Condensation and Collapse of Vapor Bubbles Injected in Subcooled Pool

Abstract

We focus on condensation and collapse processes of vapor bubble(s) in a subcooled pool. We generate the vapor in the vapor generator and inject it/them to form vapor bubble(s) at a designated temperature into the liquid at a designated degree of subcooling. In order to evaluate the effect of induced flow around the condensing/collapsing vapor bubble, two different boundary conditions are employed; that is, the vapor is injected through the orifice and the tube. We also focus on interaction between/among the condensing/collapsing vapor bubbles laterally injected to the pool. Through this system we try to simulate an interaction between the vapor bubble and the subcooled bulk in a complex boiling phenomenon, especially that known as MEB (microbubble emission boiling) in which a higher heat flux than critical heat flux (CHF) accompanying with emission of micrometer-scale bubbles from the heated surface against the gravity is realized under a rather high subcooled condition.

A study visualizing the collapse of vapor bubbles in a subcooled pool

“…In this paper, the interaction between vapor bubble and liquid water was studied in isolation from other complex factors, such as wall effect, Marangoni effect etc., by injecting vapor bubble into a subcooled pool. Similar research method was also used by Ueno et al [20][21][22]. The effects of liquid subcooling and vapor volumetric flow rate on the vapor bubble surface, collapse process and the emitted microbubbles are researched visually.…”

“…The injection rate was controlled by the steam regulating valves and a bypass valve, and was obtained by measuring the volume variation of vapor bubble before detachment in the water tank pool under saturation condition. Similar way was also used in the experiments of [20][21][22]. The measurement process of the vapor bubble volume would be introduced in the part of image data processing.…”

“…Afterwards, Suzuki et al [19] obtained similar results and proposed a simple correlation of MEB. Ueno et al [20][21][22] proposed a simplified approach to analyze the formation mechanism of MEB. They injected vapor bubbles into a subcooled pool to study the interaction between vapor and cold bulk as well as the collapse process of vapor bubbles.…”

“…Hence, Suzuki et al [19] and Ueno et al [20][21][22] considered that the cold bulk would have a significant effect on the formation of MEB. In this paper, the interaction between vapor bubble and liquid water was studied in isolation from other complex factors, such as wall effect, Marangoni effect etc., by injecting vapor bubble into a subcooled pool.…”

Experimental investigation of transition process from nucleate boiling to microbubble emission boiling under transient heating modes

“…They found that the microbubbles were resulted from cavitation caused by collapse of vapor bubbles. Condensation process of a single vapor bubble in MEB was investigated by Ueno et al through injection vapor bubbles into a subcooled pool. It was found that the formation of fine surface waves caused by strong condensation across the interface could accelerate instability of bubble surface and cause the collapse of the vapor bubble.…”