(i)
POLICY STATEMENT
After Sales Service
We, P.A HiltOn Ltd., attaChconsiderable imlXJrt8nce in being able to rctain die confidence and goodwill
of our clientsin offeringan eff~tive after salesservice. Every effort is madeto answerclients
comspondence
promptlyand to POvide a rapid follow up of sparesand repl.:ementpaJUby
mainlainingcomprehensive
stocksof components
usuallyavailableex-stock.
SbouJd c.JrclientSencounterany difficulty in operadngor mainlaining a Hilton prodoct we would ask
that as a first step
they
con~t
the Hilton
Hilton Ltd.
lepresentativein their country or, in the ab~nce of a local
~ntati't'e,
write
direct
to P.A.
.
In die extreme~ a problem may arise in the ~m
of equipmentwhich could seriouslydisrupt
a te.:hing or researchschedule.In suchcircwnstancesrapid advicefraIl the manufacturm is desirable
and we wish our cUents10know d1atHiltons' will acceptfrom them a transf~ chargetelephonecall
from anywherein die wmld.
We ask OlD'clients to trea1d1is servjce as an en1~gelx:y service only and to use it sparingly and wisely.
Pl~
do be awue of the time diff~rx:es that may exist and. before making a telephone call, make
notes of the JX'Oblemyou wish to describe. English is a preferred language. Our te)eP1one number is
~~y
(01794) 388382"andme telephOOC
is normallymannedbetWeen
0800and 1700hrsGMT
every day. Advux:e notice of an impending telepoonc call by Fax would be appreciated.
Eachproduct manufact1D'ed
by P.A. Hilton Ltd., is testedunderopenlting conditionsin (XU'permanent
in...~ons before ~h.
Visitors to HorselxidgeMill are encomagedto opeI31C
and evaluateour
equipmentwith initial guidancefl'oo1a Hilton engi~.
(ii)
EDUCATION AND TRAINING EQUIPMENT
In a:cordancewidt the ElectromagneticCompatibility (Amendment)ReguJations1994 (51 No 3080)
andEMC Directive89f334'EEC
andCE MarkingDirective93/68/EEC.
This aPJIIrahJS
complies with the abovedirectives under die following clause:
The useof the ~
outsidedie clusroom. JatKJratory.
sUJdyarea<X'similar such
place invali~
confonnity with the protectionrequirementsof the Elecb'Omagnetic
Compatibility Directive (89/336'EEC)and could lead to prosecution.
P.A. HILTON LIMITED
HorsebridgeMill, King's Sombome,
SO20 6PX,
Stockbridge.Hampshire,
England.
Tel No; National Romsev (01794) 388382
International
+44 1794 388382
Fax No. +44 1794 388129
(ill)
INDEX
~
SAPF:rY IN THE USE OF EQUIPMENT
1
THE FREE AND FORCED CONVECTION HEAT TRANSFER UNIT
6
Introduction
6
Receipt of Equipment
6-
Description
7
InstaUation Requirements
7
Commissioning
EXPERIMENTS:
11
13
1. To demonsttatethe relationshipbetweenpower input and surfacetemperature
in free convection.
IS
2. To demonstratethe relationshipbetweenpower input and surfacetemperature
in fm'Cedconvection.
17.
3. To demODSttate
the useof extendedsurfacesto improve heat ttansferfrom
the surface.
19
4. To detemrinethe temperaturedistribution along an extendedsurface.
21
S. Comparisonof a horizontal and flat plate in free convection.
23
DIAGRAMS:
RCCB Installation
TransformerConnections(llOV units)
24
24
2S
~
1
SAFETY IN THE USE OF EOUIPMENT
Before~~n~
to inslall. commissionor opet8tedie ~uiJXDentdescri~ in dtis instnK:tionmanual.
we requestyou to read dJefollowing notesto alen you to potentialhazardsso that dley may be avoided.
AlmoUghdesignedfor safe ~,
any laboratory equipmentmay involve ~ses
or pnx:edures
which are potentially hazardous. The map potential hazardsare listed below. Those .-nicularly
relevant to d1isitem of e(luipnent are highlighted for your infonnatioo by the following symbol - .
. INJURY nmOUGH MISUSE
. INJURY FROM ELECIRIC SHOCK
0 FIRE OR EXPLOSION FROM HIGfn. Y INFLAMMABLE UQUIDS OR V APOURS (c.g.
KEROSENE)
0 rolSONING FROM TOXIC MATERIALS (c.g. MERCURY)
0 INJURY FROM HANDLING LARGE OR IlEA VY COMPONENTS
. INJURY FROM ROTATING COMPONENTS
. BURNS FROM COMroNENrs AT HIGH TEMPERAruRES
0 SCALDING FROM BOILING UQUIDS OR HOT V APOURS (c.g. S1EAM)
0 INJURY FROM FAST MOVING AIR STREAMS OR HIGH PRESSUREAIR HOSES
0 INJURY FROM CORROSIVEUQUIDS
0 DAMAGE 1'0 BYESIGIn"
0 DAMAGE 1'0 HEARING
0 DAMAGE 1'0 a.oTHING
ACCIDENTS CAN BE A VarnED JXOvi~ that equipment is leguJariy maintained and staff and
sblden~ are madeaWaleof potcntial hazards. A list of generalsafetyrules is inclu~ on Page2 to
assistsIaff and sbJdenuin d1isregard.
The list is not intendedto be fully comprehensive,but for guidanceonly.
2
GENERAL SAFETY RULFS
1. Follow RelevantInstructions
(a) Beforeattemptingto install, commissionor operateequipment,all relevantsuppliers/manufacwrers
insb'UCtiODS
and local lCguJaUODS
should be understoodand implemented.
(b) It is irresponsible and dangerousto misuse equipment or ignore instructions, regulations or
warnings.
(c) Do not exceedspecified maximum operatingconditions (e.g. temperawre,pressW'e,speed,etC.).
2.
Installation
(a) Use lifting tackle where possibleto inslall heavy equipmenL Where manual lifting is necessary
bewareof suainedbacksand crushedtoeS. Get help from an assistantif necessary.Wear safety
shoeswhereappropriate.
(b) Extreme care should be exercised to avoid damage to the equipment during handling and
unp.:king. When using slings to lift equipment,ensurethat the slings are attachedto sbUctural
framework.and do not foul adjacentpipework, glassware,etc. Whenusingfork lift bUcks,position
the forks beneathSb'Ucturalframework ensming that the forks do nOt foul adjacent pipework,
glassware,etc. Damage may go unseenduring commissioningcreating a potential hazard to
subseqoontOpeIators.
(c) Where special foundationsare requjred follow the instructionsprovided and do not imJXOvise.
Locate heavy equipment at low level.
(d) Equipmentinvolving inflammableor con-osiveliquids should be sited in a containmentarea or
bond with a capacity of SO%greaterthan the maximum equipmentcontentS.
(e) Ensure d1atall services are compatible with the equipment and that independent isolaUX"Sare always
provided and labelled. u~ reliable conn~tions in all instances, do not improvise.
(1) EnsuredJatall equipmentis reliably eanhedand connectedto an elecbical supply at the C<ITeCt
voltage. The electrical supply must inc<Xparatean Earth LeakageCircuit Breaker (ELCB) or
ResidualCurrentCircuit Breaker(RCCB) to protect the operatorfrom severeelecbic shockin the
event of misuseor accident
(g) Potendalhazardsshouldalwaysbe die flISt considerationwhendecidingon a suitablelocation for
equipment Leave sufficient spacebetweenequipmentand betweenwalls and equipment
3.
Commissionin2
(a) Ensure that equipment is commissionedand checked by a competentmember of staff bef(B'C
pennitting studentsto Operateit.
4.
Ooeration
(a) Ensurethat swdentsare fully awareof me potential hazardswhen operatingequipment
(b) Studentsshouldbe supervisedby a competentmemberof staff at all times when in the laboratory.
No one should operateequipmentalone. Do not leave equipmentrunning unattended.
3
(c) Do oot allow snxIentSto derive their own experimentalproceduresW11ess
they are ccxnpetentto
oo~.
(d) Scrk>usinjury can result from tOochingapparentlysWiooary equipmentwhen usinga sIroOOscqJe
to 'freeze' rotary motion.
5. Maintenance
(8) Badly maintained~uipment is 8 JK>tentialhazard. Ensure mat 8 competentmember of staff is
leSIXXlSible
for m-ganising
maintenance
andre~ 00 a plannedbasis.
(b) Do oot permit faulty equipmentto be operated Ensuremat repairsare carried oot competentlyand
checkedbefore studentsare pennitted to operatetlte equipment
6.
Usin2 Elecbicitv
(8) At least (XlCCea;h month, c~k that ELCB's (RCCB's) are operating correctly by pressingthe
TEST ootton. The circuit breakermust Dip when the button is pressed(failure to Dip meansthat
the ~
is DOt~Ied
and 8 ~
must be effectedby 8 competentel~Dician before the
equipmentor el~Dical ~ly
is used.
(b) EJectricityis tile commonest~
and sbldentsrespectiL
of accidentsin the laboratory. Ensuredw all membersof staff
(c) EosauedJatdie el~aical supplyhasbeenuonnecled from die ~uiJXDentbeforeattempang
IeIBirs CX'adjustments.
(d) WaI« and electticity are not compatible and can causeseriousinjury if dtey come into contacL
Nev« ~
ponablc electtical awliances adj.:-ent to equipmentinvolving water unlesssome
form of constraintor barri« is incorporatedto prevent~cidental contaCL
(e) Always discoonectequipmentfrom the elecbical supply when not in use.
7.
A voidin2 Fires or ExDlosion
(a) Ensmed18tme Jabomt«y is provided with adequatefire extinguishersappropriateto me potential
bazaIds.
(b) Where inflammableliquids are used,smoking must be forbidden. Notices shouldbe displayedto
enforcethis.
(c) Beware siIr.e fine JX>wders
or dUStcan sJX>ntanoously
ignite under certain cooditions. Empty
vesselshaving containedinflammable liquids can-contain vaJX>ur
and explode if ignited.
(d) Bulk quantitiesof inflammableliquids shooldbe stOredou~de the lab<ntory in 8::cordancewith
local regulatioos.
(e) Storagetanks on equipmentshouldnot be overfilled. All spillagesshould be immediatelycleaned
up, carefully disposingof any contaminatedcloths, etc. Bewareof slippery floors.
(f) When liquids giving off inflammable vapoms are handledin the laboratOry.the area should be
ventilated by an expl~ion-proof exb'.:tion sySIem. Vents on the equipmentshould be connected
to the exttaction system.
4
(g) StUdentsshould not be allowed to prepare mixtures for analysis or other purpose without competent
supervision.
8. Handling;Poisons.Corrosive or Toxic Materials
(a) Certainliquids essentialto me opezationof equipment,for examplemercury,are poisonousor can
give off poisonousvapours. Wear 8ppr\)fn-'l8te
protectivecl<Xhingwhen handlingsuchsubstances.
Cleanup any spillageimmediatclyand ventilate~
Bewareof sliRJeryflOOlS.
thoroughlyusingextractionequipment
(b) Do IK>tallow food to be brought intO(X'consumedin the 1a0000tOry.
Never usechemicalbeakers
as drinking vessels.
(c) Where poisonousYalX>ulsare involved. smokingmust be forbidden. Noticesshould be displayed
to enforcethis.
(d) Poisons and very tOxic materials must be kept in a locked cupboard or store and checked regularly.
Use of s.x:h substances soould be supervised.
(e) When diluting concentratedacids and alkalis, the acid or alkali should be addedslowly to water
while stirring. The reverseshould neverbe attempted.
9. AvoidinR Cuts and Burns
(a) Take care when handling sharpedgedcomponents. Do not exen undueforce on glassor fragile
items.
(b) Hot surfacescannotin m~t casesbe totally shieldedand can produceseverebums even when not
'visibly' hot Usecommonsenseandthink which.-ns of die equipmentare likely to be hot.
10. Eve Protectioo
(a) Gogglesmust be worn whenev~ mere is risk to die eyes. Risk may arise from powders.liquid
splabes. vapomsor splinters. Bewareof debris from fast moving air StreamS.Alkaline solutions
are ~u1ar1y dangerousto the eyes.
at a sarong~
of light such as a laser or Xeoon art: lamp. Ensure that
equipmentusing sucha sourceis JX)sitioned
so that passers-bycannotaccidentallyview the source
or Ietl~red ray.
(b) Never kX>k ~y
(c) F~Ji~! for eyeirrigationshooldalwaysbe available.
11. Ear Protection
(a) Ear JXOIeCtors
mUStbe worn when operalingnoisy equipment
12. Clothing;
(a) Suitableclothing should be worn in the laoorarory. Loose garmentscan causeseriousinjury if
caughtin roWing ~hinery.
Ties, rings on (mgers,etc., shoold be removedin thesesitUations.
(b) Additionalprotectiveclodting shouldbe availablefor all membersof staff and studentsas
appopriatc.
,
s
13. Guardsand SafetYDevices
(a) Guardsand safetydevicesale installed on equipmentto protect dte operator. The equipmentmust
DOtbe ~
widt slx:h devicesremoved.
(b) Safety valves. cut-outs or odler safety devices will have been set to protect the equipment
Incerf~1x:e with dIesedevicesmay a'ea1ea potential hazard.
(c) It is not possibleto guard me operatcxagainstall contingencies. Use common senseat all times
when in me 1aboratay.
(d) Before swting a rolating machine,make sure staff are aware bow to stop it in an em~gerx:y.
(e) Ensurethat ~
control deYkesare always set at zero before starting equipmeoL
14. First Aid
(a) If an accidentdoesoccur in the Iaborat(X'yit is essentialthat first aid equipmentis available and
d181d1e~CX'
knows how to use iL
(b) A nodce giving details of a JX'Oficientfirst-aider should be prominently displayed.
(c) A 'short list' of die antidotesfor the chemicalsused in a particularlaboratoryshouldbe
prominendydisplayed.
6
R920 FREE AND FORCED CONVECTION REA T TRANSFER UNIT
INTRODUCTION
Heat ttansferby simultaneousconductionand convection,whed1erfree or forced, fomls the basis of
m~t indusuial heatexchangersandrelatedequilXtlent.The measurement
andpredictionof heattransfer
coefficientsfor such circumstancesis achievedin d1eHilton unit by studyingd1etemperawreIX'Ofiles
and beatflux in an air duct wid1associatedflat and extendedttansfersmfaces. The vertical duct is so
constructedthat d1eair tempeI8bUeand velocity can be readily measured.and a variety of "plug-in"
mooulesof heatedsolid surfacesof known dimensionscan be JX'eSented
to d1eair stteam for detailed
StUdy.A fan simatedat d1etop of die duct providesd1eair streamfor forcedconvectionexperiments.
An independentbench-mountedcoosolecontains temperawremeasW'ement,
power control, and fan
speedcontrol circuits with ippiUfK"1ate
insuumenration. TemperatW'emeasW'ement,
to a resolution of
O.loC, is effectedusing themlistor sensorswith direct digital read-outin °C.
Air velocity is measuredwith a portableanemometermountedon the duct
The}X>wer control ciICuitprovidesa continuouslyvariable,electricaloutputof 0-100Watts with a direct
~-out
in Watts.
Using the insuumentationprovided. free and forced convective heat transfer coefficients may be
detenninedfoc
A Oat smface
An army of cylinders (pinned heat sink)
An army of fins (rmned heat sink)
ElK:hmodule may be usedindependently,on the bench, to establishfree convectioncoeffICientsfor
horizontalorientation.
The apparatusis fully self-contained
RECEIPT OF EOUIPMENT
Salesin die United Kin2dom
The apparatusshould be carefully unpackedand the componentscheckedagainstdie PackingList
Any omissionsor breakagesshould be notified to P.A. Hilton Limited within three days of receipt.
SalesOverseas
The awaratm shouldbe carefully Wl~
and the componeRtscheckedagainsttheP.:king LisL
Any omissionsor breakagesshould be notified immediately to me InsuranceAgent stated on me
InsuranceCertificate if me goods were inslD'edby P.A. Hilton Limited.
Your own insure:sshould be notified immediatelyif insurance was arrangedby yourselves.
7
DESCRIPnON
(Refer to Fig.l, Page8)
The apparabIScoosistsof a v(ztjcal rectangulard~t supportedby a bench mounted stand(1). A flat
plare (3), pinned (4), or finned (5) exchangermay be installed in d1ed~t and securedby a quickreJeue CaICh(18) on each side. Ea::h exchanger incorporatesan elecbic healing element with
tbennOStaIic
pro~tion againstoverheating.The tempc~
at thebaseof ~h exchangeris monitored
by a ~
~
(19) with connectinglead (7).
The exchangerin use may be viewed through an -=rylic wiIKIow (14) in d1ewall of the duCL
An upward now of air may be generatedin the dtK:twith a variable~
fan (21) mounted at the top.
Air velocity in the duct, whethernatlD'8lor forced, is indicated00 a JX)rtableanemometer(2) held in
a lxacket (15) on the duct wall. The ~mometer sen.wr(16) is inserteddlrough the wall of die duct
A th«mistor probe (6) ~ts
measurementof the in-goingandout-goingair temperatures,
together
with surfacetemperabJreS
of exchangerpins and fins.
Th~
remperatmes are detennined by insezting die probe dtrough access iK>les (20) in the duct wall.
An electric console (8) inc(XJ)Oratesa solid Stale IX>werregulator with a digital read-out to coob'Ol and
indicate power supplied to the exchanger on tesL The exchanger is connected to die coosole via die
supply lem (10). A variable low voltage D.C. supply is provided for the fan via the supply 1eOO(17).
A digital read-out indicates the temperature using a thenniStOr probe connected to a flexible lead (6).
Power is sUWUedto the equipmentvia a supply lead (9) connectedto the rear of the coosole.
INST ALLA nON REOUIREMENTS
The equipmentshouJdbe installed 00 a finn, level work surface.
A singlep~
el~lrical supplyis requiled.
No other services arc necessary.
11
COMMISSIONING
(Refer to Fig. 3. Page 10)
22O/240VUnits
A Residual Current Circuit Breaker is provided to be wall mountednear to where the unit will be
located. Connectthe 3m lengthof cablep-ovided to a suitablefIXedpower supply via a fusedisolating
oudet for SA which complies with the l<x:alelecttical installationregulations.
Brown cable
BI~ cable
GreenlY ellow cable
LIVE or LINE
NEUI'RAL
HARm or ground
Connect the Live and Neutral of me other end of this cable to the tOp terminals of the RCCB. The
earthwire is connectedto the separatetenninal strip (seeDiagramRCCB107at the rear of me manual).
The power cable will be found emerging from the rear of the uniL This is connectedto the lower
tenninals of the RCCB and the earth tenl1inalsttip.
110/120VUnitS
A suitablyrated ttansfonneris sUWliedwim me unit and allows input voltagesof between110and 130
VoltS (in 5 volt steps)to be connected.
The unit and RCCB are connectedin the samemanneras descn"bed
for 22OV units above. However,
the 3m cable is connectedto the output of die transformerand not directly to the supply.
Before conn~ting the SUWlycable to the ttansformer, the local mean voltage should be measured.
When this hasbeendetennined.the Live input of the supplyshouldbe connectedto the terminal having
the nearestvoltage label. The Neutral of the supply is connectedto the OV tenninal and the Earth or
Ground of the supply is conn~ted to the tenninallabelled"En or ~
(seedjagramTRANIOOat the
rear of the manual).
The supply cable. cable gland and switChedand fusedoutlet shouldbe suitable for supplying lOA and
be to a standardcorrespondingto the local regulations.
The transfonner should be placed in a JX'Otected
JX)sition,but whereair can circulate freely.
The RCCB is operatedby use of the ONIOFF lever.
In die event of an eard1leakageoccurring, die RCCB will switch off, isolating die supply from die
RCCB onwards. However,dlis will only operatesuccessfullyif die unit is connectedto a good eardl.
Should die RCCB trip. die mains supply to the unit shouldbe disconnectedand the causeof the fault
detennined. The RCCB can then be reset to the "ON" position and the unit operated.
Every three mondtsthe RCCB shouldbe checkedby a competentperson. To do this, switChon roth
at the mains and the unit Pushthe "TEST" buttOnon dIe RCCB and ensurethat the unit is isolated.
If d1epower remainson.d1eRCCB is faulty and will need to be replacedby a qualified electrician.
12
Having coonectcd the exchanger to the electrical supply. correct operation should be checked as follows:
Tmn the heaterpower coob'Ol(A) and fan speedconttol (B) fully anti-clockwise.
Connectdie fan supply lead (17) at die baseof the duct to die socket(C) beneathdie fan speedcontrol
on die instrumentconsole.
Connectthe thermistorprobelead (6) to the socket(D) beneathme temperaturemeteron the instrument
colWole.
Conn~t d1eheatersupply lead (10) to d1e~ket (E) beneathdie power control knob on the instrument
console.
Clamp die flat plate heatexchanger(3) into the duct using the two toggle clamps(18) and connectthe
supply lead to the socketon the cover.
C~t
the exchangertemperabJrelead (7) to the socket(F) on the heat exchanger.
Install die folD' batteries in die anemometer (2) as shown on die cover. Carefully lOCaledie anemometer
~on
(16) into die bush fitted into die duct. and place me meter into die bracket (15) situated on die
side of dte duct.
Depressthe black and red buttonson eachside of the anemometer,this will checkthe condition of the
battezyautomatically. If the lX>interis within the greensectoron the meterthen the battery is in good
condition. If die needleis not in the greensectorthis indicatesthat the battery needsreplacing.
To set d!e anemometerto die zeroposition. fit the blanking cup over the probe headto isolate it from
any air movement Pressthe red buttonand adjustthe knmled wheelat the top of the anemometeruntil
d!e pointer is aligned wid! d!e zero on die scale.
Switch d1eequipmenton by depressingthe ON/OFF switch on die left hand side of the console.
Check d1atthe L.E.D. temperablremeter and wattmeterare illuminated. Check d1atthe tempemtme
meter indicatesambienttemperablre.
Inaease d1eheaterIX>werin the exchangerby rotating the IX>wercontrol knob clockwise. The power
suppliedto the exchangershouldbe shown in watts on the meter.
Switch on die fan and iIK:reasedie speedby rotating die fan speedconb'Olknob (B) clockwise.
Depressme red button on the side of the anemometerand observethat the air velocity is indicatedon
the metel'scale.
Connectthe exchangertemperabD'e
lead (7) to me socket(D) on me console. Checkthat me
temperature
meterindicatestheincreasing
temperabJre
of theheatexchanger
melalwork.
Set the heaterpower control knob and fan speedcontrol knob to minimwn (anti-clockwise).
Set the ON,.oFF switch on the consoleto die OFF position.
Commissioningof die equipmentis now complete.
(
13
8920 FREE AND FORCED CONVECTION MEAT TRANSFER UNIT
Ex~riments:
1.
To demonstratedie relationshipbetweenpower input and surf.:e temperabJrein free convectioo.
2. To demonstratethe relationshipbetweenpower input andsurf~ tempel31urein f<Xcedconvection.
3.
To ckmoDSb'ate
dle ~
4.
To determinethe temperaturedistribution along an exteOOed
swface.
s.
C~D1
of extendedsurf~
to improve tM:a1
transfer from dle surf.:e.
of a horizontalaIxi flat platein freeconvection.
NO~
This instructionmanualrefersto 5 ex~ents
whkh canbeperfonnedwith the unit
1. Free convection from a vertical OatsurfKe
2. Fcxcedcon~tion fnxn a vertical flat surface
-
3. Fretlfcxcedconvection Conslant c~s section (Pins)
4. FretlfOrted convection - Varying crosssectioo(Fins)
E. Free convectionfrom a 00riz0n1alflat surfKe
Widt the Oat surfaceexperimentS(I, 2 and 5) it may be found difficult to achieve stabletemperature
coOOitionsdue to thennal inatia and the inherently low convectiveheat transfer~ff1CienL Because
of ~ ~nsitivity of d1ehealerJX)werCORttOl,
care is requiredto ~hieve stable temperabD'es.
N.B. (a) Current poduction modelsare fitted with a 10 turn JX>tentiometer
to reducesensitivity.
(b) Power input requiredfor steadystatecooditionsbetweenSOOC<~900Cwill be found to vary
between8PIXOximatelylOW and 2OW. Very delicate adjusunentis required of the JX>wer
connol. especiallyat the lower temperatures.
(c) The heatersin the experimentalmoduleshavea temperaturelimit device which interruptsthe
po~ supply at lOOOCand remakesit when ~ temperat1D'e
has fallen to aOOut8SoC.
(d) ClDtent prociuctioomodelsare fitted with a wattmeterwith a 3 digit display iOOicating00.0
to 99.9 Waas. The display will indicate 00.0 at zero or lOOWwhich may be distinguished
by the position of the potentiometercannot knob. With the knob turned fully clockwise.the
meta: will measurebetween110 and 120 Watts (indicatedby 10.0 to 20.0)
The generalJI'OCedure
enumeratedbelow should be found helpful in the rapid establishmentof s~y
tempezaturecorxIitions.
GeneralExnerimentalProcedure
1. Note ambientair temperature(I.).
2. Set fan control and note velocity.
3. Set ~
IX>wercontrol so that the Wattmeter indicatesabout 80 to 9OW.
4. Observethe rise of heatertemperawre(~ indicatedby the digital thennometerand when this reads
IPII'Oximately45°C. reduceIX>werinput to zero. It will be seenthat the rate of temperaturerise
willledoce to zero at a heatertemperabJreof aPIJ'Qximately
500c.
5. Carefully adjustthe heatercontrol to stabilisethe temperahD'e
at about500Carx1nOteInput Power.
Q Watts, and heatertemperature.ltt. when the readingsare steady.
6. ~
this proceduref(X' incrementsof heatertemperatureup to a maximum of 900C.
14
Free Conv~tion
In this ~
die fan shouJdbe switcheddr. 01eck that the anemometerindicateszero vekx:ity.
~
Convection
Fan speedmay be controlledto provide a rangeof ~s
fcx inClemen~of air velocity. The readings
may be of remperanueagainst a JX>wersetting, or JX>werrequired to achieve a steady remperatme
coOOitioo.Incrementsof velocity betw~ about 1.0 m/s and maximwn (awroximately 2.5 m/s) are
~ended.
TemoeratureProbe
111epobe is intendedfor d1emeasmementof temperat1Be
within the duct and may be insertedthrough
the tappingpoints on the left-handside. The probe tip shouldbe smearedwith a little beatconducting
paste!ran me blbe povjded if smfa::eternperablreS
are to be measured.
,
.
15
L
TO DEMONSTRATE THE RELATIONSIUP BETWEEN POWER INPUT AND SURFACE
TEMPERATURE IN FREE CONVECTION.
EauiomentSet-Un:
Summaryof Theorv:
A heatedsurfacedissipatesheatprimarily througha processcalled convection. Heat is also dissipated
by conductionand radiation,howevertheseeffectsare not consideredin this experimenL Air in contact
with die hot surf~ is heatedby the surfaceand rises due to a reductionin density. The heatedair is
Ieplacedby cooler air which is in bJm heatedby the surfaceand rises. This processis called free
convection.
The honer me temperabJre of die surface. me greater me convective currents and me more heat (power)
will be dissipated.
If morepower is suwlied to a surface,the temperatureof the surfacemust rise to dissipatethis power.
Readin2sto be taken:
p~ the finned heat exchangerinto the teStdUCL Record the ambientair temperawre(t,.). Set the
heaterpowercontrol to 20 Watts. Allow sufficient time to achievesteadystateconditionsbeforenoting
the heatedplate temperature(fH). Repeatthis procedureat 40. 60 and 80 Wans.
Results: Ambient air temperawre (t,.) =
oc
Input Power
HeaterTemp. (ftt)
W
°c
20
40
60
80
~-~
°C
17
2.. TO DEMON~
TE THE RELA TIONSIUP BETWEEN POWER INPUT AND SURFACE
TEMPERATURE IN FORCED CONVEC"nON.
EauiomentSet-Un:
Summaryof Theorv:
In free convectioo the heat transferrate from the surface is limited by the small movementSof air
generatedby d1isheaL More heatis transferredif the air velocity is increasedover the heatedsurface.
This ~
of assisting die movementof air over the heatedsurfaceis called Forced Convection.
Thereforea heateds~
experiencingforced convectioowill havea lower surfacetemperaturethan
that of die sames~
in free convectionfor the samepower inpuL
Readin2sto be taken:
Place dJefinned heat exchangerinto me duct Note me ambientair remperature(tJJ. Set the heater
power control to 50 Watts. Allow sufficient time to achievesteadystateconditionsbefore noting the
heatedplate temperature(fH). Set me fan speedcontrol to give a reading of 0.5 m/s on the thermal
anemometer,allow sufficient time to .:hieve steadystareconditions. Recordheatedplate temperature.
Repeatthis procedureat 1.0 m/s and 1.5 m/s.
Results: Ambient aU temperabJIe (tJ
=
Power input WatU
=
Air Velocity
m/s
0
0.5
1.0
1.5
oc
Watts
HeaterTemp. (~)
°C
~-~
°C
18
PlOt a rraph of air velocity against temperabD'e.
0
10
20
'30
1.0
50
60
70
80
°C
,
19
3. TO DEMONSTRATETHE USE OF EXTENDED SURFACES TO IMPROVE REAT
TRANSFERFROM THE SURFACE.
EauitJlnentSet-Un:
Swnmarv of Theory:
Heat transfer from an obj~t can be improved by increasingthe surfacearea in contact with the air.
In practiceit may be difficult to increasethe sizeof thebody to soil In thesecircumstancesthe surface
area in contact with the air may be increasedby adding fIDSor pins nama! to the surface. These
feanuesare called extended~
A typical exampleis the useof fins on the cylinder and headof
an air cooledpetrol engine. The eff~t of extendedsurfacescan be demonstratedby comparingfinned
and pinned surfaceswith a Oatplate under the sameconditionsof power input and air flow.
Readin2Sto be taken:
Pl.:e dte flat plate heat exchangerinto dte dl.:t Record dte ambient air temperawre(t~. Set the
heaterpower control to 75 Watts. Allow the temperabJre
to rise to 800C,men adjustthe healerpower
control to 20 Watts 1D1tU
a steadyreading is obtained. Recordheatedplate temperabJre
(fH). Set me
fan speedcontrol to give 1 m/s using the thennalanemometer.Repeatthis procedureat 2 and 2.5 m/s
for the flat plate. Replacedie flat plate with the finned plate andrepeatexperiment Replaceme finned
plate widt the pinned plate and repeatexperiment
=
Results: Ambient air temperanlre(t...)
Powerinput
=
Air Velocity
m/s
0
1.0
2.0
2.5
oc
20 Watts
HeaterTemp. (~)
°C
~ - tA
oC
20
Plot graIiIS of vekx:ity againsttemlaablre for each of the plates.
Comment00 die corre1atioobetweentotal surface area of the heat exchangerand the temperature
achieved.
Further ExDerimen~:
Inaeae power inlXlt and repeatexperiments.
Air
Velocity
m/s
I
21
4. TO DETERMINE THE TEMPERATURE DI~UTION
ALONG AN EXTENDED
SURFACE.
EauiomentSet-Uo:
Summaryof Theory:
For a heatexchangerto be 100%efficient me completeextendedsurfacetemperaturemust be the same
as die t.ck plate. In practice,however,dlis doesnot occur becauseheatmust flow along a pin or fin
by condtx:tion,which causesa temperaturegradientto occur. The steeperthe gradientthe lessefficient
the heatexchanger. The efficiency, however,must not be confusedwith surfacearea,e.g. comparing
pinned and finned. In reality die pin is more efficient. but in dlis particularcaseme fm is marginally
mCX'e
efficient becauseof its surfacearea.
Readin2Sto be taken:
Measurefrom the back plate me distancesof the three accessholes on me pinned and finned heat
exchanger.Place the pinned heatexchangerinto the duct Note the ambientair temperature(t.,.). Set
the beaterpower control to 60 Watts. Allow sufficient time to achievesteadystateconditionsbefore
noling the heatedplate temperatlD'e(ftt). Insen me temperawreprobe into me duct through me hole
nearestthe heatedplate, ensmingthat the tip of the probe is in contactwith the pin. A small amount
of heatconductingcompoundon me tip will ensurea good thennalcontaCt Note this temperature(tJ.
Recordme pin tempcrahD'eS
(~and t:s)using the remainingtwo holes. Repeatthis procedureat 1.0m/s
and2 m/s.
Remove the pinned heat exchangerand rep1a:ewith the finned heat exchanger. Repeatcomplete
experiment
Results: Ambient air tem~
(tJ =
=
=
=
°C
=
mm
Powerinput
DisWlceof nearesthole
Distanceof middlehole
Distanceof farthesthole
Watts
mm
mm
22
Temperature°C
AU Velocity
m/s
It
~
t,
~
0
1.0
2.0
Plot graPIs of surface temperabJre against disrance from back plate for die two heat exchangers at
various air velocities.
°C
For a htat exchanger to be 100% efficient, the whole of me extended surface must be at the same
tempel'abJreas the back plate.
In prw:Dce d1is C8lJDOt(X:Cm'because the flow of heat along the pins or fins by conduction
tempel'atme gradjcnt to occur.
The greater d1is gradient, the less efficient
causes
a
the heat exchanger will be.
The efficiency of the heatexchangermust not be confusedwith the effect of a changein surfacearea.
For example,if the pinnedand finned heatexchangerssuppliedwith the equipmentare compared,the
pin is more efficat than the fin (slightly smaller tcmpelaturegradient),but the finned exchangerhas
a si-snificantly larger surf~e area than the pinned exchanger and can dissipate more heat for the same
surface tcmperabJre.
23
S. COMPARISON OF A HORIZONTAL AND FLAT PLATE IN FREE CONVECTION.
EauinmentSet-Un:
Summarv of Theory:
When a temperawre differerx:e is established between a wall and a stationary fluid, the fluid adjacent
to the wall will move upward if the wall temperat1D'eis higher man that of the fluid. and downward if
the wall temperawre is lower. Density gradients are set up in the fluid resulting in booyancy forces and
free convective currents. The rate of heat transfer depends mainly on the fluid motion. The oriencation
of the plate affects this movement of air. A horizontal plate restricts the movement of air and reduces
the heat transfer. The same plate mounted vertically will give improved heat transfer.
Readin2s to be taken:
Place the flat plate exchanger horizontally onto a suitable surf~.
Record die ambient air temperature
(tJ. Set the heater power control to 15 Wans. The smface temperature of die flat plate (~ can be
recorded using the tcmpClanJre probe. the tip of die probe being held in contact with the surface by
hand. To ensure good conta:t the thermal comppound should be used. Allow sufficient time to achieve
steady state conditions before noting die heated plate temperature. The plate temperature should be
taken at the centre of the plate. Place the flat plate vertically taking care not to touch the heated smface
widt yourbands.Re~
theexperimenL
Results:Ambientair tem~
Power input
(t.J =
=
°C
15 Watts
HeaterTemp. (~)
°C
fn-t;.
°C
Horizontal
Vertical
Commenton the effecu of plateorientationon ~e
temperabJre.
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FREE AND FORCED CONVECTION HEAT
TRANSFER UNIT,
Series H920
Unit No.
c"~""~'.-~~.4--
~
.Q!l
H820T
I." 1
1
I~ 5
18m 6
I~ 7
len 8
18m 9
I~ 10
I~ 11
I~ 12
111,,11
E4J8
ES/95
H920J3/1
H96OI3/1
1
1
1
1
1
3 core C8J1e,3m long
EaItI ~
for Erx:kllure
Clear P\8tic Cover
Clear PlMtic InsU\mentCall«
ProductEnvelopecon~~:
-1
Experi~n",
i4.~
SPARES:
Item 13
UM on .~
RCCBEncIc»ure
-.
aperaq atxtMai*n.,~ M81ua1-EngiIh,Ref:H920M'E/.3t£.~3
i.'=--:;:-'=ft~,g,eM::'-.1:,.-.;::~.18:;:x..;.;:.-;.
~.1£..-;- ;;-::'--=-:8ft. :"'.=t,Ileae~."-'--,'--'---
1
1
.
PackingUst
Tat Sheet
'."!:.-:.. ~i8;.-::.-:,:,
~,,~18
.
age'.':~.;;.-.8:~-;-;-~r44:':.-=':ttte':a.-.i.o.-.:-1t
1 set
2 -
1
.~.~.
H,,"o /.>"1""
Air velocitymeterwid1~
Flat plate exchangermodule
Pimed exd\8nger moctIle
Finnedexchangermodule
Probelead
Exchanger~Pef8ture I88d
EI~c8I console
Man input I88d
Heaterlead (fitted)
Heat sink com~
(~
tube)
EaItI Leakagec.cuit Q'e8k8r
~
.'
Lflf..l,~~
DIIC;.~
Frw and FOC'ced
ConvecDI H88t rr-'-
ACCESSORIES:
18m 2
1-"
1 r
I~ 3
I~ 4
1
1 -
Job No.
Spaf8 comprising:
Wsh boier elementWE51/375
Therm. safetyswI'=hNo. ~314
Heat sink com~
(20m -.be)
1.5V 'M' BaiBrie8 (E5/90)
Fan motor
181:'-::-
~
TEST
(16"'" 184)
FREE AND FORCED CONVECTION HEAT
TRANSFER UNIT, Series H920
--
Job No.
If~
G'
Unit No. .J.Itf~ Q,/ 1.s7.1.4
-Aeeulta
EARTHCONTINUITY
Check1\. the h)/kJwing
are com~
Console~
to 1\. 8arf\ of 1\. lead ~.ac:
to 1\. mamin.:
8td front panel
Flat, PlMed and FinnedHeaterModules
o£(
~
DigilalThennome~
;../
Check for ~ntW'luity will me18r.
VISUALCHECKS
Visuallyched<die foIbwing:
Consoleand duct (Includng PerspexwindoN)for any dents and Sa'a~.
Locationand ftt of h
Them.a- ~ome.r
flree healermodJlesin h
Ioca- wl~i
duct.
in tie bfad(et.
<:"~
~.
'7
Checkdlat h ~nect voltageand W8nilg labelsare fitted m ~ malne.
OPERAT1ONALCHECKS
Sean
U1eFlat PIa~ heater mociJIe m u. diet 8Id ~nect
fte hea~r and ~peraUJre Iea$ m 118ccnaoIe.
Connect =nsoIe to mans elecmcaIsupplyand swi~ on. The nea1 lamp shouldiDuninate.
Fit tie anemoIMl8r10d'Ieduct, and "m on. Selectd'Ievelodty scale. Slidetie ~ver overtie sensinghead and
zero tie meI8r. SIde bad( d'Iecover 10exposed'Ieheadand fit p~ ink) duct witl ~
in cirectionof airftow.
Apply powerto tie hea.. (Note tlat d'IeWattmeIBrreads010 99.9 W. and valuesabove99.9 W will comme~
againat 0.) Ched<mat d'Ie_mperabJrerises. Ensuremat the d'lenna cut-outopera~ at 100OC:t10.C.
T~ on fie fan n
ensureanemometershowsdlanging air velodly. (showdream 2.2 m/s at maxmwn flow witt!
fie Rat plate). Q)serve that fie heater temperabJrefalls and the heater cu1Sin at approx 8500 %SoC.Tum off Ite
hea.r.
Rema.-eu,e ~peraDJre lead and connectd1et1ennis~ probe U)the temperaDJre
indicak)rsocket Ensuret1at
the probeopera18S,
.,d loca- k1all sevenpositions.
, Db.'r
Cuj"~v1
g".iI~{
euT/~
,-"""
OK
01"(
Repeatd1eprocedurefor t\e pinnedand limed heatermodules.
PACKING
Removeall ~mponents from ~ duct.
Remove
~
fromU\eanemometer.
Pack and mari( all i18ms.
SUPPLYVOLTAGEAT TIME OF TEST:~.>'I.~
V
TESTEDBY: H. "". 11r5 toCJ..t".'"
P.A. HILTONLTD., HORSEBRIDGE
MILL, KING'SSOMBORNE,HAMPSHIRE,S020 6PX, ENGLAND