Pool boiling of R-134a on ZnO nanostructured surfaces: and heat transfer

Abstract

An experimental study was carried out to investigate the pool boiling performance of R-134a onZnO nanostructured heating surfaces. ZnO nanostructured heating surfaces were fabricated by the thermal evaporation technique followed by heat treatment. Nanostructured ZnO thin films were applied on the bare aluminum heating substrate, furthermore pool boiling performance was carried out with R-134a. Experimental data were recorded at heat fluxes ranging from 9.37 to 72.23 kW/m2k. It was found that with a rise in the thickness of nanostructured ZnO thin film, the wall superheat was decreased and the maximum decrement in wall superheat was observed for nanostructure ZnO thin film with 300 nm thickness. It was also observed that the heat transfer coefficient (HTC) of the ZnO nanostructured surfaces increased with the rise in thickness of coating. The highest value of HTC for ZnO-300 surface was61% greater than the bare Al heating surface.