On the collision dynamics of a water droplet containing an additive on a heated solid surface

Abstract

An experimental study is presented for water-droplet impingement containing an additive upon a heated stainless-steel surface. A solution of 30% (mass fraction) sodium acetate trihydrate, CH3COONa3H2O, was used for the experiments. The impaction process was recorded using a high-speed digital camera at 1000 frames per second. The initial droplet diameter was fixed at 2.7 ± 0.1 mm and all experiments were performed in atmospheric air. Three different impact Weber numbers were considered, namely 15, 80 and 181. The droplet-evaporation lifetime was measured as a function of temperature for 30% (mass fraction) sodium acetate trihydrate. Collision dynamics were investigated for each impact Weber number, with the temperature of the stainless-steel surface varied from film evaporation to film boiling. The temporal variation of the liquid-film diameter was measured as a function of temperature for each impact Weber number. Experiments were also performed using water for direct comparison of the collision dynamics with the additive-containing droplets. The collision dynamics were observed to be different for water droplets containing an additive at low impact Weber number, but became increasingly similar as the impact Weber number was increased.