ThetotaluncertaintiesofthemeasurementsareestimatedtobeÆ1.01%forthewaterandtheantifreeze-watersolutiontempera-tures,Æ2.05%forpressures,Æ1.00%forpowerinputstothe
K.Bakirci,D.Colak/Energy44(2012)996e1004
999
Table2
Instrumentsusedinthesystemformeasurements.InstrumentMeasurement
Rotameter
Themass owratesoftheantifreeze-watersolution(approximately50%)
Copper-constantanThetemperatureoftheantifreeze-waterthermocouples
solutionenteringandleavingthegroundheatexchanger,theinletwater
temperaturetoandexitwatertemperaturefromheatingunit
Bourdon-typemanometersThepressuresofthecondenserandevaporator
MeteorologicalstationTheoutdoorairtemperaturesandhumidityWattmeterTheelectricalpowerinputtothecirculatingpump
Electroniccounter
Instantaneouspowerconsumptionsofthecompressor
NTC(negative
Thegroundtemperatureatthedepthof53m
temperaturecoef cient)sensor
compressorandÆ3.00%forthecirculatingpumps.TheuncertaintyinreadingvaluesofthetableisassumedtobeÆ0.20%.Thetotaluncertaintiesassociatedwithmass owrateofthewaterandantifreeze-watersolutionareestimatedtobeÆ7.15%.ThetotaluncertaintiesassociatedwithenergyreceivedfromtheðQ_conÞandwithheatextractedfromthegroundðQ_condenser
groÞareÆ7.23%.
ThetotaluncertaintiesassociatedwiththeCOPandCOPSareÆ7.30andÆ7.28%,respectively.
3.Climatepropertiesandenvironment3.1.Weatherdata
Theexperimentalgroundsourceheatpumpsystemwasestab-lishedandtestedinErzurumprovincehavinganaltitudeof1869mandthecoldestclimateinTurkey.TheclimaticconditionsofErzurumforlong-termaveragevalues(monthlyaverageminimum,maximumandmeanoutdoortemperature,themonthlyaveragesofrelativehumidity,windvelocity,solarradiationandsunshinedurationsfortheheatingseason)aregiveninTable1.TheannualheatingandcoolingdegreedaysforErzurumwithabasetemper-atureof18 Carefoundtobe4870[24].
ThehoursofthesmallesttemperaturebinofÀ19.5 C(À21 C/À18 C)observedforErzurumintheEastAnatoliaRegionofTurkeyare17inJanuaryandFebruary.Also,thehoursofthetemperaturebinfromÀ21 Cto18 CforErzurumare7498intheaverageof1995e2005.Thisprocedurecanaccountforthepart-loadperfor-manceofheating,ventilatingandair-conditioningequipmentaswellasforthevaryingperformanceofheatpumpsystemsandprimaryHVACequipment[25].
3.2.Soilcharacteristics
Erzurumisanintermountainsedimentarybasinwith
aMiocene-Quaternaryvolcanicbasement,andesiticebasalticlava owsand ssureeruptionslava.ThegroundstructureinthecitycentreofErzurumispredominantlyalluvialstructureuntilthethicknessof1kmfromsurface.Also,thegroundstructureofthecitycentreisgravel,sandandalittleclay.ThelocalityofPalandoken(inthesouthoftheCentre)isthevolcanicrockpiecesconsistingofbasalt.ThelocalityofSanayi(inthewestoftheCentre)issand,thingravelandalittleclaysometimesand,thelocalityofDadaskent(intheeastoftheCentre)isthinsandandclay[18].
3.3.Environment
Ingeneral,CO2emissionsarehighasfossilfuelsareusedinourcountry.Theheatpumpsconsumelessprimaryenergythanconventionalheatingsystemsand,theyareanimportanttech-nologyforreducingemissionsofgasesthatharmtheenviron-ment[5].Theheatpumpsystemsarethemostef cientformofelectricheating,providingtwotothreetimesmoreheatingthantheequivalentamountofenergytheyconsumeinelectricity.Signi cantemissionreductionsareavailablethroughtheapplicationoftheheatpumpsystem(HPS)inbothresidentialandcommercialbuildings[26].Residentialfossilfuelheatingsystemsproducedanywherefrom1.2to36timestheequivalentCO2emissionsoftheHPS.TheCO2emissionreductionsfrom15%to77%wereachievedthroughtheuseoftheHPS[27].Itisknownthattheheatpumpssigni cantlyreducetheCO2emis-sionseverydaywhilsttheyprovidecentralanddomestichotwaterheating[28].Theheatpumpsofferthemostenergy-ef cientwaytoprovideheatingandcoolinginmanyapplica-tions,astheycanuserenewableheatsourcesinoursurround-ings[29].
4.Energyanalysis
Themeasuredvaluessuchasthetemperaturechangesofthewaterandtheantifreeze-watersolution,the owratesandtheelectricalpowerinputwereusedtodeterminetheperformancethesystem.TheusefulheatobtainedfromthecondenserQ_of
conis
calculatedas,
Q_con¼m
_wcwðTcwoÀTcwiÞ(1)
Theextractedheatfromthegroundisgivenbythefollowingequation;
Q_gro¼m
_awcawðTeaiÀTeaoÞ(2)
wherem
_wandm_awarethe owrateofthewaterinthecondenserandtheantifreeze-watersolutionintheevaporator,respectively.TheCOP(theheatpump)iscalculatedas;
COP¼
Q_W
con(3)
comTheCOPS(theoverallsystem)iscalculatedas;
COPS¼
Q_W
con
comþW(4)
pThepowerinputtoacirculatingpumpW
_piscomputedfromthefollowingequation;
W
_Vp¼IppcosðfÞ(5)
whereIpisthecurrentofthepump,Vpisthevoltageofthepumpandcos(f)isthepowerfactor.
1000
Table3
Technicaldetailsoftheexperimentalset-up.
Location:Erzurum,Turkey(lat.39.55 N;long.41.16 E)Weatherinformation(yearlyaveragevalues)Averageoutdoortemperature( C)Minimumoutdoortemperature( C)Maximumoutdoortemperature( C)Averagerelativehumidity,(%)Averagesunshineduration(h)