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A significant driver for the development of future commercial vehicles is likely to be the introduction of fuel consumption related legislation in various regions around the world. The application of a waste heat recovery system to the powertrain of such vehicles is seen as a possible step, amongst many, to help them achieve the required fuel economy. In particular, the Rankine Cycle (a closed steam cycle) is often proposed as a potential means for deriving work from the engine exhaust heat. Rankine Cycle systems are already in use in off-highway applications, such as stationary engines or marine power-packs. However, the technical and commercial viability of these systems for on-highway, principally long haul truck application is as yet unproven. Aspects such as the in-use economy benefits, the system performance density, the component robustness and all interactions with the other vehicle systems have to be evaluated.

The car air conditioning system causes approximately 0.5 l/100 km excess fuel consumption on average. To meet future fuel consumption and emission regulations improvements in the AC system are called for. To consistently assess improvements in air conditioning power consumption, specific driving and temperature profiles are defined. It is shown that improvements can be achieved by: Better thermodynamic component and system design Refrigerant expansion device sized for efficiency rather than maximum performance System control strategies such as variable air recirculation Measurement of a refrigerant circuit on a system test bench reveal that the energy requirement for A/C can by reduced by 15% to 30% compared to current state of the art AC system technologies. Only part of the presented measures are based on electronic controls however only the combination of all will lead to a significant reduction.