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Phase Change Materials thermal sinks

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Re: Phase Change Materials thermal sinks

Postby Zymurgy Bob » Sun Feb 28, 2010 2:42 pm

airhill wrote:Look EF this is what happens. you don't need a 'paper' its just a physical property of the substance, this is probably why Zymurgy remembered the need for stirring.

"Glauber's Salt
Upon continued cycling, three distinct layers can be identified within the container. The bottom layer will be anhydrous sodium sulfate unable to mix with the water, the next layer will be the decahydrate crystals and the top layer will be freewater unable to mix with the bottom anhydrous layer.

Other heat storage materials which involve heat storage capacity because of latent heat of fusion during phase change include organic paraffin materials. Such paraffins are congruently melting compounds which do not exhibit stratification andsuper cooling properties. They do, however, self insulate upon crystallization and are flammable. When liquid paraffins begin to solidify they to do so first at the edges which are exposed to contact with the container in which they rest. Crystallinestructure of the solid paraffins at or near the outer edges of the mass of material is such that it effectively insulates the liquid paraffin. In other words, it reduces the heat flow rate from the liquid paraffin to the walls of the container throughwhich heat is transferred for use to condition space. This characteristic reduces the effectiveness and usefulness of the heat stored in the center of a paraffin mass"

Thanks, airhill. That sounds very much like what I was incompletely and imperfectly remembering. Interestingly for our purposes, that boundary crystallization would seem to effect energy retrieval more than energy storage, so the principal might still be useful to us.

And thanks for reminding me of Glauber's salts, which fascinated me as a kid because they were used in ice-cream scoop handles to keep the scoop/ice-cream interface from sticking. (Between uses, the scoops stood in a container of warm water)
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