A Single Long NiTi Tube Compressive Elastocaloric Regenerator: Experimental Results

Abstract

Elastocaloric cooling is an environmentally friendly alternative to the current vapor-compression refrigeration technology, and the development of an efficient operation strategy is significant for its commercialization. In this article, the cooling performance including the temperature span, specific cooling power, and coefficient of performance for a novel single long NiTi tube compressive elastocaloric regenerator (tube outer diameter 5 mm, wall thickness 1 mm, and initial length 305 mm) was comprehensively characterized under different operation parameters (operation cycle time, loading/unloading time, heat transfer fluid timing, flow time, and utilization). The single long NiTi tube compressive elastocaloric regenerator achieved maximum temperature span, specific cooling power, and coefficient of performance of 5.7 K, 135 W∙kg−1, and 4.7, respectively under an applied strain of 2.5%. It was found that the most important factors for obtaining a good cooling performance of the single long NiTi tube compressive elastocaloric regenerator were a short operation cycle time, a proper heat transfer fluid timing, and a proper heat transfer fluid utilization. The dependences of the temperature span on the cycle time and heat transfer fluid utilization factor were in agreement with the existing experimental data for a parallel plate tensile elastocaloric regenerator. A thinner tube wall thickness and advanced cross-section geometry for the regenerator may further improve the cooling performance of the compressive elastocaloric regenerator.

Keywords: Shape memory alloys, elastocaloric refrigeration, heat transfer