refrigerantion complete 2

8/15/2019 Refrigerantion Complete 2

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E

TITLE

Variation in refrigeration coefficient of performance at various process temperatures

INTRODUCTION

Refrigeration is used widely in various applications from industrial to domestic

situations, mainly for the storage and transport of perishable foodstuff and chemical

substances. It has the prime functions to remove heat from a low temperature

region, and it can also be applied as a heat pump for supplying heat to a region of

high temperature.

OBJECTIVETo investigate the variation in Coefficient of Performance (CP!R of a vapor

compression refrigeration system.

THEORY

" refrigeration cycle wor#s to lower and maintain the temperature of a controlledspace by heat transfer from a low to a high temperature region.

.

Refrigeration duty is another term for the cooling effect of the refrigeration system,which is the rate of heat being removed from the low temperature region withspecified evaporation and condensation temperatures. The unit for $duty%measurements is in &atts (for ' ton of refrigeration )*'+&!.

igh Temperature Reservoir,

QH

Wnet

QL

-ow Temperature Reservoir, T-


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3.1 The Vapor Compression Cyce

Ideal refrigeration systems follows the theoretical Reversed Carnot Cycle

process. In practical refrigerators, compression and epansion of a gas andvapor miture presents practical problems in the compressor and epander.Therefore, in practical refrigeration, compression usually ta#es place in thesuperheated condition and a throttling process is substituted for the isentropicepansion.


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The cycle /

' 0 1 Condensation of the high pressure vapour during which heat istransferred to the high temperature region.

1 0 ) "diabatic throttling of the condensed vapour from the condensing tothe evaporating pressure.

) 0 2 3vaporation of the low pressure li4uid during which heat is absorbedfrom the low temperature source.

2 0 ' Isentropic compression of the vapour, from the evaporating to thecondensing pressures.

Ener!y Trans"er #naysis

Compressor

4'51 h1 0 h' 6 w

If compressor is adiabatic, 4'51 7 and w h' 0 h1

Power re4uirement, P m (h' 0 h1 !, where m is the flow rate of wor#ing fluid perunit time.

Condenser

415) h) 0 h1 6 w

w 7, therefore 415) h) 0 h1 and rate of heat re8ection 915) m ( h) 0 h1 !

3pansion valve

4)52 h2 0 h) 6 w

w 7 at the epansion valve, and the process is adiabaticTherefore h2 h)


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E$apora%or

425' h' 0 h2 6 w

w 7, therefore 425' h' 0 h2 and rate of heat absorbed 925' m ( h' 0 h2 !

Coe""icien% o" &er"ormance 'CO&(

12

4114

r Phh

hh

w

qCO ef

−

−

==

−

)Y*BOL) #ND UNIT)

:ymbol

9uantity ;nit

Cp :pecific eat < #g5'

=5'> >orce ?h :pecific enthalpy < #g5'I Current "

m @ass flow rate #gAs? Rotational speed RevAmin4 eat Transfer per unit

@ass

< #g5'

Q eat Transfer Rate &

T Temperature =V Potential Bifference Voltsw &or# per unit @ass < #g5' "ngular velocity Rad s5'


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#&R#TU)

T :eries Computer -in#ed Refrigeration ;nit (3dibon!.

T :eries Computer Controller

&ROCEDURE

a( Con+enser,-a%er an+ e$apora%or,-a%er


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a. :elect water as a heat source by opening valves "V:52 and "V:5*.Thenclic# $:T"RT%

b. "d8ust the water flow rate at the condenser to * -Am and ) -Am at theevaporator (evaporator load!.

c. Then clic# $C@PR3::R%

d. &hen the system is stabiliDed, start recording the data by clic# $:T"RT:"VI?E%

e. :et the sampling rate at '17 second per sample.f. Record the data for si minutes () samples F )G7 second!. $:TP

:"VI?E%g. Then increase evaporator load to * -Am and repeat step (c! to step (f!.

( Con+enser,-a%er an+ e$apora%or,air a. :elect air as a heat source by opening valves "V:5) and "V:5*.Then clic#

$:T"RT%b. "d8ust the water flow rate at the condenser to * -Am and ad8ust the air flow

of the evaporator until *7H of the maimal flow (evaporator load!.c. Then clic# $C@PR3::R%d. &hen the system is stabiliDed, start recording the data by clic# $:T"RT

:"VI?E%e. :et the sampling rate at '17 second per sample.f. Record the data for si minutes () samples F )G7 second!. $:TP

:"VI?E%g. Then increase evaporator load to '77H and repeat step (c! to step (f!.

c( Con+enser,air an+ e$apora%or,air a. :elect air as a heat source by opening valves "V:5) and "V:5G. Then

clic# $:T"RT%b. "d8ust the air flow of the condenser to maimum flow ('77H! and *7H of

the maimal flow at the evaporator (evaporator load!.c. Then clic# $C@PR3::R%d. &hen the system is stabiliDed, start recording the data by clic# $:T"RT

:"VI?E%e. :et the sampling rate at '17 second per sample.f. Record the data for si minutes () samples F )G7 second!. $:TP

:"VI?E%g. Then increase evaporator load to '77H and repeat step (c! to step (f!.

+( Con+enser,air an+ e$apora%or,-a%er a. :elect water as a heat source by opening valves "V:52 and "V:5G.Then

clic# $:T"RT%


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b. "d8ust the air flow of the condenser to maimum flow ('77H! and ad8ustthe water flow rate at the evaporator to ) -Am (evaporator load!.

c. Then clic# $C@PR3::R%d. &hen the system is stabiliDed, start recording the data by clic# $:T"RT

:"VI?E%

e. :et the sampling rate at '17 second per sample.f. Record the data for si minutes () samples F )G7 second!. $:TP

:"VI?E%g. Then increase evaporator load to * -Am and repeat step (c! to step (f!.

RE)ULT

Da%a )/mmary Tae


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E0perimen% #

&or#ing fluid Cond5 water

3vap 5water Condenser cooling load :C51 *-Am

3vaporator heatload

Time(s!

:T51(C!

:T5)(C!

:T52(C!

:P5'(bar!

:P51(bar!

:C5'(-Ah!

:&5'(&!

:C5) ) -Am '17 )G.*G *.JK J.K' J.2) '.J' 1G.*J 2J7.7J

127 )*.G) G.)2 '*.'* J.G7J '.JJ )7.7) 2+G.7J

)G7 27.7' +.)) '*.72 K.*G 1.7* 1K.+1 2JK.72

:C5)* -Am '17 27.K+ J.2K '1.G1 K.J' 1.'1 )7.'J 2JG.'+

127 2'.'' +.'* '1.G7 K.+J 1.77 1K.*' 2JG.71

)G7 2'.'J G.JG '1.*K K.+J '.K+ 1K.+K 2GJ.K*

E0perimen% B

&or#ing fluid Cond5 &ater

3vap5 "ir Condenser cooling load :C51 *-Am

3vaporator heatload

Time(s!

:T51(C!

:T5)(C!

:T52(C!

:P5'(bar!

:P51(bar!

:C5'(-Ah!

:&5'(&!

>an power at evap*7H '17 27.22 '2.)K 11.1K K.+7 1.7K 1K.+* 2J'.2*

127 2'.+J '*.J' 11.1) '7.7+ 1.1G )'.*2 2K7.7K

)G7 21.12 'G.7* 1'.J* '7.'+ 1.1+ )'.G' 2+K.77

>an power at evap'77H '17 2'.*1 'G.1K 1).J2 '7.7) 1.)' )1.*K 2J1.J7

127 21.2* '+.+* 12.+2 '7.)G 1.2G )2.7' 2K7.'J

)G7 2).72 'J.*J 1*.'* '7.*+ 1.*G )2.** 2K).J+

E0perimen% C

&or#ing fluid Cond5 "ir

3vap5 "ir Condenser cooling load >an power at


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condenser '77H

3vaporator heatload

Time(s!

:T51(C!

:T5)(C!

:T52(C!

:P5'(bar!

:P51(bar!

:C5'(-Ah!

:&5'(&!

>an power at evap

*7H '17 21.** 'G.*+ 1).'+ K.J* 1.'G )7.*+ 2+G.1* 127 2).G1 '+.)' 1).7G '7.1' 1.)2 )1.2* 2J2.G*

)G7 22.1+ '+.*K 1).17 '7.2) 1.)J )1.)1 2JK.KJ

>an power at evap'77H '17 2).JK 'G.J7 12.)' '7.2) 1.)2 )1.KK 2J1.K2

127 2*.2J 'K.17 1*.2G '7.KJ 1.G) )2.J+ 2K+.+G

)G7 2G.)2 17.7G 1*.K* ''.1G 1.+1 )G.1' *72.))

E0perimen% D

&or#ing fluid Cond5 "ir 3vap5 &ater Condenser cooling load :C51 *-Am

3vaporator heatload

Time(s!

:T51(C!

:T5)(C!

:T52(C!

:P5'(bar!

:P51(bar!

:C5'(-Ah!

:&5'(&!

>an power at evap*7H '17 2*.2K '1.7J '2.2) '7.JK 1.)2 )7.K7 2J1.7)

127 22.J' '7.)+ '2.++ '7.*7 1.17 )'.'7 2+G.G7

)G7 22.+' K.K) '2.JK '7.22 1.'G )7.JJ 2+1.2G>an power at evap'77H '17 2*.)+ ''.2+ '*.K' '7.GK 1.)) )'.7K 2++.*+

127 2*.*) '7.K* '*.K1 '7.+) 1.1+ )7.+2 2J2.K1

)G7 2*.*J '7.K) 'G.72 '7.+) 1.1+ )7.'+ 2J).KJ

Res/% )/mmary Tae

E& #

Time's(

Vre" 'm3 2s(

V'm3 24!(

mre" '5!2s(

h3'5J25!

h6 '5J25!

7e$ap'48(

CO&


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( (

'17+.)J)357G

7.777J*'

7.77JGJ KJ.'G 1GJ.'+ '.2+G ).7+2

127J.)21357G

7.777J*)

7.77K+J KK.1* 1GJ.*1 '.G** ).2+G

)G7J.1*G357G

7.77'J72

7.772*J '72.J* 1+7.1* 7.+*J '.*2K

"verage CP 1.GKK

'17J.)J)357G

7.777JGJ

7.77KGG '7G.1* 1+7.G+ '.*JJ ).1GG

127J.'K+357G

7.777JG+

7.77K2* '7G.7J 1+7.G1 '.*** ).'KK

)G7J.1+*357G

7.777JG+

7.77K*2 '7G.7J 1+7.G1 '.*GK ).)2G

"verage CP ).1+7

E& B

Time's(

Vre" 'm3 2s(

V'm3 24!(

mre" '5!2s(

h3'5J25!(

h6 '5J25!(

7e$ap'48(

CO&

'17J.1G2357G

7.777JGG

7.77K*2 '7*.G) 1+7.2K '.*+1 ).1G*

127

J.+G'

357G

7.777J

+'

7.7'77

G '7+.GK 1+'.7K '.G22 ).)*2

)G7J.+J'357G

7.777J+1

7.7'77+ '7J.1' 1+'.1) '.G21 ).21J

"verage CP ).)2K

'17K.7*)357G

7.777J+7

7.7'72' '7+.2J 1+'.7) '.+7) ).*1+

127K.22+357G

7.777J+2

7.7'7J' '7K.17 1+'.*' '.+** ).+))

)G7K.*K+357G

7.777J++

7.7'7K2 ''7.)7 1+'.J' '.+G+ ).+1K

"verage CP ).GG)

E& C

Time's(

Vre" 'm3 2s(

V'm3 24!(

mre" '5!2s(

h3'5J25!

(

h6 '5J25!

(

7e$ap'48(

CO&

'17 J.2K1 7.777J 7.77K+ '7G.2J 1+7.+2 '.G7G ).)+1


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357G GJ J

127K.7'2357G

7.777J+1

7.7'7)2 '7J.21 1+'.1K '.GJ2 ).2+*

)G7J.K++357G

7.777J+*

7.7'71G '7K.*+ 1+'.G' '.GG) ).)K2

"verage CP ).2'2

'17K.'G)K357G

7.777J+*

7.7'72+ '7K.*+ 1+'.G' '.GK+ ).*'2

127K.GJG'357G

7.777JJ'

7.7'7KK ''1.22 1+1.27 '.+*J ).*)1

)G7'7.7*J)

357G7.777J

J* 7.7'')+ '').K7 1+1.J7 '.J7+ ).*J)

"verage CP ).*2)

E& DTime's(

Vre" 'm3 2s(

V'm3 24!(

mre" '5!2s(

h3'5J25!(

h6 '5J25!(

7e$ap'48(

CO&

'17J.*J))357G

7.777JJ7

7.77K+* ''K.K+ 1+1.1+ '.2J* ).7J'

127J.G)JK357G

7.777J+2

7.77KJJ '7K.K) 1+'.+' '.*KJ ).)*)

)G7J.*++J357G

7.777J+*

7.77KJ7 '7K.G1 1+'.G1 '.G)+ ).2G*

"verage CP ).1KK

'17J.G)G'357G

7.777J+J

7.77KJ2 ''7.K) 1+'.KJ '.*J* ).)'K

127J.*)JK357G

7.777J+K

7.77K+' '''.') 1+1.72 '.*G1 ).11'

)G7J.)J7G357G

7.777J+K

7.77K*) '''.') 1+1.72 '.*)) ).'GK

"verage CP ).1)G

)#*&LE C#LCUL#TION

Vo/me "o- ra%e o" re"ri!eran%9


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V́ =SC −1 x 1hr

3600 s x 1m

3

1000 l

¿26.58 x 13600

x 11000

7.383 x 10−6

m3

s−1

Vo/me%ry o" re"ri!eran%

Lased on the properties given at temperature and pressure, the volumetry is

interpolated based on the given pressure of :P5'

:tate '

Pressure/ J77 #Pa

Volumetry/ 7.777J2*J m)A#g

:tate 1

Pressure/ J*7 #Pa

Volumtery/ 7.777J*17 m)A#g

Volumetry=(0.0008520−0.0008458) x ( (8.43∗100)−800)

850−800 +0.0008458

0.000851m3/kg

*ass "o- ra%e9


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massflow rate , ḿ= V́

Volumetry

¿ 7.383 x10−6

m3

s−1

0.000851m3kg

−1

0.00868 kg s−1

En%hapy H3

Lased on the properties given at temperature and pressure, the volumetry is

interpolated based on the given pressure of :P5' (J.2K Lar!

:tate '

Pressure/ J77 #Pa

3nthalpy/ K*.2+ #


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268.17 kJ k g−1

Hea% asore+ 2 E$apora%e+ Hea%9

Qevap (kW )=ṁ (h4−h3)

¿0.00868 kg s−1 x (268.17 kJ k g−1−98.16 kJ k g−1)

¿1.476 kW

CO&9

COP= Qevap

(Work

1000)=

1.476

( 480.08

1000) ).7+2


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8.*UH#**#D :UL5H#IRI BIN 8#N R#:#LI ; O?

DI)CU))ION

#( 8ha% e""ec% on %he CO&re" as %he oa+ increase+@ 8hy@

"s the heat load increases, the evaporator superheat rises. Conversely, as the

heat load decreases, the evaporator superheat falls. The CPref Increase if the

difference of temperatures decrease where temperature in evaporator rise or

temperature in condenser falls.

Lecause, when the heat load is higher than nominal, the li4uid refrigerant in the

evaporator coil starts to boil sooner. That is, when under nominal load the last bit

of evaporation occurs at the coil outlet, but under high load conditions this last bit

of evaporation occurs upstream from the coil outlet. ThatMs why the values of

CPref not increase nor decrease because load and CP ref are directly

proportional.

B( 8ha% is %he e""ec% o" cooin! me+i/m on %he a$era!e re"e!era%ion CO&@

8hy@

" refrigerant in gas form is generally the cooling medium agent used in modern

refrigerators. It used Chloro5>luoro5Carbon (C>C!, but it was found to be harmful

to the environment. &hen it compressed, it heats up. It passes through the warm

coils on the outside of the refrigerator and passes its heat into the air in the room

though a process #nown as thermodynamics. Thermodynamics is when a hot

and cold substance is in close proimity to one anotherN the cooler substance will

get warmer, and the hot substance will get cooler. "s it cools under pressure, the

gas becomes a li4uid. The refrigerant has made its way through the coils and

piping in the refrigerator, it warms and eventually ma#es it bac# to the evaporatorcoils where it is once again compressed and cooled through thermodynamics and


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epansion to begin the process all over again.

The cold air created in the condenser area is circulated throughout the

refrigerator to aid in cooling. The fans blow air from the freeDer into vents that

allow some of the cold air. The temperature of the air and the design of the

appliance allow the temperature to remain below freeDing in the freeDer while

remaining in the range in the refrigerator area.

C( 8ha% +o yo/ /n+ers%an+ y %erm oa+@ Ai$e e0ampes o" ac%/a oa+s in

re"ri!era%ion prac%ise in a +omes%ic in a room an+ in a "ac%ory.

The amounts of refrigerating load Q L (#&! that re4uired by refrigerant in the

evaporator to etract the rate of heat. "lso have refrigeration effectq L (#or eample, in domestic usually the loads are food li#e fishs, meats, fruits,vegetable

and others that we #eep it in our refrigerator at home in a small 4uantity. Lut in

factory, the loads not only foods. :ometime they put steel, or pro8ect sample or

something that need certain temperature to #eep itMs characteristic and material

microstructure maintained same because it sensitive to the temperature. ;sually the

factory use large of refrigeration system because they #eep their product in a large

4uantity.


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8.*UH#**#D :UL5H#IRI BIN 8. R#:#LI ;


18/27

MOHD HAFIDZI BIN YUSOF

2011197021

DI)CU))ION# 8ha% e""ec% on %he CO&re" as %he oa+ increase+@ 8hy@

&hen the load is increased, we can see that the value of CP ref also increases.

It is because this reason is not economical to refrigerate to a lower temp to what

it is needed. The value of CP of freeDers is approimately half of the value CP

of heat refrigerator. In economic side, it means that it will cost twice as much to

cool the heat products with refrigerated air that is cold enough to cool freeDer

product. CP of a refrigerator also decrease with decreasing refrigeration

temperature. Therefore, it is not economical to refrigerate to a lower temperature

than needed. The siDe of the compressor and the other components of a

refrigeration system are determined on the basis of the anticipated heat load

(refrigeration load!, which is the rate of heat flow into the refrigerator.

B 8ha% is %he e""ec% o" cooin! me+i/m on %he a$era!e re"ri!era%ion CO&@

8hy@The condenser temperature was increased and then decrease. This situation

occurs when the load is increase. It is because the dry bulb temperature

increases. This because condenser is heat re8ected, as been #nown more

load supply then it absorb heat from the evaporator then compress by the

compressor. The important thing is the 4uantity of the heat supply to the

system from the surrounding. The power input is important because from its

4uantity, it can #now how much must be paid for and constitutes the main item

of the running cost. In a way or another, if the usage of electricity is high,

certainly it may result to a higher cost and be very costly. &hereas, at lower

electricity power consumption, it will certainly be more economical and lower

down the cost factor.


19/27

C 8ha% +o yo/ /n+ers%an+ y %erm oa+@ Ai$e e0ampes o" ac%/a oa+s in

re"ri!era%ion prac%ice in a +omes%ic in a room an+ in a "ac%ory.

"s we #now, refrigeration is the device which transfers of heat from a low5

temperature medium to a high5temperature. -oad can be divided into two

types, which are sensible load and latent load. :ensible load results when

heat entering the conditioned space that causes dry bulb temperature toincrease. -atent load occurs when moisture entering the space causes the

humidity to increase.

In a room

"ctual load of refrigeration in a room was introduced which are not

eperienced by the coil. They are piping sensible heat gain as the cold

pipe passes through warm surroundings and pumping heat gain as the

pump does wor# on the water. TodayMs refrigerators use much less energy

as a result of using smaller and higher efficiency motors and compressor,better insulation materials, larger coil surface areas, and better door seals.

In a "ac%ory

>igure 1/ The cross section of a refrigerator showing the relative magnitudes of various effects that constitute the predictable heat load

The use of refrigerators in factory and industrial sectors is said to be costly,

but new improvement had changed the situation. Lecause of the factors such

as better insulating material that dissipated more heat, higher efficiency yet

smaller compressor and motors, larger coils surface area, and also better


20/27

door seals to prevent air from going in and out, refrigerator use less energy

than it was when it is first invented. To ensure that certain amount of load can

be applied in the refrigerator, special compartments are used. The whole shell

of the refrigerator is sealed to avoid from water lea#age or moisture migration

into the insulation since moisture degrades and decreased the effectiveness

of insulation. -arger loads are possible to practice and placed in refrigerator

nowadays because of the uses of thinner but more effective insulation that will

minimiDes the space occupied by the compressor and the condenser.

MOHD HAFIDZI BIN YUSOF

2011197021

CONCLU)ION

In this eperiment, we #now that CP of the refrigeration system increasedconsiderably relative to the single stage. "s a result, the CP of the refrigeratorwould increase, when load increased. The refrigeration duty and compressor wor#also increased when load is increased. eat re8ected from condenser, remainconstant when load is applied.


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DI)CU))ION *UH#**#D *#H#DHIR BIN *OH#*ED D#LI


22/27

CONCLU)ION *UH#**#D *#H#DHIR BIN *OH#*ED D#LI


23/27

DI)CU))ION )H#:ULR#IN BIN #*R#N


24/27

types, which are sensible load and latent load. :ensible load results when

heat entering the conditioned space that causes dry bulb temperature to

increase. -atent load occurs when moisture entering the space causes the

humidity to increase.

• In a room

"ctual load of refrigeration in a room was introduced which are not eperienced by

the coil. They are piping sensible heat gain as the cold pipe passes through warm

surroundings and pumping heat gain as the pump does wor# on the water. TodayMs

refrigerators use much less energy as a result of using smaller and higher efficiencymotors and compressor, better insulation materials, larger coil surface areas, and

better door seals.

• In a factory

The use of refrigerators in factory and industrial sectors is said to be costly, but new

improvement had changed the situation. Lecause of the factors such as better

insulating material that dissipated more heat, higher efficiency yet smaller

compressor and motors, larger coils surface area, and also better door seals to

prevent air from going in and out, refrigerator use less energy than it was when it is

first invented. To ensure that certain amount of load can be applied in the

refrigerator, special compartments are used. The whole shell of the refrigerator is

sealed to avoid from water lea#age or moisture migration into the insulation since

moisture degrades and decreased the effectiveness of insulation. -arger loads are

possible to practice and placed in refrigerator nowadays because of the uses of

thinner but more effective insulation that will minimiDes the space occupied by the

compressor and the condenser.

CONCLU)ION) )H#:ULR#IN BIN #*R#N


25/27

"s a conclusion, the value of CPref is proportional to the value of load. It means

that when the load increased, the value of the CPref also increased.

@;"@@"B >"RIB L ".R"@"? 17''KJ''''

DISCUSSION

From the result, the coe!c!ent o "erorm#nce !s !ncre#se$ #s the lo#$ !s !ncre#se$ #t

e%"er!ment # #n$ c &ec#use the 'or!n lu!$ th#t !s use$ #t the con$enser #n$ e*#"or#ter !ss#me 'h!ch #t the e%"er!ment # !s us!n '#ter 'h!le #t the e%"er!ment c !s us!n #!r+ For the

e%"er!ment & #n$ $, the coe!c!ent o "erorm#nce !s $ecre#se$ &ec#use$ the 'or!n lu!$

th#t !s use$ #t e*#"or#ter #n$ con$enser #re $!erent #n$ #lso $ue to the e*#"or#ter he#t lo#$+

he eect o cool!n me$!um on the #*er#e rer!er#t!on COP !s to !ncre#se$ the *#lue o

COP &ec#use the cool!n me$!um !s con$ucts he#t rom one or more he#t sources #n$

tr#ns"orts !t to # he#t e%ch#ner, 'here the he#t !s remo*e$ #n$ $!s"ose$+

Domest!c rer!er#tors h#*e t'o t-"es 'h!ch !s # s!nle $oor resh oo$ rer!er#tor or # t'o.

$oor rer!er#tor+

/ s!nle $oor resh oo$ rer!er#tor cons!sts o #n e*#"or#tor "l#ce$ e!ther #cross the to" or

!n one o the u""er corners o the c#&!net+ he con$enser !s on the c o the c#&!net or !n

the &ottom o the c#&!net &elo' the hermet!c com"ressor+ Dur!n o"er#t!on, the col$ #!r rom

the e*#"or#tor lo's &- n#tur#l c!rcul#t!on throuh the rer!er#te$ s"#ce+ he shel*es !ns!$e

the c#&!net #re constructe$ so #!r c#n c!rcul#te reel- "#st the en$s #n$ s!$es, el!m!n#t!n the

nee$ or # #n+ h!s rer!er#tor h#s # m#nu#l $erost, 'h!ch re0u!res th#t the rer!er#tor &e

turne$ o "er!o$!c#ll- (usu#ll- o*ern!ht) to en#&le the &u!l$u" o rost on the e*#"or#tor to

melt+ oth the outs!$e #n$ !ns!$e !n!sh !s usu#ll- e$.on en#mel+ Porcel#!n en#mel !s

oun$ on steel c#&!net l!ners+ he !nter!or o the un!t cont#!ns the shel*es, l!hts, thermost#ts,

#n$ tem"er#ture controls

he t'o.$oor rer!er#tor.reeer com&!n#t!on !s the most "o"ul#r t-"e o rer!er#tor+ It !s

s!m!l#r to the resh oo$ rer!er#tors !n construct!on #n$ the loc#t!on o com"onents e%ce"t !tsomet!mes h#s #n e*#"or#tor or &oth the reeer com"#rtment #n$ the rer!er#tor

com"#rtment+ /lso, ! !t !s # rost.ree un!t, the e*#"or#tors #re on the outs!$e o the c#&!net+

ec#use o the t'o se"#r#te com"#rtments #n$ the l#rer c#"#c!t-, these t-"es o rer!er#tors

use orce$ #!r to c!rcul#te the #!r throuh the !ns!$e o &oth com"#rtments+ he t'o.$oor

rer!er#tor #lso h#s one o the ollo'!n three t-"es o e*#"or#tor $erost s-stems 'h!ch !s

m#nu#l $erost, #utom#t!c $erost, or rost.ree+

here #re t'o t-"es o #utom#t!c $erost!n+ here #re the hot #s s-stem #n$ the electr!c

he#ter s-stem+ he hot #s s-stem, throuh the use o soleno!$ *#l*es, uses the he#t !n the

*#"or rom the com"ressor $!sch#re l!ne #n$ the con$enser to $erost the e*#"or#tor+ heother s-stem uses electr!c he#ters to melt the !ce on the e*#"or#tor sur#ce+


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/ rost.ree rer!er#tor.reeer h#s the e*#"or#tor loc#te$ outs!$e the rer!er#te$

com"#rtment+ On the runn!n "#rt o the c-cle, #!r !s $r#'n o*er the e*#"or#tor #n$ !s orce$

!nto the reeer #n$ rer!er#tor com"#rtments &- # #n+ On the o "#rt o the c-cle, the

e*#"or#tors #utom#t!c#ll- $erost+

In # room, the s"ec!!c#t!on th#t nee$s to no' !s the ch!ll!n or ree!n t!mes no' 'ore$out, the s!e o the room c#n &e $eterm!ne$+ o #ch!e*e th!s, the o"er#t!on o the 'hole

#tto!r m#- h#*e to &e ch#ne$ #n$ #lso the lo' o c#rc#sses to #n$ rom ch!ller or reeer,

the "os!t!on o $oors #n$ so on+

I !t s!e #n$ "os!t!on o the room h#s &een r!!$l- !%e$ &eore th!s st#e, the cool!n t!mes

$eterm!ne$ #&o*e '!ll not &e met+ When lo#$!n # ch!ller the $oors #re !n*#r!#&l- let o"en

or lon "er!o$s #llo'!n # ull- est#&l!she$ #!r lo' to t#e "l#ce to #n$ rom the room

e!ther rom r#*!t- throuh # s!nle $oor or &- # throuh lo' o #!r ! more th#n one $oor !s

o"en+

/nother "o!nt to not!ce !s th#t the lo#$ on the room, 'hen use$ #s # store, e*en 'hen theouts!$e tem"er#tures #re *er- h!h, !s *er- sm#ll com"#re$ to &oth the "e# #n$ #*er#e lo#$

#n$ !s or the most "#rt $ue to the e*#"or#tor #ns runn!n cont!nuousl-+ he lo#$ then

!ncre#se 'hen the $oors #re o"ene$ #n$ the room !s '#she$ out or "oss!&l- unlo#$e$+ W#rm

c#rc#sses #re then lo#$e$ !nto the room #n$ the lo#$ r#"!$l- re#ches the "e# "ro$uct lo#$

th#t occurs #t the en$ o the lo#$!n "er!o$+ here#ter, the $oors #re close$ #n$ the lo#$

r#"!$l- $ecl!nes+ /t the en$ o the ch!ll!n c-cle, the $oors #re ##!n o"ene$ to remo*e the

c#rc#sses #n$ the !n!ltr#t!on lo#$ so c#use$ !ncre#se+

In #ctor-, # rer!er#tor !s $es!n to m#!nt#!n the reeer sect!on #t .13C #n$ the rer!er#tor

sect!on #t 5C+ Lo'er reeer tem"er#tures !ncre#se ener- consum"t!on '!thout !m"ro*!n

the stor#e l!e o roen oo$ s!n!!c#ntl-+ D!erent tem"er#tures or the stor#e o s"ec!!c

oo$s c#n &e m#!nt#!ne$ !n the rer!er#tor sect!on &- us!n s"ec!#l."ur"ose com"#rtment+

he s!e o com"ressor #n$ #nother com"onents o # rer!er#t!on s-stem #re $eterm!ne$ on

the s!s o the #nt!c!"#te$ he#t lo#$ (or rer!er#t!on lo#$), 'h!ch !s he#t lo' !nto the

rer!er#tor+ he he#t lo#$ cons!sts o the "re$!ct#&le "#rt, #n motor6 $erost he#ters #n$ the

un"re$!ct#&le "#rt+

7UH/77/D F/8ID /+8/H7/N 2911:31111

CONCLUSION

/s # conclus!on, the coe!c!ent o "erorm#nce o *#"or com"ress!on rer!er#t!on!s o&t#!ne$

us!n the rer!er#nt enth#l"- &- #ssum!n there !s no he#t tr#nser occurs or c#lle$ #n


27/27

#$!#t!c s-stem+ he re$uc!n o the tem"er#ture h#s o"t!m!e the *#lue o coe!c!ent o

"erorm#nce $ue to !ts lo#$ #n$ the 'or!n lu!$+

REFERENCES

1+ Yunus A. Cengel, Michael A. Boles, hermo$-n#m!cs; /n

refrigerantion complete 2

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