LAUSR

Abstract This article presents experimental results for the confined and unconfined nucleate boiling of saturated HFE7100 (C 4 F 9 OCH 3 ) at atmospheric pressure and using nanostructured copper discs as heating surfaces. The nanostructures studied consisted of nanoparticles of maghemite (Fe 2 O 3 ) on the heating surface, comprised of a copper disc. Different values for the diameter (10 and 80 nm) and roughness ( R a = 0.02 µm and 0.16 µm) were studied. The nanoparticle adhesion on the heating surface plays a more important role in the confined boiling process than the surface roughness. As an original result, it was demonstrated that for a confinement with a gap length of 0.1 mm and heat flux of 40 kW/m 2 the heat transfer coefficient (HTC) increased by 31% and 100% for the cases with the deposition of nanoparticles of 10 nm and 80 nm, respectively. However, without the nanoparticles the HTC decreased by 21% when compared with the reference case, that is, a smooth plate ( R a = 0.02 µm) and unconfined boiling.