November 19, 2021 report
'Triple Leidenfrost effect' seen in dissimilar drops in a hot pan
Bob Yirka
news contributor
A small team of researchers from Benem茅rita Universidad and Universidad de las Am茅ricas Puebla, in Mexico and Universit茅 de Poitiers, in France, has found a "triple Leidenfrost effect" in dissimilar drops in a hot pan. In their paper published in the journal 糖心视频ical Review Letters, the group describes a type of "bouncing" they observed with different types of drops hovering over a hot surface.
Prior research has shown that the reason drops of water zip around in a hot pan, is because water at the bottom of the drops is vaporized鈥攖hus, the drops hover like air-hockey pucks. This phenomenon has come to be known as the Leidenfrost effect. In this new effort, the researchers have found another drop behavior associated with the Leidenfrost effect.
The work involved dropping two types of liquid onto a hot surface and then tilting the surface to force the drops to run into each other. They wanted to know if the two drops would merge. Instead they found that sometimes one of the drops would start bouncing off of the other.
Over several trials, the researchers tried several liquids: water, ethanol, methanol, isopropanol, acetone, hexane, chloroform, acetonitrile, toluene and formamide. They found that sometimes the two drops mixed right away, while sometimes they did not. After much trial and error, they found differences in properties of the two drops and their relative size to one another. Two drops of water, for example, because they have identical properties, merge right away. A drop of ethanol and a drop of water, on the other hand, have very different properties. When a small drop of ethanol was placed next to a large drop of water, the smaller drop bounced off of the larger drop several times before they merged.
The researchers found that the bouncing was due to the difference in boiling point and evaporation speeds of the two substances. They found that there was a Leidenfrost effect happening between the two drops鈥攖he hotter drop worked as a hot surface for the cooler drop; its vapor pushed the cooler drop away. They have labeled this phenomenon as a "triple Leidenfrost effect."
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More information: F. Pacheco-V谩zquez et al, Triple Leidenfrost Effect: Preventing Coalescence of Drops on a Hot Plate, 糖心视频ical Review Letters (2021). . Arxiv:
Journal information: 糖心视频ical Review Letters
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