Holographic Interferometric Study of Heat Transfer Associated With a Single Vapor Bubble Sliding Along a Downward-Facing Heater Surface

Heat transfer associated with a single vapor bubble sliding along a downward-facing heater surface was studied experimentally to understand the mechanisms contributing to heat transfer enhancement. Heater surface was made of polished silicon wafer of length 185 mm and width 49.5 mm. Saturated and subcooled performance fluid PF 5060 at atmospheric pressure was used as the test liquid. The heater surface was at 75° inclination to the vertical for the experiments reported here. Single vapor bubbles were generated at an artificially formed cavity at the bottom end of the heater surface. Holographic interferometry was used to obtain the temperature profile around the bubble as it slides along the heater surface near the top end of the heater plate. From the fringe patterns, the temperature gradient around the bubble interface was measured and heat transfer into or out of the bubble was computed. In addition to these experiments, the volumetric growth of the vapor bubble as it slides along the heater surface was obtained using direct high-speed photography for the same experimental conditions. Heat transfer from the wall was estimated utilizing inputs from both interferometry studies as well as the volume growth data. Results are given for a range of liquid subcoolings and wall superheats, and are compared with previously published works.