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Please refer to the Price Engineer’s HVAC Handbook for more information on Radiant Heating and Cooling

S E C T I O N H

Engineering GuideRadiant Products

H-2 All Metric dimensions ( ) are soft conversion. © Copyright Price Industries Limited 2011. Imperial dimensions are converted to metric and rounded to the nearest millimetre.

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RadiantProductsEngineering Guide

Introduction To Radiant Heating and Cooling

Radiantheatingandcoolingsystemsofferanenergyefficientalternativetoall-airsystems.Inmost cases, the supply air volume oftheairhandlingsystem is limited in sizeto satisfy only the ventilation and latentloads,withtheradiantsystemmakingupthe balance of the heating and coolingloads.Thiscomfortablemethodofheatingandcoolingmaysaveenergy,spaceandbuildingmaintenancecosts.Thefollowingpagesofferanintroductiontotheproducts,systemsanddesignmethodology,aswellastheadvantagesandlimitationsofradiantheatingandcooling.

Managementofheat loadscangenerallybeclassified into twodifferent types:all-air systems or hybrid systems. All-airsystems have been themost prominentinNorthAmericaduringthe20thcenturyandhavebeeninusesincetheadventofairconditioning.Thesesystemsuseairto

serviceboththeventilationrequirementaswellasthebuildingcoolingload.Ingeneral,thesesystemshaveacentralairhandlingunit(orrooftopunit)thatdeliversenoughcoolorwarmairtosatisfythebuildingload.Diffusersmountedinthezonedeliverthisairinsuchawayastopromotecomfortandevenlydistributetheair.Inmanycases,theamountofairrequiredtocoolorwarmthespace or the fluctuations of loadsmakedesigninginaccordancetotheseprinciplesdifficult.Draftisnotuncommon,andsomeceilingdiffusershavebeenknownto“dump”atlowcapacities.

Hybridsystemshavetwocomponents:anair-sideventilationsystemandahydronic(orwater-side)radiantsystem.Theair-sideisdesigned tomeetallof theventilationrequirements for thebuilding,aswell assatisfyalllatentloads.Itisa100%outsideairsystemandbecausetheprimaryfunction

of thesupplyair system isventilationasopposed tocooling, itcanbesuppliedathighersupplyairtemperaturesthanistypicalofoverheadairdistributionsystems.Thewater-sideisdesignedtomeetthebalanceofthesensiblecoolingandheatingloads.These loads may be handled by water based products, such as radiant panels, whichtransfer heat mainly by thermal radiation, andchilledsails,whichtransferheatusinga combination of thermal radiation and naturalconvection. RadiantpanelshavebeenusedforsensibleheatingandcoolinginNorthAmericanbuildingsforoverhalfacentury,andareawidelyrecognizedand well-establishedtechnology. Chilledsailswere originally developed in Europe inthe late 1990s, and are a relatively newtechnologyinNorthAmerica.

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© Copyright Price Industries Limited 2011. All Metric dimensions ( ) are soft conversion. Imperial dimensions are converted to metric and rounded to the nearest millimetre. H-3


Figure 1: Examplesofradiantheatingandcooling

Radiant heating and cooling systemsprovideaneffectivemethodforsatisfyingtheheatingand/orcoolingloadsofaspacewhilepromotingahighlevelofoccupantcomfortandenergyefficiency.

Hydronicsystemshavebeensuccessfullyused in several applications havingdramatically different characteristics. Someexamplesofareaswhere radiantsystemshavebeenappliedinclude:

• GreenBuildings • Hospitals• BurnCenters • IsolationRooms• Schools • DataCenters• OfficeBuildings • Airports• Cafeterias • TelevisionStudios• Theaters • Casinos

Benefits of Air-Water SystemsTherearemanybenefits toheatingandcoolingusingradiantpanelsandchilledsails. Advantagesofthesewaterbasedheatingandcoolingsystemsoverothermechanicalsystemsinclude:• Energyandsystemefficiency• Reducedsystemhorsepower• Indoorenvironmentalquality• Improvedindoorairquality• Increasedthermalcomfort• Reducedmechanicalfootprint• Lowermaintenancecosts• Improvedsystemhygiene

Radiantsystemsareagoodchoicewhere:• Thermalcomfortisamajordesign

consideration• Areashavehighsensibleloads• Areas require a high indoor air quality

(100%outdoorairsystem)• EnergyconservationisdesiredEnergy EfficiencyTheheattransfercapacityofwaterallowsforareductionintheenergyusedtotransportanequivalentamountofheatasanall-airsystem(Stetiu,1998).Thesereductionscanbe found primarily through reduced fanenergy.

The higher chilledwater supply (CHWS)temperaturesusedwithactiveandpassivebeam systems, typically around 58 °F[14.5°C],providemanyopportunitiesforareductioninenergyuse,includingincreasedwater-sideeconomizeruse.ThisincreasedCHWS temperature also allows formorewater-sideeconomizerhoursthanwouldbepossiblewithothersystemswhereCHWStemperaturesaretypically~45°F[7°C].

Concepts and Benefits

Indoor Air QualityDepending on the application, undermaximum load, only ~15 to 40% of thecoolingairflowinatypicalspaceisoutdoorairand is requiredbycode tosatisfy theventilation requirements.The balance ofthesupplyairflowisrecirculatedairwhich,whennottreated,cantransportpollutantsthrough the building. Radiant systemstransferheatdirectlyto/fromthezoneandare often used with a 100% outdoor airsystemwhichexhaustspollutedairdirectlyto the outside, reducing the opportunityforVOCsandillnesstotravelbetweenairdistribution zones.

NoiseRadiant systems do not usually havefan powered devices near the zone.Thistypicallyresultsinlowerzonenoiselevelsthanwhatisachievedwithall-airsystems.Insituationswherepassivebeamsareusedinconjunctionwithaquietairsystem,suchasdisplacementventilation,theopportunitiesfor noise reduction increase further.

Reduced Mechanical FootprintThe increased cooling capacity of waterallowsthetransportsystemtobereducedinsize.Itisgenerallynotunusualtobeabletoreplace~60ft²[6m²]ofairshaftwitha 6in. [150mm]waterriser, increasingtheamountoffloorspaceavailableforuseorlease.Duetothesimplicityofthesystems(i.e.reductioninthenumberofmovingpartsand the elimination of zone filters, drainpans,condensatepumps,andmechanicalcomponents),theretendstobelessspacerequiredintheinterstitialspacetosupporttheHVACsystem.

Lower Maintenance CostsWithnoterminalunitorfancoilfiltersormotorstoreplace,asimplecleaningisallthat is required in order tomaintain theproduct.


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When To Use Radiant Systems

Hygienic SystemWith the elimination of the majority of filtersanddrainpans, there isa reducedriskofmoldorbacteriagrowthintheentiremechanical system.

Radiant systems such as radiant panelsand chilled sails arewell-suited to someapplications and less so to others. As aresult,eachapplicationmustbereviewedforpotentialbenefitsaswellasthesuitabilityofthesetypesofsystems.Oneconsiderationwhichcanassistinthedecisiontoemployhydronicsystemsasopposedtoanall-airsystem, is the air-side load fraction—orthepercentageofthetotalairsupplythatmust be delivered to the zone to satisfycodeanddehumidification requirements.Table1showstheloadfractionforseveralspaces.Inthetablethebestapplicationsforhydronic systems are those with the lowest air-sideloadfractionastheyaretheonesthatwillbenefitthemostfromtheefficienciesofhydronicsystems.Anotherfactorwhichshouldbe examined is the sensibleheatratioorthepercentageofthecoolingloadthat issensibleasopposed to latent.Thelatent loadsmustbesatisfiedwithanairsystemandoffersomesensiblecoolingatthesametimebecauseofthetemperatureofdehumidifiedair.Ifthetotalsensiblecoolingloadissignificantlyhigherthanthecapacityoftheairsuppliedtosatisfythelatentloads,aradiantsystemmightbeagoodchoice.

Commercial Office BuildingsInanofficebuildinghydronicheatingandcoolingsystemsprovideseveralbenefits.Thelowersupplyairvolumeoftheairhandlingsystemprovidessignificantenergysavings.In addition, the smaller infrastructurerequiredtomovethislowerairflowallowsforsmallplenumspaces, translating intoshorterfloor-to-floorconstructionorhigherceilings.Thelowersupplyairvolumeandelimination of fans at or near the spaceoffersasignificantreductioningeneratednoise.Oftenthelowerairflowtranslatestoreheatrequirementsbeingreduced.Inthecaseof100%outsideairsystems,thelightingloadcapturedinthereturnplenumisexhaustedfromthebuilding,loweringtheoverallcoolingload.

SchoolsSchools are another application that canbenefitgreatlyfromradiantpanelsandchilledsailssystems.Similartoofficebuildings,thebenefitsofalowersupplyairvolumetothespacearelowerfanpower,shorterplenumheight, reduced reheat requirement, andlowernoise levels (oftenacriticaldesignparameterofschools).

Hospital Patient RoomsHospitals are unique applications in thatthe supply air volume required by localcodesforeachspaceisoftengreaterthantherequirementofthecoolingandheatingload.Insomecasesthestandardorcoderequires thesehigherair-changerates forall-air systems only. In these cases thetotalair-changeraterequiredisreducedifsupplementalheatingor cooling isused.This allows for a significant reduction insystemairvolumeandyieldsenergysavingsandotherbenefits.

Furthermore, because these systems aregenerally constant air volume with thepotentialtoreducetheprimaryair-changerates,reheatandthecoolingenergydiscardedaspartofthereheatprocessisasignificantenergysavingsopportunity.Dependingontheapplication,a100%outsideairsystemmay be used. These systems utilize no returnairandnomixingofreturnbetweenpatientrooms,potentiallyloweringtheriskofhospitalassociatedinfections.

Hotels / Dorms Hotels,motels,dormitories,andsimilartypebuildings can also benefit fromhydronicsystems. Fanpowersavingsoftencomefrom the elimination of fan coil units located intheoccupiedspace.Theenergysavingsassociatedwiththese“local”fansissimilarinmagnitudetothatoflargerairhandlingsystems.Italsoallowsfortheeliminationof the electrical service required for theinstallation of fan coil units as well as a reduction in the maintenance of the drain andfiltersystems. The removalof thesefansfromtheoccupiedspacealsoprovideslowernoiselevels,whichcanbeasignificantbenefitinthesleepareas.

ApplicationTotal Air Volume (Typ.)

Ventilation Requirement (Typ.)

Air-Side Load Fraction

Office 1cfm/ft2[5L/sm2] 0.15cfm/ft2[0.75L/sm2] 0.15

School 1.5cfm/ft2[7.5L/sm2] 0.5cfm/ft2[2.5L/sm2] 0.33

Lobby 2cfm/ft2[10L/sm2] 1cfm/ft2[5L/sm2] 0.5

PatientRoom 6 ach 2 ach 0.33

Load-drivenLab 20 ach 6 ach 0.3

Table 1: TypicalloadfractionsforseveralspacesintheUnitedStates

LimitationsThereareseveralareasinabuildingwherehumidity canbedifficult to control, suchas lobby areas and locations of egress.These areasmay see a significant shortterm humidity load if the entrances are not isolated insomeway(revolvingdoorsorvestibules). In theseareas,achoiceofacomplimentarytechnologysuchasfancoilunitsordisplacementventilationisideal.

Otherapplicationsmayhavehighairflow/ventilationrequirements,suchasanexhaustdriven lab. The majority of the benefitprovidedbythehydronicsystemislinkedtothereductioninsupplyairflow.Assuch,theseapplicationsmaynot seesufficientbenefittojustifytheadditionofthehydroniccirculationsystem,makingthemnotlikelytobeagoodcandidateforthistechnology.


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Products - Radiant Panels

OperationRadiantpanelsmainlyusethermalradiationtohandletheheatingorcoolingloadsofaspace.ThermalradiationheatexchangeisbasedondifferencesinsurfacetemperaturesasdiscussedinChapter3—IntroductiontoHeatTransfer from the Price Engineer'sHandbook.Radiantpanelsaddenergytoorremoveitfromaroommainlyusingradiationwith surfaces in the room, but also directly tooccupants(Figure 2).Toalesserextent,thepanelsalsoheatorcoolaroomthroughconvectionoftheroomairasitisheatedorcooledbythepanelsurface.

Because radiant panels can handle thesensibleportionofabuildingloadtheymustbepairedwithanairsystemforventilationand latent load removal. In heating, forexample,heatfromwarmwateristransferredtothepanelsurfaceviaconduction.Theheatpasses through the tubing, themountingextrusion(the‘fin’),andthepanelitself,tothepanelsurface.Atthesurface,heatisbothradiated to other surfaces in the room and transferredtoroomairvianaturalconvection.

Theheattransferthrougharadiantpanelcaneasily be modeled with a thermal resistance circuit, as in Figure 3. The resistance circuit represents the actual components of aradiantpanel.Thenodesrepresentvarioustemperatures of the panel componentsurfaces,andthe‘resistors’representtheheatconductionthroughthepanelcomponentsandtothesurroundingroom.The t̅w node representsthemeanwatertemperaturethattransfersthroughthecoppertubingtotheactualpanel components. Toachieve themaximum possible surface temperatureof thepanel,Tsurf, the conduction from the pipe to the fin to the panel surfacemustbemaximized,or,inversely,theresistancemustbeminimized.Thiscanbeachievedbyusingmaterialsthatarehighlyconductivesuchascoppertubingandaluminumforthefinandpanel.Evensurfacecontactbetweenthe water tubing and the fins decreasesresistance,alongwiththermalpastewhichcanbeappliedbetweenthefinandthepanelsurface tohelpspreadheatevenly to thepanelsurface(Figure 4)

RADIATION

Figure 2: Radiationpathways

Rconv,s

Tair, ceiling

Tpanel, outer insulation

Rinsulation

AUST,ceiling

Rrad,s

Rconv,room

Tair, room

Fin

SurfaceAUST, room

Tsurf, panel

Rrad,room

Rfin

T fin, ave

Rpanel surface Copper tubing with

Towards slab

Towards room and occupants

AUST = Area-weighted temperature of all indoor surfaces of walls, ceiling, floor, windows, doors, etc.

Figure 3:Thermalresistancecircuitdiagramofamodularradiantpanel

Without Thermal Paste

With Thermal Paste

Figure 4: Surfacetemperaturedistributionofaradiantpanel



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Interconnect

Return

The amount of thermal energy that istransferredtotheroomsurfacesviaradiationisdependentontheviewfactorsfromthepaneltothevariousroomsurfaces,alongwiththeemissivityofthepanelsurface.Alargertemperaturegradientresultsingreaterthermalradiation.Also,theviewfactorsfromthepaneltotheroom,aswellastheemissivityofthepanelsurfaceaffectthetemperatureofthereceivingsurface.RefertoChapter3—IntroductiontoHeatTransferoftheEngineer'sHandbookforfurtherdetailsonthetheoryofradiantheattransfer.Insulationonthebackofthepanelhelpsdecreasetheamountofheatthattravelsbyradiationorconvectiontotheceiling.

ApplicationsRadiantpanelscanbeappliedtovirtuallyany space, especially areas with highsensible loads,areas that requireahighindoorairquality,orareaswherethermalcomfortandenergyconservationaremajordesignconsiderations.Typicalapplicationsofhydronicradiantpanelsarehospitals—includingpatientrooms,isolationrooms,andburncenters—schools,datacenters,officebuildings,andairports.

1. Linear Radiant Panels Linearradiantpanelsareconstructedofaseriesof integratedaluminumheatsinksand copper tubing. Multiple heat sinksformthevisiblefaceofthepanelandarejoinedviatongue-and-grooveconnections.Insulatedbackinghelpskeep the radiantexchangelimitedtotheoccupiedspace.Thecomponentsoflinearradiantpanelscanbeseen in Figure 5.

2. Modular Radiant PanelsModular radiant panels are designed tobe integrated intooralongsidestandardsuspendedceilingsystemsortosuspendfromtheceilinginanexposedapplication.Thevisiblesideofthemodularradiantpanelis a formed steel or aluminum sheet to whichthealuminumheatsinksareattached.Coppertubingrunsthroughtheheatsinks,andinsulatedbackinghelpskeeptheradiantexchangelimitedtotheoccupiedspace.Thecomponentsofmodularradiantpanelscanbe seen in Figure 6.

Connecting Radiant PanelsBothlinearandmodularradiantpanelscanbe connected in series, as shown below. The panelsaresuppliedwithstraight tubing,using180°returnconnectionsforendpanelsandinterconnectsbetweenpanels.Atypicalseriesapplicationofpanelsisaperimeterlayoutwiththepanelsrunningfromwalltowallwhereaneventemperaturedistributionacrossseveralpanelsisdesired.Thelooseconnectionpiecesallowthepanelstobetrimmedinordertofit.Intheseapplications,thefinalconnectionsaredoneinthefield(Figure 7).

Products - Radiant Panels

Figure 5:Componentsofalinearradiantpanelwithoutinsulation

Figure 6:Componentsofamodularradiantpanelwithoutinsulation

Figure 7:Seriesconnectiondetailsforlinearradiantpanels

DESIGN TIPLinearandmodularradiantpanelscanbeconnectedinseriesina‘cloud’configuration,providedthepanelsurfacetemperaturesdonotvarysignificantlyandwater-sidepressuredropismaintainedatacceptablelevels.Agroupingof4to6modularpanelsat2ft[600mm]wideand4ft[1200mm]longiscommonasthepanelsurfacetemperaturewilltypicallybewithin2to4°F[1to2°C]acrossthegroupingincoolingor10to20°F[6to12°C]inheating.


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Products - Chilled Sails

OperationChilled sails provide a functional anduniquealternativetoconventionalradiantpanels. Sails couple the radiant coolingeffectsofstandard radiantpanelswithaconvectivecomponent. Incoolingmode,chilledsailscreatenaturalconvectionbycoolingthesurroundingairasitpassesoverthesurfacefacingtheplenum.Astheairfallsintotheoccupiedzone,wherewarmair ispulledover thesail, theconvectivecoolingcapacityofthesailiscoupledwiththeradiantcapacityofthecoolsailsurface,resultinginacoolingcapacitygreaterthanthatofstandardradiantpanels.Incooling,theapproximatebreakdownofheatmodetransferofchilledsailsis30%bythermalradiationand70%bynaturalconvection.

Ageneralairflowdiagramofanexposedchilledsailinheatingandcoolingmodecanbe seen in Figure 8.Incertainapplications,sailscanalsobeusedforheating.Inheatingmode, the sails use radiation only to heat the zone below. Because sails have noinsulation on their reverse side, heat isradiated not only towards the room, but alsotowardsthebuildingstructure.Astheslabwarms,itinturnhelpsheattheroomtoasmallextentbythermalradiationandnaturalconvection.

Likeradiantpanels,chilledsailscanalsobe analyzed using a thermal resistancecircuitdiagram,asseeninFigure 9. The resistance circuit represents the actualcomponentsofachilledsail. Thenodesrepresentvarioustemperaturesofthesailcomponentsurfacesortheconditionsoftheroom,andthe‘resistors’representtheheatconductionthroughthepanelcomponentsor heat transfer between the sail and the room.Themeanwatertemperature,t̅w, node representsthemeanwatertemperaturethattransfersthroughthecoppertubingtotheactualsail.Mostchilledsailsareonesingleextrusion,whichmeansthatthe‘fin’and‘sail’areonesolidpieceofaluminum.Tomaximize heat transfer through the sail,or, conversely, tominimize resistance, amaterialwith high thermal conductivity,suchasaluminum,istypicallyused.

AsseeninFigure 10, a chilled sail transfers heat to a room with a combination of radiationandnaturalconvection.Becausechilled sails have no insulation on theirreversesides,heatistransferredfromthecoppertubing/fintotheslabandplenum.

The heat transfer from the sail to the room hasthreecomponents:naturalconvectionwith the room air, thermal radiation with the room surfaces, and thermal radiation from thetopofthesailwitheitherthesuspendedceilingorthefixedceiling,dependingonthedesigndetails.

Figure 8: Airflowpatternofanexposedchilledsailincoolingandheatingmode

Cooling

Heating

Sail

Sail

Figure 9: Thermalresistancecircuitdiagramofachilledsail

Figure 10: Typicalchilledsail


Towards slab

Towards room and occupants

Tair, room AUST,room

Rrad, room

Rrad, ceiling

Tair,ceiling

Rconv, ceiling

Rconv, room

R fin/sail

AUST,ceiling

Tsurface, fin/soil Sail/Fin

Copper tubing with

Top Bottom


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Incoolingmode,themajorityoftheheattransferoccursbynatural convectionaswarm air rises due to natural buoyancy forces,passesoverthechilledsails,cools,and then sinks down into the occupiedzone.Inheatingmode,heatistransferredmainlythroughthermalradiationwithroomsurfaces,where it increases theaverageunheatedsurfacetemperatureoftheroom(AUST).Aswarmairrisespasttheheatedsails, natural convection occurs, whichresults in warmer return air. Because sails arewater-onlysystems,theycanonlyhandlethesensibleportionofabuildingloadandmustbepairedwithafreshairsystemforventilationandlatentloadremoval.

ApplicationsTheircoolingcapacityanduniquedesignmakechilledsailsanexcellentalternativetopanelsystems,particularlyinapplicationsthathaveanarchitectural focus. Typicalapplicationsofchilledsailsincludeoffices,meeting/conference rooms, theaters,studios,lobbies/foyers,waitingareas,oranyareaswereradiantpaneluseisappropriate.Chilledsailsaredesignedforarchitecturalappealandaretypically installedinT-barceilinggridsorfreelysuspended.

Figure 11:Exposedchilledsails

Figure 13: Activeandinactivesections

Figure 12: Continuous chilled sail sections


ComponentsChilledsailsaretypicallyconstructedfromcopper piping and aluminumextrusionsdesigned to optimize capacity, as wellas for architectural appeal (Figure 11).Exposedchilledsailsareofteninstalledasthefinishedceilingbyeitherinstallingasacloud, as shown in Figure 11,orcombiningactiveandinactivesectionsforacontinuouslook,asseeninFigure 12.

Chilledsailsaredesignedtobe installedeitheropentotheroomorbeloworbehind

aperforatedceiling,andmaybeinstalledinlargeordiscretesections.Ineithercase,theoperationofthechilledsailrequiresthataportionoftheceilingisopentoallowaircirculationtotherearoftheassembly.Forinstallationsbehindaperforatedceilingorinstalledasacloudinanopenceiling,thisisgenerallynotanissue.Forinstallationswhere the sails are installed in a ceilingsystem,thisisoftenaccomplishedbyusingnon-activesectionsofsail toallowairtopassuptotheareaabovetheceiling,asshow in Figure 13.

Passive Elements for Return Passive Elements for Return

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075

80

90

100

10 20 30 40 50 60 70

Capa

city

of S

ail,

%

Free Area as a Percentage of Sail Area

Figure 16:Typicalpipingofasailwithanoddnumberofpasses

Figure 17:Typicalevennumberofpasses

Figure 14:Freeareavs.activeareaofsail Figure 15: Clearance between chilled sail and slab

00 1 2 3 4 5 6

20

40

60

80

1000 50 100 150

Effe

ctiv

e Ca

paci

ty o

f Sai

l, %

Clearance Between Chilled Sail and Slab, in.

Clearance Between Chilled Sail and Slab, mm

Water Supply

Sail 1 Sail 2 Sail 3

Water Return

Flex HoseFlex Hose

Water Supply

Flex Hose


Theamountoffreeareavs.activeareaofsailwillaffecttheperformanceofthesailsystemaccordingtoFigure 14.Inallcases,theamountofspacebetweenthebackofthesailandthestructuralslabwillaffectthelevelofcirculation,andtherebytheconvectivecoolingcomponent.ThiscapacityisaffectedaccordingtoFigure 15.


Connecting Chilled SailsDependingonthewidthoftheunit,thesailsmayhaveconnectionlocationsonoppositeends. Sails with an odd number of sections willhave connectionsonoppositeends,and even number of sections will haveconnections on the same ends, as seen inFigures16and17below.Flexhoseisgenerallyusedtoconnectthewaterflowbetween the units.


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1. Determine the ventilation requirementTheventilationrequirementshouldbecalculatedtomeetventilatiowncodes.Forexample,usingASHRAEStandard62-2004todeterminetheminimumfreshairflowrate:

L1

where Qoz= minimumfreshairflowrate,cfm[L/s] Rp = outdoorairflowrateperperson,cfm/person[L/s(person)] Pz = zonepopulationormaximumnumberofoccupantsinzone Ra = outdoorairflowrateperunitarea,cfm/ft2[L/sm2] AZ = zonefloorareaornetoccupiedareaofthezone,ft2[m2]

2. Determine required supply air dew-point temperature to remove the latent load

L2

where qL = latentload,Btu/h[W] Qs = supplyairflowrate,cfm[L/s] ΔW= differenceinhumidityratiobetweenthesupplyairandtheroomcondition, lbm,w/lbm,DAorgr/lbm,DA[kgw/kgDAorgw/kgDA]

Typically,themoisturecontentoftheventilationairwillbesufficientlylowintheheatingseasontooffsettheinternalgains.

3. Determine the occupied zone humidity ratio if there is excessive latent coolingFromequationL2:

L3

where Woz = humidity ratio of the room condition, lbm,w/lbm,DAorgr/lbm,DA[kgw/kgDAorgw/kgDA] WSA=humidityratioofthesupplyair,lbm,w/lbm,DAorgr/lbm,DA[kgw/kgDAorgw/kgDA]

IfWozisdeterminedtobetoolowforcomfort,humidificationoftheventilationairshouldbeconsidered.

4. Determine the supply air volumeThesupplyairvolumeisthemaximumvolumerequiredbycodeforventilation,andthevolumerequiredforcontrollingthelatentload:

L4

where QL = airflowraterequiredforcontrollingthelatentload,cfm[L/s]

5. Determine the heating capacity of the supply air

IP L5

SI L5

where qs,air=heatingcapacityofthesupplyair,Btu/h[W] ρ =fluiddensity,lbm/ft3[kg/m3] cp =specificheatatconstantpressureBtu/hlb°F[kJ/(kgK)] Qair=supplyairflowrate,cfm[L/s] Δtair=airtemperaturechange(treturn - tsupply),°F[K]

Design Procedure – Heating


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6. Determine the heating required from the water side

L6

where qs, hydronic=heatingcapacityofthewaterside,Btu/h[W] qt =totalsensibleheatingcapacity,Btu/h[W]

7. Determine an appropriate temperature loss through the panels Specifyapanelsurfacetemperature,thenfindtherelatedmeanwatertemperature,t̅w.



Figure 18: Connectionbetweenmeanwatertemperatureandpanelsurfacetemperatureor, tpanel-troom=0.74(t̅w - troom)

0 10 120

0 10 20 30 40 50 60

0

10

20

30

40

50

60

70

80

90

0

5

35

45

50

t w - t

room

[R]

t w - t

room

[K]

20 30 40 50 60 70 80 90 100 110

10

15

20

25

30

40

tpanel - troom [K]

tpanel - troom [R]

8. Determine the heat transfer coefficients for the radiant panelsThenaturalconvectioncoefficientis:

IP L7

SI L7

Where hc,natural=naturalconvectioncoefficient,Btu/hft2°F[W/m2K] ta =roomtemperature,°F[K] tpanel=paneltemperature,°F[K] Dh =hydraulicdiameter,ft[m]

Dh = 4Apanels / Ppanels L8

Where Apanels=surfaceareaofactivepanels,ft2[m2] Ppanels=thepipeinternalperimeter,ft[m]


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Theforcedconvectioncoefficientis:

IP L9

SI L9

Where hc,forced=forcedconvectioncoefficient,Btu/hft2°F[W/m2K] ach =airchangerate,cfm/ft2[m3/hm2]

Thetotalconvectioncoefficientis:

L10

Where hc,total=totalconvectioncoefficient,Btu/hft2°F[W/m2K]

9. Determine the specific capacity of the radiant panelsTheconvectiveheattransferpersquarefoottothepanelisdetermined:

L11

where q̋c =convectiveheatfluxorconvectiveratepercrosssectionalarea,Btu/hft2[W/m2] qc=convectiveheattransferrate,Btu/h[W] A = surface area of the medium, ft2[m2]

Assumingthatthewalltemperatureisequaltotheairtemperature,theradiantheatexchangewiththepanelisdetermined:

IP L12

SI L12

where q”r =radiantheatflux,Btu/hft2[W/m2] AUST=area-weightedtemperatureofallindoorsurfacesofwalls,ceiling,

floor,windows,doors,etc.(excludingactivepanelsurfaces),°F[°C]

Thetotalheattransferperunitoffaceareais

L13

where q̋o=totalheatflux,Btu/hft2[W/m2]

10. Determine the area of panels required

L14

where Apanels =areaofpanels,ft2[m2]

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Example 1 - Patient Room (IP)

Considerthepatientroomshowninthefigurebelow.Thepatientroomincludesatelevision,monitoringequipmentandoverheadlighting.Thetemperatureset-pointis75°Fwithaminimumrelativehumidityof40%.Theroomis10ftwideand20ftlong,witha9ftceiling.Theattachedtoiletroomis5ftwideand7ftlong,withan8ftceiling.Thereisoneexteriorwallandwindow.Thesupplyairtemperatureinheatingmodeisresetto95°F,withtheheatingwatertemperatureat175°F.

DetermineThewaterflowrateandpressuredropfortheheatingpanelsrequiredtohandletheheatingload,assuming15°Foutdoorairtemperature

Overnightinwinter,theenvelopelossis4800Btu/handtheinternalgainsatthattimearelimitedtothepatientload:

Design Considerations

Patient 160Btu/h

Medical Staff/Visitors 0

Television 0

Medical Equipment 0

Overhead Lighting 0

Envelope -4800Btu/h

Total -4640Btu/h

Patient latent load 155Btu/h

Determine the Ventilation RequirementForthisexample,localcodereferstoASHRAEStandard170-2008fortheHVACsystem.AccordingtoASHRAEStandard170-2008,patientroomswithauxiliaryheatingrequire4achofsupplyair,ofwhichtwoareoutdoorair.

Determine the required supply air dew-point temperature to remove the latent loadFromequationL2:

Usingtheventilationrate:

PATIENT ROOM

Corridor

10 ft

20 ft

5 ft

7 ft


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Inthiscase,thesupplyairisamixofthereturnairandtheventilationair.Thismixtureofoutdoorair(attheoutdoorconditions,assumingsaturatedairat15°Fwithahumidityratioof12.5gr/lb)andreturnair(assumingthatitisatthedesignconditionsof75°F,40%RH–52.5gr/lb),willhavemorethanenoughcapacitytohandlethelatentload.Inapplicationswherehumidityiscritical,furtheranalysismaybedonetodeterminetherequirementofhumidification.FormoreinformationrefertoChapter5—IntroductiontoPsychrometricsofthePriceEngineer'sHandbook.

Determine the heating capacity of the supply airUsingequationL5:

Determine the heating required from the water side

Determine an appropriate temperature loss through the panelsUsingameanwatertemperatureof:

Determine the heat transfer coefficients for the radiant panelsUsingequationL7andtherelationforDhfromequationL8,thenaturalconvectioncoefficientisdetermined:

Duetotheconfigurationoftheroom,itcanbeassumedasafirstestimationthatthepanelswillbearrangedattheperimeterwheretheloadis,andrunthewidthoftheexposure(10ft).Assumingalsoa2ftwidthofpanel:

UsingequationL9,theforcedconvectioncoefficientisdetermined:

UsingequationL10,thetotalconvectioncoefficientisdetermined:


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Determine the specific capacity of the radiant panelsUsingequationL11,theconvectiveheattransferpersquarefoottothepanelisdetermined:

Theoutsideairtemperaturehasasignificantimpactontheinsidesurfacetemperaturesofexteriorwalls.Theexteriorwalltemperatureisdeterminedwithanhvalue,convectiveheattransfercoefficientofaverticalwall,of1.46Btu/(hft2°F)andaUvalue,overallheattransfercoefficient,of0.315Btu/(hft2°F):

Theaverageunheatedsurfacetemperatureis:

t

Calculatingtheradiantheatexchange:

FromequationL13,thetotalheattransferperunitoffaceareais:

Determine the area of panels requiredUsingequationL14:


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Therefore,theassumptionofpanelsize(20ft2)usedtocalculatethehydraulicdiameterisappropriate.

TheflowraterequiredtomanagetheloadwithapanelΔTof10°Fis:

Forsimplicity,a2ft×10ftPriceRPLlinearradiantpanelisselected.

Thispanelwith0.41gpmwillhaveapipevelocityof0.55fps,whichcorrespondstoaReynoldsnumberof1900,whichisinthelaminarrange.Forabetterselection,theflowrateisincreasedto1.3gpm,whichcorrespondswithaReynoldsnumberof6400,whichisintheturbulentregion.Fromtheperformancechart,thisalsoincreasesthepressuredropfrom0.31ftto3.7ft,whichwillallowbetterflowcontrolofthepanel.

Recalculatingthetemperaturelossinthepanelaswellasthecapacity:

Thisincreaseincapacitywillresultinonlyrequiring15.7ft2,thoughitismorepracticaltostaywiththeoriginalsizeinordertomaintainaesthetics(thepanelwillrunthelengthoftheperimeter)aswellasastandardmodulesize(24in.wide).Panelscanbedesignedtohavebothactiveandinactivesectionstomaintainaesthetics.

Whenrunningtheentirelengthoftheroom,thetrimandseriesoptionwillallowthepaneltobetrimmedonsiteiftheroomsizevariesslightlyduringconstruction.

PATIENT ROOM

Corridor

Panel


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Considerthepatientroomshowninthefigurebelow.Thepatientroomincludesatelevision,monitoringequipmentandoverheadlighting.Thetemperatureset-pointis24°Cwithaminimumrelativehumidityof40%.Theroomis3mwide,6mlong,andhasa3mceiling.Thereisoneexteriorwallandwindow.Thesupplyairtemperatureinheatingmodeisresetto35°Candtheheatingwatertemperatureis72°C.

PATIENT ROOM

Corridor

3 m

6 m

1.75 m

2.25 m

DetermineThewaterflowrateandpressuredropfortheheatingpanelsrequiredtohandletheheatingload,assuming-10°Coutdoorairtemperature.

Overnightinwinter,theenvelopelossis1400Wandtheinternalgainsatthattimearelimitedtothepatientload:


Patient 50 W

Medical Staff/Visitors 0

Television 0

Medical Equipment 0

Overhead Lighting 0

Envelope -1400W

Total -1350W

Patient latent load 45W

Determine the Ventilation RequirementForthisexample,localcodereferstoASHRAEStandard170-2008fortheHVACsystem.AccordingtoASHRAEStandard170-2008, patientroomswithauxiliaryheatingrequire4achofsupplyair,ofwhichtwoareoutdoorair.

Determine the required supply air dew-point temperature to remove the latent loadFromequationL2:


Example 1 - Patient Room (SI)


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Inthiscase,thesupplyairisamixofthereturnairandtheventilationair.Thismixtureofoutdoorair(attheoutdoorconditions,assumingsaturatedairat-10°Cwithahumidityratioof1.8g/kg)andreturnair(assumingthatitisatthedesignconditionsof24°C,40%RH–7.4g/kg),willhavemorethanenoughcapacitytohandlethelatentload.Inapplicationswherehumidityiscritical,furtheranalysismaybedonetodeterminetherequirementofhumidification.FormoreinformationrefertoChapter5—IntroductiontoPsychrometricsofthePriceEngineer'sHandbook.

Determine the heating capacity of the supply airUsingequationL5:

Determine the heating required from the water side

Determine an appropriate temperature loss through the panelsUsingameanwatertemperatureof:

Determinetheheattransfercoefficientsfortheradiantpanels

UsingequationL.7andtherelationforDhfromequationL.8,thenaturalconvectioncoefficientisdetermined:

Duetotheconfigurationoftheroom,itcanbeassumedasafirstestimationthatthepanelswillbearrangedattheperimeterwheretheloadis,andrunthewidthoftheexposure(3m).Assumingalsoa600mmwidthofpanel:





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Determine the specific capacity of the radiant panelsUsingequationL11,theconvectiveheattransferpersquarefoottothepanelisdetermined:

Theoutsideairtemperaturehasasignificantimpactontheinsidesurfacetemperaturesofexteriorwalls.Theexteriorwalltemperatureisdeterminedwithanhvalue,convectiveheattransfercoefficientofaverticalwall,of8.29W/(m2K)andaUvalue,overallheattransfercoefficient,of0.055W/(m2K):


Calculatingtheradiantheatexchange:




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Therefore,theassumptionofpanelsize(1.8m2)usedtocalculatethehydraulicdiameterisappropriate.

TheflowraterequiredtomanagetheloadwithapanelΔTof5Kis:

Forsimplicity,a600mm×3000mmRPLlinearradiantpanelisselected.

Thispanelwith0.027kg/swillhaveapipevelocityof0.24m/s,whichcorrespondstoaReynoldsnumberof4300withapressuredropof1.2kPa,whichisagoodselection.

Whenrunningtheentirelengthoftheroom,thetrimandseriesoptionwillallowthepaneltobetrimmedonsiteiftheroomsizevariesslightlyduringconstruction.

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Corridor

Panel


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Design Procedure – Cooling

1. Determine the ventilation requirementTheventilationrequirementshouldbecalculatedtomeetventilationcodes.Forexample,usingASHRAEStandard62-2004todeterminetheminimumfreshairflowrate:

L1

2. Determine required supply air dew-point temperature to remove the latent load

L2

Iftherequiredhumidityratioisnotpractical,recalculatethesupplyairvolumerequiredwiththedesiredhumidityratio.

3. Determine the supply air volumeThesupplyairvolumeisthemaximumvolumerequiredbycodeforventilationandthevolumerequiredforcontrollingthelatentload:

L4

4. Determine the sensible cooling capacity of the supply air

IP L5

SI L5

5. Determine the sensible cooling required from the water side

L6

6. Determine an appropriate temperature rise through the panels Apaneltemperaturecorrectionisunnecessarybecausethetemperaturedifferentialbetweenthewaterandairissmallincoolingmode.Forpanelsandsailsthataredesignedwell,thesurfacetemperaturecanbeapproximatedtobethemeanwatertemperature:

L15

where tw =meanwatertemperature,°F[K] tCHWS=chilledwatersupplytemperature,°F[K] tout =chilledwaterreturntemperature,°F[K]

7. Determine the heat transfer coefficients for the radiant panelsThenaturalconvectioncoefficientis:

IP L16

SI L16


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Design Procedure – Cooling

Theforcedconvectioncoefficientis:

IP L9

SI L9

Thetotalconvectioncoefficientis:

L10

8. Determine the specific capacity of the radiant panelsTheconvectiveheattransferpersquarefoottothepanelisdetermined:

L11

Assumingthatthewalltemperatureisequaltotheairtemperature,theradiantheatexchangewiththepanelisdetermined:

IP L12

SI L12

Thetotalheattransferperunitoffaceareais:

L13

9. Determine the area of panels required

L14


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Example 2 - Small Office (IP)

Considerasmallofficewithasouthernexposure.Thespaceisdesignedfortwooccupants,acomputerwithLCDmonitor,T8florescentlighting,andhasatemperatureset-pointof75°F.Theroomis10ftwide,12ftlong,and9ftfromfloortoceiling.Theownerexpressedinterestinusingradiantpanels.

12 ft

9 ft 10 ft

SMALL OFFICE

Window

Space ConsiderationsOneoftheprimaryconsiderationswhenusingaradiantheatingandcoolingsystemishumiditycontrol.Aspreviouslydiscussed,itisimportanttoconsiderboththeventilationrequirementsandthelatentloadwhendesigningtheair-sideofthesystem.

Theassumptionsmadefortheexampleareasfollows:

• Load/personis250Btu/hsensibleand155Btu/hlatent• Lightingloadinthespaceis6.875Btu/h/ft²• Computerloadis300Btu/h(CPUandLCDMonitor)• Totalskinloadis1450Btu/h• Specificheatanddensityoftheairare0.24Btu/lb°Fand0.075lb/ft³respectively• Designconditionsare75°F,with50%relativehumidity• Designdewpointis55°F


Occupants 2

Set-Point 75°F

FloorArea 120ft²

ExteriorWall 108ft²

Volume 1080ft³

qoz 800Btu/h

ql 825Btu/h

qex 1450Btu/h

qT 3075Btu/h

Determinea)Theventilationrequirement.b)Thesuitablesupplyairandsupplywatertemperatures.c)Thetotalconvectiveheattransfercoefficientforradiantpanels.


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Solutiona) Determine the ventilation requirementTheventilationrequirementshouldbecalculatedtomeetventilationcodes.Forexample,usingASHRAEStandard62-2004todeterminetheminimumfreshairflowrateforatypicalofficespace:

b) Determine required supply air dew-point temperature to remove the latent loadFromequationL2:


Atthedesignconditions(75°F,50%RH),thehumidityratiois65gr/lb,requiringadifferenceinhumidityratiobetweenthesupplyandroomairof:

Fromthefigurebelow,thedewpointcorrespondingtothehumidityratiois40°F,whichistoocoolforstandardequipment.Evaluatingthehumidityratioatseveraltemperaturesledtotheselectionofadewpointof50°Finordertouselessexpensivecommonequipmentwhilealsominimizingthesupplyairvolumerequiredtocontrolhumidity.

Humidity Ratio

Dew Point lb/lb gr/lb

40 0.00543 38

45 0.0065 46

50 0.0075 53

55 0.0095 67

0.000

0.002

0.004

0.006

0.010

0.012

0.014

0.016

0.018

0.020

0.022

0.024

0.026

0.028

0.030

35 40

12.5

13.0

13.5 10%

20%

30%40%

50%60%70%80%90

%

14.0

14.5

15.0

45 55 60 65 70 80 85 90 95 100 105 110 115 120

65

Dry Bulb Temperature, ºF

Enthalpy - Btu/lb

of Dry

Air

Hum

idity Ratio, lbw /lb

DA

70

75

80

85

15

20

25

30

35

40

45

50

60 65

Volume - ft3/lb of Dry Air

Saturation Temperature, ºF

Relative Humidity

40

45

50

55

60

35

0.0075

50



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Therequiredairvolumetosatisfythelatentloadis:

Thesupplyairvolumetotheofficeisthemaximumvolumerequiredbycodeforventilationandthevolumerequiredforcontrollingthelatentload:

c) Determine the heat transfer coefficients for the radiant panelsForpanels and sails that aredesignedwell, the surface temperature canbe approximated tobe themeanwater temperature. Assumingachilledwatersupplytemperature2°Fabovethedewpointinordertominimizethepotentialforcondensationandatemperatureriseof4°Fthroughthepanelleadstoameanwatertemperatureof:

UsingequationL16,thenaturalconvectioncoefficientisdetermined:





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Example 2 - Small Office (SI)

Considerasmallofficewithasouthernexposure.Thespaceisdesignedfortwooccupants,acomputerwithLCDmonitor,T8florescentlighting,andhasadesigntemperatureset-pointof24°C.Theroomis3mwide,4mlong,and3mfromfloortoceiling.Theownerexpressedinterestinusingradiantpanels.

Space ConsiderationsOneoftheprimaryconsiderationswhenusingaradiantheatingandcoolingsystemishumiditycontrol.Aspreviouslydiscussed,itisimportanttoconsiderboththeventilationrequirementsandthelatentloadwhendesigningtheair-sideofthesystem.

Theassumptionsmadefortheexampleareasfollows:

• Load/personis65Wsensibleand55Wlatent• Lightingloadinthespaceis25W/m²• Computerloadis80W(CPUandLCDMonitor)• Totalskinloadis425W• Specificheatanddensityoftheairare1.007kJ/kgKand1.3kg/m³respectively• Designconditionsare24°C,with50%relativehumidity• Designdewpointis13°C


Occupants 2

Set-Point 24°C

FloorArea 12m²

ExteriorWall 12m²

Volume 36m³

qoz 210W

ql 300W

qex 425W

qT 935W

Determinea)Theventilationrequirement.b)Thesuitablesupplyairandsupplywatertemperatures.c)Thetotalconvectiveheattransfercoefficientforradiantpanels.

3 m

4 m

3 m

SMALL OFFICE

Window


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Solutiona) Determine the ventilation requirementTheventilationrequirementshouldbecalculatedtomeetventilationcodes.Forexample,usingASHRAEStandard62-2004todeterminetheminimumfreshairflowrateforatypicalofficespace:

b) Determine required supply air dew-point temperature to remove the latent loadFromequationL2:


Atthedesignconditions(24°C,50%RH),thehumidityratiois9.5g/kgofdryair,requiringadifferenceinhumidityratiobetweenthesupplyandroomairof:

Fromthefigurebelowthedewpointcorrespondingtothehumidityratiois5°C,whichistoocoolforstandardequipment.

Evaluatingthehumidityratioatseveraltemperaturesledtotheselectionofadewpointof10°Cinordertouselessexpensiveequipmentwhilealsominimizingthesupplyairvolumerequiredtocontrolhumidity.

Humidity Ratio

DewPoint g/kg

5 5.5

7.5 6.75

10 8

12.5 9.25

Dry-Bulb Temperature, ºC

Entha

lpy - k

J/kg o

f Dry

Air

30

25

20

15

10

5

050454035302520151050

0

45

40

35

30

25

20

15

50

55

60

65

70

75

85

90

95

100

105

105110 115 120 125

Volume - m3/kg of Dry Air

Saturation Temperature, ºC

Relative Humidity

Hum

idity Ratio, gw /kg

DA

30

10

5

15

20

0.78

0.80

0.82

0.84

0.86

0.90

0.92

0.94

0.96

10%

20%

30%40%

50%60

%70%80

%90%

25

8


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Therequiredairvolumetosatisfythelatentloadis:

Thesupplyairvolumetotheofficeisthemaximumvolumerequiredbycodeforventilationandthevolumerequiredforcontrollingthelatentload:

c) Determine the heat transfer coefficients for the radiant panelsForpanelsandsailsthataredesignedwell,thesurfacetemperaturecanbeapproximatedtobethemeanwatertemperature.Assumingachilledwatersupplytemperature1Kabovethedewpointinordertominimizethepotentialforcondensationandatemperatureriseof2Kthroughthepanelleadstoameanwatertemperatureof:

UsingequationL16,thenaturalconvectioncoefficientisdetermined:




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PerformanceRadiantpanelsperformancedependsonseveralfactors:

• Thedifferenceinsurfacetemperaturesbetweenthepanelandthesurroundingsurfaces

• Themeanwatertemperatureandthepanelthermalresistance

• Viewfactorofthepaneltothesurfacestobecooled/heated

• Waterflowrate• Emissivityandabsorptionofaffected

surfacesThe water flow rate in the coil affectstwoperformancefactors.First,theheattransferbetweenthewaterandthepanelisdependentonwhethertheflowislaminar(poor), transitional (inconsistent) orturbulent(good).Secondly,italsoaffectsthemeanwatertemperature.

Thehigher the flow rate, the closer thedischarge temperature will be to theinlet,therebychangingtheaveragewatertemperature imposed on the panel. Astheseparationbetween themeanwatertemperature and the surrounding roomtemperature (ΔT) increases,sodoes thecapacity.Inheating,theΔTislimitedbythermalcomfort.Incooling,theΔTisalsolimited by two factors, thermal comfort and condensationprevention.Goodpracticefor panel selection in cooling avoidscondensation by limiting the enteringwater temperature to the room’s dewpoint + 2 °F [1 K]. The most commondesignconditionforspacesincoolingis 75°F[24°C]at50%RH,producingadewpointof55°F[13°C]andlimitingenteringwatertemperaturetoaminimumof57°F[14°C].

Figure 19 shows the effect on the flowrate, indicated byReynolds number, onthecapacityofatypicalradiantpanel.Asindicatedonthechart,increasingtheflowrateintothetransitionalrange(Re>2300,showninblueonthegraph)increasestheoutputofthepanel.

Product Selection

Figure 19: Radiantpanelcapacityvs.waterflow

400 2000 4000 6000 8000 10000 12000

50

60

70

80

90

100

Cap

acity

, %

Re

Thewaterflowrateislargelydependentonthepressuredropandreturnwatertemperaturesacceptable to thedesigner. Inmostcasesthewaterflowrateshouldbeselected tobefullyturbulent(Re>4000)underdesignconditions. The difference between the mean watertemperatureisdefinedas:

L17

and the room/surrounding surfacetemperatures are the primary driverof panel performance.The larger thisdifferenceis,thegreatertheradiantandconvectivetransferratesare.AsnotedinequationL12,theradiantenergyexchangebetween two surfaces is based on the absolutetemperaturetothefourthpower.Conversely,alowertemperaturedifferencewillreducetheamountofpotentialenergyexchange,andtherebycapacity.Asaresult,itisdesirablefromacapacitystandpointtoselectentrywatertemperaturesaslowaspossibleincooling,whilemaintainingitabovethedewpointintheroomtoensuresensiblecoolingonly.

The location of radiant panels relative toloadsinthespaceinfluencestheircapacityandisgreatlydependentontheviewfactorof thepanel to theobjects that are tobeconditioned. When used in spaces withhigh solargain, suchasperimeter zones,thecapacity increasesas thesurroundingsurface temperature increases.Assurfacetemperatures change throughout theday, panel capacity changes accordingly.Furthermore,asthedistancebetweenthepanelandtheaffectedsurfaceincreases,theviewfactordiminishes,thusreducingdirectradiantexchangebetweenthetwosurfaces.Panelplacementisbasedonacombinationofsurfacetemperatureanddistancetotheoccupant in order to ensure an effectiveoperativetemperatureisachieved.Locatingpanelsalongglassperimeterswithoutlowemissivity coatingsmay have a negativeeffectonenergyuseassomeenergywillbelosttotheoutdoorsthroughtheglass.


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Example 3 - Small Office Panel Selection (IP)


Occupants 2

Set-Point 75°F

FloorArea 120ft²


Volume 1080ft³

qoz 800Btu/h

ql 825Btu/h

qex 1450Btu/h

qT 3075Btu/h

hc, total 0.823Btu/hft°F

Qs 38cfm

Ts 50°F

tCHWS 57°F

tpanel 59°F

Determine

a)Theareaofpanelsrequired.b)Theareaofpanelsrequiredassuming95°Foutdoorairtemperature.c)Theflowrateforthepanelsfrom(b).d)Apracticallayoutandpipingarrangementforthepanelsfrom(b).

12 ft

9 ft 10 ft

SMALL OFFICE

Window

Considerthesmallofficepresentedinthepreviousexample.


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Solution

a) Determine the sensible cooling capacity of the supply airUsingequationL5:

Determine the sensible cooling required from the water-side

Determine the specific capacity of the radiant panelsUsingequationL11,theconvectiveheattransfertothepanelisdetermined:

UsingequationL12andassumingthatthewalltemperatureisequaltotheroomairset-pointtemperature,theradiantheatexchangewiththepanelisdetermined:



Usingmultiplesof4ft2,whichisastandardceilingtilesizedat2ft×2ft,thetotalarearequiredis76ft2.



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b)Theareaofpanelsrequiredassuming95°Foutdoorairtemperature

Theexteriorwalltemperatureisdeterminedwithanhvalue,convectiveheattransfercoefficient,of1.46Btu/(hft2°F)andaUvalue,overallheattransfercoefficient,of0.693Btu/(hft2°F):


Recalculatingtheradiantheatexchangeandtotalheattransferfrom(a):



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SMALL OFFICE

Light

Panel

PanelPanel

Panel Panel

SMALL OFFICEPanel Panel

Panel

Panel

Light

c) The flow rate for the panels from (b)

d) A practical layout and piping arrangement for the panels from (b) Inordertofitthepanelsfrom(b)inalay-inceiling,a48in.×24in.RPMmodularpanelisselected.Referringtotheproductdatasheet,aflowrateof1.02(~1gpm)hasawaterpressuredropof0.17ft.

Usingthesepanelswouldrequireaquantityof:

Ifthesepanelsareconnectedinseries,thetotallooppressuredropwouldbe:


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Example 3 - Small Office Panel Selection (SI)


Occupants 2

Set-Point 24°C

FloorArea 12m²

ExteriorWall 12m²

Volume 36m³

qoz 210W

ql 300W

qex 425W

qT 935W

hc, total 4.71W/m2K

Qs 22.5L/s

Ts 10°C

tCHWS 14°C

tpanel 15°C

Determinea)Theareaofpanelsrequired.b)Theareaofpanelsrequiredassuming35°Coutdoorairtemperature.c)Theflowrateforthepanelsfrom(b).d)Apracticallayoutandpipingarrangementforthepanelsfrom(b).


3 m

4 m

3 m

SMALL OFFICE

Window


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Solution

a) Determine the sensible cooling capacity of the supply airUsingequationL5:

Determine the sensible cooling required from the water-side

Determine the specific capacity of the radiant panelsUsingequationL11,theconvectiveheattransfertothepanelisdetermined:

UsingequationL12andassumingthatthewalltemperatureisequaltotheroomairset-pointtemperature,theradiantheatexchangewiththepanelisdetermined:



Usingmultiplesof0.36m2,whichisastandardceilingtilesizedat600mm×600mm,thetotalarearequiredis6.48m2.



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b)The area of panels required assuming 35 °C outdoor air temperatureTheexteriorwalltemperatureisdeterminedwithanhvalue,convectiveheattransfercoefficient,of0.255W/(m2K)andaUvalue,overallheattransfercoefficient,of0.121W/(m2K):


Recalculatingtheradiantheatexchangeandtotalheattransferfrom(a):



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SMALL OFFICE

Light

Panel

PanelPanel

Panel Panel

SMALL OFFICEPanel Panel

Panel

Panel

Light

c) The flow rate for the panels from (b)

d) A practical layout and piping arrangement for the panels from (b) Inordertofitthepanelsfrom(b)inalay-inceiling,a1200mmx600mmRPMmodularpanelisselected.Referringtotheproductdatasheet,aflowrateof0.07(~0.075kg/s)hasawaterpressuredropof0.69kPa.

Usingthesepanelswouldrequireaquantityof:

Ifthesepanelsareconnectedinseries,thetotallooppressuredropwouldbe:


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Example 4 - Small Office Chilled Sail Selection (IP)



Occupants 2

Set-Point 75°F

FloorArea 120ft²


Volume 1080ft³

qoz 800Btu/h

ql 825Btu/h

qex 1450Btu/h

qT 3075Btu/h

CoolingCapacityofHydronicSystem 2049Btu/h

tCHWS 57°F

tpanel 59°F

DetermineTherequiredareaandpossiblelocationofchilledsails.

SolutionThedifferencebetweentheroomairtemperatureandthemeanpaneltemperatureis:

Referringtotheproductdatapage,thespecificcapacityofthechilledsailisdeterminedusingthistemperaturedifference:

12 ft

9 ft 10 ft

SMALL OFFICE

Window


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Example 4 - Small Office Chilled Sail Selection (IP)

Determine the area of sails requiredUsingequationL14:

Selectingasailthatis10ftlongand4.5ftwideprovides45ft2ofsailarea.Fromtheperformancetable,thispiped-inserieswillresultinapressuredropof2ft.

24 in. × 96 in. Price CSA

(troom - t̅w), °F Capacity, Btu/h Water Flow Rate, gpm Head Loss, ft

14 635 0.35 0.356

16 740 0.41 0.488

18 848 0.47 0.642

20 959 0.53 0.816

Basedon4°Fwatertemperaturedrop

SMALL OFFICE

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Example 4 - Small Office Chilled Sail Selection (SI)


3 m

4 m

3 m

SMALL OFFICE

Window


Occupants 2

Set-Point 24°C

FloorArea 12m²

ExteriorWall 12m²

Volume 36m³

qoz 210W

ql 300W

qex 425W

qT 935W

CoolingCapacityofHydronicSystem 557W

tCHWS 14°C

tpanel 15°C

DetermineTherequiredareaandpossiblelocationofchilledsails.

SolutionThedifferencebetweentheroomairtemperatureandthemeanpaneltemperatureis:

Referringtotheproductdatapage,thespecificcapacityofthechilledsailisdeterminedusingthistemperaturedifference:


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Example 4 - Small Office Chilled Sail Selection (SI)

Determine the area of sails requiredUsingequationL14:

Selectingasailthatis3mlongand1.5mwideprovides4.5m2ofsailarea.Fromtheperformancetable,thispiped-inserieswillresultinapressuredropof6kPa.

600 mm × 2908 mm Price CSA

(troom - t̅w), K Capacity, W Water Flow Rate, kg/h Head Loss, kPa

8 186 79 1.06

9 217 93 1.46

10 249 107 1.92

11 281 120 2.44

Basedon4°Cwatertemperaturedrop

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References

ASHRAE(2004a).Standard 55-2004—Thermal environmental conditions for human occupancy.Atlanta,GA:American SocietyofHeating,RefrigerationandAir-ConditioningEngineers,Inc.

ASHRAE(2004b).Standard 62.1-2004—Ventilation for acceptable indoor air quality.Atlanta,GA:AmericanSocietyfor Heating,RefrigeratingandAir-ConditioningEngineers.

ASHRAE(2005).Standard 138-2005—Method of testing for rating ceiling panels for sensible heating and cooling. Atlanta,GA:AmericanSocietyforHeating,RefrigeratingandAir-ConditioningEngineers.

ASHRAE(2007).Humidity control design guide.Atlanta,GA:AmericanSocietyforHeating,RefrigeratingandAir- ConditioningEngineers.

ASHRAE(2008a).ASHRAE handbook—Applications.Atlanta,GA:AmericanSocietyforHeating,Refrigeratingand Air-ConditioningEngineers.

ASHRAE(2008b).Standard 170-2008—Ventilation of health care facilities.Atlanta,GA:AmericanSocietyforHeating, RefrigeratingandAirConditioningEngineers.

ASHRAE(2009).ASHRAE handbook—Fundamentals.Atlanta,GA:AmericanSocietyforHeating,Refrigeratingand Air-ConditioningEngineers.

ASHRAE(2010).Standard 55-2010—Thermal environmental conditions for human occupancy.Atlanta,GA:American SocietyforHeating,RefrigeratingandAir-ConditioningEngineers.

Awbi,H.B.&Hatton,A.(1999).Naturalconvectionfromheatedroomsurfaces.Energy and Buildings, 30,233-244.

Babiak,J,.OlesenB.W.,&Petras,D.(2009).REHVA guidebook no. 7: Low temperature heating and high temperature cooling.Brussels,Belgium:FederationofEuropeanHeatingandAir-conditioningAssociations(REHVA).

Beausoleil-Morrison,I.(2000).Theadaptivecouplingofheatandairflowmodellingwithindynamicwhole-building simulation.PhDThesis,UniversityofStrathclyde,Glasgow,UK.

Behne,M.(1999).Indoorairqualityinroomswithcooledceilings,mixingventilationorratherdisplacementventilation. Energy and Buildings, 30,155–166.

Berglund,L.,Rascati,R.,&Markel.,M.L.(1982).Radiantheatingandcontrolforcomfortduringtransientconditions. ASHRAE Transactions, 88(2),765-775.

Conroy,C.,&Mumma,S.A.(2001).Ceilingradiantcoolingpanelsasaviabledistributedparallelsensiblecooling technologyintegratedwithdedicatedoutdoor-airsystems.ASHRAE Transactions, 107(1),571-579.

CSA(2010).CSA Z317.0-10—Special requirements for heating, ventilation, and air-conditioning (HVAC) systems in health care facilities.Mississauga,ON:CanadianStandardsAssociation.

DIN(2003).Ventilationforbuildings—Ceiling-mounted radiant panels supplied with water at a temperature below 120 °C –Part 2: Test method for thermal output (English version of DIN EN 14037-2).Berlin,Germany:Bueth VerlagGmbH.

DIN(2004).Ventilationforbuildings—Chilled ceilings -Testing and rating (English version of DIN EN 14240). Berlin, Germany:BuethVerlagGmbH.

Fisher,D.E.(1995).Anexperimentalinvestigationofmixedconvectionheattransferinarectangularenclosure.PhD Thesis,UniversityofIllinois,Urbana,IL.

Fitzner,K.(1996).Displacementventilationandcooledceilings—Resultsoflaboratorytestandpracticalinstallations. ProceedingsfromIndoor Air ’96.Nagoya,Japan.

Incropera,F.P.&DeWitt,D.P.(1996).Fundamentals of heat and mass transfer (4thed.).NewYork,NY:JohnWileyandSons.

ISO (2005). ISO Standard 7730-2005—Ergonomics of the thermal environment–Analytical determination and interpretation of thermal comfort using calculation of the PMV and PPD indices and local thermal comfort criteria. Geneva,Switzerland:InternationalStandardsOrganization.

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References

JeongJ.&Mumma,S.A.(2003).Impactofmixedconvectiononceilingradiantcoolingpanel.HVAC&R Research, 9(3),251-257.

Kochendörfer,C.(1996).StandardtestingofcoolingpanelsandtheiruseinsystemPlanning.ASHRAE Transactions, 102(1),651-658.

Min,T.C.,Schutrum,L.F.,Parmelee,G.V.,&Vouris,J.D.(1956).Naturalconvectionandradiationinapanelheatedroom. Heating Piping and Air Conditioning (HPAC),153–160.

Mumma,S.A.(2002).Chilledceilingsinparallelwithdedicatedoutdoorairsystems:Addressingtheconcernsof condensation,capacityandcost.ASHRAE Transactions 2002(2),220–231.

Mundt,E.(1990).Convectionflowsabovecommonheatsourcesinroomswithdisplacementventilation.Proceedings from Roomvent 1990.Oslo,Norway.

Nickel,J.(2002).1.3-Heatingandcoolingwithceilings.Technical report 87/2002e: Cooling and heating systems. Aachen,Germany:KrantzKomponenten.

Novoselac,A.,Burley,B.,&Srebric,J.(2006).Newconvectioncorrelationsforcooledceilingpanelsinroomswith mixedandstratifiedairflow.HVAC&R Research, 12(N2),279-294.

Novoselac,A.&Srebric,J.(2002).Acriticalreviewontheperformanceanddesignofcombinedcoolingceilingand displacementventilationsystems.Energy and Buildings, 34(5),497-509.

Olesen,B.W.,Sliwinska,E.,Madsen,T.L.,&Fanger,P.O.(1982).Effectofbodypostureandactivityonthethermal insulationofclothing:Measurementsbyamoveablethermalmanikin.ASHRAE Transactions, 88(2),791-801.

PriceIndustries(2011).Price engineer's HVAC handbook—A comprehensive guide to HVAC fundamentals. Winnipeg, MB:PriceIndustriesLimited.

Schiavon,S,Bauman,F.,Lee,K.H.,&Webster,T.(2010).Development of a simplified cooling load design tool for underfloor air distribution systems, final report to CEC PIER program.Berkeley,CA:CenterfortheBuiltEnvironment, CenterforEnvironmentalDesignResearch,UniversityofCaliforniaatBerkeley.

Stetiu,C.(1998).RadiantcoolinginU.S.officebuildings:Towardseliminatingtheperceptionclimateimposedbarriers. DoctorialDissertation,EnergyandResourcesGroup,UniversityofCaliforniaatBerkeley,CA.

Tan,H.,Murata,T.,Aoki,K.,&Kurabuchi,T.(1998).Cooledceiling/displacementventilationhybridairconditioning system—Designcriteria.ProceedingsfromRoomvent ’98.Stockholm,Sweden.

Virta,M.,Butler,D.,Gräslund,J.,Hogeling,J.,Kristiansen,E.L.,Reinikainen,M.,&Svensson,G. (2004).REHVA guidebook no. 5: Chilled beam application guidebook.Brussels,Belgium:FederationofEuropeanHeatingand Air-conditioningAssociations(REHVA).

Yin,Y.,Zhang,X.,&Chen,Q.(2009).Condensationriskinaroomwithhighlatentloadandchilledceilingpaneland withairsuppliedfromliquiddesiccantsystem.HVAC&R Research, 15(2),315-327.

Zhang,H.,Huizenga,C.,Arens,E.,&Yu,T.(2005).Modeling thermal comfort in stratified environments.Berkeley,CA: CenterfortheBuiltEnvironment,UniversityofCalifornia.

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