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,lMechanical Engg.- NiT RaiPur TE,CH-E,D

DOMESTIC REFRIGERATOR TEST RIG

AIM:

To conduct performance test on Vapour Compression type Ice plant tutor and to

find out co-efficient of performance (COP)

SYSTEM C OMP OI\ENTS/SPECIFICATION :

1. Refiigeralor: vEDtrOCON, model: vAE,173AN2010, 170 \t ,"-2. Compressor: -Model: ASB45R, R-13-41..

,

2. Ai1 Cooled condenser:

3. Fan motor with blade: Il35 F{P

./' 4. F.xpansion Device -Capillary

-,'5. Filter Drier -make: INDFOS, Type: DM-50

6. Energy meter -make: BENTEX, Input: 3200impikwh, 5-20 amps

7. Thermostat

8. Pressure/compound gauges: For.HP-LP Measurement.

-/'g.Digital Temperature Indicator: -50 to + 199'9 'C

v'' 10. Thermocouples: ktype (CLlAl)- 5 nos

,*/ 1L Refrigerant: R-134a

(D om e s tir WJrig erot o r trainer

of Mechanical Engg.- NIT Raipur

DESCRIPTION:

The apparatus is a laboratory

unit, portable-trolley mounted,

TECH-ED

scale working model of a Refrigeration cycle

housed on a Powder coated MS square tube

frame.

A Domestic / household refrigerator of VEDIOCON make is fitted on the

frarne containing, compressor with Thermostat, air cooled condenser with fan

motoL, Capillary Expansion and evaporatorl fieezer

The pressure gauges, Energy meter and digital temperature indicator with

selector switch are mounted on the control panel.

THEORY:

Now days, the refrigerator has become an essential parl of a household

rather than a luxury. It is used for preserving food and there by reducing waste.

The primary function of a refrigerator or freezer is to provide food storage

space maintained at low temperature for the preservation of food. Its essential

secondary function is the formation of ice cubes for domestic consumption.

They are usually specified by the internal gross volume and the deep fi'eezer's

volume. ,,

. .",---*.,.1

A storage temperature of 0' C to Aiic (273 K TO 277 K) is satisfactory for the

preservation of most of the fresh foods. For the shorl term storage of frozen

foods (such as in a domestic refrigerator), temperatures much below the

freezingpoint are required. The fi'eezers are generally provided at the top

porlion of the refi'igerator space. In some refiigerators, freezers are provided at

bottom. This arrangement seems to be based on the heat transfer considerations

but it rnay be noted that the time taken to cool products kept at upper porlion

would be more.

Q) o m e s tic fuf rig erat o r trainer

,pt. of Mechanical Engg.- NIT Raipur

I:\ lp(1r'ilt()1'

cnilrI* t'cr,r.e rri.,oilll)l.lt'ln1

i.'lr pi I Ilrr.r

t u lit'

Kitr.hrrn iril=

:50{'

(),,iJl

( lrrtilcri,ru"ct;ilr

( 't ltl'il)l r.':s.t

The mechanical vapor compression cycle as well as absorption cycle

may be adopted for domestic refi'igerators and freezers, but the mechanical

vapor compression system is actually used over absorption system, because ofits compactness and more efficient use of electrical energy, as shown in figure.

The refrigerant used is generallt,*-134A The compressor is mounted at the

bottom of the refrigerator frame. The power of compressor canvary according

to size of therefiigerator, (i.e. 75W,92W,125 W, 180 Wetc.). The

condenser is put at the back about 40 to 60 mm away from the cabinet. The

condenser may be either chassis type or tube and wire type. In the former, the

condenser tube is mounted on a metal sheet which acts as fins. The tube and

wire type condensers are quit simple in which few tubes are held tightly under

wire frame from both sides. These wires act as cylindrical fins increasing the

TECH-EI)

(D o m e stic fu {rig erat o r trsiner

4t. of Mechanicai Ettgg.- NIT Raipur TtrCII.ED

rate of heat transfer. The capillary tube is kept in contact with the evaporator

inlet pipe. A drier is connected between the receiver and the evaporator to

eliminate traces of moisture if any'

The evaporator coil is wrapped around the freezer in a suitable manner to

give efficient heat transfer. Some times, the freezer charnber is made from a

pair of sheet joined together in such away that the passage between the sheets

act as an evaporator coil. The cooling of lower space is accomplished by fi'ee

convection (due to density gradient). The thermostatic sensing element is

provided to the evaporator coil which can control temperature in the freezer up

to -15" c in steps or continuously depending upon the type of controlling switch

employed.

The refrigerator body is provided with good quality insulation in order to

prevent heat transfer into the system. usually 60 to 100 mm thick glass loose-

fill fiber or glass rolls or thermo cole is used since the conductivity of these

insuiating materials are quite low'

Theprincipalpartsareshownonthediagram,andpathofthe

refrigerant flow is also shown on the diagram. The pressure is maintained at

different levels in fivo parts of the system by the expansion valve (high side

float vaive). The function of the expansion valve is to allow the liquid-

refrigerant under high pressule to pass at a controlled rate into the low-pressure

parl of the system. Some of the liquid evaporates passing through the expanston

valve, but greater portion is vaporized in the evaporator ,atlow pressure (low

temperature). The liquid refi'igerant absorbs its latent heat of vaponzation fiom

the air, water or other material, which is being cooled' The function of the

compressor is to iucrease the pressure and temperature of the refrigerant above

E om e s ti c fufrig erat o r'Ir ain er

pt. of Mechanical Engg.- NIT Raipur TE,CH.EI)

atmospheric, which will be ready to dissipate its latent heat in the condenser' In

passing through the condenser, the refrigerant gives up the heat, which is

absorbed in the evaporator plus the heat equivalent of the work done upon it by

the compressof. This heat is transferred to the air or water, which is used as

cooling medium in the condenser'

l

lLi

C,ompressor

-l --L

l1 r- _ _-----_-l

-, EvaPorator I

1 l-- -- - --,- |

P"p*t4?evicel

BLOCKDIAGRAMoFVAPOURCOMPRESSIONCYCLE,

The standard vapour compression cycle consists of following process:

1. Process, I-2 replesents reversible adiabatic compression fi'om

saturated vapol to the condensel plessure or superheated Vapor'

2. Proces s 2-3 represents reversible heat rejection at constant pressure,

de preheating and condensation'

3. Process 3-4 represents ireversible constant enthalpy expansion fiom

saturated liquid to the evaporator pressure'

4. Process 4-1 represents reversible heat addition at constant pressule

(Evaporation to saturated vapor) , '

(D om e s tit Rcfig erat o r.{rainer

4t. of Mecl:ranical Engg.- NIT Raipur TE,CI{.E,I)

The refiigerants such as R-l2, R-22, and R-134a (commercially known as

freons) are used as working medium because of their properties, which are

required as refrigeration cycles.

Performance of standard vapour compression cycle:

Process 1-2 is the compression process where in Mechanical work is to

be supplied to a compressor. This is the quantity to be spent. Process 4 -1

represents the useful refrigeration effect. The index of performance is defined

as coefficient of performance.

1. T1 :Temp.of refiigerant at inlet of compressor' .,'2. T2: Temp.of refi'igerant at outlet of compressor '-'"

.,...

3. T3 : Temp.of refrigerant at outlet of condenser ".,'/

4. T4: Temp.of refrigerant at outlet of expansion ,,

5. T5 : Temp.at Evaporator.

A o me s tic fufi9 erat or'Trainer

;pt. of Mechanical Engg.- NIT Raipur' TE,CH-ED

OPERATII{G PROCEDURE:

1. Put ON mains (DP Switch)

2. Now switch on the coffIpressor, by using a rotary switch provided

3. Allow the fieezer to cool f%gc.Io achieve this temp., it wiil take

approximately 1 t0 1 lz hrs. (Depending on ambient temp. and Power)

4. Fol COP calcuiation,,

A. Put known quantity of water/ brine solution in a bowl I platethen

keep that inside the freezer.

B. Note down the initial temperature of water / brine solution

C. Allow it to cool for some time, simultaneously note down the

respective readings for every 1-0 minutes duration till it reach 5

**s-9D. Calculate the COP using given formulae.

5. T'hen switch off the Compressor using Rotary ON/OF'F switch and

mains

'r "il

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A o m e stic fuf-rig er at or lfrainer

I

CALCULATIONS:

Jept. of lr4echanical Engg.- NIT Raipur TE,CH.EI)

F Theoretical COP

COPtr, h1 -h4h2 -hI

From t34a charl,

h1 : Enthalpy inkJ/kg coffesponding to pressure P1 & temperature T1

(Vapour Phase)

h3 : Enthaipy in kJ/kg corresponding to pressure P2 &. temperature T3

But, h3 : h4

h2:Enthalpy in kJ/kg corresponding to pressure P2& temperature T2

coP.ornot : Tl_T2-T1

Temperature of refrigerarrt" @

T1 : inlet of compressor in degree K

T2 : outlet of compressor in degree K

A ome s tir fuf rig erato r'lrain er

,J,. of lt""hanical Engg.- NIT Raipur' TECI{-ED

COP (actual)

a,where,

mw : Mass ofwater : ....... Lg

Co* : 4.18 KJ/kg dg k

,'- -':\\

Tr: Final chilled water temP' in dg C

.ia-"

ti ;- initial water temP in dg C....

.-' ,

w: sx3604-txEmc

where,

n: no. of impulse of energY meter

t: time taken

Compressor inPut

Emc : energy meter constant :3200 imp/kWh

Relative COP

COP (r.erative) COP tu.tuun

COP (theor.itical)

(D ome s tic frefrig erat or'lrain er

Jept. of Mechanical Engg.- NIT Raipur TECHJED

SLNO

P1

Psi

P2psi

T]oc

T2oc

T3oc

T4oc

T5oc

EMtimefor 5

irnp

Duration

1

TABIJLAR COLUMI{

' D ome stir Ref-rig erator tiaincr