2.6. Concentration Boundary Layer and Gradients

Try these first

1. 1.

   Define the term 'mass transfer coefficient'.

   Hint

   Think about what it measures.

2. 2.

   What is the primary driving force for diffusion?

   Hint

   From high to low concentration.

3. 3.

   What does the concentration boundary layer affect?

   • Turbulence
   • Mass Transfer
   • Velocity

   Hint

   Think about how substances move across phases.

4. 4.

   True or False: Diffusion is always dominant in turbulent flow.

   • True
   • False

   Hint

   Consider the characteristics of turbid vs. calm waters.

5. 5.

   Calculate the expected flux of a substance at a boundary layer given a concentration difference of 0.5 mol/m^3, and a mass transfer coefficient of 1.2 m/s.

   Hint

   Remember the relationship between flux, concentration difference, and mass transfer coefficient.

6. 6.

   Discuss how increasing the turbulence of a flow would affect mass transfer rates at the boundary layer. Provide a qualitative reasoning.

   Hint

   Think about chaotic fluid movement versus smooth layering.