2 April 2008 Carbon nanotube (CNT) fins for enhanced cooling of shape memory alloy wire
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Abstract
A commonly noted disadvantage of shape memory alloys is their frequency response which is limited by how fast the material can be cooled. This paper presents a feasibility study of using vertically aligned carbon nanotubes (CNT) as microscopic cooling fins to improve convective heat transfer. Using DC plasma enhanced chemical vapor deposition (PECVD), aligned CNT's were successfully grown directly on ½ of the surface of a 0.38 mm diameter SMA wire, achieving desirable thermal contact. Cooling speeds were measured with a thermal imaging camera, and the effective convective coefficient was extracted from the temperature profiles using a basic cooling model of the wire. From this model, the effective convective coefficient was estimated to have increased by 24% (from 50 W/m2K for untreated SMA wire to 62 W/m2K for the nanotube treated wire), indicating that the deposition of CNT's indeed increased performance. By extrapolating these results to full wire coverage, up to a 46% improvement in frequency response with zero weight or volumetric penalties is predicted. Further improvements in cooling performance are likely to occur with higher CNT densities and longer nanotube lengths, allowing further developments of this technology to benefit many future applications utilizing high-speed miniature/micro-scale SMA actuators.
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Anupam Pathak, Anupam Pathak, Joseph AuBuchon, Joseph AuBuchon, Diann Brei, Diann Brei, John Shaw, John Shaw, Jonathan Luntz, Jonathan Luntz, Sungho Jin, Sungho Jin, } "Carbon nanotube (CNT) fins for enhanced cooling of shape memory alloy wire", Proc. SPIE 6929, Behavior and Mechanics of Multifunctional and Composite Materials 2008, 69291K (2 April 2008); doi: 10.1117/12.774147; https://doi.org/10.1117/12.774147
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