‘Triple Leidenfrost effect’ seen in dissimilar drops in a hot pan

Figure 1. (a) Experimental setup. (b) Direct coalescence of two water drops in Leidenfrost state. (c) Consecutive bouncing of an ethanol droplet (clear one) towards a water droplet (tinted with methylene blue) throughout a number of seconds earlier than coalescing. (d) Path of an acetonitrile droplet (tinted in blue) bouncing a number of occasions towards a water drop. The snapshots present that the water droplet, initially clear, turns bluish all of the sudden when the droplets coalesce. In (b)–(d), the elapsed time is indicated in seconds in every snapshot, with t=0s similar to the second of coalescence [scale bars: (b) and (c) 10 mm, (d) 5 mm]. Credit: DOI: 10.1103/PhysRevLett.127.204501

A small crew of researchers from Benemérita Universidad and Universidad de las Américas Puebla, in Mexico and Université de Poitiers, in France, has discovered a “triple Leidenfrost effect” in dissimilar drops in a hot pan. In their paper revealed in the journal Physical Review Letters, the group describes a sort of “bouncing” they noticed with various kinds of drops hovering over a hot floor.

Prior analysis has proven that the explanation drops of water zip round in a hot pan, is as a result of water on the backside of the drops is vaporized—thus, the drops hover like air-hockey pucks. This phenomenon has come to be often known as the Leidenfrost impact. In this new effort, the researchers have discovered one other drop conduct related to the Leidenfrost impact.

The work concerned dropping two kinds of liquid onto a hot floor after which tilting the floor to power the drops to run into one another. They needed to know if the 2 drops would merge. Instead they discovered that typically one of many drops would begin bouncing off of the opposite.

Over a number of trials, the researchers tried a number of liquids: water, ethanol, methanol, isopropanol, acetone, hexane, chloroform, acetonitrile, toluene and formamide. They discovered that typically the 2 drops blended immediately, whereas typically they didn’t. After a lot trial and error, they discovered variations in properties of the 2 drops and their relative measurement to at least one one other. Two drops of water, for instance, as a result of they’ve similar properties, merge immediately. A drop of ethanol and a drop of water, alternatively, have very totally different properties. When a small drop of ethanol was positioned subsequent to a massive drop of water, the smaller drop bounced off of the bigger drop a number of occasions earlier than they merged.

An ethanol droplet bounces round a water droplet earlier than finally merging. The temperature of the concave steel floor is 250 C . Credit: F. Pacheco-Vázquez et al.
Ethylene glycol (clear) and chloroform (blue) have such totally different boiling factors that the vapor layer between the droplets is seen once they collide.. Credit: F. Pacheco-Vázquez et al.
When droplets of ethylene glycol and chloroform merge, the chloroform droplet explodes as a result of its boiling level (54 C) is a lot decrease than that of ethylene glycol (190 C). Credit: F. Pacheco-Vázquez et al.

The researchers discovered that the bouncing was because of the distinction in boiling level and evaporation speeds of the 2 substances. They discovered that there was a Leidenfrost impact occurring between the 2 drops—the warmer drop labored as a hot floor for the cooler drop; its vapor pushed the cooler drop away. They have labeled this phenomenon as a “triple Leidenfrost effect.”

Leidenfrost impact drops discovered to be self-propelled

More data:
F. Pacheco-Vázquez et al, Triple Leidenfrost Effect: Preventing Coalescence of Drops on a Hot Plate, Physical Review Letters (2021). DOI: 10.1103/PhysRevLett.127.204501 . Arxiv: arxiv.org/abs/2107.00438

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‘Triple Leidenfrost impact’ seen in dissimilar drops in a hot pan (2021, November 19)
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