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7/24/2019 Energy Balance Untuk Teknik Kimia
http://slidepdf.com/reader/full/energy-balance-untuk-teknik-kimia 1/19
E N E R G Y
A N D
E N E R G
Y
B A L A
N C E
T
I M P E N G
A J A R
P E N G A
N T A R
I L M U
K E T E K N
I K A N
7/24/2019 Energy Balance Untuk Teknik Kimia
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INTRODUCTION
Energy is expensive….
Efective use o ener! is i"#ort$nt t$s% or c&e"ic$' enineers(Topics of this chapter
Ener! )$'$nce
Ener! $n* ener! tr$nser
+or"s o ener! , Kinetic - Potenti$' - Intern$' Ener!
Ener! tr$nser , .e$t $n* /or%
Usin t$)'es o t&er"o*!n$"ic *$t$
Mec&$nic$' ener! )$'$nces
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TYPICAL PROBLEM0
Power requirement for a pump Pure mechanical energy
balance Heat / Wor calculation for a !esire! change
"emoval of heat from reactor
#ombustion problem
"equirement of energies for each apparatus
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1(2 +ORM0 O+ ENERGY3 T.E +IR0T LA/ O+ T.ERMODYNAMIC0$orms of energy Kinetic ener! , *ue to t&e "otion o t&e s!ste"
Potenti$' ener! , *ue to t&e #osition o t&e s!ste"
Intern$' ener! , *ue to t&e "otion o intern$' "o'ecu'es U , ro" t&er"o*!n$"ic c$'cu'$tion
$orms of energy transfer .e$t 456 , ener! 7o8 *ue to te"#er$ture *iference /or% 4/6 , ener! 7o8 *ue to t&e *rivin orce ot&er t&$n
te"#er$ture *iference 4orce9 tor:ue9 vo't$e9 ;6
c
K g
mv E
2
2
=
h g
g m E
c
p =
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ENERGY BALANCE ON CLO0ED 0Y0TEM0
%alance equation
&$inal 'ystem Energy( ) &*nitial 'ystem Energy(
+ &,et Energy Transfer(
*nitial 'ystem Energy
$inal 'ystem Energy
,et Energy Transfer
ki pii E E U ++
kf pf f E E U ++
W Q +
W Q E E U k p +=∆+∆+∆
The -rst law ofThe -rst law of
thermo!ynamicsthermo!ynamics
for close!for close!
systemssystems
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IMPORTANT POINT0
!epen!s on composition state temperature of the
system. ,early in!epen!ent of pressure for i!eal gasesliqui!s soli!s.
0 + 1 2!iabatic process
*f there are no moving parts W + 1
Potential energy change !ue to the changes in height
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1(< ENERGY BALANCE0 ONOPEN 0Y0TEM0 AT 0TEADY 0TATE
$low wor an! shaft wor
+'o8 8or% , 8or% *one on s!ste" )! t&e 7ui* itse' $t t&e in'et $n*t&e out'et
0&$t 8or% , 8or% *one on t&e s!ste" )! $ "ovin #$rt 8it&in t&e
s!ste"
f s W W W +=
ProcessUnit
)/(
)/(
2
3
m N P
smV
in
in
)/(
)/(
2
3
m N P
smV
out
out
out out inin f V P V P W −=
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0PECI+IC PROPERTIE0
'peci-c properties
4Pro#ert!6 - 4A"ount 4M$ss9 Mo'e nu")er9;66
=o'u"e 9 ener!9 ; E>tensive #ro#erties
0#eci?c vo'u"e9 s#eci?c ener!9 ; Intensive #ro#ert!
E>$"#'e6
=o'u"e , e>tensive #ro#ert! *e#en*s on s!ste" si@e
0#eci?c =o'u"e , intensive #ro#ert! in*e#en*ent o s!ste" si@e
),...(),( 3 kJ U cmV Extensive properties
),.../(ˆ),/(ˆ 3mol kJ U mol cmV Intensive properties
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ENT.ALPY
*t is convenient to !e-ne the following property for the
calculation of energy balance for 3owing systems. Ent&$'#!
0#eci?c Ent&$'#!
PV U H +≡
V P U H
ˆˆˆ +≡
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T.E 0TEADY0TATE OPEN 0Y0TEM ENERGYBALANCE
W Q E E U k p +=∆+∆+∆
f s W W W +=
out out out ininin f V P mV P mW ˆˆ −=
c
K g
mv E
2
2
∆=∆
h g
g m E
c
K ∆=∆
U mU ˆ∆=∆V P U H ˆˆˆ +≡
sk p W Q E E H +=∆+∆+∆
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1( TABLE0 O+ T.ERMODYNAMIC DATA H ' 4… Thermo!ynamic function
Tables of Thermo!ynamic 5ata
T$)u'$tion o v$'ues o t&er"o*!n$"ic unctions 4U9 .9 =9((6 $t v$riouscon*ition 4T $n* P6
It is i"#ossi)'e to %no8 t&e $)so'ute v$'ues o U 9 . or #rocess"$teri$'s On'! c&$nes $re i"#ort$nt 4 ∆U9 ∆.9;6
Reerence st$te
C&oose $ T $n* P $s $ reerence st$te $n* "e$sure c&$nes o U $n*. ro" t&is reerence st$te t$)u'$tion
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0TEAM TABLE0
#ompilation of physical properties of water
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1( ENERGY BALANCE PROCEDURE0
'olve material balance 6et all the 3ow rate of streams
5etermine the speci-c enthalpies of each streamcomponents
Usin t$)u'$te* *$t$
C$'cu'$tion
#onstruct energy balance equation an! solve it. sk p W Q E E H +=∆+∆+∆
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1(1 MEC.ANICAL ENERGY BALANCE0
#hemical equipment &"eactor 5istillation columnEvaporator Heat exchanger…(
.e$t 7o89 intern$' ener! c&$nes 4ent&$'#! c&$ne6 $re"ost i"#ort$nt
0&$t 8or%9 %inetic ener!9 #otenti$' ener! c&$nes $re
ne'ii)'e
7echanical equipment &Pump "eservoir PipesWells Tans Waste 5ischarge…(
.e$t 7o89 intern$' ener! c&$nes $re ne'ii)'e
0&$t 8or%9 %inetic ener!9 #otenti$' ener! c&$nes $re "osti"#ort$nt
Q H ≈∆
sk p W Q E E H +=∆+∆+∆
W E E k p =∆+∆
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MEC.ANICAL ENERGY BALANCE0
W Q E E U k p +=∆+∆+∆
mW mQU z g
g
g
v P s
cc
/)/ˆ(2
2
=−∆+∆+
∆
+
∆
ρ
mW F z
g
g
g
v P s
cc
/
2
2
=+∆+∆
+∆
ρ
02
2
=∆+∆
+∆
z g
g
g
v P
cc ρ
ρ /1ˆˆ == out in V V
)lossfriction( /ˆ mQU F −∆=
0,0 == sW F
Bernoulli Equation
Important equation for the calculationOf equipments consist of pipes, tanks and pumps
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EAMPLE
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EERCI0E
R = 8!"##$% &'()"'mol)"
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