MICRO-HEAT EXCHANGERS FABRICATED BY DIAMOND MACHINING

Machining of thin metal foils with specially contoured diamond cutting tools allows the production of small and very smooth fluid microflow channels for micro heat exchanger applications. Heat exchanger plate wall thickness, as well as fin dimensions, may be carefully controlled and machined to dimensions on the order of tens of micrometers. The plates are stacked and bonded with the vacuum diffusion process to form a cross-flow, plate-type heat exchanger. These fabrication techniques allow the production of small heat exchangers with a very high volumetric heat transfer coefficient and inherent low weight. The design and fabrication process for a copper-based, cross-flow micro heat exchanger has been developed. The micro heat exchanger provided a volumetric heat transfer coefficient of nearly 44 MW/m3 K under very conservative design and operating conditions. This corresponds to a volumetric capacity nearly 20 times that of more conventional compact heat exchangers. High thermal capacity, coupled with low cost and ease of production, make these devices practical in areas where high thermal flux in a small volume is required. The methods and procedures for this type of micromachining closely parallel those for precision machining.