Maintaining thermal comfort is one of the key areas in vehicle HVAC design wherein airflow distribution inside the cabin is one of the important elements in deciding comfort sensation. However, the energy consumption of air conditioning system needs to stay within the efficient boundaries to efficiently cool down the passenger cabin otherwise the vehicle energy consumption may get worsened to a great extent. One approach to optimize this process is by using numerical methods while developing climate systems.
The present paper focuses on the numerical study of cabin aiming and cabin cool-down of a passenger car by using computational fluid dynamics (CFD). The main goal is to investigate the cabin aiming with a view to figure out the minimum average velocity over the passengers at all vent positions. Cabin aiming ensures substantial amount of airflow reaches to the passengers as well as every corners of the cabin across the wide climatic range. After the cabin aiming, airflow field inside the cabin was predicted and then the transient behavior of temperature field during cool down was predicted considering appropriate cabin heat loads including that of solar irradiation and cabin soaking. The study shows that flow field on passengers as well as inside the cabin strongly influences the overall cool down rate.
Steady state and transient analysis were carried out in STAR-CCM+ software to figure out the flow field and temperature field respectively. The numerical prediction of flow field, cabin cool down rate were further validated with that of experimental results and it proves to be very useful tool to use at the early stage of design cycle to optimize the HVAC system in terms of performance, development time and cost.
