Orientation-Independent Atomization Heat Transfer Cell for Thermal Management of Microelectronics

This paper describes a new gravity-independent version of a two-phase cooling, closed heat transfer cell, similar to a thermosyphon. 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. A piezoelectric diaphragm pump is used to supply a constant stream of liquid to the VIDA atomizer enabling gravity-independent operation. The atomized secondary droplets continually coat the heated surface with a thin liquid film that evaporates. The resulting vapor is condensed on internal surfaces of the heat transfer cell as well as the liquid working fluid. The condensed liquid is collected and returned to the atomizing driver by the piezoelectric diaphragm pump. A small-scale gravity independent VIDA atomizer generating spherical droplets of relatively uniform diameter and having sufficient momentum to reach the remotely located heated source has been constructed. Initial test data described in this study include the operating characteristics of the VIDA spray and heat transfer capabilities. Heat dissipation levels as high as 195 W have been measured from an evaporation surface held below 120°C at atmospheric pressure.