Reduction of MAC Power Requirement in a Small Car 2010-01-0803

In recent times, Mobile Air Conditioning (MAC) power consumption reduction has become an area of interest for OEMs worldwide due its significant impact on the fuel efficiency. On small cars with rear mounted and small capacity engines, MAC power consumption presents a formidable challenge to the climate control development engineers due to the spread layout of the system aggregates. Critical parameters which contribute significantly towards the higher MAC power consumption are mechanical, electrical and thermal loads.

The present work describes various ways towards the reduction of MAC power consumption through simulation and experimentation without compromising on the cooling performance and passenger comfort.

Using 1D KULI simulation, refrigerant circuit has been analyzed for proper selection (piston or vane type compressors), right sizing and location of system components. Front and rear mounted HVAC unit layouts are also analyzed to study the effects of refrigerant pipe dimensions and bends on power consumption. Front-end airflow over condenser is improved through 3D CFD analysis by optimizing bumper openings, air escape route and avoiding hot air recirculation along with analyzing the effect of gravity flaps on condenser fan shroud. IP ducts are designed through 3D air flow analysis for minimum airflow resistance which reduces blower motor wattage. Simulation results are validated through system bench calorimeter and vehicle level tests. A close correlation is observed between test and simulation results. The heat ingress inside the cabin is minimized by experimentally evaluating various options of cabin insulation material for roof, firewall, floor panels and tinting of glasses. Present study discusses the significance of various parameters and identifies the potential areas for the reduction of overall MAC power consumption.