Structural properties of glancing angle deposited nanostructured surfaces for enhanced boiling heat transfer using refrigerant R-141b

Titanium dioxide (TiO2) coated nanostructured surfaces for nucleate pool boiling heat transfer were experimentally studied. A 600 nm thick TiO2 nanostructured coating over a TiO2 intermediate layer (100 nm-thick thin film) was fabricated with two different azimuthal rotations 120 rpm and 460 rpm on two separate copper heating surfaces using the glancing angle deposition (GLAD) technique. A nanostructure with 600 nm-thick coating without an intermediate layer was synthesized on a copper heating surface at an azimuthal rotation of 460 rpm by applying the same technique. Pool boiling experiments were performed on all the surfaces, including the one natural copper surface and one treated surface at atmospheric pressure using R-141b to analyze the boiling heat transfer performance. The TiO2 nanostructured surface with the intermediate layer provided higher heat transfer activities than the surface without the intermediate layer. The modified 600 nm thick TiO2 nanostructured surface using 460 rpm azimuthal rotation of GLAD technique with the 100 nm thick TiO2 intermediate layer surface had a significantly enhanced boiling heat transfer performance compared to that of the 600 nm thick TiO2 nanostructured surface using 120 rpm azimuthal rotation of GLAD technique with the 100 nm thick TiO2 intermediate layer surface, treated surface, and natural copper surfaces. The surface fabrication technique would alter the thermodynamic performance of a surface, especially in the case of energy conversion devices, to expedite the heat transfer.