Experimental study on impact patterns and dynamics characteristics of NaCl water droplet with different concentrations on heated surface

This paper reports the experiments for NaCl water droplet with various concentrations impact on heated surface (50 similar to 400 degrees C) at Weber numbers from 67 to 101. The impact patterns, spread diameters, residual energy and rebound times were studied in detail. The results show that the patterns can be divided into deposition, partial rebound, rebound, breakup and jet ejection for droplet with different concentrations impact on heated surface, and mapped the distribution of patterns based on the T-w/T(sat)lgWe and T-w/T(sat)lgRe parameters. In the deposition region, stable spreading diameter decreases with increasing concentration. At high surface temperatures, high concentration droplets boil more violently due to the intense Marangoni effect and the fluid heat transfer coefficient increases. Moreover, the models of the relationships between the dimensionless maximum spreading factor and Weber number and Reynolds number were established, which optimizes the prediction of spreading of droplets with different concentrations. Based on the energy conservation equation, residual energy was found to decrease with increasing concentration. Rebound time decreases with increasing concentration. Moreover, droplet breakup is resulted from boiling bubbles and lateral splashing of atomized droplets. Besides, the NaCl water droplet is more likely to breakup and jet ejection compared to pure water droplet.

Automated summary

This study investigates the impact of NaCl water droplets with various concentrations on a heated surface. The results show that the impact patterns can be categorized into different types, and models are established to predict the spreading behavior of droplets with different concentrations. Additionally, high concentration droplets exhibit more violent boiling and have lower residual energy and rebound time.