IMPROVING MINI- AND MICROCHANNEL HEAT TRANSFER BY ACOUSTIC FIELDS

The operation of high-performance electronic systems (e.g., computers, RF electronics, and solid state lasers) is currently limited by thermal management issues. There is a need to maintain these devices within their acceptable operating range while removing heat in excess of 1 kW/cm2 flux and 1 kW/cm3 heat density as well as hot spot mitigation above 5 kW/cm2. Results in this study demonstrate that insonation at frequencies near the resonance of bubbles smaller than minimum flow channel dimensions improves heat removal at certain flows. Further, the greatest enhancement in heat transfer is observed in an operating region far from dry out conditions. The ultrasonic management of bubble size is hypothesized as the reason for the enhanced performance. In the single-phase region insonation appears to add heat to the system through absorption of acoustic energy faster than subcooled bubble nucleation appears to enhance heat removal.