Cooling with Plastics
A research group at Pennsylvania State University has developed special polymers that cool when an electric voltage is applied. This so-called electrocaloric effect is based on a change in the structure of the molecule chains. When no current is flowing, the molecules are randomly oriented, and thus exhibit relatively little ordering. When a voltage is applied, the molecules orient themselves in the same direction. In the course of this rearrangement, they give off heat and become cooler.
The investigations showed that temperature changes of up to 12 K could be achieved with copolymers of polyvinylidene chloride und polytriflouroethylene. The electric voltages required had to be between 80 and 120 V. as soon as the electric voltage is removed, the material returns to the initial temperature. The working range of these so-called polar polymers is currently about 70°C. By mixing with other types of polymers, it is expected that the working temperature range can be lowered further in the future.
Cooling systems such as those used in refrigerators or air conditioning system presently employ gases that undergo temperature changes upon compression or expansion. The drawback of these systems is that they require use of compressors and cooling coils, and thus occupy quite a bit of space. In addition, noise is generated when the compressor is operating during cooling.
In the opinion of the researchers, polar polymers could replace these cooling systems in the future. Additional applications include cooling of electronic components, many of which are air-cooled today. The resultant space savings in such applications could play an important role. Cooled protective clothing and actively cooled packaging are other conceivable applications.
The Pennsylvania State University
USA PA 16802
Tel: +1 814 863-8407
Fax: +1 814 863-8561
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