Effects of asymmetric cooling and surface wettability on the orientation of the freezing tip

Starostin, Anton; Стрельников, В. Н.; Dombrovsky, Leonid A.; Shoval, Shraga; Gendelman, Oleg; Bormashenko, Edward

doi:10.1680/jsuin.22.01081

Cited by 6 publications

(3 citation statements)

References 35 publications

(45 reference statements)

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“…As such, any modification in the heat transfer direction due to asymmetry in the contact angle will modify the location of the pointy tip. , When adding PVA, the frozen-induced swellability of the solution will be modified and controlled by the PVA hydration number, i.e., the number of molecules able to bind to the polymer chain. PVA has two different but constant hydration numbers, under or above the overlap concentration .…”

Section: Resultsmentioning

confidence: 99%

Unidirectional Freezing of Polymer Solution Droplets

Kharal,

Louf

2023

Langmuir

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Ice templating provides a means of generating textures with a well-defined topography. Recent applications involve the freezing of water droplets, with or without colloids, on flat or textured surfaces. An interesting feature of water droplets freezing on a substrate is the formation of a pointy tip at a constant angle, regardless of the substrate temperature, surface energy, or droplet volume. Here, by adding the polymer to water, we demonstrate how to manipulate and even prevent the formation of such an icy tip. We find that the sharpness of the tip decreases with increasing polymer concentration until completely disappearing above the overlap concentration, while the total freezing time increases concomitantly. Building on these observations, we combined simple geometrical arguments with heat flux measurements to model and connect the spatial and temporal evolution of polymer droplets under unidirectional freezing. Together our results provide new ways to control the shape of frozen droplets for ice templating or microstructure fabrication, with applications in tissue engineering, separation membranes, and soft robotics.

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Section: Resultsmentioning

confidence: 99%

Unidirectional Freezing of Polymer Solution Droplets

Kharal,

Louf

2023

Langmuir

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“…To take into account the latent heat

of phase change for substances whose phase change is characterized by the melting/solidification point

one can use an equivalent additional capacity in the temperature range of

, where

, as it was done in refs. [ 36 , 37 , 38 ]:

…”

Section: Discussionmentioning

confidence: 99%

Apple-like Shape of Freezing Paraffin Wax Droplets and Its Origin

et al. 2023

Self Cite

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Paraffin wax stores energy in the form of latent heat at a nearly constant temperature during melting and releases this energy during solidification. This effect is used in industrial energy storage. At the same time, the possible deformation of even small volumes of material as a result of phase change is insufficiently studied. In this paper, the physical nature of such deformation, probably for the first time, is studied on the example of a droplet of paraffin wax. An unusual change in the shape of a melted droplet of paraffin wax placed on a relatively cold glass plate was observed in the laboratory experiments. As the droplet solidifies, its upper surface becomes nearly flat, and a dimple is formed in the center of this surface, making the droplet look like a fruit (pumpkins are more commonly shaped like this, but the authors prefer apples). A series of experiments, as well as physical and numerical modeling of the droplet’s thermal state, taking into account the formation of a mushy zone between liquidus and solidus, made it possible to understand the role of gravity and gradual increase in viscosity and density of paraffin wax on changing the droplet shape and, in particular, to clarify the mechanism of formation of the dimple on its upper. It was shown that the mushy zone between the liquidus and solidus of the paraffin wax is responsible for the dimple formation.

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“…To take into account the latent heat L m of phase change for substances whose phase change is characterized by the melting/solidification point τ = τ m one can use an equivalent additional capacity in the temperature range of τ m − ∆τ < τ < τ m + ∆τ, where ∆τ τ m , as it was done in refs. [36][37][38]:…”

Section: A Model Of Cooling and Solidification Of A Paraffin Wax Dropletmentioning

confidence: 99%

Apple-Like Shape of Freezing Paraffin Wax Droplets and its Origin

Roy¹,

Shoval²,

Shvalb³

et al. 2023

Preprint

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Paraffin wax stores energy in the form of latent heat at a nearly constant temperature during melting and releases this energy during solidification. This effect is used in industrial energy storage. An unusual change in the shape of a melted droplet of paraffin wax placed on a relatively cold glass plate is studied. As the droplet solidifies, its upper surface becomes nearly flat and a dimple is formed in the center of this surface, making the droplet look like a fruit (pumpkins are more commonly shaped like this, but the authors prefer apples). A series of experiments, as well as physical and numerical modeling of the droplet's thermal state, taking into account the formation of a mushy zone between liquidus and solidus, made it possible to understand the role of gravity and gradual increase in viscosity and density of paraffin wax on changing the droplet shape and, in particular, to clarify the mechanism of formation of the dimple on its upper.

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Effects of asymmetric cooling and surface wettability on the orientation of the freezing tip

Cited by 6 publications

References 35 publications

Unidirectional Freezing of Polymer Solution Droplets

Unidirectional Freezing of Polymer Solution Droplets

Apple-like Shape of Freezing Paraffin Wax Droplets and Its Origin

Apple-Like Shape of Freezing Paraffin Wax Droplets and its Origin

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