Flow Regime Transition in Inner Grooved Minichannel Cold Plates for Cooling Hybrid Electric Power Electronics

Report No. ARL-TR-6170
Authors: Darin J. Sharar, Nicholas R. Jankowski, and Avram Bar-Cohen
Date/Pages: January 2013; 30 pages
Abstract: Forced flow of fluids undergoing phase change in traditional single-phase cold plates is an effective way to manage waste heat removal of vehicle power electronics. Such cold plates come in a variety of standard styles, ranging from circular-tubed cold plates and flat-tube cold plates, to more exotic designs such as louvered and offset fin cold plates. The mechanisms of heat transfer in a two-phase system are different than single-phase, and as such, improvement can be made by custom designing cold plates for two-phase operation. Past research has focused on surface modifications that enhance nucleate boiling, convective vaporization, or both during two-phase operation. The method that has gained the most attention is the use of inner grooved tubes for performance improvement in refrigeration applications. Despite the popularity of inner grooved tubes, the flow mechanisms that deliver performance enhancement are not fully understood. The absence of phenomenological insights and physical models makes it difficult to transition inner grooved tube technology from conventional refrigeration equipment to cold plates. Therefore, understanding the physical mechanisms underpinning two-phase performance enhancement in inner grooved tubes is at the heart of this report.
Distribution: Approved for public release
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Last Update / Reviewed: January 1, 2013