Session: K13-02 Pool Boiling Fundamentals

Paper Number: 117408

117408 - Understanding Heat Transfer Mechanisms Near Growing Bubbles During Nucleate Boiling 

The rapid advancement of nanotechnology and microelectronics has posed huge challenges to the thermal management of extreme heat loads discharged from tightly confined areas in many electrical systems. Boiling heat transfer associated with bubble growth is perhaps one of the most efficient cooling methodologies due to its large latent heat during phase change. Despite significant enhancement of heat removal rates, numerous questions remain regarding the fundamentals of bubble growth mechanisms, a major source of enhanced heat dissipation. This work aims to accurately measure three-dimensional (3D), space- and time-resolved, local liquid temperature distributions surrounding a growing bubble that help better explain the heat transfer to bubble growth. An artificial cavity of  in diameter is fabricated on a rectangular-shaped heat sink as nucleate sites. The dual tracer laser-induced fluorescence (LIF) thermometry technique is combined with high-speed imaging to capture transient temperature distributions of the single bubble. This technique has successfully provided fluid temperatures with unprecedented accuracy at micrometer resolution, i.e., within 0.3 ºC at a 30 μm resolution. Two temperature-sensitive fluorescent dyes, fluorescein and sulforhodamine B are used as temperature indicators in the LIF technique to improve measurement accuracy. A laser light sheet scanned across the entire measurement volume excites the fluorescent dye, and an optical system involving a color beam splitter gives the intensity distribution of the individual fluorescent dyes on a high-speed camera. The obtained experimental data are compared with models and data available in the literature to validate the accuracy of the techniques. Also, the temperature is used to quantify time-resolved heat fluxes contributing to mass transfer near the growing bubble. The results show the dominant heat transfer mode for fast bubble growth and therefore provide reliable methodologies to engineer surface and fluid properties for enhanced heat transfer without a trial-and-error process. Comprehensive 3D temperature information will validate the existing theoretical and experimental thermal transport models. 

Presenting Author: Myeongsub Kim Florida Atlantic University