An experimental study on the effect of nanoparticle shape on the dynamics of Leidenfrost droplet impingement

Extensive investigations have been carried out on the thermo-hydrodynamics of nanofluid droplet interaction with heated and non-heated flat surfaces. However, the influence of shape of nanoparticles on the dynamics of droplet impingement on heated flat surfaces is yet to be explored in detail. In this study, hydrodynamics of nanofluid droplet impingement process on heated and mechanically polished aluminum substrate was studied using dissolved Al₂O₃ nanoparticles having spherical as well as cylindrical shapes. Nanofluids of 0.3% volume fractions were prepared from spherical Al₂O₃ particles of mean size less than 50 nm and from cylindrical Al₂O₃ particles of 2-6 nm in diameter and 200-400 nm in length. It was observed that, the impact dynamics is different from that of base pure fluid owing to the presence of nanoparticles. Leidenfrost temperatures of both nanofluids were dropped drastically in comparison with pure liquid. Further, the residence time, spread factor as well as retraction height also exhibit a different behavior against the base fluid. Detailed investigations were carried out for different Weber numbers (We = 18-159) and surface superheat and results obtained were compared with de-ionized (DI) water.