TransForum, Vol. 2, No. 4

UNDERHOOD THERMAL MODELING UNDERGOES BIG IMPROVEMENTS

Argonne and its partners simulate intense heat in confined spaces

A stream of air roars through narrow openings into near-total darkness before being captured, compressed, and ignited. This complex process, involving hundreds of variables, repeats thousands of times each minute as exhaust fans and coolant systems struggle to combat rising temperatures. Could you accurately simulate such an environment?

Now automotive engineers can, thanks to new high-performance computer models being developed by Argonne and industry partners in collaboration with General Motors, Ford, and DaimlerChrysler. The modeling software simulates complex fluid flows and heat transfer in underhood systems for automobiles, including hybrid-electric vehicles and conventional passenger cars.

A CFD component-level model is used in the vehicle design stage to help predict cooling system performance.

A large model (6 million cells) shows CFD software capabilities in assessing the aerodynamic performance of the vehicle and the effectiveness of the thermal management system.

More power electronics and increasingly complex vehicle operating conditions require early diagnosis and correction of potential heat load problems to help reduce design time and cost. This is why scientists from Argonne have teamed with research partners like Analysis and Design Application Company (adapco) of Melville, NY, to improve underhood heat load modeling.

Using computational fluid dynamics (CFD) software, the researchers plan to eventually extend the software to model three-dimensional fluid flow and heat transfer for entire vehicles, providing a "virtual test facility" that could help vehicle manufacturers assess the interdependence of underhood components, study heat-load conditions, and identify critical components.

According to David Weber, Associate Director of Argonne's Reactor Engineering Division, "The automotive industry is moving away from using only experimental testing for validating vehicle designs and is starting to use more analytical testing, which helps predict vehicle performance before it's built. Argonne's ability to provide numerical models that more accurately simulate car and truck underhood system performance will soon help vehicle manufacturers reduce the number of prototypes they need to build. The potential savings for these manufacturers is enormous."

The availability of faster and cheaper computers and the increasing use of sophisticated computer-aided design by carmakers has helped numerical modeling gain wider acceptance in the automotive industry. Modeling speed and accuracy have increased dramatically. "Our first underhood thermal model was developed for Mercedes in the mid-1990s, and the process took more than a year. Now we can build that same type of model in a matter of weeks," says Steve MacDonald, adapco president.

MacDonald explains that adapco has benefited from Argonne's experience in developing models that represent entire vehicle systems. "Our strength was in specific component-level modeling, and we were able to integrate this knowledge with Argonne's expertise in systems-level models."

As the researchers further refine the underhood models, they plan to extend their work to include underhood thermal management for trucks and other heavy vehicles. John Hull of Argonne's Energy Technology Division explains that "managing underhood airflow is especially critical for optimizing the design of trucks to improve fuel economy and reduce aerodynamic drag."