Heat transfer foot print on ceramics after thermal shock with droplet impingement: Development of thermal shock tolerant material with hydrophobic surface

Abstract

We perform a systematic study of the thermal shock experienced by the alumina during quenching by cold water droplet impingement with heated surface temperature ranging from 125°C to 475°C for Weber number ≈32. We explore the effect of surface heat transfer mode on the thermal shock experienced by the material. It is found that the variation of residual strength translates into the mode of boiling heat transfer, hence surface heat flux. The material remembers the degree of thermal shock; the heat transfer foot print is embedded in the residual strength. This finding speaks to a possibility of developing a ceramic detector for heat transfer modes in extreme environments. This study finds that superior thermal shock tolerance can be achieved by removing the heat transfer footprint with reduced heat flux. By promoting the film boiling with nano-fractal hydrophobic surface, we achieved superior thermal shock tolerance for alumina substrates. This is a novel approach to reduce thermal shock by controlling the heat transfer with surface modification, different from conventional, yet expensive, method of improving the bulk material properties.