Air Conditioning Lab Unit A660

7/22/2019 Air Conditioning Lab Unit A660

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EDUCATION AND TRAINING EQUIPMENTDeclaration of Conformity:Directives (where applicable) 89/392JCEE as amended by 91/368/EEC

89/336/CEE72/23/CEE

We declare that the following unit complies with the above EEC directives:A660 Air Conditioning Laboratory Unit

The use of the apparatus outside the classroom, laboratory, study area or similarsuch place invalidates confonnity with the protection requirements of theElectromagnetic Compatibility Directive (89/336/EEC) and could lead to local.prosecution.For and on behalf ofPA. niL TON LIMITED

Technical Director

P .A. HILTON LIMITEDHorsebridgeStockbridge.England.Tel No. National Romsev (01794) 388382International +44 1794 388382Fax No. +44 1794 388129

[email protected]:

Mill, King'sHampshire.Sombome,SO20 6PX.


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(iii)INDEx.

~SYMBOLS AND UNITS 2SUFFDCES and/or STATES 3SCHEMA TIC DIAGRAM 4CONTROL PANEL DIAGRAM 6

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INTRODUCTIONAir ConditioningAir Conditioning PlantHygrometersComfort ConditionsHuman Comfort

OPTIONAL UPGRADESOrder of Installation 10II

121213242S2627282929292929

INST ALLA TION AND COMMISSIONINGAccessoriesInstallationDescriptionSpecificationServices RequiredUseful DataOperationShutting Down After UseIcing at EvaporatorHigh PressureCut-OutHigh TemperatureCut-Out (In Duct)High TemperatureCut-Out (Steam Generator)

RECOMENDED TEST CONDITIONSHumidificationDe-humjdificationUnit CapabilitiesEnergy Transfers

3030303030323232

MAINTENANCEEarth LeakageTestingRefrigeration CircuitLeak Detection 32


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1Re-chargingCleaningSuperheatControlManometersCare of BoilerWet Bulb SensorsTesting the RCCB

DETERMINATION OF HEAT LOSS FROM BOILER 3S3636363841

THEORYComposition of AirBehaviour of Moist AirSummary of Definitions and TermsThe Psychrometric Chart

SAMPLE TEST RESULTS AND CALCULATIONSObservation SheetDerived Results

444S46474747 .495053555658

SPECIMEN CALCULATIONSCalculation of Air Mass Flow RateApplication of Energy and Mass BalancesbetweenA and BBoiler-Theoretical Evaporation RateRefrigeration SystemApplication of Energy and Mass Balancesbetween B and CVolumetric Efficiency of CompressorApplication of Energy Balance between C and 0To Oetennine the Specific Heat Capacity (Cp) of Air

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SPECIMENSObservation SheetDerived Results Sheet

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A660A DIGITAL TEMPERATURE UPGRADE KITOperationMaintenance

67707273

A660B RECIRCULATING DUcr UPGRADE KITSchematic DiagramIntroduction .Description


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In Duct Orifice CalibrationOperating ProcedureWet BulbsDegree of RecirculationSample Test Resultsand Calculations 77

AC660A COMPUTER LINKED UPGRADE and AC660B SOFfW ARE UPGRADEIntroduction 8385

APPENDICESA: A660A Digital Temperature Upgrade Kit Installation InstructionsB: A660B Recirculating Duct Upgrade Kit Installation InstructionsC: AC660A Computer Linked Upgrade KitD: AC660B Software UpgradeE: A660C PID Control Upgrade KitF: A660D Environmental Chamber UpgradeKit


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2SYMBOLS AND UNITS

Symbol QuantityFundamental --

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AreaEnthalpySpecificEnthalpyCurrentMassFlow Rateit

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PowerPressure Absolute)Heat TransferHeat Transfer RateElectrical ResistanceTemperature Customary)Specific VolumeTime IntervalOrifice Differential PressureRelative HumidityPercentageSaturationSpecific HumidityChange or DifferenceBar = 105N mo:= 105Pa = 100 kN mo]

Presentationof Numerical DataIn this manual, numerical quantities obtained during experiments, etc., are expressed n a non-dimensional manner. That is, the physical quantity involved has been divided by the units in whichit has been measured.As an example:

150=loJ Nm-2his indicates thator p = 150 x I j3 N m-2alternatively p = 150 kN mol


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7INTRODUCTION

Air ConditionlneAir Conditioning, which may be described as the control of the atmosphereso that a desiredtemperature, humidity, distribution and movement is achieved, is a rapidly expanding activitythroughout the world.Obvious applications for air conditioning are homes,hospitals, public meeting places,mines, shops,offices, factories, land, air and sea transport, but there are numerous other applicatiQns n whichhuman comfort is not the prime consideration. These include textile and printing industries,computers, laboratories, photographic and pharmaceutical ndustries, manufacture, nspection andstorage of sensitive equipment, horticulture, animal husbandry, ood storage and many others.

Air Conditionine PlantAir conditioning plant usllally consistsof a numberof components e.g. fans, ilters, heat exchangers,humidifiers, etc.) enclosed in a sheet metal casing. Intake to the plant is usually from a cleanexternal atmosphere plus, in some cases,air recirculated rom the building) and delivery from theplant is via ducting to suitable distribution points. Alternatively small self-containedpackagedunitsmay be used to air condition individual rooms or enclosures.

ComponentsTo remove nsects, eavesand other large.1!!m- Coarse - usually wire mesh.airborne particles." To removemost of theine paper or viscous or electrostatic type.airborne dust.~- are required to cause he air movement and to make good the pressure drop

due to the duct and system resistances.Heat Exchan2er5 which usually are finned on the air side, are needed o increaseor decrease heair temperature.

Heaters may use stearn,hot water or electricity as the heating mediumCoolen may be supplied with chilled water or may be of the direct expansiontype in which liquid refrigerant boils at a low temperature within the heatexchanger.are used to increase he moisture content of the air. Water may be sprayeddirectly into the air, may be evaporated rom a moist surface,or alternatively,steam may be injected into the air. The latter also results n heating of the air.

Humidifiers

Dehumidifiers are used to reduce he moisture content of the air. This is usually achievedbycooling the air below its dew point so that surplus moisture is precipitated.Sometimeshygroscopic materials are used o achievedehumidification, but, ofcourse, these require regeneration.are speciallyshaped affles hroughwhich the air flows and which removeentrainedwaterdroplets rom the air stream.Eliminators

are employed to blend two streams of air to achievea desired condition and/oreconomy.

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Instruments are needed o sense he condition of the air at various stations, and to vary theand Controls output of the components o bring about the desired final condition. In manyinstallations these may fonn part of a total building energy managementsystem.

Associated EauiDmentmay include:~ - for humidification and/or for the air heaters.Refri2eration Plant - for the air coolers/dehumidifiers.

HV2rometers are instruments or measuring he,moisture.content of the atmosphere.There are many types of hygrometer ranging from the paper hygrometer which relies on the changeof dimensions of vegetable matter with moisture content, to electronic sensors.Electronic sensorsusually operate on a capacitive principle. Two electJically conducting surfacesare separatedby thin insulating material. This fonns a capacitor in an electronic circuit.The insulating material used s hygroscopic absorbswater) and changes olume depending upon itswater content. This change n volume affects he thicknessof the material md hence he capacitance.The change n capacitance s sensedby the electronic circuit and this gives an output that may besensedby additional electronics and displayed digitally or sent to a computer.Unfortunately such sensorsare relatively expensiveand have imited accuracy of the order of:!:3% .RH). While this is acceptable or general purposes, t is not sufficiently accurate or use with theHilton Air Conditioning Laboratory Unit A660.The Hilton Air Conditioning Laboratory Unit employs the well kno\\n wet and dry bulb type ,hygrometer for detennining air condition. This is the most accurate method and is still used inwhirling hygrometers which fonn the standard by which other sensing methods are compared. Abrief description of the operation of the wet and dry bulb sensors used on the Hilton AirConditioning Laboratory Unit A660 are given in this manual in the Theory section.

Comfort ConditionsAll animals consume ood (Chemical Energy),do work and reject most ot the unusedenergy to theirsurroundings-principally to the atmosphere.A man ejectsup to about400W (accordingo his level of activity) to tl-.eatmosphere.This heatloss is accounted or by a combination of convection and radiation from his body surfaces, andevaporation of moisture from his lungs and skin.As the air temperature increases, he amount of heat which can be rejected by convection andradiation decreases, hus the evapordtion component must increase. If the relative humidity of theatmosphere s already high, evaporation will be sluggish, skin surfacesb~ome wet, and the personfeels uncomfortable. In hot ~ humid conditions, personnelare quickly exhaustedand are unableto maintain vigorous activity. In addition, theseconditions favour the growth of moulds and fungi - :some of which causeskin ailments.Very low humidities on the other hand. cause apid evaporation rom the lungs, hroat, eyes,skin andnasal passages nd these can also causediscomfort.

Human Comfort :..Depending upon their physical activity, clothing and surroundings, most people are comfortable in ~_.gentlymoving air (free of draughts) which is at about 20Cand which has a relative humidity of


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9about 50%. However, there is considerable variation of what is considered comfortable betweenindividuals and betweennations, and in any case, here is a zoneof temperatureand humidity aroundthe "ideal" which is acceptable o most people. The prime function of many air conditioning plants.is to provide a comfortable environment in terms of air freshness, emperature, humidity andmovement.The Hilton Air Conditioning Laboratory Unit A660 allows the processes overning air conditioningto be demonstratedand investigated. It also allows students o investigate the measurementandcalculation of all the thermodynamic processes nvolved in the heating, cooling. humidification anddehumidification of air.With the addition of optional items the A660 may be expanded o allow demonstration ndmeasurement f the mixing of tWo air streams,electronic thermometry,computeriseddata acquisitionand environmental control.The Hilton Air Conditioning Laboratory Unit A660 and its optional extra componentsare a valuableteaching aid for students n a wide range of courses rom technician to graduate evel.


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10OPTIONAL UPGRADES:The baseunit has a straight-through duct. Product description:

A660 Air Conditioning Laboratory UnitThe supplied unit will have a product code:

A660220 for electrical supply 380/415 Volts, 3 Phase+Earth+N (5 wire supply) 50 Hz.OR A660110 for electrical supply 200/220 Volts, 3 Phase+Earth (4 wire supply) 50/60 Hz.Both units use single-phasecomponents,but require 3-phase supplies.normal single-phasecapacity. The total current exceedsThe loads on the S-wire model are between Line and Neutral 220/240Y.The loads on the 4-wire model are Line to Line 200/220Y.

Installation of the 200/220V 3-phase 4 wire supply) 50/60 Hz model includes he correct positioningof a wire in the compressorstep-up transformer. Full details appear ater in this section.The following upgrades may have been received, if ordered together:

AC660A Computer Linked Upgrade (Factory Fitted)or AC660A Computer Linked Upgrade Kit (Supplied in kit form for installation on site)Installation instructions are contained n Appendix C of this manual.AC660B Computer Linked Software Upgrade (Supplied on disk)Software installation instructions are contained n Appendix D of this manual.A660A Digital Temperature Upgrade Kit(Shipped in individual packing case, accompaniedby packing list)Installation instructions are contained n Appendix A of this manual.A660B Recirculating Duct UpgradeKit(Shipped in individual packing case, accompaniedby packing list)Installation instructions are contained n Appendix B of this manual.A660C pm Control Upgrade Factory Fitted)or A660C pro Control Upgrade Kit(Supplied in kit fonn for installation on site)Installation instructions are contained n Appendix E of this manual.A660D Environmental Chamber Upgrade Kit(Shipped in individual packing case, accompaniedby packing list)Installation instructions are contained in Appendix F of this manual.


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11ORDER OF INST ALLA TION WHEN RECEIVED WITH OPTIONAL UPGRADES (notfactory fitted):


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Remove the unit from its packing case and examine it for damage in transit.contact the insurers without delay. If damage s found,~The Air Conditioning Laboratory Unit dissipates o its surroundingsa maximum of about 6 kW ofsensible heat plus 4 kW as latent heat (water vapour) and has an air delivery of about 0.13 m3s'l.It is desirable hat the intake conditions should be constant, hus, he unit should be placed in a roomwith sufficient volume and ventilation that ambient conditions are not materially changed when itis operating.The unit must be positioned so that there is no obstruction to the air inlet or to the air flow throughthe condenser.ACCESSORIES:C30/2S 2PF20/2 2CS7/8 IC30/14 ICIO/2 IC30/18 IA660/6/1 IA660/6/2 IR633n/1 IR633n/2 IA66on/1 ISFI/SS 12SF3/2 12SFI/S6 12C20/24 4IM3/2 41M12/8 4IM3/5 2IM3/6 IAS71/4/1 1C4S/3 IA660/IO/I ILAJ/184 IAS74/37/1 1C20/4 IE38/4S ISF20/l 2

Reinforced Supply and Drain Hose, 15mm push fitStem Elbow, 15mmRI34a PressureEnthalpy DiagramR 134a Thennal PropertiesTablesEncapsulatedPsychrometric Chart, SI unitsPsychrometric Tables, 700 to 1100 mbarSchematic Diagram, A3Schematic Text Diagram, A4A3 Schematic HolderA4 Schematic HolderDust CoverM6 SS WasherM6 Nylon WasherM6 x 25 Hex Head BoltRubber Stopper, 25mm dia.300mm Spirit in Glass Thennometer, 0 to 50CWet Bulb Spirit in Glass Thennometer, 0 to 50C150mm Spirit in Glass Thennometer, 0 to 50C150mm Spirit in Glass Thennometer, -10 to +1 10CWater Measuring CylinderCompressorCharging Valve Key10/1lmm Open Jaw SpannerUnpacking Case LabelEvaporator GasketHose Clip, 13 to 20mm8mm Nut RunnerM6 Plastic Fluted NutSet of Manometer Accessories Fluid, filling syringe, scales)Product Envelope containing:Experimental, Operating and MaintenanceManualTest SheetPacking ListWiring Diagram


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13Installation

Remove complete unit from packing case and check with Packing ListBefore discarding any packing material ensure hat all items are identified and checked againstthe Packing List. Ensure the Sparesare also identified.Detach the downstream duct from its storage position under the main duct. Examine the twowet bulb water reservoirs and refer to Figure 7 on Page 22. If necessary set the internalreservoir o the correctheightof I OOmm fitting the duct o the unit. .2.

Remove the bolted supportangle from the evaporatorower flange and put to one side forrefitting later. -Fit the rubber evaporatorgasket (AS74/37/1) and downstreamduct to the evaporator lange usingthe M6 x 2Smm hex head screws (SFI/56) and M6 washers SF3/2) provided. Refer to FigureI on Page 14. Refit the lower support angle on the outside of the duct flange.

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Ensure that the flange is not over-tightened as damage to the evaporator flange will result.Ensure that the flange is tightened evenly.Ensure that no powcr connection has yet been made..Refer to the wiring diagrams supplied in colour and Figure 2 on Page 1S for 220V 3ph SO/60Hzunits (Drawing No 6602SM) and Figure 3 on Page 16 for 41SV 3ph SOHzunits (Drawing No66O22M). .The 2 x I.OkW re-heaters and duct thennostat in the downstream duct are connected o thecables in the loose flexible conduit leading from the control panel. Note that the cables aremarked with numbers that correspond o the wiring diagrams n Figures 2 and 3.Locate the appropriate wiring diagram for the unit and in Area 2A of the diagram locate theI.OkW Air Heater (First Reheat)and I.OkW Air Heater SecondReheat). By convention he firstreheater s closest to the fan.Using the 415V 3ph 50Hz wiring diagram, Figure 3, as an example. Connect the red wirelabelled 253 to one side of the 1.0kW Air Heater First Reheat). Connect the black wire labelled254 to the other side and ensure hat the black link 254 to 257 is made between both heaters.Connect the red wire labelled 256 to the remaining tenninalA connector block fitted to the downstream duct allows the earth lead from the heaten(green/yellow stripe) to be connected o the earth lead in the conduit 255.Connect the wires labelled 251 and 252 to the thennostat as shown in the diagramNote that for operator safety it is essential hat the earth leads are connectedconectly.Connection of the heaters for the 220V 3ph SO/60Hzunits are carried out in a similar mannerwith reference o the diagram, Figure 2. Note that in the case of 220V 3ph SO/60Hzunits theheatersare connectedbetween phasesand connections o both ends of the heatersare red. Thecorrect cable numbers should always be observed according to the diagram.Finally. fit the plastic terminal cover to the duct with the hex head screws provided


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207 220V Joh SO/60HzMachines onlyThe condensing unit supplied is suitable for operation on BOrn 50Hz and 60Hz electricalsupplies. However, it is only available for operation on 220/250 Volt supplies. Therefore a stepup transfonner is provided to increase he voltage supplied to the condensing unit (ONL Y) toa suitable value.

The transfonner is located on the lower frame adjacent o the condensing unit itself. Refer toFigure 4, Page 17.This will beemove the screws securing the transfonner cover and locate the brown wire.factory fitted to the 230V input tenninal of the transfonner.

It will be necessary o measure he line' to linez voltage of the local supply.be undertaken by a competent person.This should only

Once he local line to line voltage has been measured, onnect he brown wire to the transfonnertenninal that correspondsas close as possible to the measuredvalue. Replace he transfonnercover and secure with the original screws.

8 nov Joh SO/60HzMachines-Main Wirin2 ConnectionIf required by the local regulations, the following should be carried out by a competentelectrician.Refer to the wiring diagram 6602SM and the detailed view of the main switch enclosure,FigureS on Page 18.The unit can draw up to 32 Amps on each phaseand the supply conductors should be sized forthis current according to the local regulations.Remove he main switch and enclosure cover to gain access o the terminalsConnect he three ines (LI, L2, L3) and the earthing conductor (E) as shown in the main switchdiagram. Strain relief for the supply cable or suitable conduit should be titted according to thelocal regulations.For operator safety t is essential hat a low impedanceearth of adequatesize is connected o theunit earthing tenninal.Refit the main switch and cover.440V Joh 50Hz Machine!If required by the local regulations, the following should be carried out by a competentelectrician.Refer to the wiring diagram 66022M and the detailed view of the main switch enclosure,6 on Page 19. "igure

The unit can draw up to 20 Amps on each phaseand the supply conductors should be sized forthis current according to the local regulations.Remove he main switch and enclosure cover to gain access o the tcrminalsConnect he three lines (LI, L2, L3) and the Neutral (N) and Earth to the main switch as shownin the diagram.For operator safety it is essential hat a low impedanceearth of adequate ize is connected o theunit earthing terminal.Refit the main switch and cover


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219, Water SupplyThe boiler requires fresh water (if possible distilled or de-mineralised) at a maximum rate of 10litre/hour with a minireum head of 2m.

The boiler feed point is a I Smm push-fit fining labelled "cold water inlet" locatedbelow the fan.Connect this to the local water supply via an isolating valve using the water inlet tube assembly1/1"bore (C30/4) and elbow (PF20/2) supplied in the accessories it.It is recommended hat when the unit is not in use he locally supplied isolating valve is closed.Water will not flow to the boiler until electrical power is supplied to the machine.Inside the boiler are two electrical level sensers hat control the water solenoid valve.Connecthe remaining hose to the overflow connection and position thee free end in a floorlevel open drain.Water OverflowIn the unlikely event of component failure, the overflow pipe allows excesswater to flow fromthe tank and prevent water entering the air duct. Reduce he level by draining into a receptacle.The solenoid valve will open again to refill. Note than an open pipe extends rom the copperoverflow pipe vertically upwards and ends ust below the frame. Do not block this as it is asyphon break.To test operation of the unit turn on the electrical supply and the water isolating valve.Turn on the unit main switch on the instrument panel, see control panel diagram on Page6, andwater will be heard to flow into the boiler tank.Observe he sight glass on the steamgenerator ank. Water should be seen n the sight glass and'then the level sensor will close and turn off the solenoid valve.

10. InstrumentationThe air condition is measured by four pairs of wet and dry bulb thermometers.The wet bulb thennometers are pre-assembled IMI2/8) and the dry bulb thennometers areselected rom the OC to 50C 300mm thennometers IM3/2) supplied.A sectional view of a typical wet bulb station is given in Figure 7 on Page 22.To support the wet and dry bulb thermometers n the duct. rubber discs (C20n4) are suppliedand these are carefully slid over each thermometer from the top down towards the measuringbulb.Adjust the height of the rubber discs so that when inserted n the measuring station holes in theduct the measuring bulbs are at approximately mid duct height.Tl and 1'2 are retained by thumb screws at the fan inlet.Th~ accuracy of the wet and dry bulb measurementwill influence the overall accuracyof ~nergybalances elating to the air stream. To ensurema.~imummeasurementaccura


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A660: CROSS SECTIOr-JOF DUCT THROUGH WET BULB RESERVOIRt6V

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23It is recommended hat the wet bulb thennometersare kept wet when not in use to prevent thewicks drying out. This is best achieved by keeping the wet bulb reservoir full to its minimumlevel.The wet bulb reservoir should be connected, hen filled with distilled or demineralisedwater sothat scale depositsdo not build up on the wick material. Replacementwick material is suppliedfor future use (RMX8/2).The refrigeration system thermometer pockets (13, 14 and 15) are designed to accept either1SOmmO-SOChermometers IM3/S), or -10 to + 110C hermometers 1M3/6). The appropriatethermometer for the three measuring stations will depend upon the local conditions and theconditions established n the air duct. If the red spirit reachesa temperaturenear the top of theO-SOC ube then insert the higher l:al\ge heanometer.

II. ManometerRemove the blanking caps from the two manometer tubes and retain for future use.Connect the grey plastic tube supplied to the tapping point on the side of the downstreamductand to the left hand tapping on the manometer.When the unit is in its final position in the laboratory, adjust the manometer level by releasingthe right hand mounting screw and adjusting according to the integral spirit level.With no air flow adjust the knurled nut on the right hand manometer apping until the red fluidis at the zero mark.

12. Fan Speed AdiustmentRefer to Control Panel Schematic, Page 6. Switch on the power supply to the unit. Check allcontrol panel s\vitches are otTo Isolate the water supply.Rotate the fan speed control fully clockwise to maximum speed. Switch on the main switch.The main solenoid will click and the fan will start. Reduce fan speed to the minimum stop(fully anti-clockwise) and observe manometer scale. It should be approximately 3mm HID ormore.The following should only be carried out by a competent person as the adjustment has tobe carried out with the power switched on.~linimum fan voltage s adjustable y means f a single rim potentiometeritted to the FanSpeedControl nside he control panel. The control panelhinged id must be openedo gainaccesso the inside. CAUTION - LIVE ELECTRICS!Locate the potentiometer on the fan speedcontrol circuit board. This is a squareplastic deviceapproximately 2cm x Icm x O.5cm with a small brass screw head on the top.With the Fan Speed Control in the minimum (fully anti-clockwise) position, rotate thepotentiometer to vary the fan speed to achieve 3mm H2O duct pressure.Before closing the control panel, take this opportunity of testing the RCCB in accordancewiththe instructions listed in the MAINTENANCE section.The installation is now complete


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24DESCRIPTION - THE HILTON AIR CONDITIONING LABORATORY UNIT A660(Please efer to Sthematic Diagram, Page 4)Note that optional upgradesA660A Digital TemperatureUpgradeKit and AC660A Computer LinkedUpgrade Kit. and the item label numbers are shown.With the exception of filtration and mixing, the Hilton Air Conditioning Laboratory Unit has beendesigned o demonstrateand to evaluate he energy ransfersoccurring in all the processeswhich arerequired in an air conditioning plant.The unit is mounted on a mobile frame which houses he refrigeration unit and stearngeneratorUntreated air entering the ducting passes n seri~ through

2.346.

An axial flow radial fan with speed control (9) and (10).Steam can be added by a steam njector after the fan discharge (3).A pre-heater 4).A cooler/dehumidifier with a precipitate water outlet (5) and (22).Are-heater (6).An air measuring duct orifice (7) and manometer 14).

The arrangementof a pre-heaterbefore the evaporator/coolingcoil is I.ot standard air conditioningpractice, but the heater has been included at this point close to the !i.earn injector for a specificteaching purpose.If the local relative humidity is close to saturation, njection of steam can simply result in the ductrunning with water as the air cannot absorb more vapour than that required to saturate t at the givendry bulb temperature. ,The addition of sensibleheat as well as the steam raises he dry bulb temperature and takes he airaway from the saturatedcondition to a lower Relative Humidity.Similarly, the location of steam injection before the evaporator/cooling coil is not normal for airconditioning where humidity control is required. This would usually be located after theevaporator/cooling coil. However, in locations where the relative humidity is very low, the abilityto demonstrate he de-humidification process would be impossible. Therefore by injecting steambefore the evaporator/cooling coil the relative humidity of incoming air can be raised close tosaturation so that dehumidification &nd the mass ransfer processcan iJe demonstrated.In caseswhere he humidity and temperature ontrol upgrade A660C) is purchased,he stearninjector s relocatedo a pre-installed oint after the evaporator/coolingoil.With the physical arrangementdescribed above and by selection of the individual heaters.steaminjection and refrigeration/cooling system, the following data may be readily obtained:

(a) The condition of the air before and after the various processes via wet and dry bulbsensors).(b) The energy transfer rate at each heater, he boiler, fan and refrigeration unit.(c) Air mass flow rates.(d) Pressuresand temperaturesof refrigerant.(e) Refrigerant mass flow rate.(f) The generation of a refrigeration cycle diagram on a pressure-enthalpy chart for therefrigerant in use. The analysis of the energy transfers n the refrigeration system.(g) Rate of precipitation at cooler.This infonnation, combined with thc use of air and refrigerant tables or charts. enables the operatorto demonstrate and evaluate all the effects likely to be met in an Air Conditioning Plant. The unitis alsoan excellent vehicle for demonstrating energy transfers in steady now processessince itincludes heating. cooling and work transfer (at the fan).


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25SPECIFICATIONDuct Centre line length: A660 = 2298mrnA660B = 6098mm 100% fresh

A660B =6886mm 100% recirc.Material: PVCThermal conductivity: 0.16 W/mKMaximum temperature:70C

Air Throughput 0.14 m3 s.t (max)Pre-heater Extended fin electric heating elements. 2 x 1.0 kW (nominally) at220V .Effective iength: 1.414mExposedubesurface rea:0.0355mExposed fin surface area: 0.2876mCooler Direct expansion,extended in coil. Cooling rate approx. 2.0 kW51S"o.d. copper tube, 20swg.

4 rows deep x 5 rows high: 0.253m1exposed o air flow.61 fin plates: 4.227m1exposed o air flow.Re-heater Extended in electricheatingelements. 2 x 0.5 kW (nominally) at220VEffective ength: 1.414mExposedubesurface rea:0.03SSm1 .Exposed fin surface area: 0.2876m1Fan Centrifugal (variable speed). Power input approx. 120W, at 240V50Hz. .R.P.M.: 0-2400Power: 0-0.9A, 210WVolts: 220-240Humidifier Electrically heatedand working at atmospheric pressure. Fitted withwater level float switch and in line solenoid valve.Heaters: I x 1.0 kW and 2 x 2.0kW at 220V (nominally).Volume: 2.5 litres (to mid-sight glass) under control of level controlfloat switch.Overflow protection: A second loat valve will open circuit at 4 litresin the event of failure of the level control float switch.

Water Solenoid Valve:Orientation: AnyInlet Pressure:0-45 barPower Consumption: 19vA

Refrigerator Hennetic unit with air cooled condenser.Refrigerant: R 134aTetrafluoroethaneCFJCH2FCompressorspeed: 2700 to 3000 rev.minl at 50Hz. accordingto load. 3300 to 3600 rev.minl at 60Hz.Swept volume: 25.95 cmJ rev'l.

INSTRUMENT A TION - A660 (with no optional uDllrades)Orifice plate with inclined tube manometer.Range: O-12mm Water

Air Flo\vMeasurement


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264 pairs Wet and Dry Bulb glass hennometers300mm long.emperatureMeasurement

RefrigerantCircuit 3 x 300mm Glass thennometers.

SAFETY Refrigerator high pressurecut-out.Temperature imit (50"C) thermostatsat the pre-heaterand re-heaterstations. .All moving parts are enclosed.All electrical components are individually switched by miniaturecircuit breaker switches o protect against overload and short circuit.The unit is protectedby a ResidualCurrent Circuit Breaker which cutsoff the power should the current n and out differ by more than 30mA,as in a leakage o earth situationTo ensure heaters are not switched on without air flowing, the fanspeed egulator is pre-set o give an adequateair flow as soon as thethree phasemains switch is closed.

SERVICES REQUIREDElectrical Either 380/440 volt, 3 phase,50Hz. 5 wire system comprising3 phases,neutral and earth.Typical line currents can be up to 20 Amps per phase.

Or 2. 208/220 volt, 3 phase, 50 or 60Hz. 4 wire systemcomprising 3 phasesand earth.Typical line currents can be up to 32 Amps per phase.Approximately 10 litre per hour at a minimum head of 2m. (Toreduce scaling in the boiler this water should, if possible, be distitledor de-mineralised.) Note this can be a smatl reservoir specificatly forthe unit and does not have to be a mains supply.

Water


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27USEFUL DATA (see also.Specification)

Note: For 380/440V 3ph. 50Hz. machines, the heaters are connected line to neutral and the heatervoltage may be between 220 and 254V.

For 200/220Y 3ph. 60Hz. machines, the heaters are connected line to line and the heater voltage maybe between 200 and 220Y.The fan power input can be detennined from the graph (Figure 12) on Page 48 relating the FanPower Consumption to Supply Volts.The specific heatof air Cplir= 1.005kJ kg" 1


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28OPERATION(Please efer to Schematic Diagram, Page 4, and the Control Panel Diagram, Page 6)Check the wet bulb reservoirs filled to the level mark.Turn on the water supply to the boiler and supply power to the unit. Turn on the main switch onthe left of the control panel and the water solenoid valve will be heard o open. (In addition, the fanwill run as soon as the main switch is turned on.) The panel voltmeter will indicate supply volts L Ito N (415Y units, or LI to L2 (220V units).Ensure hat water is visible in the sight glass of the steam generator before turning on any of thesteam generator water heaters. .The eight switches on the control panel are combined double pole switches and miniature circuitbreakers. These control all of the heatersand he compressorof the refrigeration system as ndicatedby the labels on the panel.The MCB button on the left of the control panel (or two buttons in the caseof a 220V 3ph SO/60Hzunit) protect the fan supply from overload conditions. If the buttons protrude from their normalposition then a fault condition will be indicated and the causeshould be investigated. It will alsoopen circuit the supply to the main magnetic contactor. The unit is therefore shut down when thefan MCB is tripped.To reset hese circuit breakerssimply press he button back in.Note that if the fault still exists the button will not remain in a locked position.

illOn the left of the control panel is the fan speedcontrol. Turning the speed control clockwise willincrease he fan speed.and anti-clockwise will reduce speed.Pressing he biased switch will cause an volts to be displayed by the voltmeter.Note that the minimum pressure ndicated by the manometer should not drop below 3mm watergauge when the fan speed control is fu\Jy anti-clockwise. This should be set as part of the(nsta\Jationand Commissioning procedure. See Fan SpeedAdjustment, Page23.

Obtainin2 Stable ConditionsThe unit should be started according to the above procedureand, depending upon the parameters obe investigated, he appropriate controls turned on or adjusted.The time taken for the unit to stabilise will vary dependingupon the local ambient conditions.can vary from 10 minutes to 20 minutes. ThisThe humidification processcan be started more rapidly if all the water heatersare turned on untilthe water is boiling. Then turn off the heaters hat are not required.Note that the refrigeration plant will not begin to stabilise from initial start up until the refrigerantshown in the variable area glass flowmeter is a column of liquid without bubbles.When changesare made to the conditions upstreamof the evaporator. he refrigerant flow rate willbe seen o alter due to the increasedor decreased eat loadi~g.


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29Shuttin2 Down After UseBefore switching ofT:(a) Switch off all boiler heaters.(b) Switch off all air heaters.(c) Switch off refrigeration circuit.

(d) Set the fan to maximum speed.Then allow the fan to run for at least five minutes to dry the ducting, after which the main switchand isolator may be switched off.Turn off the locally supplied water isolating valve and drain the steamgenerator o reducescale buildup.

Icin2 at EvaoontorAt low air flow rates, accompanied by low ambient temperature, it is possible for the R134aevaporating conditions to fall below OC/300 kN moJ.If this happens, t is probable that ice will fonn on the air side of the evaporator ubes and fins andon the expansion valve.While no damage s likely to occur if operated n this condition for a few minutes, it is inadvisableto operate in this condition since the ice will eventually stop the air now.Icing can be avoided by increasing the air flow rate and/or switching on the air pre-heaters.

Hi2h Pressure Cut-OutIf the condenserpressureexceeds 1400 kN m-2gauge e.g. due to restriction of cooling air flow), ahigh pressurecut-out will switch otTthe refrigeration compressor,but the air fan will continue to run.'The high pressurecut-out is adjacent o the compressor.When the condenser pressure has fallen to about 800 kN m-1 gauge, the compressor willautomatically re-start if the control panel switch is still in the On position-

Hieh Temperature Cut-Out (In Duct)In duct thennostats are !ocated at the pre-heater and re-heater stations to limit the maximumtemperature to 50C. In the event that this temperature s exceeded he main contactor relay willopen, turning off the power to all of the heaters (boiler, pre-heater and fe-heater). The fan willcontinue to run and so help to cool the duct.Once the temperaturehas reducedat both thennostats, he main contactor relay will close and supplypower to the heaters.

Hi2h Temperature Cut-Out (Steam Generator)The three heater elements fined to the stearn generator are fined with automatic reset hightemperature cut-out devices. In the event that the user forgot to turn on the water surply to thesteam generator the elements would boil dry and overheat. The thermostats will turn off the powerat the heater and prevent a dangeroussituation developing.The thermostatswill operate more than once, but it is not recommended hat the situation is allowedto occur repeatedly as Ihe healers will eventuallv fail.


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30RECOMMENDED TEST CONDITIONSProvided the air temperature s not allowed to exceedSOOC, ny operating conditions may be used.However, satisfactory results are more likely to be achieved f the following points are noted(a) l~umidification

When humidification is required, the rate of steam njection should not exceed hat which. canbe absorbedby the air.If it is found that mist is seen some distancedownstreamof the steam distributor, either,(i) Reduce he heat input to the boiler, or .(ii) Increase he air flow rate, or(iii) Increase he air dry bulb temperatureby switching on more pre-heat.

(b) De-humidificationWhen it is intended to demonstratede-humidification, the air should be fairly humid(say. 650/.) at Station B. If necessary, team may be injected.(i)The cooler has a large surface area on which the condensation akes place. Due to this,an appreciable ime elapsesbefore condensates discharged rom the drain at the samerate as it is precipitated.

(ii)

The changeof moisture content of the air is easily determined rom the product of theair mass low rate and the change of specific humidity. Agreement between his, andthe drainage ate wilt be obtained after a sufficient period under steady conditions.(iii)

Unit CaoabilitiesAs shown in the following observations and specimen calculations, the Air Conditioning LaboratoryUnit may be used to demonstrate and evaluate energy and mass balances in most of the processesfound in practical air conditioning plant, (i.e. heating, cooling, humidification, and de-humidification).In addition. the unit may be used:(i) To detennineCp for air. (From Q = ri1 Cp t\t. when 0) is constant)

To provide a hot, cold, humid or dry condition under which articles may be placed. (Thearticle must be capable of insertion into the duct through the orifice plate.)(ii)

To estimate he volumetric efficiency of the compressorTo draw the cooling curve for a boiler and estimate heat loss at various temperaturedifferences.

Ener2v TransfenAll the processes n the Air Conditioning Laboratory Unit may be treated as steady flow processeswith insignificant changesof kinetic and potential energy.Thus. for any portion of the unit treated as an open system

Q-P=4Henthalpy rate(s) of the fluid(s) entering\H is the enthalpy rate(s) of the nuid(s) leaving


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31Q is the heat transfer rate (positive if ill the system)it is the work tra.'1sfer ate (electrical or mechanical) positive if f!:Q!!!, the system).


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32MAINTENANCEWARNING:Earth Leaka2e Testin2.Due to local legislation some establishmentsmaintain a register of electrical appliancesand subjectthem to periodic tests for earth leakageand earth continuity.Before conducting any fonn of test that will subject the unit or its components o abnonnal voltages,disconnect the power supply to the following optional components f they are fitted: '

A660A Digital TemperatureUpgradeAC660A Computer Linked UpgradeThe digital temperature ndicator in the A660A kit and the data logger in the AC660A kit are bothplugged into a 4-way socket at the rear of the unit. Unplugging them will disconnect hem from thesystemThese components are likely to be permanently damaged if not disconnected before the othercomponents of the A660 are tested.

.4 kg of R134a before it left theBefri2eration CircuitThe refrigerant circuit was correctly charged with approximatelyP A. Hilton Ltd., works.If it is found that there is continuous gassing n the R 134a lowmeter it is possible that a leak hasoccurred.The refrigeration condensingunit is of a standardand widely used type. It can be serviced by anygood refrigeration ontractor. ~Note that the unit should not be charged with any refrigerant other than.Jot;~~:: ~134a)."Drop in" replacement or alternatives are.!!Q! suitable for use with this ~~Z~The unit contains sufficient Ester oil for its lifetime operation. Do not add any oil to the refrigerantcircuit.

Leak Detection(i) Assuming that the refrigerant pressuregauges ead aboveatmosphericpressure, eaks are readilydetected by normal methods,e.g. electronic leak detector, or soap solution.Note that electronic leak detectors previously used for detecting CFC 12 are often not suitablefor detecting leaks of HFC 134a. Check with the leak detector supplier for their suitability.

(ii) If the refrigeration circuit is completely discharged, he systemmay be pressurised through thecharging valve) to about 600 kN m-2gauge with dry nitrogen. Having located and rectified theleak, the refrigeration circuit must be evacuated o IOmm.Hg.Abs. o ensure no moisture existsin the circuit, before it is re-charged.

Always slacken the gland nut before turning the service valves. Retighten after movement.10/11mm open aw spanner s provided for this purpose.

Re-chareineHaving established hat there are no leaks in the circuit, a cylinder of Rl34a should be connectedto the charging point in the compressorsuction line. Purge he connecting pipe with R 134abeforetightening the connection to the compressor.


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33Turn the back seating valve spindle on the compressorsuction line two turns clockwise and allowthe pressure n the system to rise to about 600 kN mo2. hen switch on the compressor and allowrefrigerant to flow into the circuit. Only R134a gas (not liquid) must be allowed to enter the system(i.e. the valve on the R13'~acylinder must be at the top).The charging processshould be interrupted at intervals of 2-3 minutes to allow the plant to stabilise.Continue to charge he circuit until the gassing n the flow meter ceases and then add a further 0.5kg.Back. seat the charging valve and disconnect the Rl34a cylinder. Retighten the glanc;inut on theservice valves and replace the caps.Cleanine: .The air cooled condensermust be kept clean. If dust or fluff is seen o build up on the heat transfersurfaces, t may be removed with a soft brush or with a compressedair jet.

Superheat ControlThe superheatcontrol is set to give approximately 3 to 5 K of superheatat normal conditions. If itis necessary o adjust this, remove the cap nut from the expansionvalve. Rotate he screw clockwiseto increase the superheat. Any adjustments must be made with the unit running and in smallincrements (i.e. 1,4 urn), allowing time for the unit to stabilise between each adjustment. Afteradjustment, replace the cap nut.

ManometersThis has been correctly filled and had a sealing cap fitted before leaving our works. The cap mustbe removed and the appropriate tube fitted before the manometer s used. If the manometerneedsre-filling or topping up, the correct fluid (supplied with the unit) should be used. If an alternativeis used, ensure hat it has the correct specific gravity as stated on the manometerscale.Care of BoilerIf distilled or demineralised water is used, the boiler should require little attention.If untreated water is used:(i) It is possible that the heating elementswill require de-scaling after prolonged operation. Localexperience with the de-scaling of the heating elements n electric kettles will guide the user inthis matter.(ii) There may be a tendency for the water in the boiler to "foam" as the concentrationof impuritiesincreases.

Foaming will cause he water level in the sight glass to behave erratically and water may bedischarged with the steam nto the duct. If this happens,switch off the heatersand turn off thewater supply. Drain the water from the boiler through the drain point provided. Then turn onthe water, check that the level rises to the normal position and switch on the heating elementsas required.The frequency at which the boiler must be drained and re-tilled will be found by experienceit is, of course, advisable to do this before foaming occurs.

Water for Wet Bulb SensorsIt is necessary o use distilled or demineralised vater to fill the reservoir for the wicks of the wetbulb sensors. This is to prevent impurities building up in the wicks and reducing their absorptionproperties.


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34The condensate rom the air cooling/de-humidifying section may be regardedas distilled water andcan be used for the above purpose.If it becomesnecessary o replace he wicks on the wet bulb sensors, t is essential hat the new wickis in f1rn1 hennal contact with the bulb. This is achievedby pulling the wick in an axial direction(which will cause t to contract circumferentially) and then securing it with heat shrink sleevingsupplied.T~tinl! the RCCBThe Residual Current Circuit Breaker (RCCB) is situated inside the control panel adjacent to thepower cable connector and main switch.The RCCB should be tested by a comoetent oerson at intervals as required by the local regulations.Remove he hex head screws and open the switch panel. Supply power to the unit and turn on themain switch. Press the button marked 'Test' or 'T' on the RCCB, but DO NOT TOUCHANYTHING ELSE INSIDE THE UNIT. The large lever on the RCCB should turn from the ON('I') to OFF ('0') position immediately and the unit isolated rom the supply. If this does not occur,the RCCB may be faulty and needs o be repaired/replacedby a qualified electrician.Return the lever to the ON ('I') position and the unit should be switched on again. Close and securethe switch panel in position with the hex head screws.


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35DETERMINATION OF HEAT LOSS FROM BOILERNote that this can only be undertaken if the A660A Temperature Upgrade Kit has been fittedor if a thermocouple type temperature indicator is available.Tape a thennocouple onto the outer surface of the boiler at about the mid water depth.Switch on the heaters and raise the water temperature o 100C.Switch off the heating elements and then note, at intervals:(i) The temperature ndicated by the thennocouple.(ii) The time(iii) The ambient temperature (tJ. .Draw a graphof temperature . time, and rom this estimatehe rate of cooling ~ when hetemperatures t OOC. L\time

Figure 8

From the dimensions of the boiler calculate the mass of water present (mw)' The water equivalent(mJ of the boiler is 0.54 kg.

Heat loss rate from boiler, Q = (m. + m.> x 4180 (~> WA timeThis is at a temperaturedifference of (100 - t.) K.

Thus,

Q=AI .33 ~KTypically, for the boiler


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36THEORY(Note: In the following, "stearn" and "water vapour" are interchangeable.)IntroductionFresh air contains about 23% oxygen and 76% nitrogen by mass. The remainder is composed ofsmall quantities of other gasesand vapours, and of these he most important is water vapour. Thevaponr content of the atmosphere s loosely referred to as the HumiditY.Although the water vapour content is usually very small, (usually < 2%), it has a considerableeffecton the rate of evaporation from moist surfacesand materials. An understandingof the moisturecontent of the atmosphereand of how it may be controlled is an important part of the education ofall engineersand technologists.

Behaviour of Moist AirDalton's and Gibb's Laws give us the following conclusions,(i) Each gas or vapour in a mixture obeys ts own physical laws as if it were the sole occupant of

the space, at the same emperatureas the mixture.(ii) The enthalpy, internal energy and entropy of a mixture is the sum of the enthalpies, internalenergiesand entropies respectively, which each constituent would have if it alone occupied thespace at the same emperatureas the mixture.

Examole (See p-v diagram for steam)Let us consider air of specific humidity, i.e.massof steammass of dry airof 0.0 at atmosphericpressureand 20C. The density of this air will be approximately 1.2 kg mo)The composition of I.Om} of this "air" will be:

lQ.Q.x 12 =101 188 kg of dry air (i.e. the gases)

.2 = 0.012 kg of HzO101From Dalton's Law the H2O behavesas ifit was the sole occupant of the space 1.0m3).H2O is at 20C and has a specific volume of: Thus the

-L = 83 m3 kg"0.012 (Point A)

From steam ables we see hat at 20C, VI = 57.8 mJ kg-I and P...= 0.0234 bar (2.34 kN m-2), PointB). The steam at A is therefore superheated nd at a lower pressure han 0.0234 bar.At low densities, water vapour very nearly obeys Boyle's Law, thus

p" V" = PBVB= 0.0234x 57.8 = 0.0163 bar (1.63 kN m-2)

83p"In a stearn/air mixture, the ratio actual ressure 0 steampressure of saturated steam at the same emperatureis called he RelativeHumidity +).


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37

.~..p..!;., _.2...,.

p - V ~grOIl for SleoII

\\\

200( ~.B0"2.34

"* 0';::::~~:~:;;

~0016 c5(0.0087 , x. 0.56 ~

v-;Jkg-:r4778 83

Figure 9

If our sample of air is cooled, at constant volume, to 14C the steam will just become saturated v.= 83m} kg"' at 14C, Point C).This temperature s known as the Dew Point.If the air is cooled, in thennal equilibrium, to a temperaturebelow the dew point, the steam in itmust become wet, e.g. if the steam is cooled to 5C (Point D) when v. = 147m] kg-I, the drynessfraction (x) will be y- = .J1 = 0.56

v. 147Thus, of the 0.012 kg of H2O in the air,0.56 ;It 0.012 = 0.0067 kg will be saturatedsteamand, 0.44 x 0.012 = 0.0053 kg will be saturatedwater (liquid).


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38The liquid may appear as mist (i.e. suspendedwater droplets), or as condensation on the coolingsurface.~: In this example it has been assumed hat(i) the air is cooled at constant volume(ii) the water vapour obeys Boyle's LawHowever, he resultsare also substantially orrect or constant ressure ooling over the sametemperatureange.From the foregoing it will be seen hat if the relative humidity is high, (up to 1000/0)he air cannotabsorbmoresteamunless ts temperatures raised). -The lower the relative humidity, the greaterwill be the readinesswith which air absorbsmore steam.It is now necessary o define some tenns of reference.

Summary or Definitions and TermsHumidityWhen an atmosphere as a large water vapour component, e.g. n a room containing large quantitiesof exposedhot water), we say (loosely) that the humidity is high.Morc clearly defined terms are:(i) Absolute or Specific Humidity I) is the ratio (in a given atmosphere),

moss of water vapour (~)ossof dry air kg

(ii) Percentap;e elative Humiditv (cjI) s the ratio,p.p. = partial pressure of the steam in an atmospher;;x 100 (%)saturation pressure of steam at the same temperature

(iii) Percentae.e aturation (~) is the ratio,

mass of steam in a given atmoshperex 100 (%)mass of steam to salUrate the atmosphereat the same temperature

Under nonnal atmosphericconditions, the Relative Humidity=PercentageSaturation(within1%).~:

The easewith which the air takes up moisture from any surfaceor processdependsupon how closethe air is to being saturated ather than its absolutevapour content.The relative humidity or percentage aturation s therefore of greater significance than the absoluteQ! specific humidity when drying or air conditioning processes re being considered.


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39Measurementor Air ConditionDew Poin!The dew point is the temperature t which the steam n the air becomes aturated nd thereforebegins o condenseo a liquid.Above the dew point the steam in the air is superheatedat a pressure < Pili for the temperature.Below the dew point the water in the air will be a mixtUre of saturatedsteam and liquid water.Hence by slowly cooling a polished metal surface and observing when water begins to condenseasmist, the dew point temperaturecan be determined f the temperatureof the surface s known. Thepartial pressureof the steam n the atmosphereat the dew point temperature s the saturationpressureof the water vapour at that temperature. Hence f~e know the atmospheric emperatureand the dewpoint temperature,we can determine the Relative Humidity with reference o the Relative Humiditydefinition.For example, if the Ambient temperature s 20C and the dew point temperaturehas been measuredas 11C, from Steam ables

Saturation Pressure0.02337 Bar absolute0.01312 Bar absolute

Temperature20CII"C

0.013120.02337Relative Humidity = x 100%= 56.1%

.The measurementof dew point temperature s carried out to measureair condition, but the use of"wet and dry bulb" temperature measurement s more convenient.Wet and Dry Bulb Temperature MeasurementIf a steam of air flows past a temperature sensor having a wet sleeve of cotton or linen around it,the temperature recorded will be less than the actual temperatureof the air.The temperature alls due to evaporation from the wetted sleeveand as a result there is a transfer ofheat from the air to the wetted sleeve o sustain the evaporation.The temperature falls to a steady state value called the wet bulb temperaturewhen the rate of heattransfer balances he loss of energy due to vaporisation.The actual temperature of the air is sometimes called the dry bulb temperature to emphasise hedestination.The lower the relative humidity of the air the more rapid the evaporation from the wet bulb and thelarger the difference between the wet bulb and dry bulb temperature.When the air is saturated RH = 100%) the wet bulb, dry bulb and dew point temperatureare thesame.Since the evaporation. and hencewet bulb temperature, ependsupon the heat and mass ransfer ratestrom the wetted sleeve, any slight draught increases he wet bulb depression. It is found, however,that though the wet bulb temperature falls for velocities up to approximately 2 mIs, it remainssensibly constant up to approximately 40 rn/s.


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40Provided hat the air velocity remainswithin this range, he relative humidity can be determined romthe wet and dry bulb temperaturesalone.The wet bulb temperature within the 2 m/s - 40 m/s air velocity range is often referred to as the"Sling temperature".The following equation may be used o determine he vapour pressurePv of the water in the air.

P. - P., - 101.325(t~ - t..,kPa CC

Where p., = Saturatedvapour pressureat tsli..,., = Sling wet bulb temperature,., = Dry bulb temperatureA = 6.66 x I O~K" when siinS OC=5 94 x 10'" Ko1when t. < OoCsI,n.(Ref. Chartered nstitute of Building Services Engineers Guide, Volume C, 1988.)For example, if the dry bulb temperature s 25C and the "Sling" wet bulb temperature s 20.6C,then,From Steam Tables at 20.6C PsiD 2.426 kPa= 2.426 - 101.325 6.66 x 10-4(25 20.6)= 2.426 0.2969= 2.129 PaPwHence,

p., = 3./66 kParom Steam Tables at 25CP.p-

Hence, from the definition, Relative Humidity =2.1293.166 x 100%67.2%

The above method allows relative humidity to be determined from wet and dry bulb temperaturesand also allows for computerisedmonitoring and calculation of relative humidity.From Relative Humidity and dry bulb temperature all of the other relevant parameters may bedetermined by calculation, from tables or the psychrometric chart.


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41THE PSYCHROMETRIC CHARTWhile it is possible to calculate the properties of moist air from Dalton's and Gibb's Laws, it is farmore convenient to use the encapsulatedpsychrometric chart provided.For the majority of situations the standard arge psychrometricchart supplied in the spareskit (PartNo C 10/2) will be sufficiently accurate.This chart is calculated for a barometric pressureof 1013.25mBar which is a figure for a standardatmosphereat sea evel.However. under extreme weather conditions or at-very high or very low (below sea evel) altitudesthe effect of barometric pressurewill become significant.In order to allow for thesesituations a set of small charts are also supplied that cover the range from700 mBar to 1100 mBar in 2S mBar steps.In order to use hesecharts measure he local barometric pressureand convert ifnecessary to mBar.Note: mBar = 0.001 Bar = 100 N/m2= 0.749mm MercuryThe nearest applicable chart should then be used for all calculations under those conditions.Given any two independentproperties, a state point may be marked on the chart, and from this anumber of properties may be determined. The properties related by the chart are: .(i)(ii)(iii)(iv)(v)(vi)

Dry bulb temperatureWet bulb temperature sling)Specific volumeSpecific humiditySpecific enthalpyPercentagesaturation (which may be taken as equal to relative humidity)

It should be noted that the specific enthalpy scale s the enthalpy of the dry air ~ the enthalpy ofthe steam associatedwith it (both reckoned from OC) but expressed n kJ/kg of 5!!Y. air.ExampleObserved Wet bulb temperature = 20.6CObserved Dry bulb temperature = 25CThe state point on the psychrometric chart is located at the intersectionof 25C Dry bulb and 20.6CWet bulb (sling) - see Figure 10, Page 42.From the chart it will be seen hat, at this state, the air has the following properties:

(i) Specific volume (v) = 0.862 m]/kg(ii) Specific humidity (co) = 0.0135 kgikg(iii) Specific enthalpy (h) = 59.3 kJ/kgand (iv) Percentagesaturation = 67%The percentagesaturation may be compared with the Relative Humidity calculated from the samewet and dry bulb conditions of 25C dry bulb and 20.6C wet bulb.From the chart, PercentageSaturation= 67%By calculation on Page 40, Relative Humidity = 67.2%


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44SAMPLE TEST RESULTS AND CALCULATIONSThe following pages give typical observations and derived results from a test with the AirConditioning Laboratory Unit.Note that if the AC660A Computer Linked Upgrade Kit has been fitted. the test results may beautomatically recorded using the data ogging software. The data may then be converted to spreadsheet onnat and analysedon any suitable spreadsheet package. ;All, or any of the processesmay be investigated n anyone test provided that the restrictions givenin the RecommendedTest Conditions, Page 30, are heeded. iIn the following results, all of the facilities are in use and the changesof the properties of the air,i.e.

the wet and dry bulb temperaturesthe specific enthalpythe relative humidity or percentagesaturationthe specific humidity or moisture contentndare clearly illustrated and evaluatedby referring to the state points and processpaths plotted on thepsychrometric chart.It should be appreciated that individual units will give slightly different results and that localatmosphericconditions will have a large effect on the initial condition of the air. IIn addition, as stated n Useful Data on Page27, the actual output from all heaterswill be influencedby the supply voltage and this can be calculated using the heater resistance, and the local mainsvoltage which is given by the panel meter.The conditions for the following example test results were:

lkW Pre-heating2kW + IkW Steam njectionCooling/CompressoronRe-heating IkWAir flow set to a low rate of 3-4mm water gauge(fthe A660A Digital TemperatureUpgrade Kit has been itted, then eachof the temperatures eferredto on the schematic diagrams may be selectedand displayed on the digital indicator. ;


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45A660 OBSERVATION SHEET

Atmospheric Pressure: mBar2 3 4EST REF.

23.5ryWet

C.A Air at Fan Inlet 'C 18.3t1C 38.0Dry tJAfter Pre-heat orSteam Injection Wet 'C 29.2.DC 25.2ry

Wett,fter Cooling/Dehumidification C 24.7,

C 37.0ryWet

t7n After Re-heating 'C 27.4. 'C 21.5vaporator Outlet tlJDC 81.0ondenser Inlet tJ4'C 43.0ondenser Outlet tis

VAC 225upply Volts: Ll to N (415V)or LIto L2 (220V) VLkN m1(g)kN ml(g)kN m1(g)

290vaporator Outlet Pressure PI1008ondenser Inlet Pressure p~1000ondenser Outlet Pressure PJ3.9uct Differential Pressure z mm "10100an Supply Voltage- - --- -- Vr123ondensate Collected m.600ime Interval x 514.2I34a Mass Flow Rate iii.., g 5"


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4~IA660 DERIVED RESULTS

TEST REF. 2- 3 4

P, kW 0.080Fan Power(see Fan Volts v. Fan Watts curve)-1st Pre-heat Power,,2/R @ 235V p kW ,180a2nd Pre-beat PowerV1/R @ p kWC1Boiler, Lower 2kW PowerV2/R @ kWQBoiler, Upper 1kW PowerVl/R @ 23SV p kW 2.254aBoiler, lkW PowerV1/R @ 235V p kW ISSn1st Re-heat Powery2/R @ ..., p kWn2nd Re-beat PowcrV1/R @ kW(}

kN m1 (abs)vaporator Outlet Pressure 390IkN m1 (abs)ondenser Inlet Pressu~ 1109IkN m1 (abs)ondenser Outlet Pressure .101I

Evaporator Inlet 'C 8.0liCondensate Rate kg/sec 0.205.


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47SPECIMEN CALCULATIONSFrom the psychrometric chart on Page 42 the following air properties may be obtained:

h" m 51.3 kJ kg-'Q)" = 0.0109 g kg"'I, = 23.3 C~ = 18.3 ChB = 94.4 kJ kg"'Q)B = 0.0219 kg kg"t) = 38.0 Ct4 = 29.2 Chc = 75.0kJ kg-'roc = 0.0195kg kg-ts = 25.2 C~ = 24.7 C

~ = 37.0.Cta = 27.4 C ho = 86.1 kJ kg".(1)0 = 0.0190kg kg-IYo = 0.905 m) kg"

From Steam ables: For the ambient air the enthalpy of the water vapour,h. at atmospheric pressure = 2676 kJ kg-'Boiler feed water,hj at 20C (assumed) = 84 kJ kg-'

CALCULATION OF AIR MASS FLOW RATEFrom Useful Data, Page 27.

= 0.0517~ "0

. 0.0517~~~= 0.101 k! 'y-lAir mass flow rate, m,

ria,m,

APPLICATION OF ENERGY AND MASS BALANCES BETWEEN A AND Bon Page43, at a fan supply voltageof 100 Volts, the fansing the Fan Power curve, Figurepower is approximately 80 Watts.

The majority of this will result in heating of the air streams via losses n the motor and frictioneffects.For the boiler heatersat 235 VL:

~R.2352

Upper 2kW Heater Power =

24.S= 2.254kW~kW Heater Power -Rb 235247.81.155 kW


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48

Hence, Boiler Total Po~r InpIlI . 2.254 + 1.155. 3.409WFor the 1st IkW Pre-heaterat 235 V L: ~eater Power. -R,=~ 46.8= 1.lAo kW

'- ..~Ob. 3.409 kWFigure 11

For the system enclosedby the chain line:

By conservation of mass, m . 111.(1). - (I)..). 0.105(0.0219 - 0.0109). 1.15 x 10-3 I ~:IApplying SFEE,Heat Transfer Rate Work Transfer Rate - Enthalpy ChangeRateHeat Transfer Rate. Work Transfer Rate:

= Q. + Q, - -PI= 3.400+ 1.180 . 0.080kW= 4.669kW


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49

Enthalpy Change ~ate:= m.(h. - h..) - m. h.= 0.107(94.4 51.3) -= 4.515 W

IS X 10-3 X 84

This indicates a discrepancy of 154 W.There s also heat oss from the boiler, from Useful Data, Page27, heat oss rate rom boiler =1.33W/K. Allowing for a temperature ifference f 100- 23.5= 76.5K, heheat oss rom theboiler is 1.33x 76.5 = ~ . .Other discrepanciesmay be attributed to inaccuracies n measurement, he use of the psychrometricchart and heat loss from the duct.

BOILERIheoretical Evaporation RateAssumptions: !(i) Steamproduced s saturatedat atmosphericpressureand has a specific enthalpy of 2676 kJkg"'. I(ii) The feed water is at 20C and has a specific enthalpy of 84 kJ kg"'.(iii) The rate of heat transfer is 3.125kW -0.102 kW (calculated loss).

Rate of Evaporation Ah= 3.12S - 0.102 kg ,,"2676 84t 1~ ~ tn-) lrn ~-1= ._.~ x I.U &6"

This may be comparedwith 1.15 x 10.) kg s.\ obtained rom the change of specific humidity betweenA and B. ;


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.,t~: ;l:"~?'..~t..c":\t

REFRIGERATION SYSTEMThe pressures ecorded from the system are in gauge units relative to atmosphere.convert these o absolute pressure he local ambient pressuremust first be added. In order to

The ambient pressurewas 1010 mBaror 0.757mm Mercuryor 29.8" MercuryThis equates o 101 kN/m2.

390 kN m-t1109 kn mot1101 kN motHence, Evaporator Outlet = 290 + 101 =Condensernlet = 1008 + 101 =CondenserOutlet = 1000 + 101 =Note that a measurablepressuredrop exists in the condenserdue to friction effects. The condenseris a commercial unit and as such is designed by the manufacturerswith minimum cost as a primeconsideration. The evaporator,however, s purposedesigned or the A660 unit and utilises oversizediameter tube to reduce the pressuredrop to a negligible value.Using the absolutepressuresand temperatures ecordedaround he refrigeration system,a full cyclediagram may be drawn on a refrigerant Rl34a pressure-enthalpy iagram.The state points may be detenninedas follows. Refer to Figure 13 on Page51 where the state pointsare shown diagrammatically.

Evaporator Outlet/Compressor Inlet (State Point 1)Locate the 390 kN mol horizontal pressure ine and its intersection with a superheated emperatureof 21.5C (t,J. The vertical Enthalpy line hi at this point is 314 kJ kg-' and the specific volume is1.056 mJ kg.l.

Condenser Inlet (State Point 2)Locate the 1108 kN m-: horizontal pressure ine and its intersection with a superheated emperatureof 81.0C (tI4). The vertical Enthalpy line hz at this point is 364.4 kJ kg-I.

Condenser Outlet (State Point 3)Locate the 110 kn moz orizontal pressure ine and its intersectionwith the vertical sub-cooled iquidline from 43.0 saturated iquid condition.It will be found that the point in this case is Q.!! he saturated iquid line. This indicates that theliquid is not sub-cooled and reinforces the fact that the condenser s a commercial design. TheEnthalpy h) at this point is 163 kJ kg"l.After leaving the condenser he liquid enters he receiver and passes o the expansion valve whereit is assumed o expand adiabatically from 1100 kN m-z o 390 kN mol. Hence a vertical line isdrawn from State point 3 to State Point 4. The 390 kN mo2 orizontal pressure ine also correspondsto a line of constant emperaturebetween he saturated iquid and saturatedvapour conditions at 390kN mo2. The temperatureof saturation at 390 kN mo2s Soc.The state points are shown on a real R134a Pressure-EnthalpyDiagram for reference n Figure 14,Page 52. The conditions may also be determined rom the R 134a ables provided.From the test results the following conditions may be detennined for the refrigeration system:

314.0 kJ kg-.i ~,


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56/155

Ill.:1f'I

I

-+:J0O(JCUU , &O(DCUUm'11:~ /(La-adLU

a

~

d

~>t)oW

v.11.

"0~a0c-w ~n ~'0In0

:)~

,cQ~"~

0~axw


57/155


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530.056 mJ kg.'364.4 kJ kg-'161.9 kJ kg-I14.2 g/s

v -Ih -1h =h =J 4m,., =

APPLICATION OF ENERGY AND MASS BALANCES BETWEEN BAND C-- ~- ~ -

"~ ,I :/ . -"'. -" ",I

I\J..L.

he . 9'.' kJ kg-1 hC . 5.0 kJ kg-1we . 00219 kg kg-I wC . 0.0195 kg kg-1r:tJ

III, (B . -1~ . O. ~7 kg s

\ ..'~\ ..\ ,..'.." "' th1. 14.0 J kg"'

}I_b: 7"

~"C~lEnsote0123kg 116005iIe . .205 x 1)-3~ . 1619 J kg-1-1v1 . 0056 m kg

Figure ISFrom the observed and calculated data, the following parameterscan be stated or the system thatfonns the evaporator of the refrigeration system between Stations B and C of the air conditioningsystem,Calculated rate of condensation rom air stream:

= '".(Co). - Co)c)= 0.107(0.0219 - 0.019S)= 0.256 x 10-3q .I-I

Observed rate of precipitationThe discrepancy can be attributed to errors of measurement nd the use of the psychrometric chart,to water retention by the fins on the evaporator.and to re-entrainment of water into the air stream.

Application of the Steady Flow Energy Equation,Heat transfer rate. Enthalpy change rate - Work transfer rate

There is no work transfer rate between Band C, thusQ,-c : m.(hc - h,> + mh; + m,J.h. - h)

(.Thi~ tenn is frequently ignored.)


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54m.(hc - h.> + m.h; . 0.107(7594.5) 0.205 x 10-3 x 84 kW

= -2.07 kW

m,J-h. - hJ = 14.2 x 10-3(314.4 161.9)a 2.16 kW


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55Note that the true or active power would be VL Ic x Cos eJWhere Cas '2} is the power factor.The power factor is always less than 1.0 for an induction motor and is typically between 0.5 and 0.8depending upon the quality of the motor.The coefficient of perfonnance of a Refrigerator

Heat removed at Evaporator Qs-cCompressorwork W

Based upon the refrigerant enthalpy change across he compressor,W = dire! (hi - ~)

= 14.2 X 10-] (314.0 364.4)= -0.715 kW (Work into the system)

This compares with the 1645 VA electrical input.The difference may be accounted for by power factor (Cas 0). motor r R heating losses, rictionlosses and volumetric losses.From the example test results,

Qs-c (basedon refrigerantenthalpy) = 2.16 kWCoP for a refrigerator based on refrigerant enthalpy change at the compressor.- 2.160.715

3:.02CoP for a refrigerator based on electrical input,

2.161.645UlIt can be seen hat the theoretical CoP is much higher than that based on electrical input.

~Volumetric Efficiencv of CompressorVolume flow rate at compressor ntake, !~r~- . / litI - m,q VI= 0.0142 x 0.056= 7.952 x 10-4 m3 .\'-1'rom Useful Data on Page 27, assumea mean compressorspeed of

2700 + 3

y

= 2850 rpm at 50Hz.~~ 'i2t.( I'X

/),,r...

Compressor swept volume,


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56VI11. . _,i'~lf~:Swept volume7.952 x 10-4. c:c;'~'!"1.232 X 10-J

=.6iftAPPLICATION OF ENERGY BALA~CE BETWEEN C AND DFor the final Re-heaterat 23SV,

Y!R,23S2

Heaterpower Q,

46.4= 1.19 kW

,-1C - 75.0 k. hD - 86.1 kJ kgkg '~:r.'! ,wC a 0.0195 k g kg.," ,' tC

I. '1

wD . 0.0190 kg kg0 rho - 0.10 kg s

j'Or z 1.19kW

Figure 17Since there has been no increaseor decrease n the moisture content between C and D, (J)cand (J)Dshould be equal. The small discrepancy can be accounted or by observation and instrument errors.Applying the SFEE between C and D,

Q = m(ho - hc>ma(ho -hc) = 0.107(86.1 75)= +1.18kW

Discrepancies etweenelectrical input and air enthalpychangecalculationswill arise due tomeasurementnd nstrument rrors. I


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57It should be noted that since there is no change n moisture content between C and D, the enthalpychange of the air may be calculated from,

-

:- A.H = m. Cp(tO4 - tC)= m. Cp(T7 - T,>= 0.107 x 1.005[(37 + 273.15) - (25.2 + 273.15)]= 1.26 kW

The difference between this and the previously calculated value of 1.18 kW can be accOUnted for bythe factors mentioned above.

mntfIIIIIII


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58~o ~.EIERMINE THE SPECIFIC HEAT CAPACITY IC,\ OF AIRProvidedno changeof moisturecontent s involved, he specific heat capacity of air may bedetermined y any convenient teady low processe.g.heating r cooling).ProcedureHaving switched on the Air Conditioning Laboratory Unit, the air flow should be set to a convenientvalue and the pre-heatersswitched to give 2 kW (nominal) heating.When conditions have stabilised the following observationsshould be made,

TvoicaJ.20.5 C45.0 C33.0 .C17.3 C4 mm H2O110 V

Dry bulb temperatureat fan inlet t,Dry bulb temperatureafter pre-heater )Dry bulb temperatureafter re-heating t7Wet bulb tempetatureafter re-heating aOrifice differential pressure ZSupply Voltage VLFan Supply Voltage V,Atmospheric pressure

110 V1010 mbar

Typical observationsare given in the following Observation Sheet,

CalculationsSpecific volume of air at orifice (from psychrometric chart and t7 and I.) = 0.876 m) kg-IAlternatively, since the relative humidity is fairly low (18%), the specific volume may be calculatedfrom the gas equation, RT. . P~1 xJ:}3.0 273}. m3 kg-I

1.010 x IOS= 0.870 m3 k-t(The discrepancy between he two values is due to ignoring the moisture content of the air.Using the Fan Power curve, Figurepower is approximately 100 Watts. on Page 43, at a fan supply voltage of 110 Volts the fan

Air mass flow rate,: 0.0517rI~ 0. 0.0517rI kg $-1~Wja 0.110 ia .I-I

Applying the Steady Flow Energy Equation between Stations A and BFan Power .. Q, = m. (h, - hA)


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S9A660 OBSERVATION SHEET

Atmospheric Pressure. 1010 mBarTEST REF. 2 3 4

DryWet

'C 20.S.A Air at Fan Inlet 'C2Dry 'C 45.0)B Wet 'C.

After Pre-heatorSteam InjectionDryWet

'Csfter Cooling!Dehumidification 'C,Dry 'C 33.0~n After Re-heating Wet 'C 17.0.

Evaporator Outlet 'Cuf:()ndenser Inlet 'C,.Condenser Outlet 'Cl!Supply Volts: Ll to N (415V) orLito L2 (220V) VI. VAC 235Evaporator Outlet Pressure kN

m1(g)PICondenser Inlet Pressure kN

m1(g)p,Condenser Outlet Pressure kN

mZ(g)P1Duct Differential Pressure z mm H1O 4,0Fan Supply Voltage Vt 10Condensate Collected m.Time Interval 5RI34a Mass F1ow Rate g 5..ii ~,


65/155

60As there is no moisture change between A and B (there is no steam njection),. m. C,.. (t.~- A)= m. Cp.. (t) - a>

Fan Power+ Q.C = .P. m (t - )) 1

From the mains voltage VL and the Pre-heater esistances,Q = ~ + .2352, #.8 46.4= 2.39 W -

This compareswith 1.005 kJ kg-' K-' as the acceptedvalue.This proceduremay alternatively be undertakenacross Station C to Dusing Re-heating.


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61A660 OBSERVATION SHEET

Atmospheric Pressure: mBarTEST REF. 1 J 4

DryWet

'C.A Air at Fan Inlet 'CJDry 'CJ8 Wet 'C

After Pre-heatorSteam Injection t.DryWet

'C!fter Cooling!Dehumidification 'C,DryWet

'C,D After Re-heating 'C,Evaporator Outlet 'Cl)Condenser Inlet 'C'4Condenser Outlet 'C'$Supply Volts: LI to N (4ISV) orLIto L2 (220V) VI. VACEvaporator Outlet Pressure kN

m2(g)PICondenser Inlet Pressure kNml(g)PICondenser Outlet Pressur~ kN

m1(g)PJDuct Differential Pressure z mm "10Fan Supply Voltage VtCondensate Collected m~Time Interval I 5RI34a Mass F1ow Rate g 5-1it rcl


67/155

62A660 DERIVED RESULTS

TEST REF. t 1. 3 4P, kWaD Power(ste Fan Volts v. Fan Watts curve)

1st Pre-beat PowerV1/R @ 235V p kWn2nd Pre-heat Powery1/R @ p kWnBoiler, Lower 1kW PowerV /R @

kWQBoiler, Upper 2kW PowerV1/R @ 235V p kWnBoiler, lkW Powery1/R @ 23SV p kWn1st Re-beat Powery2/R @ kWQ2nd Re-beat Poweryz/R @ p kWaEvaporator Outlet Pressure PICondenser Inlet Pressure

kN ml (abs)kN ml (abs),

Condenser Outlet Pressure kN ml (abs)PJEvaporator Inlet 'C"Condensate Rate kg/sec.


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63

Free Standing Instrument Case housing a Digital Indicatorand 15-way Selector Switchwith attached wet and dry thermocouples


69/155

65OPERATIONThere are no special nstructions for operation of the A660A Digital Temperature Upgrade Kit oncecorrectly titted. When power is supplied to the A660 unit the display will automatically illuminateand display the temperatureselected.The numbers on the selector switch correspond o the temperature hannel numberson the schematicdiagram.

These are used onlyTemoerature IndicatorThe digital temperature indicator has five function keys on its front fascia.during manufactureo configure he instrument.The displaywill revert o nonnal after a 60ressing the keys may disturb the displayed value.

second delay.The individual temperaturepoints referred to in the schematicdiagram are selected and displayedon the indicator by switching to the corresponding number on the selector switch below the digitaltemperature ndicator.

MAINTENANCEIn the unlikely event that the digital temperature indicator should fail to illuminate or showunexpected emperatures,check the following. .

Failure to IlluDlinate:Check that the 3-pin UK plug is inserted correctly in the 4-way socket at the rear of the unit.

2. The digital display operatesat 220/230V on ~ local supplies.On European voltage (220V L-N) machines he supply is 1 phase and a neutral giving 230V.On 220V L-L machines he supply is 2 phasesgiving 220V.The 3-pin UK plugs contain a cartridge fuse in addition to the panel mounted miniature circuitbreakers. Check the continuity of this fuse.3.

Unexpected Temperatures Displayed:Check that the correct temperaturesensor s in the correct location. If necessary, emove thesensor rom its expected ocation and warm it to ensure ts response s correct. If necessaryandice and water mix can be used to check the values indicated by all sensors.Broken thennocouples usually result in an extreme positive or negative display or a faultindication. If this occurs, the internal thennocouple connections may be checked after firstremoving the 3-pin UK plug from its socket or disconnecting the A660 unit from its powersupply.


70/155

67


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82/155

79RECIRCULATIONIMIXING

From the test results and the psychrometric chart. at the Fresh Air Intake Station F:z, -ttt -tlJ -V, =W -,h, =

1.5mm H2O18.4C Dry bulb14.loC Wet bulb0.836 mJ kg.'0.0082 kg kg"'39.5 kJ kg-'

Hence, ~ )iii, ~ 0.0517v,= 0.OS17:::i:L~0:i36= 0.069g .I-IBy conservation of mass his equals the air dischargedat the air exit.

4.lmm H2O30.4C Dry bulb21.5C Wet bulb0.876 m' kg-.0.0124 kg kg-.62.5 kJ kg-'

At the in-duct orifice Station E:~ -~ =tit -VE =WE=hE -

The air passing hrough the fan in A also passes hrough Station E.mA : O.OS38~~

from the earlier In-duct Orifice Calibration, Page 75.Note that the value obtained for the unit in use should be used.

iii = O.OS38~ ~o:m. O.1163q.r-l


83/155

80From Figure 3 and by conservation of mass, he air flow recirculated back to the mixing section- m-m A ,= 0.1163 0.069mA m, = 0.0474 g $-1Assuming no heat loss or gain from the mixing section (adiabatic flow) and applying the SteadyFlow Energy Equation:

hA .Substituting for the known values:

hA5.68801163~ kJ kg-I

By mass balance, ~ mF WF + (mA - mF) WEiii.. w..m, w, + (mA - mF) WE

w..iii..

Substituting for the known values,WA .

= 0.JX)22 g kg-IUsing the intersectionofh,. = 46.5 kJ kg". and w,. = 0.0099 kg kg-I, the State Point A may be plotted(Refer to Page 42 Psychrometric Chart) and compared with the observed value from t. and ~"the differences can be attributed to measurementerrors and heat loss/gain from the surroundings.Note that from the Steady Flow Energy Equation and conservationof mass,

m.. h.. = mF hF + (m.. - mF) hE= m, + (mA m,)mA

It can be shown that, m~-(mA m,)This is the ratio ofFrom the mass flows 0.069

0.04741.4SS:1

~~hA h,.


84/155

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85INTRODUCTION

Windowshe data logging software supplied with the AC660A Upgrade is an interim measure.software will be supplied without further charge when available.The software provided is a fully operational copy of P.A. Hilton's HEAT97 data logging softwarewith pre-configured tiles that relate to the transducerchannels n use on the A660 unit.If the AC660A Computer Linked Upgrade Kit was factory fitted by P A. Hilton Ltd. theconfiguration files on the disc supplied will be pre-calibrated to match the transducers on theparticular machine.If the AC660A was user fitted, the calibration is carried out s part of the AC660B Software Upgradeinstallation carried out by the user.The GETTING STARTED section of the AC660B Software Upgrade manual deals with initialoperation of the data logging software.The pre-configured files for use with the factory fined AC660A are:

Channel config.fiIeConversion Factors fileOutput file66OCHAN660CON6600UT

The first screen displayed wh

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Air Conditioning Lab Unit A660

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