Heat recovery cycle in elastocaloric cooling: Numerical investigation for experimental device development

Elastocaloric cooling devices operating under a heat recovery cycle are specifically suited for high cooling-power applications, as the internal thermal exchange between the two elastocaloric beds allows higher fluid displacements and mass flow rates than active regeneration, at the cost of a reduced temperature span. In this work, a two-dimensional thermo-fluid dynamic model of a heat recovery-based elastocaloric device featuring two NiTi spiral-section beds connected through dedicated pipes is developed. A systematic parametric analysis is performed by varying the heat recovery pipe diameter, the operating frequency, and the phase time ratio. At the reference temperature lift of 15 K, the optimal configuration yields a maximum cooling power of 64 W, a cold-side temperature difference of 3.2 K, and a coefficient of performance of 4.6, with a maximum heat recovery efficiency of 84%. A direct comparison with the active elastocaloric regeneration cycle over a wide range of imposed temperature spans shows that the two modes operate in complementary performance regions. The heat recovery cycle delivers higher cooling power under low-span conditions, below 21 K, reaching 138 W at zero lift, whereas active regeneration extends the operating range up to 59 K, achieving a higher coefficient of performance but lower cooling power. These findings suggest a possible operating strategy in which the device initially runs in heat recovery mode under low temperature span conditions and transitions to active regeneration as the temperature span increases, enabling control of the operating regime through temperature management.