Session: SYMP 4-8: Shape Memory Alloy Applications

Paper Number: 140329

140329 - Eccube – Small Scale Elastocaloric Cooling Demonstrator 

Keywords:

Elastocaloric, small scale, highly efficient, latent heats, solid state phase transformation, zero GWP, environment friendly, sustainable

Abstract:

The excellent elastocaloric (EC) properties of Nickel-Titanium (NiTi) enable the development of sustainable and highly efficient heating and cooling systems. Technical motivation for EC systems includes high material COPs (coefficients of performance), high latent heats and the solid-state phase transformation, which eliminates climate damaging refrigerants. For these reasons, the US Department of Energy has declared the technology the most promising alternative to vapor-compression systems [1]. To showcase the realization of elastocalorics in a functional system an elastocaloric can cooler demonstrator with fixed cooling chamber is developed.

The demonstrator system is based on a rotary drive design and tensile loading of SMA wire bundles, which has been presented in [2,3]. Due to the design, this system architecture comes with unused space in the center of the cylindrical machine. The size of this increases with the number of bundles. The energy density is therefore limited. One possible option to avoid this disadvantage is to use the unused space as the cooling chamber for this demonstrator. In the developed demonstrator prototype, the chamber can hold a can with the size of 52x134 mm. For optimized cooling of this volume, the development process is supported by simulation [4]. A temperature drop of around 10 K is targeted. The general specifications of the demonstrator are set to an outer system diameter of 150 mm, carrying 12 bundles of 30 SMA wires of 200 µm diameter and a length of 150 mm. In operation, the rotational frequency is set to 0,5 Hz.

To use the centered space for the cooling chamber, a novel concept for air circulation is developed. By circulating the cold airflow within the cooling chamber, the inside air temperature continuously drops with each cycle. The special feature of this elastocaloric can cool demonstrator is the fixed cooling chamber inside. The airflow for this, is generated by a specific fan arrangement. For the release and absorption of the latent heats, we realize an effective strain of 5% of the superelastic SMA wires. This results in a necessary loading force of 600 N per SMA bundle, but because of simultaneous loading and unloading and the resulting work recovery, the necessary peak torque of the rotary motor is in the region of 3 Nm. To ensure that the inner chamber is stationary, the drive is provided by external toothed belts.

The paper gives a detailed description of the design process from simulation-based development to assembly and first measurements of an elastocaloric can cooler demonstration system.

 

Sources:

[1]       [1] G. William, Z. Robert, Y. Jim, and C. Johnson, “Energy Savings Potential and RD&D Opportunities for Non-Vapor-Compression HVAC Technologies,” 2014, doi: 10.2172/1220817.

[2]        [2 ]S.-M. Kirsch, M. Schmidt, F. Welsch, N. Michaelis, A. Schütze, and S. Seelecke, “Development of a shape memory based air conditioning system,” in 59th Ilmenau Scientific Colloquium, Ilmenau, Germany, 2017, p. 9. Accessed: Mar. 24, 2021. [Online]. Available: https://www.db-thueringen.de/receive/dbt_mods_00033169

[3]       [3] S.-M. Kirsch, F. Welsch, and S. Seelecke, “Energiewandler mit thermoelastischer Anordnung sowie Energiewandlersystem,” DE102016118776A1, 2016

[4]        [4 ]S.-M. Kirsch et al., “NiTi-Based Elastocaloric Cooling on the Macroscale: From Basic Concepts to Realization,” Energy Technology, vol. 6, no. 8, pp. 1567–1587, 2018, doi: 10.1002/ente.201800152.

 

 

 

 

Presenting Author: Philipp Molitor Smart Material Systems, Center for Mechatronics and Automation Technology – ZeMA gGmbH

Presenting Author Biography: Philipp Molitor

Authors:

Lukas Ehl
Nicolas Scherer
David Zimmermann
Philipp Molitor
Ivan Trofimenko
Franziska Louia
Paul Motzki