Underhood Cooling Simulation for Development of New Vehicles

This article presents the methodology used to perform complete three-dimensional thermo-fluid-dynamic simulations of the underhood compartment for new vehicles. The task is to identify major thermal risks at an early stage in the vehicle design; that is before any prototype vehicle is built and during the evolution of underhood components and external style. Thus, a better balance between simulation detail, accuracy and required time will be established.

The simulation takes into account the external vehicle style, shape of air inlets, cooling pack performances, engine and a/c heat rejection to cooling air and hot components temperature in the underhood. Both convection and radiation are simulated. Main results are found for the air flow rate and distribution on the heat exchangers and complete velocity and temperature distributions in the underhood. Two driving conditions are considered: low (climb) and high speed, based on Fiat Test Standard. Final result is a list of warnings and suggestions for vehicle thermal design.

The application of the methodology to an actual project is presented. Quite close agreement has been found with tests on early prototypes.