тепловые насосы

Воздушные sourceheatpumps Workingprinciple: Airsourceheatpumpsarerelativelyeasy (andinexpensive) toinstallandhavethereforehistorically beenthemostwidelyusedheatpumptype.However, theysufferlimitationsduetotheiruseofthe outsideairasaheatsourceorsink.Thehighertemperaturedifferentialduringperiodsofextreme coldorheatleadstodecliningefficiency, asexplainedabove.Inmildweather, COPmaybearound 4.0, whileattemperaturesbelowaround-8 ° С (17 ° F), anair- sourceheatpumpcanachieveaCOPof2.5orbetter,whichisconsiderablymorethantheCOPthatmaybeachievedbyconventionalheatingsystems.TheaverageCOPoverseasonalvariationistypically2.5-2.8,[9]withexceptionalmodelsabletoexceed6.0(2.8kW). Theworkingfluid, initsgaseousstate, ispressurizedandcirculatedthroughthesystemby acompressor.Onthedischargesideofthecompressor, thenowhotandhighlypressurizedgasis cooledinaheatexchanger, calledacondenser, untilitcondensesintoahighpressure, умеренной temperatureliquid.Thecondensedrefrigerantthenpassesthroughapressure loweringdevice likeanexpansionvalve,capillarytube,orpossiblyawork-extractingdevicesuchasaturbine.Thisdevicethenpassesthelowpressure,(almost)liquid refrigeranttoanotherheatexchanger, theevaporatorwheretherefrigerantevaporatesintoa gasviaheatabsorption.Therefrigerantthenreturnstothecompressorandthecycleisrepeated Insuchasystemitisessentialthattherefrigerantreachasufficientlyhightemperaturewhen сжимается, sincethesecondlawofthermodynamicspreventsheatfromflowingfromacoldfluid toahotheatsink.Practically, thismeanstherefrigerantmustreachatemperaturegreaterthan theambientaroundthehigh-temperatureheatexchanger.Similarly,thefluidmustreachasufficientlylowtemperaturewhen allowedtoexpand, orheatcannotflowfromthecoldregionintothefluid, iethefluidmustbe colderthantheambientaroundthecoldtemperatureheatexchanger.Inparticular, thepressure differencemustbegreatenoughforthefluidtocondenseatthehotsideandstillevaporatein thelowerpressureregionatthecoldside.Thegreaterthetemperaturedifference, thegreater therequiredpressuredifference, andconsequentlythemoreenergyneededtocompressthe fluid.Thusaswithallheatpumps, theenergyefficiency (amountofheatmovedperunitofinput workrequired) decreaseswithincreasingtemperaturedifference.