Optimization of the automotive air conditioning strategy based on the study of dewing phenomenon and defogging progress

摘要

The problem of vehicle window dewing not only affects the occupants' comfort, but also interferes with the driver's sight and potentially threatens the safety of driving as well as electronic equipment in the vehicle. Therefore, analyzing the condensation process inside the cabin is of great practical concern to improve driving comfort and safety. This study focuses on the process of condensation and defogging in the cabin of a truck model, where the outside heat dissipation and internal air conditioning system are considered together. The condensation process simulation based on the EWF (Eulerian Wall Film) model in conjunction with user defined functions was validated by comparing with experiments. Then, the flow domain around a simplified three-dimensional truck model was established to conduct the external thermal conditions. By examining various conditions of the air inlet mode, temperature, humidity and speeds of the ventilation system, it was found that the mass flow rate, inlet temperature and humidity could influence the dewing film thickness directly. Of significance, when the air conditioning system was taken as the main defogging approach, with the relative humidity set at approximately 20% and the temperature above 320 K, the dewing phenomenon was eliminated at the highest efficiency. This paper also found that the comfortable, efficiency and safety requirements could all be obtained when the relative humidity was within the range of 20% < RH < 60% and the temperature range of 292 K < T < 298 K. These results would be useful to provide suggestions for the future design of automotive air conditioning systems.