An experimental analysis of the aerothermal phenomena in the vehicle underhood is given using temperature measurements and separate measurements of convective and radiative heat fluxes. The vehicle underhood used for these measurements is instrumented by 120 surface and air thermocouples and 20 fluxmeters. Measurements are carried out on a passenger vehicle in wind tunnel S4 of Saint-Cyr-France for three thermal functioning conditions. In particular, it is shown for some components that outside air entering the engine compartment (for cooling the different components by convection) can in fact heat other components. This problem results from the underhood architecture, specifically the positioning of some components downstream of warmer components in the same airflow. To avoid this undesired situation, an optimized thermal management procedure is proposed that uses static and dynamic air deflectors during the constant-speed driving (rooting) phase of a vehicle. Much of the present paper is devoted to fluxmetric analysis of underhood thermal behavior (especially the absorption of convective heat flux); we also describe a new control procedure for implementing air deflectors in the actual car underhood.

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