Seite - 351 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2016,9, 240 Comparedwith theuseoffin-tubeheatexchangers, thecoolingandheatingefficienciesofheat pumpACsystemswere increasedbyat least20%with theuseofmicro-channelheatexchangersover aconstantheat transferarea [58]. Besideshigher-efficiency, themicro-channelheatexchangershave other advantages suchas aneeed for less refrigerant charge, compactness and lowcost. Theheat pumpACsystem(usingmicro-channelheatexchangers)wasappliedtoEVsbyWu et al. [61]. They concluded that the sizeof the indoorandoutdoorheat exchangersdecreasedby57.6%and62.5%, respectively, so theACweightwaseffectivelyreduced,whichcontributedtoanincrease inthemileage of theEV.At thesametime, this systemcouldcut therefrigerantchargeby26.5%,whichreducedthe greenhouseeffect. Thedisadvantagesof this systemwerealsopresented in thispaper. TheACsystem frequentlyworkedonthedefrostingcycle incoldweatherconditions,which immenselyaffectedthe heating capacity and theheatingperformance coefficient. Densodeveloped an ejector integrated evaporator,asshowninFigure6, toreduce thepowerconsumptionofvehiclecabinACsystems[62]. Theejectorsystemwas introduced into themarketMay2009.However, thenoiseandthe temperature distributionwere twomainchallenges indevelopinganevaporatorwith integratedejector. ȱ Figure6.Ejectorevaporatorstructure [62]. 2.4. InnovativeSystemStructure Reformingthe integral structureof theheatpumpACsystemfor theEVisalsoawidelypopular approach. Wang et al. [63] adopted three heat exchangers instead of a four-wayvalve to achieve coolingandheatingforanEVcabin. Theyconcludedthat theheatpumpACsystemwiththreeheat exchangershadadvantages indemistinganddehumidifying,but thecapacityandCOPof this system wereslightly lower thanthatof theheatpumpACsystemwitha four-wayvalve. Suzuki et al. [47] proposedarepresentativesystemstructureof theACsystemforEVs. Theconstructionandmechanism areshowninFigure7. 351