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7/25/2019 Chapter 1 Basic Thermodynamics
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1
CHAPTER 1BASIC THERMODYNAMICS
GENERAL OBJECTIVES:To understand the concept of unit .
G !"# T$ER%O&'NA%ICS
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1.1 Concept of Unit andDimension
Specifc Objectives:At the end o the unit, you i!! be "b!e to:
1# St"te the b"sic concepts in The$%odyn"%ic#
2# &esc$ibed the physic"! 'u"ntities o
the$%odyn"%ics#(# C"!cu!"te the e)"%p!es o conve$sion
"cto$s#
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1.1 What is Thermodynamics??
*$ee+ o$ds therme -he"t. / dynamics -po e$.
The$%odyn"%ics the science o energy / the study o the t$"ns e$ o ene$0y,
the o$+ done it s "3ect on %"tte$One o the %ost und"%ent"! !" s/ conse$v"tion o ene$0y p$incip!e
Conve$t he"tinto po e$
Introduction
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Examples
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8
5und"%ent"! 6nits
QUANTITY UNIT SYMBOL
Mass Kilogram kg
Time Second sLength Meter m
Temperat re !egree Kel#in K
$lectric % rrent Ampere A
L mino s Intensit& %andela cd
Amo nt o' Matter Mole mol
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&e$ived 6nits
A!! physic"! 'u"ntities hich c"n bee)p$essed in te$%s o one o$ %o$e
o the und"%ent"! units "$e +no n"s de$ived 'u"ntities#
5o$ e)"%p!e: "$e", vo!u%e, density,
ve!ocity etc since they depend onone o$ %o$e o the und"%ent"!'u"ntities#
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7%pe$i"! 6nits
The syste% o i%pe$i"! units o$ thei%pe$i"! syste% is "!so +no n "s
;$itish 7%pe$i"!# The syste% c"%e into o
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Temperature Scales
The $e!"tions bet een te%pe$"tu$e sc"!es "$e:
T ->. ? T- oC. @ 29(#14
T -o
5. ? 1# T-o
C. @ (2# T - o5. ? 1# -T->./29(#14. @
(2#
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1
6B7T COB ERS7OBS
Conversion of units is the conve$sionbet een di3e$ent units o %e"su$e%ent
o$ the s"%e 'u"ntity, typic"!!y th$ou0h%u!tip!ic"tive conversion factors #
5o$ e)"%p!es:
1 +0 ? 1 0
1 % ? 1 c% ? 1 %%1 +% ? 1 %1 hou$ ? 8 %inutes ? (8 seconds1 b"$ ? 1 ) 1 4 BD%2 ? 1 ) 1 2 +BD%21 % ( ? 1 !it$e o$ 1 !it$e ? 1 ) 1 /( % (
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11
6FT7PFG7B* 5ACTORSM ltipl&ing (actor )re'i* S&m+ol
1,,,,,,,,,,,, 1, 1- tera T1,,,,,,,,, 1, . giga /1,,,,,, 1, 0 mega M
1,,, 1, kilo k1,, 1, - hecto h1, 1, 1 deca da,21 1, 31 desi d
,2,1 1, 3- centi c,2,,1 1, 3 milli m,2,,,,,1 1, 30 micro 4,2,,,,,,,,1 1, 3. nano n
,2,,,,,,,,,,,1 1,31-
pico p
&o you +no
M ltiple )re'i* S&m+ol1, -5 &otta Y
1, -1 6etta 7
1, 18 e*a $
1, 19 peta )
1, 319 'emto ' 1, 318 atto a
1, 3-1 6epto 6
1, 3-5 &octo &
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12
6B7T COB ERS7OBS
EIA PFES:1# Conve$t 1 +%Dh to %Ds#
2# Conve$t 24 0D%%(
to +0D%(
#
Tuto$i"!: Conve$t the o!!o in0 d"t":(# ( BDc% 2 to +BD% 2J# 14 BD% 2 to BD% 24# 14 %0D!it$e to +0D% (
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1(
1. The !asic concept ofThermodynamics
Specifc Objectives:At the end o the unit, you i!! be "b!e to:
1# &efne the p$incip!es o " syste%,bound"$y, su$$oundin0#2# C!"$i y the p$ope$ties o syste%s, st"te
"nd e'ui!ib$iu%#
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1J
The P$incip!es o A Syste%
So%e %o$e notes: The bound"$y o " syste% c"n be f)ed o$
%ov"b!e# The bound"$y is the cont"ct su$ "cesh"$ed by both the syste% "nd thesu$$oundin0s#
Syste%s %"y be conside$ed to be c!osedo$ open dependin0 on hethe$ " f)ed%"ss o$ " f)ed vo!u%e in sp"ce ischosen o$ study#
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DE"I#ITI$# $" % S&STE'()$U#D%*& + SU**$U#DI#,
System" quantity of matter or a region in space chosenfor
study.
Surroundin- The %"ss o$ $e0ion outside the syste%#
)oundary The $e"! o$ i%"0in"$y su$ "ce th"t sep"$"tes the
syste% $o% its su$$oundin0s#
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A C!osed Syste%
A!so +no n "s " cont$o! %"ss o$ justsyste%
Consists o " f)ed "%ount o %"ss "ndno %"ss c"n c$oss its bound"$y -no %"ssc"n ente$ o$ !e"ve " c!osed syste%.#
Ene$0y -he"t o$ o$+. c"n c$oss thebound"$y#
o!u%e o " c!osed syste% does not h"veto be f)ed#
7 ene$0y is not "!!o ed to c$oss thebound"$ th"t s ste% is c"!!ed "n
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19
An Open Syste%
7s " cont$o! vo!u%e# ;oth %"ss "nd ene$0y c"n c$oss the
bound"$y# 7t usu"!!y enc!oses " device th"t
invo!ves %"ss Ko such "s "co%p$esso$, tu$bine o$ noLL!e#
ost cont$o! vo!u%es h"ve f)edbound"$ies "nd thus do not invo!ve"ny %ovin0 bound"$ies#
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1
7nte$"ctions o The$%odyn"%icSyste%s
T&pe o's&stem
Mass 'lo: ;ork
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1M
Open "nd C!osed Syste%
C!osed syste%
m = constant
%"ss
no
yesene$0y
A C!osed Syste% An Open Syste%
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2
P$ope$ties O A Syste%
Any ch"$"cte$istic o " syste% is c"!!ed "p$ope$ty#
5o$ e)"%p!e: p$essu$e P, te%pe$"tu$e T, vo!u%e
"nd %"ss % "nd so on# P$ope$ties "$e conside$ed to be eithe$ intensive
o$ e)tensive# 7ntensive p$ope$ties "$e those th"t "$e
independent o the %"ss o " syste% such "ste%pe$"tu$e, p$essu$e "nd density#
E)tensive p$ope$ties "$e those hose v"!uesdepend on the siLe /// o$ e)tent /// o thesyste%# E)"%p!e: tot"! %"ss, tot"! vo!u%e "nd
tot"! %o%entu%
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C$ite$ion to &i3e$enti"te 7ntensive"nd E)tensive P$ope$ties
%
TP
N
> m
> ?
T
)
@
> m
> ?
T
)
@
$*tensi#eproperties
Intensi#e
properties
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22
St"te
A thermodynamic state is " set ov"!ues o p$ope$ties o " the$%odyn"%icsyste% th"t %ust be specifed to$ep$oduce the syste%#
The individu"! p"$"%ete$s "$e +no n "sstate varia!les , state parameters o$thermodynamic varia!les #
At " 0iven st"te, "!! the p$ope$ties o "syste% h"ve f)ed v"!ues#
7 the v"!ue o even one p$ope$tych"n0es, the st"te i!! ch"n0e to "di3e$ent one#
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2J
P$ocess "nd Cyc!e
Any ch"n0e th"t " syste% unde$0oes$o% one e'ui!ib$iu% st"te to "nothe$ is
c"!!ed " p$ocess # The se$ies o st"tes th$ou0h hich "syste% p"sses du$in0 " p$ocess is c"!!ed
the p"th o the p$ocess# To desc$ibe " p$ocess co%p!ete!y, one
shou!d speci y the initi"! "nd fn"! st"teso p$ocess "s e!! "s the p"th i o!!o s"nd the inte$"ctions ith thesu$$oundin0s#
A syste% is s"id to h"ve unde$0one "cyc!e i it $etu$ns to its initi"! st"te "t the
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24
P$ocess "nd Cyc!e
i = Initial state
' = (inal state
)rocess path
Arro: sho: theprocess 'lo:
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P$ocess "nd Cyc!e
- = 'inal state1 = initial state
%Y%L$
)rocess 'rom1 to - and
ret rn to 1
(
!
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29
1. The "irst /a0 ofThermodynamics
,E#E*%/ $) ECTI2ES3
*elate the concept of the 4rst la0 of
thermodynamics. %pply the concept of the 4rst la0 of
thermodynamics.
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2
"irst /a0 of Thermodynamics
The 4rst la0 of thermodynamics $e e$s tothe$%odyn"%ic p$ocesses in hich he"t "nd
o$+ c"n be distin0uished "nd %e"su$ed# 7t is o ten e)p$essed by the st"te%ent th"t in "
the$%odyn"%ic p$ocess the inc$e%ent in theinte$n"! ene$0y o " syste% is e'u"! to theinc$e%ent o he"t supp!ied to the syste%,%inus the inc$e%ent o o$+ done by thesyste% on its su$$oundin0s#
The f$st !" o the$%odyn"%ics obse$ves thep$incip!e o conse$v"tion o ene$0y # Ene$0y c"nbe t$"ns o$%ed, i#e# ch"n0ed $o% one o$% to"nothe$, but c"nnot be c$e"ted no$ dest$oyed#
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2M
"irst /a0 of Thermodynamics
When a system undergoes athermodynamic cycle then the net
heat supplied to the system from itssurroundings is equal to the network done by the systems on its
surroundings.
d ? dQ
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(
Ener-y transfer !y heat
Ene$0y c"n c$oss the bound"$y o " c!osed syste%in t o distinct o$%s: he"t "nd o$+#
He"t is defned "s the o$% o ene$0y th"t ist$"ns e$$ed bet een t o syste%s -o$ " syste% "ndits su$$oundin0s. by vi$tue o " te%pe$"tu$e
di3e$ence# Qhen "n object is "t " di3e$ent te%pe$"tu$e $o%"nothe$ body o$ its su$$oundin0s, he"t Ko s soth"t the body "nd the su$$oundin0s $e"ch thes"%e te%pe$"tu$e, "t hich point they "$e inthe$%"! e'ui!ib$iu%#
Such spont"neous he"t t$"ns e$ "! "ys occu$s$o% " $e0ion o hi0h te%pe$"tu$e to "nothe$
$e0ion o !o e$ te%pe$"tu$e, "s $e'ui$ed by thesecond !" o the$%odyn"%ics#
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(1
Ener-y transfer !y heat
7n the$%odyn"%ics, the te$% he"t si%p!y%e"ns he"t t$"ns e$#
He"t Ko is unde$stood to %e"n the t$"ns e$o the$%"! ene$0y#
The t$"ns e$ o he"t into " syste% is$e'uent!y $e e$$ed to "s he"t "ddition "nd the
t$"ns e$ o he"t out o " syste% "s he"t$ejection#
A p$ocess du$in0 hich the$e is no he"tt$"ns e$ is c"!!ed "n "di"b"tic p$ocess#
He"t is t$"ns e$$ed by th$ee %ech"nis%s:conduction, convection "nd $"di"tion#
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(2
Ener-y transfer !y heat
Conduction o$ di3usion The t$"ns e$ o ene$0y bet een objects th"t "$e
in physic"! cont"ct Convection
The t$"ns e$ o ene$0y bet een "n object "ndits envi$on%ent, due to Kuid %otion R"di"tion
The t$"ns e$ o ene$0y to o$ $o% " body by
%e"ns o the e%ission o$ "bso$ption oe!ect$o%"0netic $"di"tion
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((
Ener-y transfer !y 0or5
Qo$+ "n ene$0y inte$"ction bet een " syste%"nd its su$$oundin0s# 6nit: + Qo$+ is the ene$0y t$"ns e$ "ssoci"ted ith " o$ce
"ctin0 th$ou0h " dist"nce# 5o$ e)"%p!e: " $isin0 piston, " $ot"tin0 sh" t "$e
"ssoci"ted ith o$+ inte$"ctions#
The :ork doned ring a process+et:een states 1and - is denoted+& ; 1- or simpl&;2
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(J
"ormal si-n convention for heatand 0or5
He"t t$"ns e$ to " syste% "nd o$+ doneby " syste% "$e positive He"t t$"ns e$ $o% " syste% "nd o$+ done
on " syste% "$e ne0"tive 5o$ e)"%p!e:
A o$+ input o 4 + : Q ? / 4 + A he"t !oss o ( + : ? / ( + A o$+ p$oduced by " syste% o 1 + : Q ? @
1 + A he"t "dded to " syste% o + : ? @ +
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(4
Internal Ener-y
7nte$n"! ene$0y The sto$e o ene$0y ithin "ny Kuid c"n beinc$e"sed o$ dec$e"sed "s " $esu!t o v"$iousp$ocesses c"$$ied out on o$ by the Kuid#
The ene$0y sto$ed ithin " Kuid hich $esu!ts$o% the inte$n"! %otion o its "to%s "nd
%o!ecu!es is c"!!ed its inte$n"! ene$0y "nd it isusu"!!y desi0n"ted by the !ette$ 6#
7 the inte$n"! ene$0y o the unit %"ss o Kuid isdiscussed this is then c"!!ed the specifc inte$n"!ene$0y "nd is desi0n"ted by u#
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(8
Internal Ener-y
The internal ener-y is the tot"! ene$0ycont"ined by " the$%odyn"%ics syste%#7nte$n"! ene$0y h"s t o %"jo$ co%ponents,+inetic ene$0y "nd potenti"! ene$0y#
E'u"tion o$ inte$n"! ene$0y
d6 ? d dQ6 2 6 1 ? 12 Q 12
E ) l f Cl
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(9
Ener-y )alance for CloseSystem
Example 1.1
% close system under-oes aprocess in 0hich there is a 0or5done from the system of 67 5and a heat transfer of 1 7 5 tothe surroundin-s. Calculate thechan-e of internal ener-y andstate 0hether it is an increasedor decreased.
E ) l f Cl
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(
Ener-y )alance for CloseSystem
Example 1.
%n internal com!ustion en-ine isactuatin- an air compressor. %tthe !e-innin- of the expansionprocess( the internal ener-y is8 7 5 . Determine the internalener-y at the end of the processif 0or5 done of 117 5#m is !ein-produced 0hile the heat re9ectedto the surroundin-s is :7 5 .
E ) l f Cl
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(M
Ener-y )alance for CloseSystem
Example 1.C"!cu!"te the ch"n0es o inte$n"! ene$0y"nd st"te hethe$ the inte$n"! ene$0y isinc$e"se o$ dec$e"se o$ the o!!o in0c"ses:/i# A syste% is $eceived 9J + he"t
"nd p$oduced J8 +B% o$+#ii# Qo$+ done by piston to "$ds the 0"s is(4 + D+0 "nd he"t $ejected is
44 + D+0#
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1.8 ;erfect ,as Specifc Objectives:At the end o the unit, you i!! be
"b!e to:1# &efne pe$ ect o$ ide"! 0"s in
te$%s o the %o!ecu!"$ %ode!#2# E)p!"in the 0"s const"nt,
unive$s"! 0"s const"nt "nd0ene$"! 0"s e'u"tion#(# &esc$ibe the !" o ide"! 0"s#
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J1
&efnition o Pe$ ect *"ses A pe$ ect 0"s o$ ide"! 0"s is " co!!ection o
p"$tic!es th"t: A$e in const"nt, $"ndo% %otion H"ve no inte$%o!ecu!"$ "tt$"ctions - hich
!e"ds to e!"stic co!!isions in hich no ene$0yis e)ch"n0ed o$ !ost. A$e conside$ed to be vo!u%e/!ess points#
The p$incip!e p$ope$ties used to defne the
st"te o " 0"seous syste% "$e p$essu$e -P.,vo!u%e - . "nd te%pe$"tu$e -T.#
T o !" s desc$ibin0 the beh"vio$ o " pe$ ect0"s "$e ;oy!e s F" "nd Ch"$!es F" #
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J2
;oy!e s F" The ;oy!e s F" :
P$ovided thete%pe$"tu$e T o "pe$ ect 0"s $e%"insconst"nt, then vo!u%e
o " 0iven %"ss o0"s is inve$se!yp$opo$tion"! to thep$essu$e P o the 0"s#
P ? Const"nt ite%pe$"tu$e $e%"ins
const"nt 7 " 0"s ch"n0es $o%
st"te 1 to st"te 2 du$in0"n isothe$%"! p$ocess ,then
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J(
;oy!e s F"
E)"%p!e 1#JA 'u"ntity o " ce$t"in pe$ ect 0"s ishe"ted "t " const"nt te%pe$"tu$e $o%
"n initi"! st"te o #22 %(
"nd (24+BD%2 to " fn"! st"te o 19 +BD% 2#C"!cu!"te the fn"! vo!u%e o the 0"s#
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JJ
Ch"$!es F" The Ch"$!es F" :
P$ovided the p$essu$e Po " 0iven %"ss o 0"s$e%"ins const"nt, thenvo!u%e o the 0"s i!!be di$ect!y p$opo$tion"!to the "bso!utete%pe$"tu$e T o the0"s#
DT ? Const"nt ip$essu$e $e%"ins
const"nt 7 " 0"s ch"n0es $o%
st"te 1 to st"te 2 du$in0"n const"nt p$essu$ep$ocess , then
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J4
Ch"$!es F"
E)"%p!e 1#4
A 'u"ntity o 0"s "t #4J % ( "nd (J4 oC
unde$0oes " const"nt p$essu$e p$ocessth"t c"uses the vo!u%e o the 0"s todec$e"ses to #(2 % ( # C"!cu!"te thete%pe$"tu$e o the 0"s "t the end othe p$ocess#
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J8
6nive$s"! *"ses F" The $e!"tion hich 0ives the vo!u%e o " 0"s
hen both te%pe$"tu$e "nd the p$essu$e "$ech"n0ed is st"ted "s e'u"tion be!o :
Bo 0"ses in p$"ctice obey this !" $i0id!y, but%"ny 0"ses tend to "$ds it#
An i%"0in"$y ide"! th"t obeys the !" is c"!!ed" pe$ ect 0"s "nd the e'u"tion is c"!!ed thech"$"cte$istic e'u"tion o st"te o " pe$ ect0"s#
Rt cons
T
PV == tan
2
22
1
11
T
V P
T
V P =
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J9
6nive$s"! *"ses F" The const"nt, R is c"!!ed the ide"! 0"s
const"nt # 6nit is B%D+0> o$ D+0># E"ch pe$ ect 0"s h"s " di3e$ent 0"s const"nt# The ch"$"cte$istic e'u"tion is usu"!!y $itten
"s
O$ o$ % +0, occupyin0 % ( ,
Anothe$ o$% o the ch"$"cte$istic e'u"tionc"n be de$ived usin0 the +i!o0$"%/%o!e "s "unit#
The +i!o0$"%/%o!e is defned "s " 'u"ntity o" "s e uiv"!ent to % + o the "s, he$e
RT PV =
mRT PV =
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6nive$s"! *"ses F" 5$o% the defnition o the +i!o0$"%/%o!e, o$ % +0
o " 0"s, e h"ve
he$e n is the nu%be$ o %o!es "nd is the%o!ecu!"$ ei0ht o the 0"s#
Since the st"nd"$d o %"ss is the +0, +i!o0$"%/%o!e i!! be $itten si%p!y "s %o!e# So,
Avo0"d$o s hypothesis st"tes th"t the vo!u%e o 1%o!e o "ny 0"s is the s"%e "s the vo!u%e o 1%o!e o "ny othe$ 0"s, hen the 0"ses "$e "t thes"%e te%pe$"tu$e "nd p$essu$e#
nM m =
nMRT PV =nT
PV MR =
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JM
6nive$s"! *"ses F" The$e o$e Dn is the s"%e o$ "!! 0"ses "t the
s"%e v"!ue o P "nd T# Th"t is the 'u"ntity P DnT is const"nt o$ "!!
0"ses#
This const"nt is c"!!ed the unive$s"! 0"sconst"nt "nd is 0iven the sy%bo! R o#
O$ since
Then,
nT PV
R MR o == T nR PV o=
o R MR =
M
R R o=
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4
6nive$s"! *"ses F" E)pe$i%ent h"s sho n th"t the vo!u%e o 1
%o!e o "ny pe$ ect 0"s "t 1 b"$ "nd 1 oC is"pp$o)i%"te!y 22#91 % ( #
The$e o$e
Conc!ution
R0 also can rewrite as 8.3 ! k"#kg$ and R %0.&8' k"#kg$
K mole J x
x x
nT
PV R
o ./4.8314
15.2731
71.22101 5===
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41
6nive$s"! *"ses F"
E)"%p!e 1#8
# J8 % ( o 0"s "$e cont"ined in " se"!edcy!inde$ "t " p$essu$e o ( +BD% 2 "nd "
te%pe$"tu$e o J4o
C# The 0"s is co%p$essedunti! the p$essu$e $e"ches 1#29 BD% 2 "nd thete%pe$"tu$e is ( oC# 7 the 0"s is "ssu%ed tobe " pe$ ect 0"s, dete$%ine:
". The %"ss o 0"s -+0.b. The fn"! vo!u%e o 0"s -% ( .
*iven:
R ? #2M + D+0>
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The F" o 7de"! *"s The ideal -as la0 is the e'u"tion o st"te o "
hypothetic"! ide"! 0"s# 7t is " 0ood "pp$o)i%"tionto the beh"vio$ o %"ny 0"ses unde$ %"nyconditions, "!thou0h it h"s seve$"! !i%it"tions#
The st"te o "n "%ount o 0"s is dete$%ined by itsp$essu$e, vo!u%e, "nd te%pe$"tu$e# The %ode$n
o$% o the e'u"tion is: P ? nRThe$e n is the "%ount o subst"nce o 0"s -"!so
+no n "s nu%be$ o %o!es. "nd R is the ide"!, o$unive$s"! 0"s const"nt# 7n S7 units, n is %e"su$edin %o!es, "nd ( in +e!vin# R h"s the v"!ue #(1J+ D+0>#
The te%pe$"tu$e used in the e'u"tion o st"te is"n "bso!ute te%pe$"tu$e: in the S7 syste% o units,+e!vin
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4(
1.6 Speci4c
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4J
Specifc He"t C"p"city
7 1 +0 o " 0"s is supp!ied ith "n "%ount o he"tene$0y su o$ + D+0>#
He"t Ko in " conct"nt vo!u%e p$ocess,
? %Cv -T 2 T 1 .
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Specifc He"t C"p"city
7 1 +0 o " 0"s is supp!ied ith "n "%ount o he"tene$0y su o$ + D+0>#
He"t Ko in " $eve$sib!e conct"nt p$essu$ep$ocess,
? %Cp -T 2 T1 .
5o$ " pe$ ect 0"s, the v"!ues o Cv "nd Cp "$e
const"nt o$ "ny one 0"s "t "!! p$essu$es "nd
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Re!"tionship ;et een Specifc He"ts
R ? Cp / Cv
Specifc He"t R"tio, ) The $"tio o the specifc he"t "t const"nt
p$essu$e to the specifc he"t "t const"ntvo!u%e is 0iven the sy%bo!
V
P
C
C =
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Specifc He"t R"tio
7n 0ene$"!, is "bout 1#J o$ di"to%ic0"ses -c"$bon %ono)ide, CO hyd$o0en, H 2nit$o0en, B 2 , o)y0en, O 2 .#
5o$ %on"to%ic 0"ses -"$0on, A$ he!iu%, He.,
is "bout 1#8# 5o$ t$i"to%ic 0"ses -c"$bon dio)ide, CO 2
su!phu$ dio)ide, SO 2 ., is "bout 1#(#
5o$ so%e hyd$oc"$bons, the v"!ue o is'uite !o , eth"ne C 2H8 , ? 1#22 isobut"ne C J H1 ,
? 1#11
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4
So%e 6se u! Re!"tionship
E)"%p!e 1#9A ce$t"in pe$ ect 0"s h"s specifc he"t"s o!!o sCp ? # J8 + D+0> "nd Cv ? #849 + D+0>
5ind the 0"s const"nt "nd the %o!ecu!"$ ei0ht othe 0"s#
)1( =
RC v )1(
=
RC p
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4M
Ch"$!es F"
E)"%p!e 1#8
An un+no n 0"s h"s " %"ss o 1#4 +0
cont"ined in " bott!e o vo!u%e 1#19% ( hi!e "t " te%pe$"tu$e o ( >,"nd " p$essu$e o 2 +P"D dete$%ine
the ide"! 0"s const"nt "nd %o!ecu!"$ei0ht o the 0"s
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EB& O5 CHAPTER 1
BEIT CHAPTER
CHAPTER 2 : BOB/5FOQ PROCESS