Understanding Refrigerations

8/14/2019 Understanding Refrigerations

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RELATED PHYSICSRELATED PHYSICS

ININREFRIGERATIONSREFRIGERATIONS


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REFRIGERATIONSREFRIGERATIONS Process ofProcess of

reducing andreducing andmaintain themaintain the

temperaturetemperature


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REFRIGERATIONSREFRIGERATIONS

EXCHANGE OF HEATEXCHANGE OF HEAT

TRANSFER OF HEAT FROM ATRANSFER OF HEAT FROM ASPACE TO REFRIGERANT ANDSPACE TO REFRIGERANT ANDVICE VERSAVICE VERSA


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LE SYSTEME INTERNATIONALLE SYSTEME INTERNATIONALdUNITES (SI)dUNITES (SI)

MassMass

- amount of material- amount of materialin a substancein a substance

measure inmeasure in gramsgrams ororkilokilogramsgrams
http://conversion.xls/http://conversion.xls/http://conversion.xls/


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SISI

ForceForce

- a push or pull- a push or pull

WeightWeight

- measure of the force- measure of the force

exerted on the body byexerted on the body bythe gravitational pull ofthe gravitational pull ofthe earththe earth


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SISI

Kilogram force (kgf)Kilogram force (kgf)- the force of gravity of- the force of gravity ofan object having a massan object having a massof 1 kgof 1 kg

NewtonNewton- mass 1kg, acceleration- mass 1kg, acceleration1 m/s21 m/s2

gravity = 9.807 m/s2gravity = 9.807 m/s2


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PRESSUREPRESSURE

kgf/cm2kgf/cm2 Pascal (Pa)Pascal (Pa) Pound per squarePound per square

inch (psi)inch (psi)


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PRESSUREPRESSURE

The deeper the moreThe deeper the morepressurepressure

The pressure is theThe pressure is the

weight of column ofweight of column ofwater above thewater above thediverdiver


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PRESSUREPRESSURE

AtmosphericAtmosphericpressure layer ofpressure layer ofgas around the earthgas around the earth

about 20kmabout 20kmthicknessthickness

Agreed unit ofAgreed unit ofpressure is Pascalpressure is Pascal(Pa) or bar(Pa) or bar

0 meter, 1bar=1atm0 meter, 1bar=1atm


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GAUGEGAUGE

PressurePressure TemperatureTemperature RefrigerantRefrigerant

0 b = 1atm0 b = 1atm

absolute pressure =absolute pressure =gauge pressure +gauge pressure +atmospheric pressureatmospheric pressure


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QUIZQUIZ

If atmosphericIf atmosphericpressure is 1 b, whypressure is 1 b, whyis the gauge show 0is the gauge show 0

at rest?at rest?

relative pressure orrelative pressure or

gauge pressuregauge pressure


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THE PRESSURE-TEMPERATURETHE PRESSURE-TEMPERATURERELATIONSHIPRELATIONSHIP

In a balloon there isIn a balloon there istwo pressure:two pressure: Internal pressureInternal pressure

External pressureExternal pressure ororatmospheric pressureatmospheric pressure


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Pressure-TemperaturePressure-Temperature

At atmosphericAt atmospheric

pressure thepressure the

internal andinternal and

external pressureexternal pressureis equivalentis equivalent

Pressure uniformlyPressure uniformly

distributeddistributed


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Increase theIncrease theinternal pressureinternal pressureand the water startand the water start

to boilto boil At 1 b pressure, theAt 1 b pressure, the

temperature is 100temperature is 100CC


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External pressureExternal pressuresmaller 0.7 bsmaller 0.7 b

The internalThe internal

pressure need lesspressure need lesspressure topressure toovercome externalovercome externalpressurepressure

At 0.7 b external,At 0.7 b external,water boil at 90water boil at 90CC


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CONCLUSIONCONCLUSION


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Every time the pressure changes, theEvery time the pressure changes, thetemperature also changestemperature also changes

At every pressure, there is aAt every pressure, there is acorresponding boiling pointcorresponding boiling point

This is call pressure-temperatureThis is call pressure-temperaturerelationshiprelationship


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CONVERSIONSCONVERSIONS


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UNIT OF HEATUNIT OF HEAT

Calorie (cal)Calorie (cal)

-1g water, 1C = 1 cal-1g water, 1C = 1 cal

Joule (J)Joule (J)- 1g water, 1C =- 1g water, 1C = 4.187J4.187J

British thermal unit (Btu)British thermal unit (Btu)

- 1lb, 1F = 1Btu- 1lb, 1F = 1Btu


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HEAT TRANSFERHEAT TRANSFER

Water and airWater and air

touch indirectlytouch indirectly

Heat passes fromHeat passes from

hotter to colderhotter to colder


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Only if there isOnly if there is


differencedifference

Heat always flows fromHeat always flows fromthe hotter body to thethe hotter body to the

colder bodycolder body

In financial industry, the richIn financial industry, the rich

didnt always give to the poordidnt always give to the poor


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BOILING OF WATERBOILING OF WATER

Water boil at 100CWater boil at 100C

If we keep boiling,If we keep boiling,temperature oftemperature of

water will stabilizeswater will stabilizes


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CHANGE OF STATECHANGE OF STATE Liquid state toLiquid state to

gaseous stategaseous state

(steam)(steam) The waterThe water vaporizesvaporizes

The temperatureThe temperaturedoes not increasedoes not increasefurtherfurther


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TemperatureTemperatureincrease from t0 increase from t0 t2t2


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At t2-t3, theAt t2-t3, the

temperature is 100Ctemperature is 100C

Changing from liquid toChanging from liquid to

vaporvapor

When liquid evaporates,When liquid evaporates,

it absorb heat-it absorb heat- latentlatent

heat of vaporizationheat of vaporization


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00CC

00C, Ice meltingC, Ice melting t0-t1 solid statet0-t1 solid state

to liquid stateto liquid state


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00CC

No more iceNo more ice Temperature startTemperature start

to increaseto increase


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Water changes from solid to liquid atconstant temperature 00CC by absorbingby absorbingheat heat LATENT HEAT OF FUSIONLATENT HEAT OF FUSION

Water changes from liquid to vapor atconstant temperature 1000CCbybyabsorbing heat absorbing heat LATENT HEAT OFLATENT HEAT OF

VAPORISATIONVAPORISATION


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To evaporate, water needs energyTo evaporate, water needs energy(heat)(heat)


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AMOUNT OF HEATAMOUNT OF HEAT


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AMOUNT OF HEATAMOUNT OF HEAT

2 and 4 -2 and 4 - latent heatlatent heat 1,3 and 5 -1,3 and 5 - sensible heatsensible heat


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REFRIGERANTREFRIGERANT

A heat carrierA heat carrierWorking fluid to vaporizes andWorking fluid to vaporizes and

condenses as it absorb/gives off heatcondenses as it absorb/gives off heatTypes of refrigerantTypes of refrigerant

- primary- primary

- secondarysecondary
http://coolpack/CoolPack.exehttp://coolpack/CoolPack.exehttp://coolpack/CoolPack.exe


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PRIMARY REFRIGERANTPRIMARY REFRIGERANT

Refrigerant used in vapor compressionRefrigerant used in vapor compressionsystemssystems

HalocarbonHalocarbon

- contain chlorine, fluorine and bromine- contain chlorine, fluorine and bromine


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Inorganic compoundInorganic compound

- an early refrigerants- an early refrigerants


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HydrocarbonHydrocarbon

- suitable for petroleum and petrochemical industry- suitable for petroleum and petrochemical industry


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REFRIGERANTREFRIGERANT2222

FREON 22FREON 22 FORANE 22FORANE 22 SUVA 22SUVA 22 MonochlorodifluoromethaneMonochlorodifluoromethane

CHCLF2CHCLF2

Whatever the names is, R22Whatever the names is, R22evaporates at -42evaporates at -42C atC atatmospheric pressureatmospheric pressure
http://coolpack/http://coolpack/http://coolpack/


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REFRIGERANT 22REFRIGERANT 22

CHCLF2CHCLF2 2 atoms of fluorine 2 atoms of fluorine

- 1 atoms of hydrogen + 1- 1 atoms of hydrogen + 1

CCL2F2CCL2F2

- 2 atoms of fluorine- 2 atoms of fluorine

- 0 atoms of hydrogen + 1- 0 atoms of hydrogen + 1- R 12- R 12


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QUIZQUIZ

Why do you thinkWhy do you thinkthe R22 gauge readsthe R22 gauge reads-42-42C at 0 bar?C at 0 bar?

At atmosphericsAt atmospherics

pressure R22pressure R22evaporates at -42evaporates at -42CC


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DANGER!DANGER!


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REFRIGERANTSREFRIGERANTS

SelectionSelection- inexpensive- inexpensive- nonpoisonous- nonpoisonous

- non corrosive- non corrosive- non flammable- non flammable- stable- stable- high latent heat of vaporization- high latent heat of vaporization- easy to condense and vaporize- easy to condense and vaporize- easy to detect leaks- easy to detect leaks


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SELECTIONSSELECTIONS


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REPLACEMENTREPLACEMENT

ODPODP GWPGWP CompositionsCompositions


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REPLACEMENTREPLACEMENT

SECONDARYSECONDARY
http://replacements.gif/http://replacements.gif/http://replacements.gif/


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SECONDARYSECONDARYREFRIGERANTSREFRIGERANTS

Fluid that carry heat from a substanceFluid that carry heat from a substancebeing cooled to the evaporatorbeing cooled to the evaporator

Change in temperature but does notChange in temperature but does notchange phasechange phase

WaterWater

BrinesBrines

Anti freezes solution of water andAnti freezes solution of water andglycol or calcium chlorideglycol or calcium chloride


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REFRIGERATING MACHINEREFRIGERATING MACHINE&&

CYCLECYCLE


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REFRIGERATION CYCLEREFRIGERATION CYCLE

1. Evaporator1. Evaporator 2. Compressor2. Compressor 3. Condenser3. Condenser

4. Expansion device4. Expansion device


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EvaporatorEvaporator

Evaporate theEvaporate therefrigerant in therefrigerant in thetubetube

Changes from liquid toChanges from liquid tovaporvapor Absorbed heat fromAbsorbed heat from

the surroundingthe surrounding

CoolingCooling


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EvaporatorEvaporator

1. evaporator inlet1. evaporator inlet 2. evaporator outlet2. evaporator outlet 3. tube3. tube 4. fin4. fin

An evaporator mustAn evaporator must

be exposed to thebe exposed to thespace to absorbedspace to absorbedheatheat


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CompressorCompressor

To compress theTo compress the

refrigerantrefrigerant

Increase pressureIncrease pressure

and temperatureand temperature

Lp - coldLp - cold

Hp - hotHp - hot


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CondenserCondenser

The condenser is hotterThe condenser is hotter

than the ambientthan the ambient


Hotter temperatureHotter temperature

always give up heatalways give up heat


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CondenserCondenser

1. condenser inlet1. condenser inlet

2. condenser outlet2. condenser outlet

3. tube3. tube

4. fin4. fin

Vapor to liquidVapor to liquid


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Expansion deviceExpansion device

Connect condenserConnect condenser

and evaporatorand evaporator

Drop the pressureDrop the pressure

from hp to lp thusfrom hp to lp thus

dropping thedropping the



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Expansion deviceExpansion device

Capillary tubeCapillary tube

Thin copper tubeThin copper tube

Interior diameterInterior diameter

and length is fixedand length is fixed



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REFRIGERATION CYCLEREFRIGERATION CYCLErefrigeratorrefrigerator



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REFRIGERATION CYCLEREFRIGERATION CYCLEoperationoperation

R22 enter evaporator asR22 enter evaporator as liquidliquid Room heat will evaporates the R22Room heat will evaporates the R22 Room will become colderRoom will become colder



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R22 is vaporize by the interior room heatR22 is vaporize by the interior room heat

R22 vapor then suct by the compressorR22 vapor then suct by the compressor



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R22 enter condenser as hp vaporR22 enter condenser as hp vapor Hot R22 gives up heat to the ambient condensationHot R22 gives up heat to the ambient condensation



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At condenser outlet vapor had turn to liquidAt condenser outlet vapor had turn to liquid

Hp liquid will enter the expansion valveHp liquid will enter the expansion valve

WINDOW UNITWINDOW UNIT


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SPLIT UNIT internalSPLIT UNIT internal


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SPLIT UNIT - internalSPLIT UNIT - internal


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PL NSPLIT UNIT


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SPLIT UNITSPLIT UNIT

OPERATING CONDITION hpOPERATING CONDITION hp


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OPERATING CONDITION - hpOPERATING CONDITION - hp

High pressureHigh pressure16.3b16.3b

HighHigh

temperaturetemperature45C45C

PER NG C ND N lOPERATING CONDITION l


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OPERATING CONDITION - lpOPERATING CONDITION - lp

Low pressure 4.8bLow pressure 4.8b Low temperature 5CLow temperature 5C

NORMALNORMAL OPERATINGOPERATING
http://operef.doc/http://operef.doc/http://operef.doc/


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CONDITIONCONDITION
http://operef.doc/http://operef.doc/


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th l f COMPRESSORth l f COMPRESSOR


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the role of COMPRESSORthe role of COMPRESSOR

A temperature of aA temperature of atrapped compress airtrapped compress airin a bicycle pump willin a bicycle pump will

increaseincrease

Compression of a gasCompression of a gascauses an increase incauses an increase in

pressurepressure andandtemperaturetemperature

COMPRESSORCOMPRESSOR


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1. intake lp1. intake lp 2. outlet hp2. outlet hp 3. lp valve3. lp valve

4. hp valve4. hp valve 5. piston5. piston 6. cylinder6. cylinder

7. connecting rod7. connecting rod 8. eccentric crank8. eccentric crank



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A. bdcA. bdc B. piston move up toB. piston move up to

compresscompress



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9. valve plate9. valve plate Pressure stablePressure stable



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pressure at 6 ispressure at 6 isgreater than hpgreater than hp

CompressionCompression

COMPRESSIONCOMPRESSION


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The valves are controlled by the refrigerantThe valves are controlled by the refrigerantitselfitself



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B-C. piston risesB-C. piston rises when the pressurewhen the pressure

in the cylinder isin the cylinder is

greater than hp, thegreater than hp, thevalve openvalve open



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D. tdcD. tdc The pressure at hp isThe pressure at hp is

equal to the cylinderequal to the cylinder

Valve closeValve close

Note: clearance space is the gap between tdc andNote: clearance space is the gap between tdc andthe piston head so that the piston will not knock thethe piston head so that the piston will not knock thevalvevalve


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COMPRESSOR - rotaryCOMPRESSOR - rotary


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COMPRESSOR - rotaryCOMPRESSOR rotary

AdvantagesAdvantages- compact and lightcompact and light

- less vibration and noise- less vibration and noise

- low power consumption- low power consumption- high durability- high durability

DisadvantagesDisadvantages

- advanced processing- advanced processingtechnology is requiredtechnology is required

- an accumulator required- an accumulator required

COMPRESSOR - scrollCOMPRESSOR - scroll


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COMPRESSOR - scrollCOMPRESSOR scroll AdvantagesAdvantages

- little fluctuation of torque- little fluctuation of torque

- low vibration and noise- low vibration and noise

- less gas leak and high efficiency- less gas leak and high efficiency

- no suction and discharge, high- no suction and discharge, highdurabilitydurability

DisadvantagesDisadvantages

- advanced processing technology is- advanced processing technology is

required; accuracy of few micronrequired; accuracy of few micron

unitsunits

- more components than rotary- more components than rotary

COMPRESSOR reciprocatingCOMPRESSOR reciprocating


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COMPRESSOR - reciprocatingCOMPRESSOR - reciprocating

AdvantagesAdvantages- no accumulator is required- no accumulator is required

- vibration are not transmitted- vibration are not transmitted

outsideoutside- rotation of both side possible- rotation of both side possible DisadvantagesDisadvantages

- heavy weight- heavy weight

- large volume- large volume

ROTARYROTARY


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ROTARYROTARY

SCROLLSCROLL


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SCROLLSCROLL

RECIPROCATINGRECIPROCATING


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RECIPROCATINGRECIPROCATING

SCREWSCREW


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SCREWSCREW

Male and femaleMale and femalegearsgears

Three step;Three step;

- suction- suction

- compresscompress

- discharge- discharge

CENTRIFUGALCENTRIFUGAL


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CENTRIFUGALCENTRIFUGAL

Impeller and voluteImpeller and volute High speed 10000rpmHigh speed 10000rpm Centrifugal forceCentrifugal force

change the gaseouschange the gaseousrefrigerant into speedrefrigerant into speedenergy, thenenergy, thenconverted to pressureconverted to pressure

energy forenergy forcompressioncompression

HEAT EXCHANGERHEAT EXCHANGER


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HEAT EXCHANGERHEAT EXCHANGER

HEAT EXCHANGER slit finsHEAT EXCHANGER slit fins


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HEAT EXCHANGER slit finsHEAT EXCHANGER slit fins

High heat radiationHigh heat radiationefficiencyefficiency

Compact and lightCompact and light

Low resistance toLow resistance toairflow, reduce noiseairflow, reduce noise

HEAT EXCHANGER HEAT EXCHANGER


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corrugated finscorrugated fins Simple structureSimple structure Low costLow cost


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TUBE hairpinTUBE - hairpin


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TUBE - hairpinTUBE - hairpin

Smooth pipeSmooth pipe

Spiral pipeSpiral pipe


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METERING DEVICESMETERING DEVICES


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METERING DEVICESMETERING DEVICES

Hand expansion valveHand expansion valve Automatic expansionAutomatic expansion

valvevalve

ThermostaticThermostaticexpansion valveexpansion valve Capillary tubeCapillary tube High pressure floatHigh pressure float Low pressure floatLow pressure float

Expansion device capillary tubeExpansion device capillary tube


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1 and 2 same length1 and 2 same length 2 is smaller2 is smaller

1 and 3 same1 and 3 same

diameterdiameter 3 is longer3 is longer



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Expansion device capillary tubeE p p y

Pressure at 1 is lowPressure at 1 is low Pressure at 2 is greaterPressure at 2 is greater

The flow depend on The flow depend on

dimension and lengthdimension and length

Pressure differentPressure differentbetween hp and lpbetween hp and lp



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p p yp p y



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Expans on dev ce cap llary tubep p y



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CompressionCompression isisincreasing theincreasing the

pressure andpressure and

temperaturetemperature ExpansionExpansion isis

decreasing thedecreasing the

pressure andpressure andtemperaturetemperature

REFRIGERANT PIPEREFRIGERANT PIPE


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REFRIGERANT PIPEREFRIGERANT PIPE

Discharge lineDischarge line- normally the same size of liquid line- normally the same size of liquid line- any increase of pressure drop will be a- any increase of pressure drop will be apenalty to the compressorpenalty to the compressor

Liquid lineLiquid line- carry liquid- carry liquid- smaller size- smaller size

Suction lineSuction line

- bigger size- bigger size- carry vapor to compressor- carry vapor to compressor

LIQUID RECEIVERLIQUID RECEIVER


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LIQUID RECEIVERLIQUID RECEIVER

Between condenser andBetween condenser andexpansion valveexpansion valve Act as a liquid supply toAct as a liquid supply to

the expansion valve andthe expansion valve andstoragestorage

Quiz; Do not use lr inQuiz; Do not use lr incapillary systems. Why?capillary systems. Why?

During off cycle, liquidDuring off cycle, liquidwill travel to evaporatorwill travel to evaporator

through cap tube whenthrough cap tube whenstart up, liquidstart up, liquidcompressioncompression

FILTER DRYERFILTER DRYER


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FILTER DRYERFILTER DRYER

Remove moisture andRemove moisture andparticles of foreignparticles of foreignobjectobject

Quiz; Why moisture?Quiz; Why moisture? Cap tube stopped upCap tube stopped up

by iceby ice

Hydrochloric acidHydrochloric acidwill corrodes metalwill corrodes metal Copper platingCopper plating

ACCUMULATORACCUMULATOR


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ACCUMULATORACCUMULATOR

Prevent liquid fromPrevent liquid fromentering theentering thecompressorcompressor

The refrigerant oilThe refrigerant oilwill return throughwill return throughsmall hole at thesmall hole at thebottom of thebottom of the

suction pipesuction pipe

MUFFLERMUFFLER


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MUFFLERMUFFLER

At discharge lineAt discharge line To break upTo break up

pressure pulses thatpressure pulses that

create noisecreate noise


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CHECK VALVECHECK VALVE


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CHECK VALVECHECK VALVE

AllowAllowrefrigerant torefrigerant toflow in oneflow in onedirection onlydirection only


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LOW PRESSURE SWITCHLOW PRESSURE SWITCH


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LOW PRESSURE SWITCHLOW RESSURE SWI H

Install at suctionInstall at suctionpipepipe

Stop when there isStop when there isabnormal lowabnormal low

pressurepressure

Understanding Refrigerations

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