Design of a Large-Power Separated Long NiTi Tube Bundle Compressive Elastocaloric Cooler

Abstract

Elastocaloric cooling and heat pumping with no greenhouse gas emission is beneficial to the decarbonization of industrial and domestic refrigeration and heating systems, and a large total cooling power at a long durability is essential for the commercialization of elastocaloric cooling technology. In this article, a separated long NiTi tube bundle compressive elastocaloric cooler utilizing 19 long NiTi tubes (outer diameter 5 mm, wall thickness 1 mm, and length 330 mm) restrained by lotus root like buckling prevention shell as the solid-state refrigerant was designed. A standalone driving subsystem with a full loading capacity of 300 kN was designed and manufactured. A heat transfer fluid subsystem using dual-piston syringe pumps two heat transfer fluid flow structures was designed and fabricated. After the long fatigue life of the NiTi tube used was validated, the latent heat of the NiTi tube elastocaloric refrigerant was determined according to the synchronized stress-strain-temperature-time data during Brayton-like loading-unloading cycles. The maximum cooling power of the separated long NiTi tube bundle compressive elastocaloric cooler was estimated to be over 600 W by a brief energy conservation analysis. The dependences of the specific cooling power on the utilization factor under parallel and serial heat transfer fluid flow structures were calculated and compared using a well-established one-dimensional numerical model. The results of this study are significant for the total cooling power increase and commercialization of the new-born elastocaloric cooling technology.

Keywords: Shape memory alloys, Refrigeration equipment, Elastocaloric cooling, Heat transfer, Tubes