A multistage elastocaloric refrigerator and heat pump with 28\u2009K temperature span

Ryan Snodgrass,David Erickson

doi:10.1038/s41598-019-54411-8

Abstract

Elastocaloric refrigerators are a promising alternative to the vapor compression cycle because they do not require refrigerants with high global warming potential. However, these coolers have yet to achieve temperatures low enough to — for example — be used as standard household refrigerators. We built one-stage, two-stage, and three-stage elastocaloric cooling systems to determine if staging of the elastocaloric effect could significantly expand temperature span. Our three-stage system achieved 1.5 times the maximum temperature span of our single-stage system, and produced the highest temperature span of any elastocaloric device to-date at 28.3 °C, where previously the record was 19.9 °C. Interestingly, we found that multistage systems can achieve equivalent temperature spans but at higher coefficients of performance compared to similarly-constructed single-stage systems.

Highlights

The vapor compression cycle has remained the primary refrigeration method since its invention almost 200 years ago
The regenerative device only reached about 5 °C below ambient when operating as a heat pump[18], and the coldest temperature ever achieved in any elastocaloric device is 7 °C below ambient28 — insufficient to be used in many refrigeration applications
The NiTi wires were placed inside slightly larger, flexible Tygon tubing (1.59 mm inner diameter), creating a small region for water to flow over the wires for heat exchange

Summary

Introduction

The vapor compression cycle has remained the primary refrigeration method since its invention almost 200 years ago. The use of HFCs (hydrofluorocarbons) is to be dramatically reduced by 2045 according to the ratified Kigali Amendment to the Montreal Protocol[8] These concerns have motivated research in more-efficient, lower-GWP refrigerants[9,10], as well as research in complete alternative methods to the vapor compression cycle[11,12]. The highest Tspan to-date was produced by a regenerative device that uses water as heat www.nature.com/scientificreports transfer medium, and that operates to active magnetocaloric regenerators[31]. This device achieved up to a 15.3 °C Tspan at a COP of 3.518, and up to a 19.9 °C Tspan under no-load cooling conditions[32].

Objectives

Methods

Results

Conclusion