(106020783) thermal engineering lecture 5.doc

8/14/2019 (106020783) thermal engineering lecture 5.doc

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Paavai Department of

UNIT- 5. 1

ME1251 THERMAL ENGINEERING

UNIT V

REFRIGERATION AND AIR CONDITIONING


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CONTENTS

TECHNICAL TERMS

5.1 Fundamentals of refrigeration

5. Common Refrigerants

5.! Re"uired #ro$erties of Ideal Refrigerant

5.% Coeffi&ient of #erforman&e 'CO#(

5.5 )a$our Com$ression Refrigeration

5.5.1 S&*emati& of a +asi& )a$or Com$ression Refrigeration S,stem

5.5. Alternati-e Refrigerants for )a$our Com$ression S,stems

5. )a$our A/sor$tion Refrigeration5.0 Com$arison /eteen )a$or Com$ression and A/sor$tion S,stem

5.2 Ton of refrigeration

5.3 Air4 Conditioning S,stem

5.3.1. oned S,stems

5.3. 6nitar, S,stems

5.17 8indo Air4&onditioning S,stem

5.17.1 +loer

5.17. #ro$eller fan or t*e &ondenser fan

5.11.! Fan motor

5.11 S$lit Air4&onditioning S,stem

5.11.1 E-a$orator Coil or t*e Cooling Coil

5.11. Air Filter

5.11.! Cooling Fan or +loer

5.11.% 9rain #i$e

5.11.5 Lou-ers or Fins

5.1 Sol-ed #ro/lems

5.1! To Mar:s 6ni-ersit, ;uestions

5.1% 6ni-ersit, Essa, ;uestions


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TECHNICAL TERMS

1. SPECIFIC HEAT

It is t*e ratio /eteen t*e "uantities of *eat re"uired to &*ange t*e tem$erature of 1

$ound of an, su/stan&e 1


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T*e amount of *eat e>tra&ted in a gi-en time is :non as refrigeration effe&t.

11. EFFECTS OF UNDER COOLING

It in&reases t*e refrigeration effe&t t*erefore t*e CO# in&reases. T*e mass flo rate of t*e

refrigeration is less t*an t*at for t*e sim$le saturated &,&le. T*e redu&ed mass flo rate redu&es

t*e $iston dis$la&ement $er minute. #oer $er tones of refrigeration losses due to redu&tion in

mass flo rate. T*e in&reased effi&ien&, ma, /e offering some e>tent /, t*e rise in t*e

&ondenser $ressure. 8or: in$ut almost remains same. T*e *eat reBe&tion &a$a&it, of t*e

&ondenser in&reases.

12. EFFECTS OF SUPER HEATING

Su$$er *eating in&reases t*e net refrigeration effe&t= /ut su$er *eating re"uires more

or: in$ut t*erefore su$er *eating redu&es t*e CO#.

No moisture &ontents in t*e refrigerant t*erefore no &orrosion in t*e ma&*ines $art.

13. PROPERTIES OF IDEAL REFRIGERANT

It s*ould *a-e lo /oiling $oint and lo freeing $oint.

It must *a-e lo s$e&ifi& *eat and *ig* latent *eat.

It s*ould *a-e *ig* t*ermal &ondu&ti-it, to redu&e t*e *eat transfer in e-a$orator and

&ondenser.

It s*ould *a-e lo s$e&ifi& -olume to redu&e t*e sie of t*e &om$ressor.

It s*ould /e non4flamma/le= non4e>$ensi-e= non4to>i& and non4&orrosi-e.

It s*ould *a-e *ig* &riti&al $ressure and tem$erature to a-oid large $oer re"uirements.

It s*ould gi-e *ig* CO# to redu&e t*e running &ost of t*e s,stem.

It must /e &*ea$ and must /e readil, a-aila/le

14. RSHF


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Room sensi/le *eat fa&tor is defined as t*e ratio of room sensi/le *eat load to t*e room

total *eat load.

15. RELATIVE HUMIDIT#

It is defined as t*e ratio of $artial $ressure of ater -a$our '$( in a mi>ture to t*e

saturation $ressure '$s( of $ure ater at t*e same tem$erature of mi>ture.

16. SPECIFIC HUMIDIT#

It is defined as t*e ratio of t*e mass of ater -a$our 'ms( in a gi-en -olume to t*e mass

of dr, air in a gi-en -olume 'ma(.

17. DEGREE OF SATURATION

It is t*e ratio of t*e a&tual s$e&ifi& *umidit, and t*e saturated s$e&ifi& *umidit, at t*esame tem$erature of t*e mi>ture.

18. DE$ POINT TEMPERATURE

T*e tem$erature at *i&* t*e -a$our starts &ondensing is &alled de $oint tem$erature.

It is also e"ual to t*e saturation tem$erature at t*e $artial $ressure of ater -a$our in t*e

mi>ture. T*e de $oint tem$erature is an indi&ation of s$e&ifi& *umidit,.

1!. SENSIBLE HEAT AND LATENT HEAT

Sensi/le *eat is t*e *eat t*at &*anges t*e tem$erature of t*e su/stan&e *en added to it or*en a/stra&ted from it. Latent *eat is t*e *eat t*at does not affe&t t*e tem$erature /ut &*ange

of state o&&urred /, adding t*e *eat or /, a/stra&ting t*e *eat.

2". PS#CHOMETRIC PROCESSES

1. Sensi/le *eating and sensi/le &ooling= . Cooling and de*umidifi&ation= !. Heating

and *umidifi&ation= %. Mi>ing of air streams= 5. C*emi&al de*umidifi&ation= . Adia/ati&

e-a$orati-e &ooling.

21. ADIABATIC MI%ING

T*e $ro&ess of mi>ing to or more stream of air it*out an, *eat transfer to t*e

surrounding is :non as adia/ati& mi>ing. It is *a$$ened in air &onditioning s,stem.

22. DR# BULB TEMPERATURE &DBT'


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T*e tem$erature re&orded /, t*e t*ermometer it* a dr, /ul/. T*e dr, /ul/

t*ermometer &annot affe&ted /, t*e moisture $resent in t*e air. It is t*e measure of sensi/le *eat

of t*e air.

23. $ET BULB TEMPERATURE &$BT'

It is t*e tem$erature re&orded /, a t*ermometer *ose /ul/ is &o-ered it* &otton i&:

'et( saturated it* ater. T*e et /ul/ tem$erature ma, /e t*e measure of ent*al$, of air.

8+T is t*e loest tem$erature re&orded /, moistened /ul/.

24. DE$ POINT DEPRESSION

It is t*e differen&e /eteen dr, /ul/ tem$erature and de $oint tem$erature of air -a$our

mi>ture.


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UNIT V

REFRIGERATION AND AIR CONDITIONING

5.1 F()*+,-)+/0 o --+o)

T*e first me&*ani&al refrigerators for t*e $rodu&tion of i&e a$$eared around t*e ,ear 127. In

1227 t*e first ammonia &om$ressors and insulated &old stores ere $ut into use in t*e 6SA.

Ele&tri&it, /egan to $la, a $art at t*e /eginning of t*is &entur, and me&*ani&al refrigeration

$lants /e&ame &ommon in some fields e.g. /reeries= slaug*ter4*ouses= fis*er,= i&e $rodu&tion=

for e>am$le. After t*e Se&ond 8orld 8ar t*e de-elo$ment of small *ermeti& refrigeration

&om$ressors e-ol-ed and refrigerators and freeers /egan to ta:e t*eir $la&e in t*e *ome. Toda,=

t*ese a$$lian&es are regarded as normal *ouse*old ne&essities.

Refrigeration is t*e $ro&ess of remo-ing *eat from an area or a su/stan&e and is usuall, done /,

an artifi&ial means of loering t*e tem$erature= su&* as t*e use of i&e or me&*ani&al

refrigeration.

Me&*ani&al Refrigeration is defined as a me&*ani&al s,stem or a$$aratus so designed and

&onstru&ted t*at= t*roug* its fun&tion= *eat is transferred from one su/stan&e to anot*er. Sin&e

refrigeration deals entirel, it* t*e remo-al or transfer of *eat= some :noledge of t*e nature

and effe&ts of *eat is ne&essar, for a &lear understanding of t*e su/Be&t.

5.2 Co,,o) R--+)0

Toda,= t*ere are t*ree s$e&ifi& t,$es of refrigerants used in refrigeration and air4&onditioning

s,stems

1. C*lorofluoro&ar/ons or CFCs= su&* as R411= R41= and R411%

. H,dro &*lorofluoro&ar/ons or HCFCs= su&* as R4 or R41!

!. H,dro fluoro&ar/ons or HFCs= su&* as R41!%a. All t*ese refrigerants are G*alogenated=G

*i&* means t*e, &ontain &*lorine= fluorine= /romine= astatine= or iodine.


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Refrigerants= su&* as 9i&*lorodifluoromet*ane 'R41(= Mono &*loro difluoromet*ane 'R4(=

and Refrigerant 57 'R457(= are &alled $rimar, refrigerants /e&ause ea&* one &*anges its state

u$on t*e a$$li&ation or a/sor$tion of *eat= and= in t*is a&t of &*ange= a/sor/s and e>tra&ts *eat

from t*e area or su/stan&e.

T*e $rimar, refrigerant is so termed /e&ause it a&ts dire&tl, u$on t*e area or su/stan&e= alt*oug*

it ma, /e en&losed it*in a s,stem. For a $rimar, refrigerant to &ool= it must /e $la&ed in a

&losed s,stem in *i&* it &an /e &ontrolled /, t*e $ressure im$osed u$on it. T*e refrigerant &an

t*en a/sor/ at t*e tem$erature ranges desired. If a $rimar, refrigerant ere used it*out /eing

&ontrolled= it ould a/sor/ *eat from most $eris*a/les and freee t*em solid.

Se&ondar, Refrigerants are su/stan&es= su&* as air= ater= or /rine. T*oug* *ot refrigerants in

t*emsel-es= t*e, *a-e /een &ooled /, t*e $rimar, refrigeration s,stem@ t*e, $ass o-er and

around t*e areas and su/stan&es to /e &ooled@ and t*e, are returned it* t*eir *eat load to t*e

$rimar, refrigeration s,stem. Se&ondar, refrigerants $a, off *ere t*e &ooling effe&t must /e

mo-ed o-er a long distan&e and gastig*t lines &ost too mu&*.

Refrigerants are &lassified into grou$s. T*e National Refrigeration Safet, Code &atalogs all

refrigerants into t*ree grou$s

rou$ I safest of t*e refrigerants= su&* as R41= R4= and R457

rou$ II to>i& and some*at flamma/le= su&* as R4%7 'Met*,l &*loride( and R40%

'Sulfur dio>ide(

rou$ III flamma/le refrigerants= su&* as R4107 'Et*ane( and R437 '#ro$ane(.

R41 9i&*lorodifluoromet*ane 'CC1 F( 9i&*lorodifluoromet*ane= &ommonl, referred to as R4

1= is &olorless and odorless in &on&entrations of less t*an 7 $er&ent /, -olume in air. In *ig*er

&on&entrations= its odor resem/les t*at of &ar/on tetra&*loride. It is nonto>i&= non&orrosi-e=

nonflamma/le= and *as a /oiling $oint of 41.0


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( It must *a-e lo s$e&ifi& *eat and *ig* latent *eat. +e&ause *ig* s$e&ifi& *eat de&reases t*e

refrigerating effe&t $er :g of refrigerant and *ig* latent *eat at lo tem$erature in&reases t*e

refrigerating effe&t $er :g of refrigerant.

!( T*e $ressures re"uired to /e maintained in t*e e-a$orator and &ondenser s*ould /e lo

enoug* to redu&e t*e material &ost and must /e $ositi-e to a-oid lea:age of air into t*e s,stem.

%( It must *a-e *ig* &riti&al $ressure and tem$erature to a-oid large $oer re"uirements.

5( It s*ould *a-e lo s$e&ifi& -olume to redu&e t*e sie of t*e &om$ressor.

( It must *a-e *ig* t*ermal &ondu&ti-it, to redu&e t*e area of *eat transfer in e-a$orator and

&ondenser.

0( It s*ould /e non4flamma/le= non4e>$losi-e= non4to>i& and non4&orrosi-e.

2( It s*ould not *a-e an, /ad effe&ts on t*e stored material or food= *en an, lea: de-elo$s in

t*e s,stem.

3( It must *a-e *ig* mis&i/ilit, it* lu/ri&ating oil and it s*ould not *a-e rea&ting $ro$erl, it*

lu/ri&ating oil in t*e tem$erature range of t*e s,stem.

17( It s*ould gi-e *ig* CO# in t*e or:ing tem$erature range. T*is is ne&essar, to redu&e t*e

running &ost of t*e s,stem.

5.4Co--) o P-o,+)- &COP'

T*e $erforman&e of refrigerators and *eat $um$s is e>$ressed in terms of &oeffi&ient of

$erforman&e 'CO#(= defined as

5.5 V+o( Co,-00o) R--+o)

Heat flos naturall, from a *ot to a &older /od,. In refrigeration s,stem t*e o$$osite

must o&&ur i.e. *eat flos from a &old to a *otter /od,. T*is is a&*ie-ed /, using a su/stan&e

&alled a refrigerant= *i&* a/sor/s *eat and *en&e /oils or e-a$orates at a lo $ressure to form a

gas. T*is gas is t*en &om$ressed to a *ig*er $ressure= su&* t*at it transfers t*e *eat it *as gained


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to am/ient air or ater and turns /a&: '&ondenses( into a li"uid. In t*is a, *eat is a/sor/ed= or

remo-ed= from a lo tem$erature sour&e and transferred to a *ig*er tem$erature sour&e.

T*e refrigeration &,&le &an /e /ro:en don into t*e folloing stages

1 2 Lo $ressure li"uid refrigerant in t*e e-a$orator a/sor/s *eat from its surroundings=usuall, air= ater or some ot*er $ro&ess li"uid. 9uring t*is $ro&ess it &*anges its state from a

li"uid to a gas= and at t*e e-a$orator e>it is slig*tl, su$er*eated.

2 3 T*e su$er*eated -a$our enters t*e &om$ressor *ere its $ressure is raised. T*ere ill also

/e a /ig in&rease in tem$erature= /e&ause a $ro$ortion of t*e energ, in$ut into t*e &om$ression

$ro&ess is transferred to t*e refrigerant.

3 4 T*e *ig* $ressure su$er*eated gas $asses from t*e &om$ressor into t*e &ondenser. T*e

initial $art of t*e &ooling $ro&ess '! 4 !a( desu$er*eats t*e gas /efore it is t*en turned /a&: into

li"uid '!a 4 !/(. T*e &ooling for t*is $ro&ess is usuall, a&*ie-ed /, using air or ater. A furt*er

redu&tion in tem$erature *a$$ens in t*e $i$e or: and li"uid re&ei-er '!/ 4 %(= so t*at t*e

refrigerant li"uid is su/4&ooled as it enters t*e e>$ansion de-i&e.


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4 1 T*e *ig*4$ressure su/4&ooled li"uid $asses t*roug* t*e e>$ansion de-i&e= *i&* /ot*

redu&es its $ressure and &ontrols t*e flo into t*e e-a$orator.


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It &an /e seen t*at t*e &ondenser *as to /e &a$a/le of reBe&ting t*e &om/ined *eat in$uts of t*e

e-a$orator and t*e &om$ressor@ i.e. '1 4 ( ' 4 !( *as to /e t*e same as '! 4 %(. T*ere is no *eat

loss or gain t*roug* t*e e>$ansion de-i&e.


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5.5.1 S-,+ o + B+0 V+o Co,-00o) R--+o) S90-,

Ad-antages of )a$our &om$ression refrigeration s,stem o-er air refrigeration s,stem

J Sin&e t*e or:ing &,&le a$$roa&*es &loser to &arnot &,&le= t*e C.O.# is "uite *ig*.

J O$erational &ost of -a$our &om$ression s,stem is Bust a/o-e 1?%t* of air refrigeration


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s,stem.

J Sin&e t*e *eat remo-ed &onsists of t*e latent *eat of -a$our= t*e amount of li"uid

&ir&ulated is less and as a result t*e sie of t*e e-a$orator is smaller.

J An, desired tem$erature of t*e e-a$orator &an /e a&*ie-ed Bust /, adBusting t*e t*rottle

-al-e.

9isad-antages of )a$our &om$ression refrigeration s,stem o-er air refrigeration

s,stem

J Initial in-estment is *ig*

J #re-ention of lea:age of refrigerant is a maBor $ro/lem

5.5.2 A/-)+:- R--+)0 o V+o( Co,-00o) S90-,0

T*e use of CFCs is no /eginning to /e $*ased out due to t*eir damaging im$a&t on t*e

$rote&ti-e tro$os$*eri& oone la,er around t*e eart*. T*e Montreal #roto&ol of 1320 and t*e

su/se"uent Co$en*agen agreement of 133 mandate a redu&tion in t*e $rodu&tion of oone

de$leting C*lorinated Fluoro&ar/on 'CFC( refrigerants in a $*ased manner= it* an e-entual

sto$ to all $rodu&tion /, t*e ,ear 133. In res$onse= t*e refrigeration industr, *as de-elo$ed to

alternati-e refrigerants@ one /ased on H,dro&*loro Fluoro&ar/on 'HCFC(= and anot*er /ased on

H,dro Fluoro&ar/on 'HFC(. T*e HCFCs *a-e a to 17K oone de$leting $otential as &om$ared

to CFCs and also= t*e, *a-e an atmos$*eri& lifetime /eteen to 5 ,ears as &om$ared to 177

or more ,ears for CFCs '+randt= 133(. Hoe-er= e-en HCFCs are mandated to /e $*ased out

/, 775= and onl, t*e &*lorine free 'ero oone de$letion( HFCs ould /e a&&e$ta/le.

6ntil no= onl, one HFC /ased refrigerant= HFC 1!%a= *as /een de-elo$ed. HCFCs are

&om$arati-el, sim$ler to $rodu&e and t*e t*ree refrigerants = 1!= and 1% *a-e /een

de-elo$ed. T*e use of HFCs and HCFCs results in slig*tl, loer effi&ien&ies as &om$ared to

CFCs= /ut t*is ma, &*ange it* in&reasing efforts /eing made to re$la&e CFCs.

5.6 V+o( A;0oo) R--+o)


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In t*e a/sor$tion refrigeration s,stem= refrigeration effe&t is $rodu&ed mainl, /, t*e use

of energ, as *eat. In su&* a s,stem= t*e refrigerant is usuall, dissol-ed in a li"uid. A

&on&entrated solution of ammonia is /oiled in a -a$our generator $rodu&ing ammonia -a$our at

*ig* $ressure. T*e *ig* $ressure ammonia -a$our is fed to a &ondenser *ere it is &ondensed to

li"uid ammonia /, reBe&ting energ, as *eat to t*e surroundings. T*en= t*e li"uid ammonia is

t*rottled t*roug* a -al-e to a lo $ressure. 9uring t*rottling= ammonia is $artiall, -a$ouried

and its tem$erature de&reases.

T*is lo tem$erature ammonia is fed to an e-a$orator *ere it is -a$ouried remo-ing energ,

from t*e e-a$orator. T*en t*is lo4$ressure ammonia -a$our is a/sor/ed in t*e ea: solution of

ammonia. T*e resulting strong ammonia solution is $um$ed /a&: to t*e -a$our generator and t*e

&,&le is &om$leted. T*e CO# of t*e a/sor$tion s,stem &an /e e-aluated /, &onsidering it as a

&om/ination of a *eat $um$ and a *eat engine

5.7 Co,+0o) ;-


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A oned air &onditioning s,stem using a room air terminal *i&* *as t*e same *oriontal

dimensions as a floor tile of a raised tile floor su&* t*at t*e terminal ma, re$la&e one tile in su&*

a floor. T*e terminal in&ludes a &ool air inlet /elo t*e floor for draing in &ooling air &ir&ulated

in t*e under floor s$a&e and a return air inlet in t*e to$ surfa&e of t*e terminal. T*e &ool air and

return air is mi>ed in a mi>ing &*am/er and dran from t*e mi>ing &*am/er /, a fan and

returned to t*e room t*roug* an outlet -ent. T*e ratio of &ool air to return air mi>ed in t*e

mi>ing &*am/er is &ontrolled /, a modulating dam$er *i&* is &ontrolled in res$onse to t*e

tem$erature of t*e return air in order to &ontrol t*e room tem$erature in t*e region of t*e

terminal in a&&ordan&e it* an adBusta/le set $oint. A *eater is also $ro-ided in t*e terminal for

t*ose o&&asions *ere t*e return air is &ooler t*an t*e set $oint.

5.!.2 U)+9 S90-,0=

A unitar, air &onditioning s,stem &om$rises an outdoor unit in&luding a &om$ressor for

&om$ressing a refrigerant= an outdoor *eat e>&*anger for *eat e>&*ange of t*e refrigerant and an

e>$ander &onne&ted to t*e outdoor *eat e>&*anger= for e>$anding t*e refrigerant@ a du&t installed

inside a one of a /uilding@ a &entral /loer unit *a-ing a *eat e>&*anger &onne&ted to t*e


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outdoor unit t*roug* a first refrigerant $i$e and a /loer for su$$l,ing t*e air *eat4e>&*anged /,

t*e *eat e>&*anger to t*e du&t@ and an indi-idual /loer unit in&luding a *eat e>&*anger

&onne&ted to t*e outdoor unit t*roug* a se&ond refrigerant $i$e and a fan for sending t*e air *eat

e>&*anged /, t*e *eat e>&*anger and dis$osed in a one in t*e /uilding= for indi-iduall, &ooling

or *eating t*e one. A&&ordingl,= &ooling or *eating o$eration is $erformed on ea&* one of t*e

/uilding= and simultaneousl,= additional indi-idual *eating or &ooling o$eration &an /e

$erformed on a s$e&ifi& s$a&e= so t*at a &ost &an /e redu&ed and &ooling or *eating in t*e

/uilding &an /e effi&ientl, $erformed.

5.1" $)*o< Ao)*o)) S90-,=

It is t*e most &ommonl, used air &onditioner for single rooms. In t*is air &onditioner all

t*e &om$onents= namel, t*e &om$ressor= &ondenser= e>$ansion -al-e or &oil= e-a$orator and

&ooling &oil are en&losed in a single /o>. T*is unit is fitted in a slot made in t*e all of t*e room=


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or often a indo sill.

8indos air &onditioners are one of t*e most idel, used t,$es of air &onditioners /e&ause t*e,

are t*e sim$lest form of t*e a ir & ondi t ion ing s,stems. 8indo air &onditioner &om$rises of t*e

rigid /ase on *i&* all t*e $arts of t*e indo air &onditioner are assem/led. T*e /ase is

assem/led inside t*e &asing *i&* is fitted into t*e all or t*e indo of t*e room in *i&* t*e

air &onditioner is fitted.

T*e *ole assem/l, of t*e indo air &onditioner &an /e di-ided into to &om$artments t*e

room side= *i&* is also t*e &ooling side and t*e outdoor side from *ere t*e *eat a/sor/ed /,

t*e room air is li/erated to t*e atmos$*ere. T*e room side and outdoor side are se$arated from

ea&* ot*er /, an insulated $artition en&losed inside t*e indo air &onditioner assem/l,.

In t*e front of t*e indo air &onditioner on t*e room side t*ere is /eautifull, de&orated front

$anel on *i&* t*e su$$l, and return air grills are fitted 't*e *ole front $anel itself is

&ommonl, &alled as front grill(. T*e lou-ers fitted in t*e su$$l, air grills are adBusta/le so as to

su$$l, t*e air in desired dire&tion. T*ere is also one o$ening in t*e grill t*at allos a&&ess to t*e

Control $anel or o$erating $anel in front of t*e indo air &onditioner.

5.1".1 B/o


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T*is is t*e small /loer t*at is fitted /e*ind t*e e-a$orator or &ooling &oil inside t*e

assem/l, of t*e indo air &onditioner s,stem. T*e /loer su&:s t*e air from t*e room *i&*

first $asses o-er t*e air filter and gets filtered. T*e air t*en $asses o-er t*e &ooling &oil and gets

&*illed. T*e /loer t*en /los t*is filtered and &*illed air= *i&* $asses t*roug* t*e su$$l, air

&om$artment inside t*e indo air &onditioner assem/l,. T*is air is t*en deli-ered into t*e

room from t*e su$$l, air grill of t*e front $anel.

5.1".2 Po-//- +) o - o)*-)0- +)=

T*e &ondenser fan is t*e for&ed draft t,$e of $ro$eller fan t*at su&:s t*e atmos$*eri& air

and /los it o-er t*e &ondenser. T*e *ot refrigerant inside t*e &ondenser gi-es u$ t*e *eat to t*e

atmos$*eri& air and its tem$erature redu&es.

5.1".3 F+) ,oo=

T*e motor inside t*e indo air &onditioner assem/l, is lo&ated /eteen t*e &ondenser

and t*e e-a$orator &oil. It *as dou/le s*aft on one side of *i&* t*e /loer is fitted and on t*e

ot*er side t*e &ondenser fan is fitted. T*is ma:es t*e *ole assem/l, of t*e /loer= t*e

&ondenser fan and t*e motor *ig*l, &om$a&t.

5.11 S/ Ao)*o)) S90-,=

T*e s$l i t a ir & ondi t ioner &om$rises of to $arts t*e outdoor unit and t*e indoor unit. T*e

outdoor unit= fitted outside t*e room= *ouses &om$onents li:e t*e &om$ressor= &ondenser and

e>$ansion -al-e. T*e indoor unit &om$rises t*e e-a$orator or &ooling &oil and t*e &ooling fan.

For t*is unit ,ou dont *a-e to ma:e an, slot in t*e all of t*e room. Furt*er= t*e $resent da,

s$lit units *a-e aest*eti& loo:s and add to t*e /eaut, of t*e room. T*e s$lit air &onditioner &an /e

used to &ool one or to rooms.
http://www.brighthub.com/tools/http://www.brighthub.com/tools/


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5.11.1 E:+o+o Co/ o - Coo/) Co/=

T*e &ooling &oil is a &o$$er &oil made of num/er turns of t*e &o$$er tu/ing it* one or

more ros de$ending on t*e &a$a&it, of t*e a ir & ondi t ion i ng s,stem. T*e &ooling &oil is &o-ered

it* t*e aluminum fins so t*at t*e ma>imum amount of *eat &an /e transferred from t*e &oil to

t*e air inside t*e room.

5.11.2 A F/-=

T*e air filter is -er, im$ortant $art of t*e indoor unit. It remo-es all t*e dirt $arti&les

from t*e room air and *el$s su$$l,ing &lean air to t*e room. T*e air filter in t*e all mounted

t,$e of t*e indoor unit is $la&ed Bust /efore t*e &ooling &oil. 8*en t*e /loer su&:s t*e *ot room

air= it is first $assed t*roug* t*e air filter and t*en t*oug* t*e &ooling &oil.
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5.11.3 Coo/) F+) o B/otending to t*e some

e>ternal $la&e outside t*e room *ere ater &an /e dis$osed off. T*us t*e drain $i$e *el$s

remo-ing de ater &olle&ted inside t*e indoor unit.

5.11.5 Lo(:-0 o F)0=

T*e &ool air su$$lied /, t*e /loer is $assed into t*e room t*roug* lou-ers. T*e lou-ers

*el$ &*anging t*e angle or dire&tion in *i&* t*e air needs to /e su$$lied into t*e room as $er

t*e re"uirements. 8it* lou-ers one easil, C*ange t*e dire&tion in *i&* t*e ma>imum amount

of t*e &ooled air *as to /e $assed. T*ere are to t,$es of lou-ers *oriontal and -erti&al. T*e

*oriontal lou-ers are &onne&ted to a small motor and t*ere $osition &an set /, t*e remote

&ontrol. On&e &an set a fi>ed $osition for t*e *oriontal lou-ers so t*at &*illed air is $assed in a


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$arti&ular dire&tion onl, or one &an :ee$ it in rotation mode so t*at t*e fres* air is su$$lied

t*roug*out t*e room. T*e -erti&al lou-ers are o$erated manuall, and one &an easil, &*ange t*eir

$osition as $er t*e re"uirements. T*e *oriontal lou-ers &ontrol flo of air in u$$er and

donard dire&tions of t*e room= *ile -erti&al lou-ers &ontrol mo-ement of air in left and rig*t

dire&tions.

5.12 SOLVEDE PROBLEMS


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1. A sling $s,&*rometer gi-es reading of 57& dr, /ul/ tem$erature 15

7& et /ul/

tem$erature. T*e /arometer indi&ates 07 mm of *g assuming $artial $ressure of t*e

-a$our as 17 mm of Hg. 9etermine 1. S$e&ifi& *umidit, . Saturation ratio.

G:-) D++=

9r, /ul/ tem$erature td D57& 8et

/ul/ tem$erature tD157& +arometer

$ressure $/D07mm of Hg

#artial $ressure $-D 17mm of Hg

To F)*=

S$e&ifi& *umidit,

Saturation ratio.

So/(o)=

S- (,*9=

8e :no t*at S$e&ifi& *umidit,

8 D

7.772! :g?:g of dr, air

S+(+o) +o=

From steam ta/le &orres$onding to dr, /ul/ tem$erature td D57&

8e find t*e $artial $ressure $sD7.7!1 /ar

D

D!.2 mm of Hg

8e :no t*at Saturation ratio.


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RESULT=

D

> > ".41

1. S$e&ifi& *umidit, 7.772! :g?:g of dr, air

. Saturation ratio. >".41

. A to stages= single a&ting air &om$ressor &om$resses air to 7/ar. T*e air enters t*e

L.# &,linder at 1/ar and 0o& and lea-es it at %.0/ar. t*e air enters t*e H.#. &,linder at

%.5/ar and 0o&. t*e sie of t*e L.# &,linder is %77mm diameter and 577mm stro:e. T*e

&learan&e -olume In /ot* &,linder is %K of t*e res$e&ti-e stro:e -olume. T*e &om$ressor

runs at 77r$m= ta:ing inde> of &om$ression and e>$ansion in t*e to &,linders as 1.!=

estimate 1. T*e indi&ated $oer re"uired to run t*e &om$ressor@ and . T*e *eat reBe&ted

in t*e inter&ooler $er minute.

GIVEN DATA=

#ressure '#%(D 7/ar

#ressure '#1( D 1/ar D 1175N?m

Tem$erature 'T1( D 0oC D 00! D !77P

#ressure '#( D %.0/ar

#ressure '#!( D %.5/ar

Tem$erature 'T!( D 0oC D 00! D !77P

9iameter '91( D %77mm 7.%m


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Stro:e 'L1( D 577mm D 7.5m

N D 77r$m @ n D 1.!

To F)*=

Indi&ated $oer re"uired to run t*e &om$ressor

So/(o) =

8e :no t*e se$t -olume of t*e L.# &,linder

D 7.72% m!

And -olumetri& effi&ien&,=

Q-

D 7.3725 or 37.25K

)olume of air su&:ed /, air $ressure &om$ressor=


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And -olume of air su&:ed /, H.# &om$ressor=

1.%m!?min

8e :no t*at indi&ated or: done /, L.# &om$ressor=

D 1!.!17!

?min D 1!.! P?min

And indi&ated or:done /, H.# &om$ressor=

D 7%!.517!

?min D 7!%.5 P?min

Total indi&ated or: done /, t*e &om$ressor=

8 D 8L 8H D 1!.! 7!%.5 D %150.2 P?min

Indi&ated $oer re"uired to run t*e &om$ressor


30/35

D %150.2 ? 7 D 3.!P8

!. In an oil gas tur/ine installation = air is ta:en as 1 /ar and !7oC . T*e air is &om$ressed

to %/ar and t*en *eated /, /urning t*e oil to a tem$erature of 577 oC . If t*e air flos at

t*e rate of 37Pg?min . Find t*e $oer de-elo$ed /, t*e $lant ta:e for air as 1.% C$ as

1P?PgP . If .%Pg of oil *a-ing &alorifi& -alue of %7=777 P?Pg if /urned in t*e

&om/ustion &*am/er $er minute. Find t*e o-erall effi&ien&, of t*e $lant.

G:-) D++=

#ressure '#% D #!( D 1/ar

#ressure '#1 D #( D %/ar

Tem$erature 'T( D 577oC D 5770! D 00!P Mass

flo rate of air'ma( D 37Pg?min D 1.5Pg?se& Mass

flo rate of fuel 'mf( D .%Pg?min D 7.7%Pg?se&

Tem$erature 'T%( D !7oC D !70! D !7!P

D 1.% @ C$ D 1P?PgP @ C-D %7=777 P?Pg

To F)*=

#oer de-elo$ed /, t*e $lant

#erforman&e of t*e gas tur/ine

O-erall effi&ien&, of t*e $lant

So/(o)=

Po$ansion 4!=


31/35

T! D T 7.0! D 00!7.0! D 57P

Similarl, for isentro$i& &om$ression %41

T1 D T%? 7.0! D !7!?7.0! D %57P

P-o,+)- o - +0 (;)-=

8e :no t*at or: de-elo$ed /, t*e tur/ine=

And or: de-elo$ed /, t*e &om$ressor=

D !03.5P?s

D 7.5?s

Net or: or $oer of t*e tur/ine=

# D 8T 4 8& D !03.5 7.5 D 153P?s D 153P8

O:-+// --)9 o - /+)=

8e :no t*at t*e *eat su$$lied $er se&ond


32/35

D mf C D 7.7% %7=777 D 177 P?s

T*erefore= o-erall effi&ien&, of t*e $lant=

Qo D 153?177 D 7.733 or 3.33K

5.13 T$O MAR? UNIVERSIT# @UESTIONS=


33/35

P+A &2 M+0'

1. Name four im$ortant $ro$erties of a good refrigerant

. 8*at is t*e differen&e /eteen air &onditioning and refrigeration

!. 8*at is t*e fun&tion of t*e t*rottling -al-e in -a$our &om$ression refrigeration s,stem

%. In a -a$our &om$ression refrigeration s,stem= *ere t*e *ig*est tem$erature ill o&&ur

5. T*e -a$our a/sor$tion s,stem &an use lo4grade *eat energ, in t*e generator. Is true of false

. Name an, four &ommonl, used refrigerants.

0. E>$lain unit of Refrigeration.

2. 8*, t*rottle -al-e is used in $la&e of e>$ansion &,linder for -a$our &om$ression refrigerant

ma&*ine.

3. 8*at are t*e effe&t $f su$er *eat and su*&ooling on .t*e -a$our &om$ression &,&le

17. 8*at are t*e $ro$erties of good refrigerant

11. Ho are air4&onditioning s,stems &lassified

1. Ho does *umidit, affe&t *uman &omfort

1!. 8*at are t*e -arious sour&es of *eat gain of an air4&onditioned s$a&e

1%. 8*at do ,ou mean /, t*e term infiltration in *eat load &al&ulations


34/35

5.14 UNIVERSIT# ESSA# @UESTIONS=

P+B &16 M+0'

1. 9ra neat s:et&* of sim$le -a$or &om$ression refrigeration s,stem and e>$lain. '1(

. E>$lain it* s:et&* t*e or:ing $rin&i$le of a"ua Ammonia refrigeration s,stem. '1(

!. E>$lain it* s:et&* t*e or:ing $rin&i$le of ater4Lit*ium /romide refrigeration s,stem. '1(

%. +riefl, e>$lain t*e &ooling load &al&ulation in air &onditioning s,stem. '1(

5. E>$lain inter= summer= and ,ear round Al& s,stem. '1(

. E>$lain unitar, Al& and &entral Al& s,stem. '1(

0. E>$lain an, four $s,&*ometri& $ro&esses it* s:et&*. '1(

2. A refrigeration s,stem of 17.5 tonnes &a$a&it, at an e-a$orator tem$erature of 41


35/35


UNIT V

Documents

(106020783) thermal engineering lecture 5.doc