Acoustic compression for the thermal management of multi-load electronic systems

Microprocessor power densities have been dramatically increasing over the past several years. If current trends continue, estimates indicate power density levels could reach 200 W/cm² in the near future. There are no commercially available cooling options for power densities at these levels, though refrigeration and evaporative spray cooling, among other things, have been discussed as potential solutions. Further complicating the problem, these power-dense microprocessors will be deployed in multi-processor workstations and servers resulting in significantly increased system level power densities. Moreover, each microprocessor within a system can undergo varying work loads that result in significant power dissipation variances which further complicate system level thermal architectures. A method is therefore sought by which numerous independent heat sources dissipating heat at very high densities can be efficiently managed. This paper introduces a unique thermal management architecture that employs vapor-compression refrigeration to cool, above the dew point, multiple independently operating microprocessors in a small volume. The refrigeration system is driven by a novel acoustic compressor technology that has the virtues of, among other things, being highly variable, oil-less, and orientation independent, and thus able to operate under significant variations in loading and deployment. The paper will also, therefore, introduce acoustic compression and discuss its application to the thermal management of electronics. A prototype 5U server with four 100 W, independently variable, heat loads demonstrating the technology has been built and experimental results will be reviewed.