Journal Publications

Abstract:

 Nanoscale thin liquid film boiling of a binary liquid mixture subjected to extremely rapid heating within molecular dynamics framework is the focus of our study. A three-phase MD simulation domain is considered where liquid argon-krypton (Ar-Kr) binary mixture rests over a solid Platinum (Pt) like substrate. The molecular system starting from freezing state is subjected to non-equilibrium boundary heating following a sufficient equilibration period to induce liquid-vapor phase change process. Depending on the mixture composition and boundary heating rate, four distinct phase change scenarios have been observed. Characteristics of different phase change scenarios have been studied in terms of important system parameters such as transient atomistic distribution, temperature, pressure, evaporation history, onset of liquid cluster splashing from the wall along with atomic kinetics parameters like COM (Center of Mass), and MSD (Mean Square Displacement). Addition of Kr with Ar that is less volatile compared to Ar, has been found to result in a delay in the evaporation onset and decrease in interaction energy. As a consequence, with the increase of Kr fraction in the binary mixture, the mobility of the evaporated atoms is hindered and the onset temperature of liquid splashing from the wall that resembles generation of “Leidenfrost Film” changes. Also, the near wall atomistic energetics is significantly influenced by mixture composition. Finally, a contour of various phase change modes for Ar-Kr binary mixtures has been presented as a function of mixture composition and boundary heating rate. Present work has been found to be aligned with contemporary works in the context of the derived heat transfer properties.

Abstract:

This study aims to explore the effect of the relative philic-phobic strength on nanoscale condensation over hybrid wetting surfaces at various philic-phobic contents through molecular dynamics simulation. The molecular system under consideration essentially consists of argon atoms (liquid and vapor) bound by two platinum substrates. Following equilibration of the simulated system at 90 K, the temperature of the lower substrate is raised to induce evaporation of the adjacent liquid argon, which eventually condenses on the upper wall, maintained at equilibration temperature. Two different hybrid wetting configurations of the upper wall have been considered, namely: functional gradient wetting (FGW) and (b) patterned wetting. The relative strength as well as the content of philic-phobic segments for both hybrid wetting configurations have been altered to explore key metrics of nanoscale condensation process such as onset of nucleation cluster, coalescence and subsequent condensate growth mode, transient as well as time averaged condensation rate and heat transfer at the condensing wall. Results obtained in the present study indicate that combining strong hydrophilic segments with weak hydrophobic segments improves the performance of a hybrid wetting surface. Nonetheless, the difference between gradient wetting and patterned wetting distribution has been found to be small for higher philic content of the condensing wall. Also findings of the present atomistic study have been found consistent with classical theories in context to heterogeneous condensate nucleation, coalescence and subsequent growth.