Best Phase Change Materials for Flexible Heating/Cooling Membrane

In summary, the conversation discusses a project that requires a flexible membrane to be heated and cooled multiple times, with a focus on finding a phase change material to use in a thin layer of silicon rubber. Magnesium nitrate hexahydrate is considered but deemed too toxic and flammable. The participants suggest using a material with low thermal conductivity and high thermal capacity, such as wax or various esters. Manufacturers and more information can be found through online resources.
  • #1
martinl
3
0
Hi All,

I'm working on a project that requires a flexible membrane be heated and cooled about 2000 times.

During the cooling process, I require the material give off heat for as long a period of time as possible. I figure a phase change material will have the highest heat capacity and give off its latent heat, over an extended period of time, while cooling at it's melting point.

So, I'm looking for a phase change material that I can imbed in a thin layer of silicon rubber to form the heat sink part of my membrane.

I considered magnesium nitrate hexahydrate (melting point 87 C), but fear that it is too toxic and flammable. The final membrane will be handled extensively and twisted and bent many times over its lifetime.

Could someone please give me some more suggestions of what else to try?
As many as possible (I may want to mix them to even out the heat transfer over the temp range)

Thanks a lot. over its lifetime.
 
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  • #2
I am not sure magnesium nitrate hexahydrate would work. If one heats a hydrated salt and removes the water of hydration, the heat is generated when the dehydrated salt is rehydrated (as in heat of hydration). That is different from a phase change. Besdies, in a closed system, where would the water go?

It would seem one needs a material with a low thermal conductivity (which works against heat up, but allows for long slow release of heat) and high thermal capacity.

Hmmm. Interesting problem.
 
  • #3
I'v pretty much given up on magnesium nitrate hexahydrate, but I think it would still work. The MNH would be completely surrounded by the rubber matrix, so the water would separate out and turn to steam (in a bubble inside the rubber), then as the substrate cools, the steam would condense to water and re-bond into the MNH - a mini closed system.
 
  • #4
I think at that temperature, the most common material is wax. There are a wide variety of formulations for wax that can give different melting points. Try http://www.thomasnet.com/nsearch.html?cov=NA&which=prod&what=wax&navsec=search&heading=93001808" for manufacturers and more information.
 
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  • #5
Try the various esters of palmitic acid. Find some that are liquid at slightly higher than room temperature. Some other compounds you might consider are, in a general class, saturated fatty acid methyl or ethyl esters, cholesteryl esters, rigid rod aromatic esters.
 

Related to Best Phase Change Materials for Flexible Heating/Cooling Membrane

What are phase change materials (PCMs) and how do they work?

Phase change materials are substances that are capable of storing and releasing large amounts of thermal energy during a phase transition, such as from solid to liquid or liquid to gas. This is due to the absorption or release of latent heat. PCMs work by changing their physical state when exposed to different temperatures, absorbing heat when they melt and releasing heat when they solidify.

What makes a phase change material suitable for use in flexible heating/cooling membranes?

A suitable PCM for flexible heating/cooling membranes should have a high latent heat capacity, meaning it can store a large amount of energy in a small volume. It should also have a narrow melting/freezing temperature range to ensure a consistent and predictable phase transition. Additionally, a good PCM for this application should have a high thermal conductivity and be chemically and physically stable over multiple heating/cooling cycles.

What are some common phase change materials used in flexible heating/cooling membranes?

Some of the most commonly used PCMs in flexible heating/cooling membranes include paraffins, fatty acids, and salt hydrates. Paraffins and fatty acids are organic PCMs that have high latent heat capacities and are relatively inexpensive. Salt hydrates, on the other hand, are inorganic PCMs that can have even higher latent heat capacities, but may be more expensive and less chemically stable.

What are the benefits of using phase change materials in flexible heating/cooling membranes?

The use of PCMs in flexible heating/cooling membranes can provide several benefits. They can help regulate the temperature in a space, reducing the need for traditional heating and cooling systems and resulting in energy savings. PCMs can also help to reduce temperature fluctuations, creating a more comfortable environment. Additionally, the use of PCMs can reduce the size and weight of heating/cooling systems, making them more compact and portable.

What are the potential limitations of using phase change materials in flexible heating/cooling membranes?

One potential limitation of using PCMs in flexible heating/cooling membranes is their relatively low thermal conductivity compared to other heat transfer fluids. This may result in longer heating/cooling times or a need for larger surface areas to achieve the desired temperature changes. Additionally, some PCMs may be flammable or toxic, requiring careful handling and disposal. The cost of PCMs may also be a limitation, as some types can be expensive compared to traditional heating/cooling methods.

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