This paper reports an experimental investigation on the spreading characteristics of nanofluid droplets impinging on aluminum substrate under the influence of several key factors such as nanoparticle volume fraction, substrate temperature, and the Weber number. Sample nanofluid used is prepared by dispersing several volumetric concentrations (1 to 5%) of titanium dioxide nanoparticles in ethylene glycol. The entire dynamic process of each droplet collision with the substrate surface and the spreading phenomena is captured by using a high speed camera and then the transient spreading diameter and height of droplet are determined. It is found that the higher the concentration of nanoparticles the larger the spreading diameter of nanofluid droplet. As the surface temperature increases, the overall spreading diameter and height of nanofluid droplet significantly decreases and increases, respectively. At larger Weber number, the final spreading of the nanofluid droplet is also found to be larger than that of lower Weber number. Present results demonstrate that spreading characteristics of nanofluid droplets impacting onto solid surface are greatly influenced by each of the aforementioned factors.
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