Thermo Equation Sheet
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Transcript of Thermo Equation Sheet
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Thermodynamics Equation Sheet
CLOSED SYSTEMS OPEN SYSTEMS
Cycle Process General Form Steady State Steady Flow (SSSF) Uniform State Uniform Flow
(USUF)
Firs
t Law
(I) = = +
!" + !! ! + !!2 + ! = !" + !! ! + !!2 + ! +!" + ! + !!2 + ! = ! + !!2 + ! +
!" + !! ! + !!2 + ! = ! ! + !!2 + ! ! ! + !!2 + ! + !! ! + !!2 + ! +!"
(I 1) (I 2) (I 3) (I 4) (I 5)
Seco
nd L
aw (I
I)
Kelvin-Plank Statement Clausius Statement 0
+ ! ! ! ! !" !! !! + !! !! !" (II 2) (II 4) !"! = !"! + !"## 0 !"! = !" + !"## 0 (II 1) (II 3) (II 5) (II 6) (II 7) = + (III 1) IDEAL GASES = (III 2) (IG 1) =
(IG 2) = !! (IG 3) = !! (IG 4) ! ! = ! ln !!!! + ln !!!! (IG 5) ! ! = ! ln !!!! ln !!!! (IG 6) ! = ! +
For Reversible Adiabtic Processes: (IG 7) ! = const,where = !!!! (IG 7a) !!!! = !!!! !!! (IG 7b) !!!! = !!!! !!!!
For Reversible SSSF Processes: = +!! !! !!2 + ! ! (III 3) Miscellaneous:
= = ! + !"
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FIRSTLAWClosedsystemQ W U KE PE ' ' ' Forpistoncase: 2
1W pdV
Isentropic: 0Q , 0W z Isovolumetric: 0W , 0Q z Others: 0Q z , 0W z Isobaric: 2 2 2 1 2 2 1 1
1 1W pdV p dV pV pV p V pV
2 1 2 2 2 1 1 1 2 1Q U U W U p V U pV H H Opensystem
cv cvQ W H KE PE ' ' ' Turbine
0cvQ , 2 1cvW m h h 1 2
1 2
t
s
h h
h hK Compressorandpump
0cvQ , 2 1cvW m h h 2 1
/
2 1
sc p
h h
h hK Forpump:(incompressibleliquid) 2 22 1 1 2 1
1 1int, int,
pcvs
rev rev
WWh h vdp v dp v p p
m m
| Heatexchange
0cvW , 2 1cvQ m h h
SECONDLAWTds du pdv Tds dh vdp EntropychangeIncompressible: 2
2 1
1
lnT
s s cT
Idealgas: 2 2
1 1
2 22 1
1 1
( ) ln ( ) lnT T
v pT T
v pdT dTs s c T R c T R
T v T p
Internallyreversibleclosedsystem: 2int,1
revQ TdS EntropybalanceClosedsystem
2
2 11
boundary
QS S
T
G V Ifwithnoheattransfer: 2 1m s sV Opensystem
jcvi i e e cv
j i ej
QdSm s m s
dt TV
Steadystate:0 j i i e e cvj i ej
Qm s m s
TV
IsentropicprocessIdealgasmodelForaironly: 2 2
1 1
r
r
p p
p p or 2 2
1 1
r
r
v v
v v andthenuseTableA22
ConstantspecificheatsUsedincoldairstandardanalysis
12 2 1 2
1 1 2 1
kk k
kp v T
p v T
UU
EXERGYClosedsystemDefinition
0 0 0 0 0( ) ( ) ( )E U U p V V T S S KE PE 0 0E U p V T S KE PE' ' ' ' ' '
Balance ^ `2 02 1 0 2 1 01
1q w db
TE E E E E Q W p V V T
TG V
RatebalanceSteadystate: 00 1 j d
j j
TQ W E
T
OpensystemDefinition
2
0 0 0( )2
f
Ve h h T s s gz Ratebalance
00 1 j cv i fi e fe dj i ej
TQ W m e m e E
T
ExergeticEfficienciesTurbines
1 2
/cv
f f
W m
e eH Compressorsandpumps 2 1/f fcve eW mH HeatexchangerNomix: 4 31 2c f fh f fm e em e eH Mix(1hot+2cold>3): 3 21 3c f fh f fm e em e eH
IDEALGASm
pV nRT RTM
V R
p pv T RTm M 8.314 / kR kJ mol K 0.287 /airR kJ kg K
CYCLESTOREMEMBERClosedsystemOttoDieselDualOpensystemRankineCogenerationBraytonCombineThermalefficiency
1net out
in in
W Q
Q QK Becarefulwithheatlossandsomeprocesseswithbothheatandwork
PROBLEMSOLVINGPROCEDURE1. Useisentropic,isobaric,orisovolumetricrelationstofindpropertiesateachpoint.2. Doenergyconservationatheatexchangerstorelatem andheat&work.3. ForRankincycle,verifythestatusofeachpointafterturbine.(mixture/superheated
vapor)4. Startfromoriginalequations.5. Becarefulwithheatloss.6. Doublecheckunits.