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In order to reduce the fuel overconsumption, new air conditioning systems fitted with externally controlled compressors have been implemented. Their operating principle consists in driving electrically (external control) the compressor displacement in order to adjust the cooling capacity delivered by the A/C system to the cooling capacity required by the passenger compartment. Therefore, it is possible to reduce the mechanical power absorbed by the compressor and by this means, the fuel overconsumption. However, this potential of fuel consumption reduction can be only achieved under the condition that the other components of the A/C system, such as the thermostatic expansion valve (TxV), are well adapted all together in order to fully take advantage of the implementation of such new type of compressors. The paper describes the different possibilities of optimization of the TxV in regard to hunting phenomena.

One of the main issue for the development of current automotive air conditioning systems concerns the reduction of the fuel consumption resulting from the A/C absorbed power. This fuel use reduction can be for one part obtained by the means of an A/C systems energetic efficiency improvement. Different technical solutions can be implemented. One of these techniques consists in the optimization, or even the control of the refrigerant subcooling at the outlet of the condenser.

The paper describes, in a first part, a conventional architecture of a heat pump system intended to both heat and cool the passenger compartment of an electrical vehicle. It indicates in particular the main disadvantages and performance limitations of such kind of systems. The second part describes an improved architecture of the system including an additional water/R134a refrigerant evaporator and integrated components allowing for an increase in heating capacity and an optimization of the volume required for their integration in the engine compartment. The paper concludes on the measured performances obtained for both heating and cooling mode and indicates the other possible advantages of the proposed system such as its ability to manage the driven batteries temperature.