Utilization of nanostructured surfaces on microchannels to enhance critical heat flux in the pool boiling

In this research, the pool boiling process on the surface structures from hundreds of nanometers to several micrometers is studied. Ten different surface structures, consisting of bare, nanostructured coatings, microchannel geometries, and multiscale surfaces, were specifically created on the copper substrates. By combining the optimal nanostructured surface on various microchannels, multiscale structures were created. During pool boiling of saturated water at the atmospheric pressure, all surfaces were examined up to CHF. By significantly enhancing bubble dynamics and increasing the density of active nucleation sites at low heat fluxes, microchannel surfaces were found to promote HTC and CHF. By delaying bubble mergence and preventing the vapor film from spreading at high heat fluxes, the nanostructured coatings enhanced HTC and CHF through the nucleation process and surface wicking. It was shown that multiscale surfaces display the distinct enhancement mechanisms at each length scale, wicking-enhanced CHF from the nanostructures, as well as elevated bubble dynamics and nucleation from the microchannel surfaces. The performance of the multiscale surfaces proved promising, both CHF and HTC showed remarkable improvements in comparison to the bare surface.