Experimental and numerical study of the flow dynamics and thermal behavior inside a car cabin: Innovative air diffusers and human body plumes interactions

In confined spaces, such as vehicle cabins, airflow and temperature distribution are the most critical factors affecting thermal comfort and pollutant dispersion. To develop innovative and energy-efficient HVAC systems, a deep understanding of the interaction of the jet flow from the air diffusers on the development process of the human thermal plume became essential to improve the knowledge of airflow patterns for optimizing ventilation system design, thermal comfort, and, indirectly, the energy efficiency. The human thermal plume is one of the most challenging phenomena to capture with optical measurement methods and validate with complex numerical models, given its unsteady nature governed by the buoyancy forces. This study aims to validate the interaction of jet flows from classical and innovative air diffusers on the thermal plume by comparing measured data and numerical simulation results. This validation was made with a specific approach by comparing PIV fields from measurements and CFD results with boundary conditions of air velocity distribution from LDV data. The PIV measurements for flow distributions at the air vents and the thermal plume of an advanced thermal manikin in the driver’s seat were performed in a 1:1 scale mock-up of a Renault Megane car cabin in a climatic chamber. The results obtained with both methods showed good agreement regarding air velocity ranges and distributions. Despite the confined cabin space restricting the development of the thermal plume, a difference in maximum velocities of 0.08 m/s was observed when the distance between the top of the head and the ceiling was doubled. With innovative air diffusers, air velocity distribution showed a more uniform flow than classical diffusers.