Experimental and theoretical investigation of bubble dynamics on vertical surfaces with different wettability for pool boiling

Abstract

Surface wettability is generally employed to manipulate the bubble dynamics to enhance the performance of boiling heat transfer. This work conducted an experimental and theoretical investigation of bubble dynamics on vertical surfaces with different wettability for pool boiling. The side-by-side comparison for bubble growth, bubble detachment diameter and frequency on superhydrophilic, superhydrophobic, and neutral surfaces were visualized, the bubbles detachment diameter and growth time in a negative exponential dependence with the subcooling degree, even a tiny difference in subcooling, such as 1–2K, contributes significantly to the shrinking of bubble volume. When the fluid was in a saturated state or the subcooling of the fluid can be neglected, the bubble was tightly adhered to the wall and cannot detach from the superhydrophobic surface, the bubbles would gather to a certain volume and then slide upward, and the first time of bubble detachment was observed when the coolant subcooling reached 2K. An energy balance model was developed to evaluate the bubble diameter in the bubble growth period, with 94% reproduction of the consolidated database within the error band of ± 40%. In addition, a new correlation is proposed for bubble detachment diameter, the new correlation performed significantly better in a broad range of contact angle, with 82% confidence interval of the consolidated datasets was ± 30%.