An assessment of air cooling for use with automotive power electronics

In this research, we evaluate the potential for air cooling to meet the stringent cooling requirements of advanced automotive power electronics. We assess air cooling of power electronic components using laminar airflow micro-channel heat exchangers. Comparisons are made with ethylene glycol systems commonly used in tandem with engine cooling. Our analysis shows that despite a lower coefficient of performance and higher parasitic losses, air cooling compares quite favorably, offering lower mass, fewer components, and a lower projected cost. Air cooling also has many significant, less obvious advantages such as simpler design and greater reliability. Micro-channel heat exchangers appear to offer the most promise and can be further enhanced by simple design changes, such as reducing passage lengths. Direct air cooling appears to be a viable option for the current generation of silicon-based power switches and will be more attractive for anticipated future electronic components made of materials that operate at higher temperatures. Continuing work includes experimentation and data validation. Recommendations for future research include fabricating and testing air-cooled inverters. A micro-channel performance estimator program we developed was found to over-project heat flux in comparison to a more detailed computational fluid dynamics model. However, the program provides an initial estimate that can be used as a quick, convenient means of estimating micro-channel heat transfer with a variety of configurations and fluids.