Torsional refrigeration by twisted, coiled, and supercoiled fibers

TL;DR

This paper explores how twisting, coiling, and supercoiling fibers like natural rubber, NiTi, and polyethylene can be used for efficient, low-cost refrigeration by exploiting entropy changes during mechanical deformation.

Contribution

It introduces a novel twist-based cooling mechanism using fiber deformation, supported by theoretical models and experimental demonstrations.

Findings

Supercoiled fibers cool when stretched due to twist changes.

A twist-based device effectively cools flowing water with high efficiency.

Theory links phase transformations in fibers to their cooling behavior.

Abstract

Higher efficiency, lower cost refrigeration is needed for both large and small scale cooling. Refrigerators using entropy changes during cycles of stretching or hydrostatically compression of a solid are possible alternatives to the vapor-compression fridges found in homes. We show that high cooling results from twist changes for twisted, coiled, or supercoiled fibers, including those of natural rubber, NiTi, and polyethylene fishing line. By using opposite chiralities of twist and coiling, supercoiled natural rubber fibers and coiled fishing line fibers result that cool when stretched. A demonstrated twist-based device for cooling flowing water provides a high cooling energy and device efficiency. Theory describes the axial and spring index dependencies of twist-enhanced cooling and its origin in a phase transformation for polyethylene fibers.