Experimental Study on Bubble Dynamics in Nucleate Boiling for Water and Ethanol on Enhanced Copper Surfaces

An experimental study is performed to investigate the effect of heat flux on bubble departure diameter and departure frequency. Quantitative measurements are obtained from high-speed visualizations of nucleate pool boiling at atmospheric pressure from smooth and finned surfaces using water and ethanol as the working fluid. The boiling surface is made of copper in both surface conditions. The bubble diameter at departure and bubble departure frequency are measured from videos, which have been recorded at approximately 3000 frames per second with a Phantom Miro e×4 camera and an AF NIKKOR 50mm f/1.8D lens. Predictions of Cole (1967) and Peebles & Garber's model of bubble nucleation behaviors are verified with the experimental data. Less effect on departure frequency rather than departure diameter for the enhanced surface is documented. The data variation in nucleate boiling both experimental and correlation-based with increasing heat flux are also investigated. A way to analyze the effect of surface condition on bubble departure diameter and frequency basis on this experimental data is proposed. Wall superheat and heat flux are also reported. For the two test fluids experimental data shows that bubble departure diameter increases with increasing heat flux. It is seen that the surface condition’s effect on bubble departure diameter is not high. But the surface condition has a significant effect on the bubble departure frequency. For the finned surface, bubble departure frequency is greater in both the two liquids compared to the plane surface. The existing correlations do not give predictions for different surface conditions. So, this experiment provides a way to analyze the effect of surface conditions on bubble departure diameter and frequency.