Pattern Evolution during Double Liquid-Vapor Phase Transitions under Weightlessness

Abstract

Phase transition in fluids is ubiquitous in nature and has important applications in areas such as the food industry for volatile oils’ extraction or in nuclear plants for heat transfer. Fundamentals are hampered by gravity effects on Earth. We used direct imaging to record snapshots of phase separation that takes place in sulfur hexafluoride, SF6, under weightlessness conditions on the International Space Station (ISS). The system was already at liquid-vapor equilibrium slightly below the critical temperature and further cooled down by a 0.2-mK temperature quench that produced a new phase separation. Both full view and microscopic views of the direct observation cell were analyzed to determine the evolution of the radii distributions. We found that radii distributions could be well approximated by a lognormal function. The fraction of small radii droplets declined while the fraction of large radii droplets increased over time. Phase separation at the center of the sample cell was visualized using a 12× microscope objective, which corresponds to a depth of focus of about 5 μm. We found that the mean radii of liquid droplets exhibit a t1/3 evolution, in agreement with growth driven by Brownian coalescence. It was also found that the mean radii of the vapor bubbles inside the liquid majority phase exhibit a t1/2 evolution, which suggest a possible directional motion of vapor bubbles due to the influence of weak remaining gravitational field and/or a composition Marangoni force.

Measuring the Transition Rates of Coalescence Events during Double Phase Separation in Microgravity

“…The DECLIC experimental setup was described extensively in previous publications [ 30 , 41 , 42 ]. DECLIC used Alice Like Instrumentation (ALI) to carry out phase separation experiments near the critical point of SF at room temperature in the weightlessness.…”

“…The DOC was filled with SF at its vapor-liquid critical point K, (45.587 C), MPa, and kg m . A sketch of the cell is shown in Figure 1 a (see also [ 41 , 43 , 44 ] for more details). The cylindrical DOC had an inner diameter of D = 10.6 mm and inner thickness of e = 4.115 mm, and was prepared with a mean density .…”

“…This study reports on the double phase separation process that takes place after a supercritical SF fluid is brought from an initial state, which is already in a two-phase state slightly below the critical temperature, to a temperature 0.2 mK below the initial value thanks to a temperature quench. Although the one-step phase separation process has been studied by several authors in weightlessness [ 11 , 12 , 13 , 24 , 28 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 ], double quench has only been the object of very few studies [ 35 , 41 ].…”

“…As discussed in detail in [ 41 ], the 0.2 mK temperature quench produced further phase separation with (1) vapor bubbles inside the majority liquid phase (the latter wetting the walls of the sample cell unit); and (2) liquid droplets inside the initially separated vapor phase. The novelty of this study is the quantitative investigation of the liquid droplets and vapor bubbles distributions, respectively, observed during the double phase separation process.…”

Phase Transitions in Wireless MESH Networks and Their Application in Early Detection of Network Coherence Loss

“…Such phenomena are well known and described. They mostly regard studies in the field of physics, electronics specifically, but also social and economic relations [6][7][8][9][10][11]. Thermodynamic processes are the most well-known and commonly observed phase changes, among which there are the changes in the state of water into ice or steam [12].…”