暖通美国标准(原版).doc

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1、NiSINGLE-FAMILYRESIDENCESHeatPumpsHeatpumpsforsingle-familyhousesarenormallyunitarysystems;thatis,theyusesingle-packageunitsorsplitsystemsasillustratedinFigure2.Mostcommerciallyavailableheatpumps(particularlyinNorthAmerica)areelectricallypoweredair-sourcesystems.Supplementalheatisg

2、enerallyrequiredatlowoutdoortemperaturesorduringdefrost.Inmostcases,supplementalorbackupheatisprovidedbyelectricresistanceheaters.Heatpumpsmaybeclassifiedbythermalsourceanddistributionmediumintheheatingmodeaswellasthetypeoffuelused.Themostcommonlyusedclassesofheatpumpequipmentareai

3、r-to-airandwater-to-air.Air-to-waterandwater-to-watertypesarealsoused.Heatpumpsystems,ascontrastedtotheheatpumpequipment,aregenerallydescribedasair-sourceorground-source.Thethermalforcoolingisgenerallyassumedtobethesameasthethermalsourceforheating.Air-sourcesystemsusingambientairas

4、theheatsource/sinkaregenerallytheleastcostlytoinstallandthusthemostcommonlyused.Ground-sourcesystemsusuallyusewater-to-airheatpumpstoextractheatfromthegroundviagroundwateroraburiedheatexchanger.Ground-Source(Geothermal)Systems.Asaheatsource/sink,groundwater(fromindividualwellsorsup

5、pliedasautilityfromcommunitywells)offersthefollowingadvantagesoverambientair:heatpumpcapacityisindependentofambientairtemperature,reducingsupplementaryheatingrequirements;nodefrostcycleisrequired;althoughoperatingconditionsforestablishingratedefficiencyarenotthesameasforair-sources

6、ystems,theseasonalefficiencyisusuallyhigherforheatingandforcooling;andpeakheatingenergyconsumptionisusuallylower.Twoothersystemtypesareground-coupledandsurface-water-coupledsystems.Ground-coupledsystemsofferthesameadvantages,butbecausesurfacewatertemperaturestrackfluctuationsinairt

7、emperature,surface-water-coupledsystemsmaynotofferthesamebenefitsasotherground-sourcesystems.Bothsystemtypescirculatebrineorwaterinaburiedorsubmergedheatexchangertotransferheatfromtheground.Direct-expansionground-sourcesystems,withevaporatorsburiedintheground,arerarelyused.Water-so

8、urcesystemthatextractheatf