Vibration-induced droplet atomization heat transfer cell for high-heat flux applications

This paper describes a unique two-phase cooling method that includes a closed heat transfer cell, similar to a thermosyphon that can be used to cool microelectronic packages. The cooling method is based upon a Vibration-Induced Droplet Atomization, or VIDA, process that can generate small liquid droplets inside a closed cell and propel them onto a heated surface. The VIDA technique involves the violent break-up of a liquid film into a shower of droplets by vibrating a piezoelectric actuator and accelerating the liquid film at resonant conditions. The droplets continually coat the surface with a thin liquid film, which evaporates on the heated surface, and the vapor is condensed on the internal surfaces of the heat transfer cell as well as the liquid working fluid. The condensed liquid is returned via gravity to the piezoelectric actuator where it is again atomized. A VIDA heat transfer cell 50 mm in diameter and 20 mm thick was constructed. Test data described in this study include the heat transfer characteristics and cooling capabilities for a small-scale cell that is suitable for cooling a desktop microprocessor during the burn-in portion of the manufacturing process. The VIDA process produces droplets of relatively uniform diameter, and the droplets have sufficient momentum to reach the remotely located heated source. Heat fluxes as high as 200 W/cm² have been measured when a chilled water heat exchanger is used as the external heat removal device.