Design and Development of NiTi Shape Memory Alloy Belt for Waste Heat Energy Recovery System

Abstract

The abundant waste thermal energy from various sources can be efficiently harvested using material-based technology. Shape memory alloy (SMA) is an efficacious material-based technology for recovering waste heat. In this work, the NiTi SMA bimorph belt has been fabricated in flash evaporation equipment using a customized substrate holder setup. The SMA bimorph belt has been developed with three different prestrain percentage of 1, 3, and 5%. The kapton polyimide substrate is prestrained using a tensile testing setup before the deposition. The actuation characteristics and material characterization of this bimorph belt with varying prestrain percentages have been analyzed. The prestrained bimorph belt with superior material properties and actuation characteristics is used for harnessing the waste heat energy. The actuation performance explored through plate heating reveals 5% prestrain in the bimorph has the maximum shape recovery ratio in both butterfly and cantilever configuration. The contact-based electrical actuation (Joule heating) showed a maximum deflection of 1 mm at 5% prestrain. The adhesion and composition of the bimorph are unaltered with varying prestrain percentage. The morphology shows smooth deposition without any pores and the mechanical strength reduces with an increase in prestrain percentage. The SMA bimorph belt with 5% prestrain generated 60 rpm with aluminum hub and 45 rpm with the polylactic acid hub in the developed prototype using simulated exhaust heat condition. © 2021, ASM International.