In
many applications, working with liquids, because of the difficulty to
contain them, is not ideal and volume expansion during the phase change
process could be a problem. For this reason RUBITHERM GmbH
has developed a range of bound PCM's.
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In the case of our PCM's, latent heat paraffins are incorporated within a secondary supporting structure, by means of a special additive. The additive is defined by the particular application, and provides a matrix in which the PCM is homogeneously distributed. An important feature is that neither the additive nor the supporting structure changes the crystalline structure of the PCM, leading to a loss of latent heat storage capacity. |
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Working principle and advantages
When the PCM reaches its melting temperature, it begins to change into a liquid within the supporting structure. The combined influence of capillary forces of the supporting material and the special cross-linking additives ensures that the PCM, even when in the liquid phase, does not leak out of the structure. This means that one always works with a "dry" material and liquid handling problems are eliminated. Free spaces within our bound PCM's allow for volume expansion of the PCM to take place within the structure and therefore it is not apparent.
Consequently, all our bound PCM's maintain their macroscopic solid form during the phase change processes. In the case of fibre boards, they also provide a structural strength which is important in many applications. Bound PCM's increase the ease of handling and in the case of our RUBITHERM® bound PCM's, a large surface area is created, which allows effective heat transfer.
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Bound PCM's are available in powder or granulate form, as well as within varying thicknesses of wood fibre or gypsum boards. A decisive factor for the heat storage capacity of the bound PCM is the porosity of the supporting material, which in turn determines the amount of PCM that can be bound within the capillary structure. Our RUBITHERM® PK is a special case, since it is not contained in a supporting structure. The combination of PCM and additive results in a special cross-linked structure which behaves like a gel when the PCM is in the liquid phase. This product has a very high heat storage capacity. |
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| Glossary: • The
Latent Heat Storage Process PCM's in thermal energy storage applications • Bound PCM's • Latent Heat Storage Unit in Heating, Ventilation and Air Conditioning? |