Thermal Bubble Dynamics Under the Effects of an Acoustic Field

Abstract

In this research, dynamics of a micro thermal bubble existing in an acoustic field have been studied by a high-speed camera and a micro temperature sensor. The micro thermal bubble was generated by a micro heater, which was fabricated by the MEMS (micro-electro-mechanical system) technique and packed into a transparent mini chamber. The acoustic field inside the chamber was generated by a piezoelectric plate that was attached on the top side of the chamber's wall. Compared with micro thermal bubble dynamics in normal conditions, several different bubble dynamic phenomena in acoustic conditions have been found, such as bubble departure and attraction around the heater, bubble oscillating in the liquid volume, etc. By theoretical analysis, the main mechanism of bubble movements is attributed to the balance between Marangoni force and acoustic force. All these bubble dynamic phenomena improve the liquid convective flow and enhance the heat and mass transfer. Thus, this investigation about acoustic thermal bubble dynamics may find some potential applications in micro fluid devices for different functions, such as heat/mass transfer enhancement, micro electronic cooling, micro heater protection, etc. Temperature measurement in both normal conditions and acoustic conditions confirmed that the heat transfer was enhanced by the acoustic field.