND CYCLES
Process:
Any c
hange t
hat
a s
yste
m u
nderg
oes f
rom
one e
quili
brium
sta
te t
o
anoth
er.
Path
:T
he s
eries o
f sta
tes thro
ugh w
hic
h a
syste
m p
asses d
uring a
pro
cess.
To d
escribe a
pro
cess c
om
ple
tely
, one s
hould
specify t
he initia
l and f
inal sta
tes,
as w
ell
as t
he p
ath
it
follo
ws,
and t
he inte
ractions w
ith t
he s
urr
oundin
gs.
Quasistatic or quasi-equilibrium process:
When a
pro
cess p
roceeds in s
uch
a m
anner
that
the s
yste
m r
em
ain
s infinitesim
ally
clo
se t
o a
n e
quili
brium
sta
te
at all
tim
es.
17
•P
rocess d
iagra
ms p
lott
ed b
y
em
plo
yin
g t
herm
odynam
ic p
ropert
ies
as c
oord
inate
s a
re v
ery
usefu
l in
vis
ualiz
ing t
he p
rocesses.
•S
om
e c
om
mon p
ropert
ies t
hat
are
used a
s c
oord
inate
s a
re t
em
pera
ture
T
, pre
ssure
P, and v
olu
me V (
or
specific
volu
me v
).
•T
he p
refix iso-
is o
ften u
sed t
o
desig
nate
a p
rocess f
or
whic
h a
part
icula
rpro
pert
y r
em
ain
s c
onsta
nt.
•Isotherm
al process:
A p
rocess
18
•Isotherm
al process:
A p
rocess
during w
hic
h t
he t
em
pera
ture
T
rem
ain
s c
onsta
nt.
•Isobaric process:
A p
rocess d
uring
whic
h t
he p
ressure
P r
em
ain
s
consta
nt.
•Isochoric (or isometric) process:
A
pro
cess d
uring w
hic
h t
he s
pecific
volu
me v r
em
ain
s c
onsta
nt.
•Cycle
:A
pro
cess d
uring w
hic
h t
he
initia
l and f
inal sta
tes a
re identical.
The P
-V d
iagra
m o
f a c
om
pre
ssio
n
pro
cess.
The Steady-Flow Process
•T
he term
steady
implie
s no
change w
ith tim
e.
The
opposite o
f ste
ady is
unsteady,
or transient.
•A
larg
e n
um
ber
of
engin
eering d
evic
es o
pera
te
for
long p
eriods o
f tim
e
under
the s
am
e c
onditio
ns,
and t
hey a
re c
lassifie
d a
s
steady-flow devices.
Du
rin
g a
ste
ad
y-
flo
w p
roce
ss,
flu
id
pro
pe
rtie
s w
ith
in
the
co
ntr
ol
vo
lum
e m
ay
ch
an
ge
with
19
steady-flow devices.
•Steady-flow process:
A
pro
cess d
uring w
hic
h a
flu
id
flow
s t
hro
ugh a
contr
ol
volu
me s
teadily
.
•S
teady-f
low
conditio
ns c
an
be c
losely
appro
xim
ate
d b
y
devic
es t
hat
are
inte
nded f
or
continuous o
pera
tion s
uch
as turb
ines,
pum
ps,
boile
rs,
condensers
, and h
eat
exchangers
or
pow
er
pla
nts
or
refr
igera
tion s
yste
ms.
po
sitio
n b
ut
no
t
with
tim
e.
Un
de
r ste
ad
y-f
low
co
nd
itio
ns,
the
ma
ss
an
d e
ne
rgy c
on
ten
ts o
f a
co
ntr
ol vo
lum
e
rem
ain
co
nsta
nt.
TEMPERATURE AND THE ZEROTH LAW OF
THERMODYNAMICS
•The zeroth law of therm
odynamics:If tw
o b
od
ies a
re in
th
erm
al
eq
uili
bri
um
with
a th
ird
bo
dy, th
ey a
re a
lso
in
th
erm
al e
qu
ilib
riu
m w
ith
e
ach
oth
er.
•B
y r
ep
lacin
g th
e th
ird
bo
dy w
ith
a th
erm
om
ete
r, th
e z
ero
th la
w c
an
b
e r
esta
ted
as two bodies are in therm
al equilibrium if both have the
same temperature reading even if they are not in contact.
20
Tw
o b
od
ies r
ea
ch
ing
the
rma
l e
qu
ilib
riu
m
afte
r b
ein
g b
rou
gh
t
into
co
nta
ct in
an
iso
late
d e
nclo
su
re.
Temperature Scales
•A
ll te
mp
era
ture
sca
les a
re b
ase
d o
n
so
me
ea
sily
re
pro
du
cib
le s
tate
s s
uch
as
the
fre
ezin
g a
nd
bo
ilin
g p
oin
ts o
f w
ate
r:
the
ice point
an
d t
he
steam point.
•Ice point:
A m
ixtu
re o
f ic
e a
nd
wa
ter
tha
t is
in
eq
uili
bri
um
with
air
sa
tura
ted
w
ith
va
po
r a
t 1
atm
pre
ssu
re (
0°C
or
32
°F).
•Steam point:
A m
ixtu
re o
f liq
uid
wa
ter
an
d w
ate
r va
po
r (w
ith
no
air
) in
e
qu
ilib
riu
m a
t 1
atm
pre
ssu
re (
10
0°C
or
21
2°F
).
P v
ers
us T p
lots
of
the
exp
eri
me
nta
l
da
ta o
bta
ine
d
fro
m a
co
nsta
nt-
vo
lum
e g
as
the
rmo
me
ter
usin
g fo
ur
diffe
ren
t g
ase
s
at
diffe
ren
t (b
ut
low
) p
ressu
res.
21
•Celsius scale
:in
SI
un
it s
yste
m
•Fahrenheit scale
:in
En
glis
h u
nit
syste
m
•Therm
odynamic temperature scale
:A
te
mp
era
ture
sca
le th
at
is in
de
pe
nd
en
t o
f th
e p
rop
ert
ies o
f a
ny s
ub
sta
nce
.
•Kelvin scale
(SI)
Rankine scale
(E)
•A
te
mp
era
ture
sca
le n
ea
rly id
en
tica
l to
th
e K
elv
in s
ca
le is th
e ideal-gas
temperature scale
. T
he
te
mp
era
ture
s
on
th
is s
ca
le a
re m
ea
su
red
usin
g a
co
nsta
nt-
vo
lum
e g
as t
he
rmo
me
ter.
A c
on
sta
nt-
vo
lum
e g
as t
he
rmo
me
ter
wo
uld
rea
d -
27
3.1
5°C
at
ab
so
lute
ze
ro p
ressu
re.
Com
parison o
f
tem
pera
ture
scale
s.
22
•T
he r
efe
rence t
em
pera
ture
in t
he o
rigin
al K
elv
in s
cale
was t
he ice point,
273.1
5 K
, w
hic
h is t
he t
em
pera
ture
at
whic
h w
ate
r fr
eezes (
or
ice m
elts).
•T
he r
efe
rence p
oin
t w
as c
hanged t
o a
much m
ore
pre
cis
ely
repro
ducib
le
poin
t, the triple point
of
wate
r (t
he s
tate
at w
hic
h a
ll th
ree p
hases o
f w
ate
r
coexis
t in
equili
brium
), w
hic
h is a
ssig
ned t
he v
alu
e 2
73.1
6 K
.
Com
parison o
f
magnitudes o
f
various
tem
pera
ture
units.
PRESSURE
Pressure
:A
norm
al fo
rce e
xert
ed
by a
flu
id p
er
unit a
rea
68 k
g136 k
g
Afe
et=
300cm
2
0.2
3 k
gf/
cm
20.4
6 k
gf/
cm
2
23
The n
orm
al str
ess (
or
“pre
ssure
”) o
n t
he
feet of a c
hubby p
ers
on is m
uch g
reate
r
than o
n t
he f
eet of
a s
lim p
ers
on.
Som
e
basic
pre
ssure
gages.
0.2
3 k
gf/
cm
20.4
6 k
gf/
cm
2
P=
68/3
00=
0.2
3 k
gf/
cm
2
•Absolute pressure
:T
he
actu
al p
ressu
re a
t a
giv
en
po
sitio
n. It is
me
asu
red
re
lative
to
ab
so
lute
va
cu
um
(i.e
., a
bso
lute
ze
ro p
ressu
re).
•Gage pressure
:T
he
diffe
ren
ce
be
twe
en
th
e a
bso
lute
pre
ssu
re a
nd
th
e lo
ca
l a
tmo
sp
he
ric p
ressu
re. M
ost p
ressu
re-m
ea
su
rin
g d
evic
es a
re
ca
libra
ted
to
re
ad
ze
ro in
th
e a
tmo
sp
he
re, a
nd
so
th
ey in
dic
ate
ga
ge
p
ressu
re.
•Vacuum pressures
:P
ressu
res b
elo
w a
tmo
sp
he
ric p
ressu
re.
Thro
ughout
this
text,
the
pre
ssure
P
24
pre
ssure
P
will
denote
absolute
pressure
unle
ss
specifie
d
oth
erw
ise.
Variation of Pressure with Depth
Wh
en
th
e v
ari
atio
n o
f d
en
sity
with
ele
va
tio
n is k
no
wn
25
Fre
e-b
ody d
iagra
m o
f a r
ecta
ngula
r
fluid
ele
ment
in e
quili
brium
.
The p
ressure
of
a f
luid
at
rest
incre
ases w
ith d
epth
(as a
result o
f added w
eig
ht)
.
In a
room
fill
ed w
ith
a g
as,
the v
ariation
of pre
ssure
with
heig
ht
is n
eglig
ible
.
Pre
ssure
in a
liq
uid
at re
st in
cre
ases
linearly w
ith
dis
tance f
rom
the
free s
urf
ace.
26
free s
urf
ace.
The p
ressure
is t
he
sam
e a
t all
poin
ts o
n
a h
orizonta
l pla
ne in
a g
iven f
luid
regard
less o
f
geom
etr
y, p
rovid
ed
that th
e p
oin
ts a
re
inte
rconnecte
d b
y
the s
am
e f
luid
.
Pascal’s law
:T
he
pre
ssu
re a
pp
lied
to
a
co
nfin
ed
flu
id in
cre
ase
s th
e p
ressu
re
thro
ug
ho
ut b
y th
e s
am
e a
mo
un
t.
Th
e a
rea
ra
tio
A2/A
1is
ca
lled
th
e ideal mechanical
advantage
of th
e h
yd
rau
lic
lift.
27
Liftin
g o
f a
la
rge
we
igh
t
by a
sm
all
forc
e b
y th
e
ap
plic
atio
n o
f P
asca
l’s
law
.
lift.
The Manometer
Measuring t
he
pre
ssure
dro
p a
cro
ss
a flo
w s
ection o
r a f
low
devic
e b
y a
diffe
rential
manom
ete
r.
It is c
om
monly
used t
o m
easure
sm
all
and
modera
te p
ressure
diffe
rences. A
manom
ete
r
conta
ins o
ne o
r m
ore
flu
ids s
uch a
s m
erc
ury
, w
ate
r,
alc
ohol, o
r oil.
28
In s
tacked-u
p f
luid
layers
, th
e
pre
ssure
change a
cro
ss a
flu
id layer
of density ρ
and h
eig
ht h is ρ ρρρgh
.
The b
asic
manom
ete
r.
Other Pressure Measurement Devices
•Bourdon tube:C
on
sis
ts o
f a
ho
llow
me
tal tu
be
be
nt
like
a h
oo
k w
ho
se
en
d is c
lose
d a
nd
co
nn
ecte
d t
o a
dia
l in
dic
ato
r n
ee
dle
.
•Pressure transducers
:U
se
va
rio
us te
ch
niq
ue
s
to c
on
ve
rt t
he
pre
ssu
re e
ffe
ct
to a
n e
lectr
ica
l
effe
ct
su
ch
as a
ch
an
ge
in
vo
lta
ge
, re
sis
tan
ce
,
or
ca
pa
cita
nce
.
•P
ressu
re tra
nsd
uce
rs a
re s
ma
ller
an
d f
aste
r,
an
d th
ey c
an
be
mo
re s
en
sitiv
e, re
liab
le, a
nd
pre
cis
e th
an
th
eir
me
ch
an
ica
l co
un
terp
art
s.
29
Various t
ypes o
f B
ourd
on t
ubes u
sed
to m
easure
pre
ssure
.
pre
cis
e th
an
th
eir
me
ch
an
ica
l co
un
terp
art
s.
•Strain-gage pressure transducers:
Wo
rk b
y
ha
vin
g a
dia
ph
rag
m d
efle
ct
be
twe
en
tw
o
ch
am
be
rs o
pe
n t
o t
he
pre
ssu
re in
pu
ts.
•Piezoelectric transducers
:A
lso
ca
lled
so
lid-
sta
te p
ressu
re t
ran
sd
uce
rs,
wo
rk o
n t
he
pri
ncip
le th
at
an
ele
ctr
ic p
ote
ntia
l is
ge
ne
rate
d in
a c
rysta
llin
e s
ub
sta
nce
wh
en
it
is s
ubje
cte
d t
o
me
ch
an
ica
l p
ressu
re.
THE BAROMETER AND ATMOSPHERIC PRESSURE
•A
tmospheric p
ressure
is m
easure
d b
y a
devic
e c
alle
d a
barometer;
thus,
the
atm
ospheric p
ressure
is o
ften r
efe
rred t
o a
s t
he barometric pressure
.
•A
fre
quently u
sed p
ressure
unit is t
he standard atm
osphere
, w
hic
h is d
efined a
s
the p
ressure
pro
duced b
y a
colu
mn o
f m
erc
ury
760 m
m in h
eig
ht
at
0°C
(ρ
Hg
=
13,5
95 k
g/m
3)
under
sta
ndard
gra
vitational accele
ration (g = 9
.807 m
/s2).
The length
or
the
cro
ss-s
ectional are
a
30
The b
asic
baro
mete
r.
cro
ss-s
ectional are
a
of th
e t
ube h
as n
o
effect on t
he h
eig
ht
of th
e f
luid
colu
mn o
f
a b
aro
mete
r,
pro
vid
ed t
hat th
e
tube d
iam
ete
r is
larg
e e
nough t
o
avoid
surf
ace t
ensio
n
(capill
ary
) effects
.
PROBLEM-SOLVING TECHNIQUE
•S
tep 1
: P
roble
m S
tate
ment
•S
tep 2
: S
chem
atic
•S
tep 3
: A
ssum
ptions a
nd A
ppro
xim
ations
•S
tep 4
: P
hysic
al Law
s
•S
tep 5
: P
ropert
ies
•S
tep 6
: C
alc
ula
tions
31
•S
tep 6
: C
alc
ula
tions
•S
tep 7
: R
easonin
g,
Verification,
and D
iscussio
n
EES (Engineering Equation Solver)
(Pro
no
un
ce
d a
s e
ase
):
EE
S is a
pro
gra
m th
at so
lve
s s
yste
ms o
f lin
ea
r o
r n
on
line
ar
alg
eb
raic
or
diffe
ren
tia
l e
qu
atio
ns n
um
eri
ca
lly. It h
as a
la
rge
libra
ry o
f b
uilt
-in
th
erm
od
yn
am
ic p
rop
ert
y fu
nctio
ns a
s w
ell
as
ma
the
ma
tica
l fu
nctio
ns. U
nlik
e s
om
e s
oftw
are
pa
cka
ge
s, E
ES
do
es n
ot so
lve
en
gin
ee
rin
g p
rob
lem
s; it o
nly
so
lve
s th
e e
qu
atio
ns
su
pp
lied
by th
e u
se
r.
Summary
•T
herm
odynam
ics a
nd e
nerg
y
�A
pp
lica
tio
n a
rea
s o
f th
erm
od
yn
am
ics
•Im
port
ance o
f dim
ensio
ns a
nd u
nits
�S
om
e S
I a
nd
En
glis
h u
nits,
Dim
en
sio
na
l h
om
og
en
eity,
Un
ity c
on
ve
rsio
n r
atio
s
•S
yste
ms a
nd c
ontr
ol volu
mes
•P
ropert
ies o
f a s
yste
m
•D
ensity a
nd s
pecific
gra
vity
•S
tate
and e
quili
brium
32
•S
tate
and e
quili
brium
�T
he
sta
te p
ostu
late
•P
rocesses a
nd c
ycle
s
�T
he
ste
ad
y-f
low
pro
ce
ss
•T
em
pera
ture
and t
he z
ero
th law
of th
erm
odynam
ics
�T
em
pe
ratu
re s
ca
les
•P
ressure
�V
ari
atio
n o
f p
ressu
re w
ith
de
pth
•T
he m
anom
ete
r and t
he a
tmospheric p
ressure
•P
roble
m s
olv
ing t
echniq
ue
