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Energies 2016,9, 240
AlthoughCO2ACsystemshave special benefits, theyhave somedisadvantages, suchas low
critical temperatureandhighoperatingpressure [22].Otherproblemsindefrostingofexteriorheat
exchangersandperformancedeteriorationundercoldambient temperatureconditionsexist inCO2
automotiveheatpumpsystemsaswell asR134aheatpumpsystems. Byre-arranging the radiator
andoutdoorheatexchangersof theCO2heatpumpsysteminelectriccars, theheatingcapacityand
COPwere increasedby54%and22%,respectively [23]. Toenhancecoolingperformance,Lee et al. [24]
presentedanelectricalACsystemwithCO2 thatusedan inverter-drivencompressor. Thecooling
capacityandCOPof this tested systemwere increasedby36.8%up to6.4kWandby30.3%up to
2.5kW,respectively.Maetal. [25]conductedathoroughreviewoftheCO2heatpumpandrefrigeration
cycle. Theyconcludedthatsomemodifications, suchasusinganinternalheatexchanger, two-stage
compression,andexpansionworkrecoveryaswellasenhancingheat transfer, could improve theCO2
transcritical cycleperformance toa level similar to thatofaconventionalheatpumpsystem.
InadditiontousingCO2,otherpossiblerefrigerants intheheatpumpACsystemincludeR1234yf,
R152a,R290,R245faandwater [26–29]. Theperformanceof theR1234yf“drop-in”automotiveAC
systemwas analyzed and comparedwith that of systemswithCO2 andR32 by experimentation
andsimulation[30]. TheCOPandcapacityofR1234yfsystemwereupto2.7%and4.0%lower than
those of R134a system, respectively, while the compressor discharge temperature and amount of
refrigerant chargewere 6.5 ˝Cand10% lower than thoseofR134a system[31]. Consequently, the
R1234yf“drop-in”ACsystemwasthemost feasiblecandidate forautomobiles fromthestandpointof
systemperformanceandoperatingconditions.However,moreworkmustbecompletedbefore the
R1234yf systemcanbewidelyaccepted inEVs [31–33]. Ghodbane [34,35]presented thesecondary
loopsystemusingR152aas theworkingfluid inmobileclimatecontrol systems. Thissystemshowed
averygoodcoolingandheatingperformance,buthadaslowerresponse to loadchanges, complex
systemconnectionsandahighcost.
2.2.Applicationof InverterTechnology
Frequencyvariationtechnology,acommonwaytosaveenergy, isalsowidelyusedinACsystems.
AnR134a automotiveAC system capable of operating as an air-to-air heat pump is described in
Figure1 [36].
Figure1.Schematicdiagramof theexperimentalautomotiveair conditioning/heatpumpsystem[36].
347
Emerging Technologies for Electric and Hybrid Vehicles
- Titel
- Emerging Technologies for Electric and Hybrid Vehicles
- Herausgeber
- MDPI
- Ort
- Basel
- Datum
- 2017
- Sprache
- englisch
- Lizenz
- CC BY-NC-ND 4.0
- ISBN
- 978-3-03897-191-7
- Abmessungen
- 17.0 x 24.4 cm
- Seiten
- 376
- Schlagwörter
- electric vehicle, plug-in hybrid electric vehicle (PHEV), energy sources, energy management strategy, energy-storage system, charging technologies, control algorithms, battery, operating scenario, wireless power transfer (WPT)
- Kategorie
- Technik