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Thermal hysteresis and its impact on the efficiency of first-order caloric materials

: Hess, Tobias; Maier, Lena Maria; Bachmann, Nora; Corhan, Patrick; Schäfer-Welsen, Olaf; Wöllenstein, Jürgen; Bartholomé, Kilian

Postprint urn:nbn:de:0011-n-5781256 (1.0 MByte PDF)
MD5 Fingerprint: d954def0a2f5fa699a97d55c0478a014
Created on: 25.2.2020

Journal of applied physics 127 (2020), No.7, Art. 075103, 28 pp.
ISSN: 0021-8979
ISSN: 1089-7550
Bundesministerium fur Wirtschaft und Energie BMWi (Deutschland)
03ET1478A; MagMed
Entwicklung einer kältemittelfreien und effizienten Kühltechnik
Journal Article, Electronic Publication
Fraunhofer IPM ()
multicalorics; thermodynamics; magnetic hysteresis; electrocaloric effect; shape memory effect; refrigerators; energy efficiency

Cooling with caloric materials could be an option to replace compressor-based cooling systems in the future. In addition to the advantage of avoiding dangerous liquid coolants, one often cites a possible higher efficiency of the calorific cooling systems compared to compressor-based systems. But is that true? The aim of this work is to assess the efficiency potential of caloric cooling systems on a very basic material level. We placed our focus on materials with a first-order phase change since they generally show a large caloric response. We derive a relation between thermal hysteresis and the dissipative losses due to hysteresis. To predict the efficiency, this relation is integrated in a Carnot-like cycle. This approach was chosen to get access to the efficiency reduction due to hysteresis without any further losses due to other nonidealities of the thermodynamic cycle. As a main finding, we present a direct relation between thermal hysteresis and the expected maximum exergy or second-law efficiency of a caloric cooling device. These results indicate that, for many caloric materials, the thermal hysteresis needs to be further reduced to be able to compete with the efficiency of compressor-based systems.