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Following the development of new technologies in Vehicle Thermal Management aiming to both enhancing the MAC System efficiency and reducing the thermal load to be managed, a prediction tool based on the AMEsim platform was developed at Advanced PD EMEA. This tool is dedicated to predict the effect of the implementation of sensors monitoring both the relative humidity and the carbon dioxide (CO2) concentration (taking into account passengers' generated moisture and CO2). This model implemented with the usual comfort inputs (CO2 and RH acceptable ranges) considers the system variables influencing the comfort and predicts the increase of both RH and CO2 concentration in the cabin compartment in any driving cycle depending on the number of occupants.

In the framework of the activities for the selection of an alternate refrigerant to comply with the R-134a ban, FIAT chose to develop a carbon dioxide (R-744) MAC system on a vehicle representing the FIAT portfolio. The vehicle model was specifically selected to deal with two critical parameters in the low cost intermediate segment: a cabin compartment of comfortable size and a tiny engine compartment. The design target was therefore a MAC system featuring both a considerable cooling capacity and efficient packaging. The prototype was built with the most up to date version of R-744 components available, allowing the evaluation of advanced technology, resulting in meaningful results. General system and component specific issues are mentioned to explain the necessity of using additional components with respect to the typical R-134a MAC system (i.e. internal heat exchanger, accumulator, expansion device and externally controlled compressor).