W13_7 BMM2513 2014-2015-S1 CHAP-7_KALAM

7/17/2019 W13_7 BMM2513 2014-2015-S1 CHAP-7_KALAM

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BMM2513

HERMODYNAMICS

Prof Dr Hj Shahrani Bin Hj AnuarOc A!"#3#1#2!

1

Cha$%r &' En%ro$(

7/17/2019 W13_7 BMM2513 2014-2015-S1 CHAP-7_KALAM


Thi) cour) focu)) on %ha$$*ica%ion of %hr+o,(na+ic)

fun,a+n%a*) in -ariou)n.inrin. )()%+ inc*u,in.nr.( ana*())/ $ro$r%i) of

$ur )u0)%anc)/ r)% *a/)con, *a an, n%ro$('

CORSE SYNOPSIS

BMM2513 THERMODYNAMICS 1

2

Cha$%r#&

En%ro$(

7/17/2019 W13_7 BMM2513 2014-2015-S1 CHAP-7_KALAM


4ECTRE SCHED4E

EE6

TOPIC

1 In%ro,uc%ion an, Ba)icConc$%

2 S()%+/ 0oun,ar(/ or7/ha%

3 Enr.( 8 .nra* nr.(

ana*()i)" Enr.( an, n-iron+n%

i+$ac%

5 Pur )u0)%anc)/ .a)9ua%ion)

: Pro$r%( %a0* an, char%& ;ir)% *a in c*o), ) )%+

EE6

TOPIC

< ;ir)% *a )%a,( =o)()%+

> Scon, *a/ ha% n.in/PMM

1! Scon, *a/ ha% $u+$

11 Scon, *a/ Carno% c(c*$rinci$*

12 En%ro$(/ n%ro$(r*a%ion)hi$)

13 En%ro$(/ i)n%ro$ic

cinc(1" Pr)n%a%ion


3

Cha$%r#&

To$ic 13' En%ro$(/ i)n%ro$ic cinc(

7/17/2019 W13_7 BMM2513 2014-2015-S1 CHAP-7_KALAM



En%ro$(

• Apply the second law of thermodynamics toprocesses.

• Dene a new property called entropy to quantify the

second-law eects.• Establish the increase of entropy principle.

• alculate the entropy chan!es that ta"e place durin!processes for pure substances# incompressiblesubstances# and ideal !ases.

• E$amine a special class of ideali%ed processes# calledisentropic processes# and de&elop the propertyrelations for these processes.

• Deri&e the re&ersible steady-'ow wor" relations.

• De&elop the isentropic e(ciencies for &arious steady-

OB?ECTI@ES

*

Cha$%r#&

7/17/2019 W13_7 BMM2513 2014-2015-S1 CHAP-7_KALAM


+

,e&ersible wor"relations for

steady-'ow andclosed systems.

reater wor"produced or

consumed/ by asteady-'ow

de&ice for lar!er

specic &olume

0e!li!ible

"inetic andpotential

ener!ies are

&'1! R-r)i0* S%a,(#=o or7

BMM2513 THERMODYNAMICS 1Cha$%r#&

To$ic 13 En%ro$(/ i)n%ro$ic cinc(

7/17/2019 W13_7 BMM2513 2014-2015-S1 CHAP-7_KALAM


&'1! R-r)i0* S%a,(#=o or7

Proof %ha% S%a,(#;*o D-ic) D*i-r %h Mo)% an,Con)u+ %h 4a)% or7 hn %h Proc)) I)

R-r)i0*

,e&ersible turbine deli&ersmore wor" than an irre&ersibleone operatin! between same

end states.

or"-producin! de&ices such as turbines deli&er more wor"# andwor"-consumin! de&ices such as pumps and compressors require less

wor" when they operate re&ersibly.

Actual

,e&ersible

a"in! heat input and wor" outputpositi&e4



7/17/2019 W13_7 BMM2513 2014-2015-S1 CHAP-7_KALAM


&'11 Mini+iin. Th Co+$r))or or7

Mu*%i)%a. Co+$r))ion i%h In%rcoo*in.

he !as is compressed in

sta!es and cooled betweeneach sta!e by passin! it

throu!h a heat e$chan!ercalled an intercooler .

To minimize compression work during two-stage compression, the pressure ratio

across each stage of the compressor mustbe the same.

P-v and T-s dia!rams for a two-

sta!e steady-'ow compressionprocess.



7/17/2019 W13_7 BMM2513 2014-2015-S1 CHAP-7_KALAM


&'12 I)n%ro$ic Ecinci) Of S%a,(#=oD-ic)I)n%ro$ic $roc)) i) i,a* $roc)) for a,ia0a%ic ,-ic) i%h

no irr-r)i0i*i%i)

h-s dia!ram for actualand isentropic

processes of an

adiabatic turbine.

urbines )sentropicE(ciency

wa ws



7/17/2019 W13_7 BMM2513 2014-2015-S1 CHAP-7_KALAM


&'12 I)n%ro$ic Ecinci) Of S%a,(#=oD-ic)I)n%ro$ic Ecinci) of Co+$r))or) an, Pu+$)

Dia!ram h-sof

actual andisentropicprocesses

of adiabaticcompressor

and pump

an you use isentropic e(ciency for a non-adiabatic

compressor8

0e!li!ible 9E:;E incompressor

0e!li!ible 9E:;E in pump

)sothermalE(ciency

<inimi%ecompressor

wor" input bycoolin!

;rocess is notisentropic since

de&ice is notadiabatic



7/17/2019 W13_7 BMM2513 2014-2015-S1 CHAP-7_KALAM

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&'12 I)n%ro$ic Ecinci) Of S%a,(#=oD-ic) I)n%ro$ic Ecinc( of No*)

h-s dia!ram of the actual andisentropic processes of adiabatic

no%%le.

>ubstance lea&in! actual

no%%le at a hi!hertemperature and lower&elocity due to friction

)n relati&ely small inlet &elocity# the ener!y balance

0o%%le )sentropic E(ciency



7/17/2019 W13_7 BMM2513 2014-2015-S1 CHAP-7_KALAM


&'13 En%ro$( Ba*anc

hn %h $ro$r%i) of %h )()%+ arno% unifor+

Ener!y and entropybalances for a system

Incra) of n%ro$( $rinci$* for a)()%+

or

En%ro$( Chan. of a S()%+/ S)()%+



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&'13 En%ro$( Ba*anc

Mchani)+) of En%ro$( Tran)fr/ Sin an, Sou%

Entropy transfer by heat transfer at constant emperature

1' Ha% Tran)fr

Entropy transfer by wor"

?eat transfer is alwaysaccompanied by entropytransfer in the amountof Q/T # where T is the

boundary temperature.

0o entropy

accompanies wor"as it crosses thesystem boundary

but may be!enerated within

the system as

wor" is dissipatedinto a less useful



7/17/2019 W13_7 BMM2513 2014-2015-S1 CHAP-7_KALAM


&'13 En%ro$( Ba*anc

Mchani)+) of En%ro$( Tran)fr/ Sin an, Sou%

2' Ma)) ;*o

Entropy transfer by mass

hen the properties of the masschan!e durin! the process

<ass containsentropy as well as

ener!y# and thusmass 'ow into orout of system is

alwaysaccompanied by

ener!y and entropytransfer.



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&'13 En%ro$( Ba*anc

En%ro$( nra%ion/ S.n

<echanisms of entropy

Entropy !eneration outsidesystem boundaries can beaccounted for by writin! an

entropy balance on ane$tended system that

includes the system and its



7/17/2019 W13_7 BMM2513 2014-2015-S1 CHAP-7_KALAM


&'13 En%ro$( Ba*anc

C*o), S()%+) he entropy chan!e of a closed system durin! a process isequal to the sum of the net entropy transferred throu!h the

system boundary by heat transfer and the entropy !eneratedwithin the system boundaries.



7/17/2019 W13_7 BMM2513 2014-2015-S1 CHAP-7_KALAM


&'13 En%ro$( Ba*anc

Con%ro* @o*u+)

he entropy of a control&olume chan!es as a

result of mass 'ow and

heat transfer.



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15

he entropy of a substance always increasesor remains constant in the case of a re&ersible

process/as it 'ows throu!h a sin!le-stream# adiabatic#

steady-'ow de&ice.

&'13 En%ro$( Ba*anc

Con%ro* @o*u+)



2 3 O CS

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• Entropy

• he increase of entropy principle

• Entropy chan!e of pure substances

• )sentropic processes

• ;roperty dia!rams in&ol&in! entropy• hat is entropy8

• he T ds relations

• Entropy chan!e of liquids and solids

• he entropy chan!e of ideal !ases

• ,e&ersible steady-'ow wor"• <inimi%in! the compressor wor"

• )sentropic e(ciencies of steady-'ow de&ices

• Entropy balance

16


Cha$%r &' En%ro$(

SMMARY

Cha$%r#&


7/17/2019 W13_7 BMM2513 2014-2015-S1 CHAP-7_KALAM



Air is compressed from an initial state of 1== ";a and 15@ to a nal state of== ";a and +5@. Determine the entropy chan!e of air durin! thiscompression process by usin! a&era!e specic heats.

Ea+$* 11 E$an)ion of air in no*

Cha$%r &' En%ro$(


7/17/2019 W13_7 BMM2513 2014-2015-S1 CHAP-7_KALAM



Air is compressed from an initial state of 1== ";a and 15@ to a nal state of== ";a and +5@. Determine the entropy chan!e of air durin! compressionby usin! property &alues from the air table heats.

Ea+$* 12 E$an)ion of air in no*

Cha$%r &' En%ro$(

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W13_7 BMM2513 2014-2015-S1 CHAP-7_KALAM