SUMMARY

Phase-change heat transfer processes during boiling and condensation are common in high-heat flux thermal management applications over a broad range of scales ranging from high-density electronics to thermoelectric industrial power cycles. Optimization of the phase change heat transfer processes requires a careful balance between boiling and condensation to ensure low surface superheat, high critical heat flux (CHF) limits, and adequate system stability. Our preliminary investigations at Georgia Tech have demonstrated that multi-scale acoustic actuation during phase change processes at atmospheric pressures can lead to control of the rate of vapor formation on and transport from heated surfaces during boiling, and to acceleration of vapor condensation within the bulk liquid. It is shown that ultrasonic actuation on the heater surface enhances vapor advection and thus increases the CHF limit, while sonic actuation in the bulk liquid accelerates vapor condensation rate using capillary waves at the vapor-liquid interface. Furthermore, acoustic actuation can be easily coupled with various textured surfaces. The proposed PhD dissertation will focus on extension of the operational domain of interfacial acoustic actuation from atmospheric to low ambient pressure that are prevalent in a broad range of applications including low pressure condensers, vapor suppression systems, low-temperature heat sinks, and high heat flux evaporators.