Quantifying Local Heat Transfer Mechanisms Around a Single Bubble During Nucleate Boiling Using LIF and TIRF Thermometry

Resolving temperature fields near a growing bubble during nucleate boiling is essential for understanding microscale heat transfer mechanisms. This study presents high-resolution thermometry around a single bubble nucleating from a cylindrical cavity embedded on the surface of a copper fin. We employ advanced thermometry techniques like Laser-Induced Fluorescence (LIF) and Total Internal Reflection Fluorescence (TIRF) to quantify temperature distributions both within the bulk fluid and at the solid-liquid interface. Using a calibrated mixture of fluorescein and Sulforhodamine B dyes, LIF captures volumetric temperature fields (20°C–90°C). On the other hand, TIRF provides sub-micron thermal mapping beneath the growing bubble using one dye. Experiments are conducted in subcooled deionized water under controlled superheat conditions, with bubble dynamics captured via synchronized high-speed imaging. The results reveal complex, time-resolved thermal gradients around the bubble base and quantify the superheated liquid layer and microlayer heat transfer mechanisms. This work offers new insights into localized boiling heat transfer and demonstrates the utility of hybrid optical diagnostics for probing interfacial thermal transport.