[Paper Review] Far from equilibrium boiling

José Graña-Otero, I. E. Parra|arXiv (Cornell University)|Oct 15, 2010

Meteorological Phenomena and Simulations2 references4 citations

TL;DR

This study investigates evaporation waves in a metastable liquid after rapid depressurization in a degassed glass tube, where the interface propagates downward at tens of cm/s due to Darrieus-Landau instability. The wave velocity scales with the initial-to-ambient pressure ratio, and a nonpropagating, self-extinguishing vaporization regime emerges at lower pressure ratios due to thermal de-stabilization from evaporative cooling.

ABSTRACT

We address an experimental investigation of evaporation waves. These waves appear when a liquid contained in a vertical glass tube is suddenly depressurized from a high initial pressure down to the atmospheric one. The state of the liquid after the release of the pressure, ambient pressure and the initial temperature, is well known to be metastable when the corresponding stable state is vapour. For moderately large evaporation rates (moderately large initial to ambient pressure ratios), the initially flat vapour-liquid interface ultimately evolves into highly corrugated front which propagates downwards into the liquid with a well defined mean velocity. This mean velocity turns out to be a function of the ratio between the initial and the ambient pressures. In addition, it has been found that for lower pressure ratios, the instability is not able to develop an evaporation wave but nevertheless leads to a somewhat more complex behavior than the simple surface evaporation as it is shown in the accompanying fluid dynamics video.

Motivation & Objective

• To investigate the dynamics of evaporation waves in a liquid metastable under rapid depressurization.
• To understand the conditions under which evaporation waves form versus nonpropagative vaporization regimes.
• To examine the role of Darrieus-Landau instability in driving the corrugated, propagating interphase.
• To analyze how evaporative cooling stabilizes the interface in low-pressure-ratio regimes.
• To characterize the dependence of wave velocity on the initial-to-ambient pressure ratio.

Proposed method

• Conducted experiments using a 25 mm diameter, 250 mm long transparent glass tube with a hemispherical bottom to eliminate nucleation sites.
• Rapidly depressurized the liquid from high initial pressure to atmospheric pressure to induce metastable vaporization.
• Used high-speed fluid dynamics video to observe interphase morphology and propagation dynamics.
• Analyzed wave propagation velocity as a function of the initial-to-ambient pressure ratio.
• Identified transition between propagative evaporation waves and nonpropagative, self-extinguishing regimes based on pressure ratio.
• Applied theoretical framework of Darrieus-Landau instability to explain the formation of corrugated interphases.

Experimental results

Research questions

• RQ1 What determines the onset of propagating evaporation waves after rapid depressurization of a metastable liquid?
• RQ2 How does the wave propagation velocity depend on the initial-to-ambient pressure ratio?
• RQ3 What physical mechanisms stabilize the interface in low-pressure-ratio regimes, preventing wave propagation?
• RQ4 Why does evaporative cooling lead to self-extinguishing behavior in nonpropagative regimes?
• RQ5 To what extent does Darrieus-Landau instability govern the morphology and dynamics of the evaporation front?

Key findings

• Evaporation waves propagate downward at velocities of several tens of cm/s, increasing with the initial-to-ambient pressure ratio.
• The wave front exhibits a highly corrugated structure due to continuous nucleation and collapse of small bubbles at the interface.
• Darrieus-Landau instability is identified as the primary mechanism driving the formation of the corrugated, propagating interphase.
• For lower pressure ratios, evaporation waves do not form; instead, a nonpropagative, self-extinguishing vaporization regime emerges.
• Evaporative cooling at the interface induces convective cooling of the bulk liquid, which stabilizes the planar interface and terminates the vaporization process.
• The absence of nucleation sites due to degassing ensures that vaporization occurs only via interfacial mechanisms, not bulk or wall nucleation.