The effect of mass diffusion on the rate of chemical ice melting using aqueous solutions

Wå̊hlin, Johan; Klein-Paste, Alex

doi:10.1016/j.coldregions.2017.04.001

Cited by 13 publications

(10 citation statements)

References 35 publications

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“…This makes the diffusion process for water molecules down to the stone surface slower for higher film thicknesses, resulting in higher allowed ice fractions until ice adhered to the surface. Using other chemicals like MgCl 2 and CaCl 2 with lower diffusivity in water ( 23 ) could possibly extend the protection time during hoar frost formation.…”

Section: Discussionmentioning

confidence: 99%

“…This indicates that there is a concentration gradient in the brine film. This is likely because the diffusion coefficient for water vapor in air, ( ;10 À5 m 2 =s), is five orders of magnitude larger than the diffusion coefficient for water in salt solutions, ( ;10 À10 m 2 =s) (22,23). The result is an accumulation of water molecules in the top layer which leads to a higher freezing temperature in the top layer than in the bottom layer of the solution.…”

Section: The Freezing Processmentioning

confidence: 99%

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Chemical Frost Protection of Road Surfaces: A Laboratory Investigation

Fjærestad

Klein-Paste

Wå̊hlin

2020

Transportation Research Record

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Anti-icing chemicals are commonly used to protect against hoar frost formation on roadways and bridges. Because of their negative impact on both environment and infrastructure, their use should be optimized. During conditions for hoar frost formation, this means that good knowledge is needed about when it is necessary to apply chemicals, and the corresponding protection time. A laboratory setup has been used to study the freezing process for a salted road surface during conditions for hoar frost formation, and a description of the process is given. It has been observed that freezing starts in the top layer of the applied solution, indicating the occurrence of a concentration gradient owing to accumulation of water molecules in the top layer. A British pendulum was used to simulate the mechanical load of traffic. The pendulum successfully destroyed the ice up to a certain ice fraction. This ice fraction was seen to depend on the amount of salt solution applied to the test sample. Finally, it has been illustrated how the maximum ice fraction can be used to calculate the amount of water allowed to be added to the road surface, and estimates of the protection time are given.

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Section: Discussionmentioning

confidence: 99%

Section: The Freezing Processmentioning

confidence: 99%

Chemical Frost Protection of Road Surfaces: A Laboratory Investigation

Fjærestad

Klein-Paste

Wå̊hlin

2020

Transportation Research Record

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“…At higher temperatures the deicer solution continues to melt at a decreasing rate, mainly widening the cavity. Wåhlin and Klein-Paste showed earlier that the melting rate of liquid deicers is controlled by the chemical potential difference (which is determined by the chemical concentration) and the diffusion of chemical into the meltwater (or, viewed reversely, the diffusion of melted water molecules into the chemical solution) ( 16 ). If a constant melting rate is achieved, then the driving force (the chemical potential difference) and the resistance (the mass diffusion) remain constant.…”

Section: Discussionmentioning

confidence: 99%

“…The (concentrated) deicer solution is thermodynamically more attractive than the ice lattice, causing the frozen water molecules to melt into the deicer solution. In chemistry the ''attractiveness'' of a given phase is better known as the chemical potential, and ice can melt as long as it is in contact with a solution that has a lower chemical potential than the ice (16). When water molecules from the ice melt, it dilutes the solution and more solid deicer chemical can dissolve as well.…”

Section: The Ice Penetration Processmentioning

confidence: 99%

“…As this process continues, the shrinking deicing particle sinks deeper into the ice, leaving a cavity filled with diluted deicer solution. The speed of the melting is found to be directly linked to the driving force (difference in chemical potential) and the diffusion coefficient of the chemicals in water (16). The melting process continues even when the deicer particle is fully dissolved, but now the additional meltwater dilutes the solution and causes the freezing point and chemical potential to rise.…”

Section: The Ice Penetration Processmentioning

confidence: 99%

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Effect of Temperature and Prewetting for Ice Penetration with Sodium Formate

Trzaskos

Klein-Paste

2020

Transportation Research Record

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Granular sodium formate (NaCOOH) is a popular deicer used at airports. It is mainly used to weaken compacted snow/ice and thereby facilitate mechanical ice removal. Earlier research has developed a set of methods quantifying deicer performance, but linking these test results to operational guidelines is difficult. The main objective of this study is to increase the knowledge of how temperature and prewetting affect the ice penetration performance of granular sodium formate. A new method to evaluate the development of ice penetration process is presented here. Ice penetration tests were performed with single grains on large, optically clear ice cubes, and digital image analysis is used to quantify the initial waiting time, penetration rate and –depth, and melted volume. Eighteen tests including dry and prewetted sodium formate grains were performed at three different temperatures (–2°C, −5°C, and −10°C). Prewetting reduced the initial waiting time (the time it takes before the particles started to penetrate) by a few minutes at −10°C, but at higher temperatures, this reduction was insignificant. The particles penetrated the ice at a constant rate. At −10°C, the particles penetrated at 10–15 mm/hour, while at −2°C this speed is about five times higher. Prewetting does not seem to have a clear beneficial effect on the penetration rate. Suggestions are given on how to capture the results from this study into operational guidelines for deicing operations at airports, using sodium formate as deicer.

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