Numerical Modeling of Forced Air Convection for Thermal Management in Automotive ECU: A Component and System Level Study
Authors: Oh Joseph , Taylor Kenneth 
Published: November 2023

Abstract
The thermal management of automotive electronic devices has become a critical technology as the power consumption and resulting heat dissipation of these devices have increased significantly. Electronic control units (ECUs) are a critical component of automotive power electronics, particularly for the development of next-generation automotive features such as Advanced Driver Assistance Systems (ADAS) and autonomous driving. In conventional vehicles, natural convection cooling was sufficient for thermal management of ECUs. However, with the exponential increase in the number of ECUs and their power capacity, natural convection may no longer suffices to deal with the increased amount of heat dissipation of advanced ECUs. This has led to the adoption of forced convection technology, either air or liquid cooling, to transfer heat to the surrounding environment. While the electronics industry has accumulated extensive experience and knowledge on the forced cooling technology, however, higher standards for safe operation in extreme and unique conditions for automotive products have challenged their direct implementation to the automotive products. ECUs commonly locate in highly limited space, and the size of ECUs is getting smaller to fit the limited space. In most automotive operating environment, the space is not free from contaminants, and ECU package designers must consider the possibility of exposure to such contaminants. This fact leads to inability to utilize direct internal forced convection cooling. Complicating matters further, the trapped air pocket inside ECUs can act as an insulation, contributing to an increase in temperature across the entire system. In addition to these challenges, the design of ECU cover plate must also ensure structural safety, which can result in inefficient from a thermal management perspective. As a result, the development of dedicated thermal management solutions that take an integrated perspective is crucial. This involves not only addressing individual heatsink geometry but also considering the entire system, including the placement of cooling fans, the arrangement of heat sources, and the overall airflow dynamics between components. By adopting a holistic approach to thermal management, automotive manufacturers can ensure that their ECUs operate reliably and efficiently in a wide range of operating conditions. This is particularly important give the increasing power consumption and heat dissipation of ECUs, which is being driven by the development of advanced automotive technologies.
This research aims to develop a numerical modeling method using coupled system simulation with computational fluid dynamics (CFD) and finite element method (FEM) to solve the conjugate heat transfer phenomenon with forced air convection cooling on plate-fin-type heatsinks. A goal of the research is to predict pressure drop and thermal resistance in various enclosure configurations at the component level. Simulation models for complete-enclosed flow and semi-enclosed flow with a bypass channel are developed to evaluate pressure drop and thermal resistance with respect to diverse Reynolds numbers. The simulation results are validated with experimental data from the references. With the validated numerical models, a parametric study with multiple geometric dimensions is conducted. The findings are extended to the system level analysis of ECU assemblies with multiple heat sources in an extreme operating condition with high temperature. The influence of the cooling fan placement is assessed in terms of hydraulic and thermal management performances. This research aims to contribute to the advancement of thermal management solutions in the automotive industry, ensuring the reliability and functionality of future automotive ECUs under extreme operating conditions.