A DFSS approach study on the effects of vehicle cabin properties on HVAC system’s cooldown performance using 1D simulation 2020-01-1258
Due to the increase in heat wave across the globe, maintaining the thermal comfort of passengers in a vehicle is becoming a challenge. Considering global warming, there is a need to shift towards greener refrigerants which in itself causes a marginal degradation in the air conditioning system performance. Also the emission norms and regulations demanding for a smaller engine if not for a hybrid or electric vehicle, there is a need for optimally designing the Heating Ventilation and Air Conditioning (HVAC) system since it is directly related with the efficiency of the vehicle. Hence maintaining the comfort level of the passengers needs further exploration than optimizing only the HVAC system. In an air conditioning system consisting of compressor, condenser, expansion valve, evaporator, blower etc., the refrigerant will be operating in two phases to absorb the heat from the cabin and rejecting it into the atmosphere. Conventionally for given system where we need more cooling, the capacity of the components can be increased in order to meet the customer comfort. But considering the fact the cabin heat load plays vital role for the overall cabin cooling, there is also a possibility of optimizing the cabin properties.
This study was conducted by considering the material properties and the areas of different components in the vehicle cabin like the windshield, side glasses, rear glasses, doors etc. By keeping HVAC system same, the contribution of each cabin component on the heat load to the vehicle cabin is studied. This was conducted using one dimensional (1D) simulation software Simcenter Amesim®. The cabin is modelled in the software by considering the individual components like glasses, seats, trims, doors, etc., and it is correlated with the average cabin temperature of vehicle test for a test cycle. This paper is about the study conducted using the 1D simulation tool for understanding the effect of different components in the cabin. This paper also focuses on reducing the average cabin temperature by finding optimum combination of materials to be used in vehicle to meet the cabin cooldown targets. All the parameters which are important for the simulation are arrived using the DFSS (Design for six sigma) approach. Input, output, noise factors and control factors for the study are arrived after few preliminary simulations and brainstorming. L18 orthogonal array was arrived using the different levels of control factors. Simulations were run for the different input and noise factors for the 18 different combinations. The simulations outputs are analyzed using the DFSS methodology which identified the impact of the various control factors on the cabin cooldown. This study helps us on understanding and deciding on the cabin components and materials during the concept phase for providing a better thermal comfort to the passengers.