Air Conditioning Lab Final1

8/17/2019 Air Conditioning Lab Final1

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Air Conditioning Lab

Authors:

Devon BrownMichael HartleyJames Sabo

Date Performed:

November 15, 2010

Date Submitted:

November 29, 2010

Submitted To:

Matt Feiler 52!0 1"th #ve N$Seattle, %#

9&105


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A. Executive Summary

'he ()r(ose o* this lab was to +ain a better )nerstanin+ o* the va(or

com(ression re*ri+eration cycle- 'o o this we meas)re the tem(erat)re an (ress)re at

.ey (oints thro)+ho)t a stoc. air conitioner- 'his allowe )s to etermine the state o*the /22 that eiste between each com(onent- %e *o)n that in between the eva(orator

an the com(ressor the /22 was a mit)re o* va(or an li)i, with a )ality o* -&" an

an enthal(y o* 21-! .J3.+- Between the com(ressor an the conenser, the /22 was a

s)(erheate va(or with an enthal(y o* 00 .J3.+- Between the conenser an the throttle,

the /22 was a com(resse li)i with an enthal(y o* &&-4 .J3.+ an in between the

throttle an the eva(orator the /22 is a mit)re with a )ality o* -2 an an enthal(y o*

&&-4 .J3.+- %e also meas)re the air velocity at i**erent sections o* the eva(orator eit

in orer to obtain the mass *low o* the air thro)+h the eva(orator o)t()t- 'his

meas)rement allowe )s to *in the total air*low thro)+h the eva(orator, which was 0-142

.+3s, an the eva(orator heat *low, which was 1-49 .%- 'he conenser heat reection rate

was calc)late to be 2-20 .% an the re*ri+erant *low rate was shown to be 0-010 .+3s,

which wo)l ieally remain constant thro)+ho)t the system- Finally, the val)es *or

coe**icient o* (er*ormance an com(ressor e**iciency are 2-09 an 0-"1 .%, res(ectively-

'hese val)es were )ite a bit lower than the ieal val)es, )e to tem(erat)re to several

ass)m(tions an heat lea.in+ to the environment- 'he low e**iciency an coe**icient o* (er*ormance o* this system ma.e it a (oor choice as a re*ri+erator- 6m(rovements, s)ch

as cascain+ or m)ltista+e com(ression with re+enerative coolin+ sho)l be mae to

increase e**iciency an (er*ormance be*ore it is )se in a realworl environment-

B. b!ective

6n this e(eriment, we loo. to )se o)r observe intrinsic val)es to etermine the

state in the i**erent sta+es o* the system- Since there are 2 states that are a mie

sol)tion, it is i**ic)lt to acc)rately etermine the states base solely on the (ress)re an

tem(erat)re- %e there*ore m)st )se o)r thermoynamic (ro(erties to acco)nt *or the

ener+y trans*er into an o)t o* the system- 'his will allow )s to etermine the enthal(y o*

the each state, allowin+ )s to etermine the state- 7ltimately, we loo. to ienti*y the

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thermal e**iciency an the irreversibility o* the system )sin+ the tools an techni)es

+aine in the co)rse-

C. Test Descri"tion

# stoc. air conitioner was chosen to etermine the (er*ormance o* a +eneral

va(orcom(ression re*ri+eration cycle- 'his air conitioner was r)n with /22- 6ts o)ter

casin+ has been remove an several sheaths have been remove an re(lace with

8lei+las to im(rove the visibility o* the system- ne (ress)re +a)+e was set )( be*ore

the com(ressor to rea the low (ress)re an another (ress)re +a)+e was set )( in

between the com(ressor an the conenser to rea the hi+h (ress)re- 'he ass)m(tion was

mae that this hi+h (ress)re remaine constant over the conenser an the eva(orator- 6n

orer to ma.e s)re that the (ress)res meas)re were acc)rate to the system, the air

conitioner was allowe to r)n *or several ho)rs to warm )(, (rior to ta.in+

meas)rements-

6n orer to *)rther analy:e the air conitioner, thermoco)(les were attache to the

o)ter s)r*aces o* the (i(es at several .ey locations- 'he *irst thermoco)(le was (lace on

the (i(e leain+ into the com(ressor- 'he secon thermoco)(le was (lace on the (i(e in

between the com(ressor an the secon (ress)re +a)+e- 'he thir thermoco)(le was

(lace on the (i(e between the secon (ress)re +a)+e an the conenser- 'he *o)rth an*i*th thermoco)(les were (lace on the (i(e between the conenser an the throttle- 'he

sith an seventh thermoco)(les were (lace on the (i(e between throttle an the

eva(orator- 'he ei+hth thermoco)(le was (lace on the (i(e a*ter the eva(orator- 'he

ninth thermoco)(le was reain+ the ambient tem(erat)re- Finally, the tenth thermoco)(le

was meas)rin+ the hot eha)st an the eleventh thermoco)(le was meas)rin+ the col

eha)st- 'he locations o* each thermoco)(le are shown below in Fi+)re 1- 'hese

tem(erat)re reain+s were meas)re a*ter the air conitioner ha reache a steay state-

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#lso, a c)rrent (robe was )se to meas)re the c)rrent in the air conitioner (owerwire an a voltmeter was )se to meas)re the volta+e at the (l)+ o)tlet- 'his in*ormation

is necessary to calc)late the electrical raw o* the air conitioner- 'hese two val)es were

ta.en twice; once, at the very be+innin+ o* the e(eriment, when only the *ans are

r)nnin+ an then a+ain, once the system ha reache a steay state- 'he *irst set o* val)es

only corres(ons with the (ower cons)me by the *ans, where as the secon set o* val)es

incl)es the (ower raw *rom both the *ans an the com(ressor-

Finally, to analy:e the mass *low o* the col air, the velocity at i**erent (oints in

the eva(orator eit was meas)re )sin+ a (itot static (robe an a i+ital water

manometer- 'he eva(orator eit was ivie 21 sections, as shown in Fi+)re B1

o**? (osition, t)rnin+ o** the *ans- #t this (oint the entire

)nit can be )n(l)++e-

4

Figure 1. Location of thermocouples andpressure gauges.

LowPressure

Condenser

Throttle Compressor

Evaporator

1

2345

6 7 8

HighPressure


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D. #esu$ts

D.%. State o* the /e*ri+erant 'hro)+ho)t the @ycle

'able 1 is(lays the conitions, etermine thro)+h irect meas)rement or calc)lation, at

each state in the re*ri+eration cycle- State 1 corres(ons to the state o* the re*ri+erant

between the eva(orator o)tlet an the com(ressor inlet- State 2 is the state between the

com(ressor o)tlet an the conenser inlet- State is the state between the conenser

o)tlet an the throttle inlet- State 4 is the state between the throttle o)tlet an the

eva(orator inlet- nly inlet tem(erat)res were )se beca)se it was reasone that

tem(erat)re losses between com(onents o* the cycle create inacc)racies in calc)lations

an ca)se com(lications- 7sin+ only inlet tem(erat)res +ives an acc)rate escri(tion o*

the re*ri+erant be*ore it )ner+oes the more rastic chan+es in the com(onents- 'hewebsite, www-thermo*l)is-net, was )se to etermine the conitions o* each state-

Tab$e %. @onitions at each state in the re*ri+eration cycle-State % State & State ' State (

Pressure 4!!-9 .8a, 15!9- .8a 15!9- .8a 4!!-9 .8aTem"erature 20-9A@ &4-!A@ 5-4A@ 2-4"A@)ua$ity *x+ 0-&" N3# N3# 0-20Entha$"y *h+ 21-! .J3.+ 00-0 .J3.+ &&-4 .J3.+ &&-4 .J3.+

S"ecific ,o$ume*v+ 0-022 m3.+ 0-019 m3.+ 9-!$4 m3.+ 0-0094 m3.+Entro"y *s+ 0-&12 .J3.+ 0-9&& .J3.+ 0-2 .J3.+ 0-4 .J3.+

State MiS)(erheateCa(or

@om(ressei)i Mi

Fi+)re 2 is a (lot o* tem(erat)re vs- entro(y thro)+ho)t the cycle- Note the (rocess lines

connectin+ states an the ome rawn *rom the sat)rate va(or an li)i lines-

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http://www.thermofluids.net/http://www.thermofluids.net/


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-igure &. 'em(erat)re$ntro(y Dia+ram o* the System

D.&. 'otal #ir Flow 'hro)+h the $va(orator

'he total air*low thro)+h the eva(orator was calc)late by a((roimatin+ the inte+ral

EC#, an m)lti(lyin+ that val)e by the ensity o* air- C is the velocity o* the air an #

is the i**erential element o* area- 'his inte+ral was estimate )sin+ a s)mmation metho

that is e(laine *)rther in the a((enices- 'he *inal val)e *or air*low was etermine to

be 0-142 .+3s-

D.'. $va(orator Heat Flow

'he eva(orator heat *low is the rate at which heat is ae to the eva(orator *rom the air

stream- 6t is the (ro)ct o* the total air*low m)lti(lie by the s(eci*ic heat o* air an by

the chan+e in tem(erat)re between the ambient tem(erat)re an the col eha)st comin+

o)t o* the eva(orator- 'his val)e was etermine to be 1-49 .%-

D.(. @onenser Heat /eection /ate'he conenser heat reection rate is the rate at which heat is remove *rom the system as

the re*ri+erant +oes thro)+h the conenser- 6t is calc)late )sin+ the balance o* ener+y

e)ation- 6eal conitions may be ass)me so that the heat reection rate is e)al to the


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heat *low into the eva(orator ae to the electrical (ower that is +oin+ into the

com(ressor- 'he heat reection rate was calc)late to be 2-20 .%-

D.. /e*ri+erant Flow /ate

'he re*ri+erant *low rate was etermine thro)+h care*)l analysis o* the re*ri+erant as it

(asses thro)+h the conenser- 'he heat reection rate, calc)late above, is ivie by the

chan+e in enthal(y o* the re*ri+erant between the conenser inlet an o)tlet to calc)late

the *low rate o* the re*ri+erant- 'his was shown to be 0-010 .+3s an ieally remains

constant thro)+ho)t the system-

D./. @oe**icient o* 8er*ormance

'he coe**icient o* (er*ormance *or the re*ri+erator is e)al to 13


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*o)r states- )tlet tem(erat)res were i+nore- 'his oes remove analysis o* the

re*ri+erant )rin+ the transition sta+es o* the cycle in between the com(onents, which

wo)l chan+e the *inal res)lts- However, chan+es are relatively insi+ni*icant, meanin+

the (hysical states o* the re*ri+erant wo)l not chan+e- 6t was also ass)me that the

throttle acts as a constant enthal(y evice, which is not entirely tr)e- 'he (rocess in

which the re*ri+erant (asses thro)+h the throttle may be moele as an aiabatic one, b)t

in reality there is heat trans*er even i* it is small- 'his ass)m(tion can lea to small

errors- #itionally, small (ress)re ro(s in the conenser an eva(orator were i+nore

to ma.e calc)lations easier- 'his also intro)ces errors in calc)lations- 'hese

ass)m(tions o intro)ce small errors, b)t they o not chan+e the etermine states o*

the re*ri+erant thro)+ho)t the cycle, which ma.es them acce(table errors *or this lab-

'able 1 shows that the re*ri+erant is a sat)rate mi between the eva(orator an thecom(ressor, a s)(erheate va(or between the com(ressor an the conenser, a

com(resse li)i between the conenser an the throttle, an a sat)rate mi between

the throttle an the eva(orator- 'hese res)lts are not chan+e by small errors )e to the

ass)m(tions liste above-

@om(arin+ the 'em(erat)re$ntro(y ia+ram evelo(e *or this lab to an ieal

re*ri+eration cycle yiels some interestin+ res)lts- 'he 's ia+ram *or the ieal

re*ri+eration cycle has state 1 an state 2 at the same entro(y- 6n the e(erimentally

etermine ia+ram, this is obvio)sly not tr)e- State 2 is at has a +reater entro(y- 6n the

ieal cycle, it is also ass)me that at state 1, the re*ri+erant is a sat)rate va(or an at

state , it is a sat)rate li)i- $(erimentally, it was shown that it is a sat)rate mi at

state 1 an a com(resse li)i at state - 'his ma.es sense, since ieal conitions

cannot be a((lie (er*ectly- 'he (rocess that the re*ri+erant )ner+oes when (assin+

thro)+h the conenser is similar in both the ieal an e(erimentally etermine

ia+rams- 'he s)(erheate va(or ro(s in tem(erat)re )ntil it reaches sat)ration an

then )ner+oes a (hase chan+e as entro(y contin)es to ecrease- 6n the ieal case, it

becomes a sat)rate li)i- 6n the e(erimental case, it becomes a com(resse li)i-

'hese is(arities are e(ecte, beca)se it is im(ossible to have a (er*ectly ieal

re*ri+eration cycle- 'he *act that i**erent tem(erat)res are meas)re between each (air

o* inlets an o)tlets shows that this is not an ieal cycle- 6t is worthwhile to com(are to

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an ieal cycle tho)+h since certain ieal conitions were ass)me thro)+ho)t

calc)lations-

'he total air*low can be ass)me to be *airly acc)rate es(ite the *act that it was

a((roimate with a s)mmation metho rather than )sin+ inte+ration- 'he metho o*

estimation is acc)rate eno)+h to +ive a si+ni*icant res)lt- 'his val)e was similar to

val)es calc)late by other +ro)(s- 'he calc)lations *or the heat absor(tion an reection

rates *or the system e(en on the air*low val)e, so any errors in that etermination were

carrie over- 'he heat absor(tion an reection rates are as acc)rate as the air*low val)e-

Similarly, the re*ri+erant *low rate is etermine )sin+ the heat reection rate an

the chan+e in enthal(y across the conenser, so its acc)racy is e(enent on the si:e o*

the errors in those val)es- 'he enthal(y val)es were etermine )sin+

www-thermo*l)is-net, which )ses thermoynamic relationshi(s between (ro(erties- 6tcan be ass)me that these are *airly acc)rate- 'he *low rate is 0-010 .+3s, which is

relatively slow b)t com(arable to other re*ri+eration cycles- 6t has the (ro(er orer o*

ma+nit)e-

'he coe**icient o* (er*ormance *or this cycle is 2-09, which is lower than ieal

val)es *o)n in Thermodynamics: An Engineering Approach- However, it is not that

m)ch lower, an it is e(ecte that it wo)l be lower- 'he coe**icient o* (er*ormance *or

a re*ri+erator is e*ine as the ratio o* the esire o)t()t to the re)ire o)t()t- 'his

means that the esire coolin+ e**ect in the eva(orator is 2-09 times +reater than the wor.

()t into the com(ressor- 'o im(rove this coe**icient o* (er*ormance, techni)es s)ch as

cascain+ an m)ltista+e com(ression with re+enerative coolin+ may be em(loye2-

@ascain+ is )sin+ two or more va(orcom(ression systems in series- M)ltista+e

com(ression with re+enerative coolin+ )ses a miin+ chamber calle a *lash chamber in

combination with com(ressors o(eratin+ at i**erent (ress)res- 6m(rovin+ the coe**icient

o* (er*ormance allows the re*ri+erator to achieve lower tem(erat)res-

'he calc)late e**iciency o* the com(ressor is 15-"G, which is low b)t e(ecte

)e to the nonieal conitions- 'he system teste in the lab oes not incor(orate newer

e)i(ment or any o* the methos isc)sse above li.e cascain+, which wo)l im(rove

e**iciency o* the system as a whole an o* the com(ressor s(eci*ically- 'he irreversibility

rate was 0-2 .%, which is abo)t 2G o* the (ower absorbe by the system- 'hat means

#

http://www.thermofluids.net/http://www.thermofluids.net/http://www.thermofluids.net/


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that 2G o* the (ower is not converte to wor. by the system- J)st as with the e**iciency

o* the com(ressor, this co)l be im(rove by the same methos isc)sse above- #ny

techni)es )se to limit ener+y trans*er between the system an the s)rro)nin+s wo)l

ecrease the irreversibility- 'his irreversibility is ca)se by *riction within the system

an heat trans*er between the com(onents o* the system an the s)rro)nin+ air-

-. Conc$usions

'he re*ri+erant enters the com(ressor as a sat)rate mi- #s it (asses thro)+h the

com(ressor, it becomes a s)(erheate va(or, which then enters the conenser- 6t becomes

a com(resse li)i in the conenser an is then e(ane into a sat)rate mi in the

throttle- 'his *inally (asses thro)+h the eva(orator, an remains a sat)rate mi be*oreenterin+ the com(ressor an starts the cycle over a+ain- 'he coe**icient o* (er*ormance

an com(ressor e**iciency val)es are si+ni*icantly less than the ieal val)es, b)t this is to

be e(ecte- 'he system )se in the lab is a sim(le re*ri+eration cycle that oes not )se

any o* the more avance methos that im(rove e**iciency an ener+y conservation, s)ch

as cascain+ or m)ltista+e com(ression with re+enerative coolin+- 6t is also an oler

system an the testin+ conitions are si+ni*icantly less than ieal- 'he system +ives an

ae)ate re(resentation o* the re*ri+eration cycle an is )se*)l *or sim(le analysis an

isc)ssion o* thermoynamic conce(ts- However, as an act)al system, its low e**iciency

an coe**icient o* (er*ormance ma.e it a (oor choice as a re*ri+erator- 6m(rovements

sho)l be mae to increase e**iciency an (er*ormance be*ore it is )se in a realworl

environment-

1. #eferences

1 8ro*essor S- Bhattacharee-


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A""endix A /aw ata

6n this e(eriment several meas)rements were ta.en- 'he *irst o* which was the

tem(erat)re at several i**erent (oints o* the air conitionin+ cycle, which are as *ollows;

Tab$e A%. 'em(erat)re reain+s *or i**erent (arts o* the cycle

'em(erat)re/eain+s


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Fan nly;@)rrent 1-14 am(sColta+e 121-0 ColtsFan an @om(ressor;@)rrent "-04 am(s

Colta+e120-5Colts

'here were reain+s o* (ress)re ta.en at i**erent sta+es o* the e(eriment- 'he reain+s

were (rovie in 8S6 +a+e, an m)st converte to absol)te (ress)re, )sin+ the

relationshi(


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6n orer to etermine the cross sectional area o* each meas)re velocity we ivie the

circ)lar eha)st into 21 i**erent sections, create with ! concentric circles, all o* which,

besies the mile circle, are ivie into *o)rths as shown below;

Tab$e B%. /aii o* circles

-igure B%. Dia+ram o* col air eha)st areas with rai)s val)es

'he areas o* each o* these re+ions


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22221

2

2 9-==25


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Tab$e B'. meas)re an converte val)es *rom (itot instr)ment

Meas)rement8oint h


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Tab$e B(. @alc)late val)es o* velocity-

Meas)rement8oint

Celocity


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Tab$e B. 8artial an *)ll mass *low rate

Meas)rement#rea

Mass Flow/ate


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D.% Finin+ the 8ower o* the @om(ressor

6n orer to *in the (ower cons)m(tion o* the com(ressor, the relationshi( can be )se;


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Since the state o)t o* the eva(orator is a mie state, the val)es o* ' an 8 cannot be )se

to acc)rately etermine the state- %e there*ore nee to etermine the enthal(y o* the

state, which can be erive *rom a similar *orm as $


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Documents

Air Conditioning Lab Final1