Sub-Zero Eutectic PCM Solutions

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This range of PCMs comprise solutions of various blends of salts that freeze below 0°C (32°F). PCM Products provide a wide range of solutions, freezing and melting at temperatures between -2°C (28.4°F) and -62°C (-79°F). The solutions are formulated to contain nucleating agents in order to minimise supercooling, and where necessary contain other additives such as corrosion inhibitors and microbiocides. This ensures long term reproducible freeze and melt cycles throughout the PCMs usage.

 

The prefix "E" in the product range stands for "Eutectic"

phase change materials

PlusICE Eutectic PCM Solutions

When salts are added to water they depress the freezing point of the water (this is why gritting or salting roads and pathways melts snow on them). Adding more salt generally depresses the freezing temperature further, but these solutions do not freeze cleanly and at a precise temperature, instead they tend to form a slush.

However, if you add a particular salt at a particular concentration the resulting solution freezes and melts cleanly at a constant temperature, releasing and storing large amounts of energy as it does so. This temperature is called the eutectic point and the composition is called a eutectic solution. This is represented in the simplified graph below:

A simple salt/water eutectic phase diagram

Eutectic Solution

The curved line on the graph represents the freezing curve.

Starting from the left of the curve, the composition is 100% water and the freezing point is 0 °C (32 °F). As salt is added the freezing point of the salt / water mixture decreases. When freezing occurs in this section of the graph, only pure water freezes out of the solution and the salt remains in solution. If more salt is added the freezing point depresses further until the eutectic point is reached at the lowest freezing point on the curve.

At this point both the salt and the water freeze out of the solution, i.e the composition of the frozen material is exactly the same as that of the solution. If even more salt is added the freezing temperature of the mixture starts to increase and anhydrous salt precipitates out on freezing.

Our eutectic solutions are usually supplied prediluted with water to exactly the correct concentrations, but on some occasions they can be shipped as either dry powders or concentrated solutions which can be made up with local water to save on shipping costs. They can be supplied in prefilled icepacks or balls as described on the Products page, or can be used on site to fill the customer's own containers. They must be kept and used in air-tight containers to prevent loss of water from evaporation, which would affect their performance. Like all our PCMs, they are available in quantities ranging from a few millilitres to multi-ton orders.

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