Experimental characterization of the effect of liquid viscosity on collisions between a multi-component droplet and a heated particle

Abstract

Understanding droplet-particle collisions is critical for regulating spray coating processes. Existing studies mainly focused on collision between a single component droplet and a particle either at room temperature or considerably higher than the boiling point. In this study, we perform experiments of a droplet impacting a heated particle with its temperature in the range of 35 °C–150 °C, where the droplet is generated from multi-component solutions with its viscosity adjusted by adding Hydroxypropyl methyl cellulose (HPMC). The collisions with droplets from 30% sodium benzoate solution show four regimes: deposition, deposition-bubble, breakup-rebound, and rebound. Byincreasingviscosity with adding 1% or 2% HPMC, only two regimes are observed: deposition and deposition-bubble. The variation of film thickness with time can be divided into three phases. The film thickness in phase I and II can be fitted by simple functions. With increasing liquid viscosity, the film thickness in phase III at different temperatures becomes consistent.