Numerical study of a double-effect elastocaloric cooling system powered by low-grade heat

Abstract

• A double-effect heat-driven elastocaloric cooling cycle was proposed. • The double-effect eC cycle can harvest low-grade heat at 120 to 160 °C. • Driving temperature difference is used to design the transition temperature of SMAs. • COP of the double-effect eC cycle is three times better than single-effect eC cycle. Elastocaloric cooling technology is a novel solid-state cooling technology based on the latent heat associated with martensitic phase transformation in shape-memory alloys. Heat-driven elastocaloric cooling cycle could harvest low-grade thermal energy other than consuming electric power, and was proposed as a new direction in this field. To improve the heat-to-cooling efficiency of heat-driven elastocaloric cooling systems, a double-effect elastocaloric cooling cycle with two beds of actuator shape-memory alloys and two beds of refrigerant super-elastic alloys is proposed in this study. The double-effect cycle utilizes the input heat two times and thus provides improved efficiency. Numerical simulations are carried out to study the characteristics of the phase transformation in both the actuators and refrigerants. The impact of phase transition temperatures of the actuator alloys, the heat source temperature, and the operating parameters on the phase transformation and cooling performance of the system is investigated. If the phase transition temperatures are properly designed, the double-effect heat-driven elastocaloric cooling system is three times more efficient than the baseline single-effect heat-driven elastocaloric cooling system.