Oscillate Boiling

TL;DR

This paper describes a novel oscillate boiling regime observed with microheaters in subcooled water, characterized by continuous bubble oscillations and potential applications in heat transfer enhancement, especially under microgravity.

Contribution

It introduces a new oscillate boiling regime driven by thermally induced bubble dynamics and Marangoni flows, with potential to improve heat transfer beyond nucleate boiling limits.

Findings

Bubble oscillates at several hundred kHz.

Stable oscillate boiling persists over millions of cycles.

Potential to surpass nucleate boiling heat transfer limits.

Abstract

We report about an intriguing boiling regime occurring for small heaters embedded on the boundary in subcooled water. The microheater is realized by focusing a continuous wave laser beam to about $10\,\mu$m in diameter onto a 165\,nm-thick layer of gold, which is submerged in water. After an initial vaporous explosion a single bubble oscillates continuously and repeatably at several $100\,$kHz. The microbubble's oscillations are accompanied with bubble pinch-off leading to a stream of gaseous bubbles into the subcooled water. The self-driven bubble oscillation is explained with a thermally kicked oscillator caused by the non-spherical collapses and by surface pinning. Additionally, Marangoni stresses induce a recirculating streaming flow which transports cold liquid towards the microheater reducing diffusion of heat along the substrate and therefore stabilizing the phenomenon to many million cycles. We speculate that this oscillate boiling regime may allow to overcome the heat transfer thresholds observed during the nucleate boiling crisis and offers a new pathway for heat transfer under microgravity conditions.