Large heat flux in electrocaloric multilayer capacitors

Abstract

Multi Layer Capacitors MLCs are considered as the most promising refrigerant elements to design and develop electrocaloric cooling devices. Recently, the heat transfer of these MLCs has been considered. However, the heat exchange with the surrounding environment has been poorly, if not, addressed. In this work, we measure by infrared thermography the temperature change versus time in four different heat exchange configurations. Depending on the configurations, Newtonian and non-Newtonian regimes with their corresponding Biot number are determined allowing to provide useful thermal characteristics. Indeed, in case of large area thermal pad contacts, heat transfer coefficients up to 3400 W m-2 K-1 are obtained showing that the standard MLCs already reach the needs for designing efficient prototypes. We also determine the ideal Brayton cooling power in case of thick wires contact which varies between 3.4 mW and 9.8 mW for operating frequencies varying from 0.25 Hz to 1 Hz. While only heat conduction is considered here, our work provides some design rules for improving heat exchanges in future devices.