Subcooled Flow Boiling Over Nanostructured Plate Integrated Into a Rectangular Channel

Sub-cooled flow boiling was investigated over nanostructured plate (of dimensions 20mm×20mm) integrated to a rectangular channel (of dimensions 33mm×9mm×33mm) at flow rates ranging from 69 ml/min to 145 ml/min. The configuration of the nanostructured plate includes ∼600 nm long copper nanorod arrays with an average nanorod diameter of ∼150 nm. The nanorod arrays are integrated to copper thin film (∼300 nm thick) coated on silicon wafer surface and GLAD (Glancing Angle Deposition) technique was implemented to form the nanostructure configuration. The dimensions and flow rates were chosen to ensure that no change in the nanostructure configurations occurred during the experiments so that the configuration could be used for many experiments. For this, applied heat fluxes (<42 W/cm2) were adjusted in such a way that the wall superheats did not exceed 30°C to avoid any damage on nanostructures. Deionized-water was propelled with a gear pump into the rectangular channel over plates with both plain and nanostructured surface, which were heated with cartridge heaters. Forced convective boiling heat transfer characteristics of the nanostructured plate is investigated using the experimental setup and compared to the results from the plate with plain surface. A significant increase in boiling heat transfer was observed with the nanostructured plate. In the light of the obtained promising results, channels with nanostructured surfaces were proven to be useful particularly in various applications such as cooling of small electronic devices, where conventional surface enhancement techniques are not applicable.