Thermodynamic cycle analysis of heat driven elastocaloric cooling system

The conventional elastocaloric cooling system is powered by mechanical drivers with more than 500 times mass over refrigerant mass, whereas the shape memory alloy actuator and heat driven cycle provide a new path for higher system compactness. Based on the thermodynamic and mechanical constraints between the actuator shape memory alloy and the refrigerant super-elastic alloy, the cycle model is implemented to investigate the characteristics of the cycle efficiency, mass ratio and driving temperature difference in terms of length ratio and cross-sectional area ratio. In addition, the impacts of Young's modulus, transformation strain and Clausius-Clapeyron coefficient are studied. Based on the multi-objective optimization technique, regarding the three different combinations of actuator and refrigerant materials, the optimum normalized COP occurs when the MDTD ranges from 52 K to 59 K, which does not further increase with higher driving temperature, implying that low-grade thermal energy at a temperature less than 100 °C is most economic to drive such a cycle. On the other hand, the heat driven cycle can be activated by MDTD down to 11 K, indicating a significant potential to harvest low-grade thermal energy. This study can promote future prototype development for solar-driven refrigerators and waste heat recovery for electronic devices.