What general steps are taken to find diffusion flux?

The correct approach involves using the Sherwood number (Sh), Reynolds number (Re), and Schmidt number (Sc) to determine the mass transfer coefficient. This coefficient is crucial because it relates the mass flux of a species to the concentration gradient that drives diffusion.

When mass transfer occurs in a fluid, it is influenced by both the momentum transfer (characterized by the Reynolds number) and the diffusion process (characterized by the Schmidt number). The Sherwood number provides a dimensionless representation of the mass transfer rate relative to the diffusion process. By calculating the mass transfer coefficient using these parameters, you can then apply it in Fick's law of diffusion to find the diffusion flux. This law states that the diffusion flux is proportional to the concentration gradient, with the mass transfer coefficient acting as the proportionality factor.

In contrast, simply using concentration gradients alone does not provide the complete context necessary for calculating flux through the mass transfer coefficient. Likewise, relying solely on the mass of the diffusing substance without considering the flow dynamics and conditions would overlook the key factors that affect how substances diffuse through a medium.