A Multi-Dimensional Approach to Truck Underhood Thermal Management

The purpose of this paper is to describe a methodology that significantly streamlines the process of truck underhood thermal management by utilizing state-of-the-art computer simulation of airflow and heat transfer. The traditional approach has been to package underhood components in the vehicle design phase based on past experience, build a prototype, test it, analyze the test results and determine any necessary design changes. The design changes are implemented and the cycle is repeated until an acceptable design is achieved. The alternative methodology, described in this paper, uses a complete 3-D CAD model of all pertinent underhood components of a heavy-duty truck with a general purpose Computational Fluid Dynamics (CFD) code to simulate underhood airflow. The heat exchangers - condenser, charge air cooler, oil cooler and radiator - were modeled using a 2-D approach that divides the heat exchanger core into cell zones and computes heat rejection cumulatively from zone to zone. As the cooling fan performance has a significant influence on airflow across the heat exchangers, the detailed geometry of the blades were considered in the fan model which was introduced in the overall computational domain using a multiple reference frame approach. These multi-dimensional models were coupled to provide an integrated methodology to assess the underhood airflow and heat transfer characteristics that can be applied both proactively - early in the design process - and reactively to analyze problems that occur with production vehicles. Results from the underhood simulation were compared to test data compiled during the development phase of a truck and are reported in this paper.