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New car developments require that in the initial cabin cool-down it will be necessary to reach a lower average cabin temperature in a shorter time. The aim is to minimize the discomfort of the driver and occupants to just a few minutes during the initial condition of a hot cabin. Today, the target is reached by increasing the evaporator size, the blower capacity, and the compressor power. All of this is done so as to have as much cooling power available in the shortest possible time. After these transient conditions the A/C system generally works at lower heat rejection and the maximum capacity of the system is used in just a few cases. To limit any increase of the A/C system power, some control strategies can be defined and applied to reduce the thermal energy stored in the cabin. This will reduce the transient phase cool-down time, and thus improve fuel economy. A strategy consists of cooling the cabin with outside fresh air before starting the cool-down by use of the A/C system.

Refrigerant charge and internal volume of the components have influence on the performance and reliability of an Air Conditioning system. A low refrigerant charge can create problems to the compressor for an improper lubrication of its parts, while an excess of refrigerant charge can increase the condensation pressure substantially with negative effects on the air temperature at the dashboard. Internal volume of the A/C components influences the refrigerant optimum charge, and among these the internal volume of the Receiver has a sensible impact on the refrigerant charge. Lower refrigerant charge is in addition the general demand of car makers both for cost reduction and for environmental reasons (less refrigerant lost in the atmosphere per car in case of car accident or leakage). The purpose of the paper is to present the results of experimental analysis on the influence of the refrigerant charge and receiver capacity on the performance of an A/C systems.