Abstract
Nickel-Titanium (NiTi)-based shape memory alloys (SMAs) enable new sustainable and environmentally friendly solid-state heating and cooling technologies. Elastocaloric (EC) heat pump systems exploit superelastic SMAs as a non-volatile, inflammable, and non-global-warming refrigerant, in contrast to the well-established vapor compression technology. The high specific latent heat released or absorbed during mechanical loading or unloading of the SMA material leads to a high temperature change in the material. As a result of the small required work input to induce the phase transformation, a high coefficient of performance (COP) can be achieved by this technology. The potential of these alloys can be exploited through an adequate thermodynamic cycle, efficient mechanical system design, and choice of suited EC materials.
A fully functional continuous operating EC heat pump system based on SMA was developed and realized recently. The EC heat pump system comprises 24 thin wire bundles of 30 wire segments in one bundle. To assist the design process of an optimized device with given performance and efficiency requirements, the air-cooling behavior of single wires and simple bundle arrangement has been analyzed, and intensive parameter studies on different airflow rates have been performed.
Regarding validating the EC heat pump system, a reproducible manufacturing process is presented for the first time, which supports the installation of at least 720 SMA segments in the same thermo-mechanical state.
This work introduces the bundle fabrication process for the first time and validates it by comparing the key thermo-mechanical values of 135 SMA bundles.
