Seite - 353 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2016,9, 240 A dual-loop cooling and heating system for automotive applications was designed and fabricated [70,71]. The structure andflowdiagramof the dual-loop system in coolingmode are shown in Figure 9 [70]. In addition to themain refrigeration loop, the systemhad two separate secondaryfluid loopsusinga50%glycol-watermixture toexchangeenergywith the refrigeration loop.Theexperimental resultsshowedthat theCOPof thissystemvariedfrom0.9 to1.8 incooling mode,while for theheatingmode it varied from2 to 5, dependingon theoutdoor air conditions. Aheatpumpcyclewithaneconomizerandamodifiedreciprocatingwas introduced[72]. Formobile application, theheatpumpwithVoorheeseconomizerdemonstratedbetterperformancecompared to the conventional heat pumpwithout economizerwhen the evaporating temperature is lower than´20 ˝C. It could increase the capacity at lowambient temperatures ofmore than two times. Wang [73] took the two-stage cycle technology andapplied it in a rail vehicleAC.Li et al. [74,75] presenteda lowtemperatureheatpumpACsystemfor fullyEVsbasedonthe two-stagecompression refrigerationcycleasshowninFigure10. Theystudiedthecharacteristicsof this systembysimulation and experimentation. The results revealed that,when the environment temperaturewas´20 ˝C, the system could still runnormallywith aCOPof 1.5. At the same time, it also possessed good performanceunder standard cooling andheating condition [75]. That is to say, this systemcould steadilyandefficientlyextenditsoperatingrange. ȱ Figure9.Ejectorevaporatorstructure [70]. 353