Fraunhofer Energy AllianceThe exhibit shows prototypes of metal woven - wire heat exchangers for latent heat storages. These kind of storages use PCM (phase change materials) as storage media. For the operation of the heat exchanger a heat tranfer fluid flows through the capillary tubes. The PCM is located on the outside of the heat exchanger. During the melting and crystallization of the PCM heat is stored or released from the storage.
Typically the thermal conductivity of PCM is low, thus limiting the thermal power of the storages.
The prototypes use an enlargement of the heat transfer surface by a metal fabric to compensate the low thermal conductivity. The heat exchanger consists of capillary tubes with a diameter of 2 mm and 100 µm wire fabric which is welded to the tubes. The actual configuration of the fabric leads to an trepled heat transfer surface compared to the bare tubes. The complete structure made of stainless steel enables the use of corrosive PCM. Compared to conventional structures like fins the wire fabric offers an considerably reduced material consumption together with an significantly enlarged surface.