Soft Air Diffusion to Improve the Thermal Comfort - a Design Approach Based on CFD Tool and Virtual Thermal Manikin

The cabin comfort is one of the most competitive issues in the automotive area of business. The thermal comfort and the environmental well-being are fundamental performances that contribute to generate the more general idea of perceived quality. The CRF developed in the past the concept so-called “healthy bubble” that was implemented in the Lancia Dialogos concept car. The passengers are surrounded by an air bubble, created by generating low velocity air flows, that are diffused through the interior panels and components (e.g. dashboard, roof, back of the seats, etc.), and by surfaces temperature control (e.g. carpet, seats, etc.). At present the original idea has generally been accepted, and different solutions to diffuse air and to control surface temperature of vehicle interiors have been proposed by some automotive supplier.

The paper describes the CFD virtual design approach developed by Centro Ricerche Fiat to define the technical specifications of the breathable panels and their position to optimize the thermal comfort for different airflow conditions. The virtual environment includes a thermal manikin that allows the calculation of the standard thermal comfort indexes (e.g. PMV). This is a key point since passengers are no more allowed to change outlet positions in order to adjust the airflow direction that invests them.

The approach has been validated on two prototype cars where diffusive panels (dashboard and door panels) have been installed.