Thermally driven squeezed-film cooling with carbon nanotube-coated gadolinium shuttles

Abstract

Abstract This paper provides thermal characterization of a thermo-magnetically actuated shuttle. The mechanism derives from a method of converting excess heat to mechanical motion that provides convective and conductive cooling of the heat source. Ferromagnetic foils transitioning between paramagnetic and ferromagnetic states drive a metallic shuttle that generates a squeezed-film cooling effect during oscillation. As a means of improving performance, carbon nanotubes are grown on the gadolinium foils for the purpose of decreasing thermal interface resistance. Experimental details of the carbon nanotube growth process and the device development are presented. Results indicate a range of interface resistances for the carbon nanotube-coated gadolinium samples (140–780 mm 2 K/W) based on growth parameters, though all are reduced relative to a bare gadolinium sample (1230 mm 2 K/W). Characterization of the different foil types during shuttle actuation is described by the shuttle frequency and an effective heat transfer coefficient. Reduced interface resistance from the carbon nanotube arrays enables increased shuttle frequency and overall heat transfer.