Session: 05-03 Advanced Cooling Technologies 2

Paper Number: 98077

98077 - Naturally-Cooled Heat Sinks for Next-Generation Battery Chargers 

Next-generation commercial battery chargers for electric vehicles require significant heat removal capacity enhancements due to their rise in power output. Due to their low cost, reliability, and simplicity, naturally-cooled heat sinks are still desired for light electric vehicles. Due to higher power levels and heat fluxes, smaller, more complex, and costly liquid cooling systems using cold plates are used for larger electric vehicles. To conform to the aims of both types of heat sink designs, operational versatility, notably gravitational orientation, cost and weight reduction, and design simplification must be explored.

For naturally-cooled heat sinks, significant heat removal capacity enhancement must be achieved while maintaining near-orientation independence and comparable cost, reliability and weight. In other words, the thermal performance of the battery charger should not be significantly hindered by its orientation (vertical, horizontal, and sideways) and, at the very least, aim to be as cheap and massive as current naturally-cooled heat sinks. The casing of a next-gen Delta-Q technologies battery charger and its increased, next-generation thermal loading are used in this study to assess potential design improvements, notably those associated with the fin arrangement. Many finned heat sinks are numerically studied in ANSYS Fluent, including combinations of inclined fins, inclined interrupted fins, straight interrupted fins, and pin fins. For the given thermal loading, numerical results and preliminary prototype testing suggest that inclined and straight fins offer significant horizontal and vertical heat removal while compromising performance in the rarely employed sideways orientation. Further improvements, such as strategically incorporating pin fins, have shown promise in mitigating these sideways orientation concerns, and these results are presented.

For liquid-cooled heat sinks, significant heat removal capacity enhancement must be achieved while minimizing cost and design complexity. Conventional cold plates are metallic and consist of many components as part of the onboard cooling loop, leading to considerable costs in manufacturing and design. Natural graphite sheet offers itself as a promising cold plate material. Natural graphite sheet (NGS) is considerably cheaper than the metals used in conventional cold plates and exhibits an in-plane thermal conductivity on par with aluminum. In addition, NGS is also significantly lighter than aluminum, offering additional weight savings. In this study, a natural graphite sheet cold plate is developed and experimentally tested, both thermohydraulically and mechanically. The cold plate is fabricated with a rapidly prototyped channel and bonded to natural graphite sheet, offering potentially considerable cost and weight savings and significant design simplification compared to commercial metallic cold plates. Experimentally, the natural graphite sheet cold plate prototype has been shown to meet performance requirements, both thermohydraulically and mechanically, and these results are presented. Further improvements to the design, particularly those concerning structural rigidity and convective performance, were also investigated; these results are also presented.

Presenting Author: Callum Chhokar Simon Fraser University