The Impact of TiO\({}_{\mathbf{2}}\) Nanoparticles on the Freezing Properties of Droplets

Abstract

To investigate the stationary nanofluid droplets effects of substrate surface temperature and particle concentration on the freezing time, deformation, and droplet contact angle during the freezing process, high-speed CCD image observation was used to study the morphological changes during the freezing process of (TiO\({}_{2}\)–H\({}_{2}\)O) nanodroplets. Nanoparticle droplets were prepared in this study using magnetic stirring and ultrasonic mixing. Three substrate surface temperatures (268, 265, and 263 K) and four concentrations of TiO\({}_{2}\) nanoparticles (5, 10, 30, and 50 mg/mL) were considered. The findings demonstrate that the addition of nanoparticles will result in the droplets appearing sanded, a considerable change in the form of the droplet tip, and a decrease in the release of bubbles upon freezing. The increase in supercooling at high concentrations (\(>5\) mg/mL) causes the droplet height to rise, its volume to expand upon freezing, and its shape to shift from ‘‘peach-core’’ to ‘‘cone-like.’’ When TiO\({}_{2}\) nanoparticles were added, the droplets’ longitudinal morphology changed throughout the freezing process, but lateral diffusion was unaffected, even though the contact angle \(\theta\) marginally shrank as concentration increased. The droplets with the lowest concentration of TiO\({}_{2}\) particles exhibit the highest longitudinal deformation rate \(\alpha\) during the droplet freezing process. As the subcooling degree increases, \(\alpha\) also rises and reaches its maximum at 263 K or 22.26\(\%\), but as the concentration of nanoparticles grows, \(\alpha\) drops, and so does the coefficient of segregation, \(\gamma\).