тепловой насос

Воздушные sourceheatpumps Workingprinciple: Airsourceheatpumpsarerelativelyeasy (andinexpensive) toinstallandhavethereforehistoricall beenthemostwidelyusedheatpumptype.However, theysufferlimitationsduetotheiruseofthe outsideairasaheatsourceorsink.Thehighertemperaturedifferentialduringperiodsofextreme coldorheatleadstodecliningefficiency, asexplainedabove.Inmildweather, COPmaybearound 4.0,whileattemperaturesbelowaround−8°C(17°F)anair-sourceheatpumpcanachieveaCOPof2.5orbetter,whichisconsiderablymorethantheCOPthatmaybeachievedbyconventionalheatingsystems.TheaverageCOPoverseasonalvariationistypically2.5-2.8,[9]withexceptionalmodelsabletoexceed6.0(2.8kW). Theworkingfluid, initsgaseousstate, ispressurizedandcirculatedthroughthesystembya compressor.Onthedischargesideofthecompressor, thenowhotandhighlypressurizedgasis cooledinaheatexchanger, calledacondenser, untilitcondensesintoahighpressure, умеренный temperatureliquid.Thecondensedrefrigerantthenpassesthroughapressure-loweringdevicelikeanexpansionvalve,capillarytube,orpossiblyawork-extractingdevicesuchasaturbine.Thisdevicethenpassesthelowpressure,(almost)liquidrefrigeranttoanotherheatexchanger,theevaporatorwheretherefrigerant evaporatesintoagasviaheatabsorption.Therefrigerantthenreturnstothecompressorand thecycleisrepeated. Insuchasystemitisessentialthattherefrigerantreachasufficientlyhightemperaturewhen сжимается, sincethesecondlawofthermodynamicspreventsheatfromflowingfromacold fluidtoahotheatsink.Practically, thismeanstherefrigerantmustreachatemperaturegreater thantheambientaroundthehigh temperatureheatexchanger.Similarly, thefluidmustreach asufficientlylowtemperaturewhenallowedtoexpand, orheatcannotflowfromthecoldregion intothefluid, iethefluidmustbecolderthantheambientaroundthecold temperatureheat exchanger.Inparticular, thepressuredifferencemustbegreatenoughforthefluidtocondens atthehotsideandstillevaporateinthelowerpressureregionatthecoldside.Thegreaterthe temperaturedifference, thegreatertherequiredpressuredifference, andconsequentlythe moreenergyneededtocompressthefluid.Thusaswithallheatpumps, theenergyefficiency (amountofheatmovedperunitofinputworkrequired) разница decreaseswithincreasingtemperature.