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Projektinfo – Detailed information on energy research

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New fluids as a heat transfer medium in air conditioning and refrigeration
Projektinfo 16/2012
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Phase change stores heat

When it comes to transporting heat from boilers to heating surfaces or supplying cooling energy to cooling ceilings, water has proved to be an excellent heat transfer medium. However, in some application areas it is now facing competition: various research groups are working on heat transfer fluids that have at least double the energy density. Phase change materials such as paraffin, which are finely distributed in water, store heat when they melt and release it again when they solidify.

The principle is not new. Back in the 1970s, Soviet and Israeli researchers developed mixtures comprising finely distributed ice in glycol or ethanol for transporting cooling energy. These so-called ice slurries are used for rapidly cooling food. They can release their cooling capacity at a constant temperature level around the freezing point until the ice has completely melted. This shows the advantage and disadvantage of this storage principle. On the one hand the mixture works precisely at the required temperature level. On the other hand, however, it can only work in this narrow temperature range in which the melting and solidification processes occur. This has led to two particular areas of research: suitable materials need to be developed for each required temperature range, and these materials must then be finely distributed in the transport fluid.

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The research projects presented here work with different types of paraffin as latent heat storage units. They can be integrated in the transport fluid in different ways: they are either emulsified as (fine) droplets that are just a few micrometres in size or as microencapsulated particles with diameters similar to that of a hair.

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Addresses

Development of micro-PCM emulsions
Fraunhofer ISE

Development of micro-PCM emulsions
Fraunhofer UMSICHT

Simulation models for PCS dispersions
RWTH Aachen, E.ON ERC, GRK

Development of cooling storage units
Imtech Deutschland GmbH & Co. KG

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BINE-Projektinfo 16/2012
(PDF, 4 pages, 1.2 MB)