Vapor bubble-bubble penetration during subcooled pool boiling in a nonionic surfactant aqueous solution

Boiling is encountered in industrial processes as an effective heat transfer method. It generates vapor to remove a large amount of heat. The evolution of vapor bubbles in a boiling liquid, especially the growth of bubbles, is one of the parameters that determine the heat transfer strength of a heating surface. The growth process of bubble is complicated due to many physical or chemical factors. Here, for the first time, we report a new phenomenon of vapor bubble-bubble interaction process (a bubble interacts with its neighboring one(s) generated at the same nucleation site) during pool boiling aided by a nonionic surfactant. The different bubble interactions are defined as bubble-bubble penetration, bubble-bubble piercing, and double penetrations. It is motivated by microbubble emission from heater in subcooled pool boiling. Bubble dynamics in aqueous surfactant solution was visualized and analyzed. Much attention was paid on the vapor bubble generation, growth, and interaction in the presence of surfactant. It is worth noting that the bubble penetration frequently occurs in the current conditions. The findings are of fundamental and practical relevance, and in the hope to contribute to better understanding of surfactant-aided boiling mechanism. (C) 2020 Elsevier Ltd. All rights reserved.