(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. ~rT1 00 <c I I~ I I~ l>r:u> I~j~ , °11 1 ZI :I: I I -4 0 =u' :.t rT1 Z -4 n m ~ }> r il K1,I' ~II ; ~ '; -f 0' I . . ~II ~II I, ~ ~ I~ I "'" ~~ n ~J 0 J II >-< ~ ~ ~ ~ > z. 01 I 24 '-".'.-.1' I I I i I . ' ~ ~ '541; S ~ ' t , t it AJ -. , I I . IVE sa I . I -- NO ,...:t: 0 <U) " r -< ~- :I: ~ m~ Z-j ~~ °> <Z V) V) ci1 -u° -u~ r:t -<m -:tJ I I , : EARTH --,-- ,-_J I t t r r , , I I I . z m , , I -+- I I I I I I I I I L__. £~ ~~~. ~ ~6 i ~ n r 0 (/) c :c m I e ~I 1 !NEJT ~:~OO."'.""'~N!'M~nn'~~~~e~ 2!~~~~~~i~.;Ij !lm~~~~~i~~1 ~ I ~1;~~;Mi~.lj~ i'e~~~; I gi~ a i ~ N .~. ~~ m ; ~ ~~ ~i ~~ ~m ~ ej~: ~e~ i l "' M ~ > ! ! i ~ i' ID I ! - -.c J .nt '- " .. "," 'C' N c m i ~ - > i.e~~ -< r VI... ~ u !~ ~ A- i! i. Iiil i i 2S .. a ~ t!" II Ii 8 Iii: .tI!~1j II i~ S ! I.a Ii . i9 . . Iii -; t't i Ii II" I! . II II ,! i~ 1,2 II . . ii:.. } 1i :Iij ll'; Q ~ U>N~ "'5)11 ~o§~ ~ a il In ~ rill' j ,.-I I E ~z ~; friO NA. W Q:N. I Ic >- ~ ~ ~ ~ 0 110 oc(a..'< :J:~W NWO ~t-~ -, I I I L -, I I I I L I ~~ffl J ' I . II' ~I ~ ~ z -w ,...0 ~ Ooz '-1'N- ~ ~., I I I I L I I I I I Jl' J:II.!)::> ~u cn tUl~5 S cn tU -II-UN N ~~~~~ Ln~~u~~~I~l-rm; '" w Ct:Ne 0 e Uln IT) 0 N ffio..z .-~o UII'I ~O ~~ 0 w ~>w ~ w z .. w f/) ~~ O;UJ O -J: UJ"-I UJr- ~f/)O O-iX mf/)OJ:OC(V) ~f/)~f/)~J: -I-Ioc(~=>~ fi \ W ~ ~ .c :. I t I ; I I I ~I V) OZ ~~ ~O . V) J::J: I ! ~ V)E C ~~ -< I I) , ) 0\152 .~ , I V) ~ z ~ UJ~~ 0 >0- ::f 0 ! N ~ LL~ ~...:J: UJojij>-<V) XV)ZC~UJ ---~ r-i i I ; I ... L. x d :f , 1" ~ Ii/h "'~-<-zs X~Q.~-V) I. _n rill' f "'Q.~UJa..(/) ~%:U..J%:UJZ -<O-<oUJ~-< UJumV)t-a..tL v- . '. , I r-- (I LI' I 1n I~ ~ L""r;~ ~ ":iT., I :.., L- ~II' I' ~ 0 I~<c UJ~O I-OZ <Q.W ;J:<-J >0 UJCI) ., ~r "I,.". , Ci ,...+ v ffio.. ~ f'~ -IZ"-.UJoc( oc(=>f/)-IZUJ ~ ""0 <0:0:0 -oz <Q.w <..J >0 wV> 1, II I. I t I I II II II I, II ~ ... Q.. 04: ~ ):. .a i G £t: ~ ~ ~'8 '"- rr\ ~ 0: ~ .« 0: l.!J ~"-\)J -z~ c=>~ l.!Jz~ Zo~ ~o£r -w :J:(/)~ => ': ~' >- ~ . , \~ i t"i w..J ~m~ t:ow (/) UJ '. D:N. 0 e u e "'~ ~ a.: ~ ! .c ~ ~ I !1!Jf1 !! ilill ~ @ ~~ . I ~ ~ 1.2~ ~~ .. i '5 - , I I I I I I .J I I I 11 il !j iII 0 =>... . ~.. =J ll. ~-t ~"'.s . -8§~ I ! ~ ~II :I:~ Oz 0..< UJ=> m £t:U Eli I ~ 11'8 ..! ~ij ~ -, m -- I I ,I -e O/J I .I I . . (8.81.., '~7) 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