2-D Modeling of Droplet Spreading Behavior on Surface of Urea using Fluent

The inconsistency in sulfur-coated urea could be affected by several factors such as the droplet spreading behavior of sulfur droplet on urea surface. One of the main factors that affected the droplet spreading behavior is the surface roughness of the urea which has been studied experimentally. However, to comprehend this factor further, improvement of the coating process is analyzed in Computational Fluid Dynamics (CFD) using FLUENT® by modeling the droplet spreading behavior on a rough urea surface with different surface roughness. The simulation is done in two phases; first the droplet spreading behavior of liquid-sulfur on smooth surface and next is to simulate the droplet spreading behavior on a rough surface based on the surface roughness of urea. A 1.8 mm droplet was used for the smooth surface with a velocity of 0.5 m/s. To predict the short term spreading behavior of a droplet, a multiphase volume of fluid model was developed and it also signifies the maximum spreading diameter resulting from the impact. For the modeling on a rough surface, the same variables will be used to predict the droplet spreading behavior on the surface of urea. The results showed that on a smooth surface, the droplet has the highest spreading factor as compared to that of a rough surface due to the homogenous surface area and the effect of wettability. SEM images of urea has shown that certain area of the urea can be seen as smooth while certain area of the urea can be seen as rough. Depending on where the droplet will be in contact with the urea, this will then very much affect the smoothness of the urea coating. Besides the surface characteristics of the urea, factors such as contact angle and velocity impact has also been taken into account.