A wet cylinder of agar gel at 278 K containing a uniform concentration of urea of 0.1 kg mol/m3 has a diameter of 30.48 mm and is 38.1 mm long with flat, parallel ends. The diffusivity is 4.72 × 10–10 m2/s. Calculate the concentration at the midpoint of the cylinder after 100 h for the following cases if the cylinder is suddenly immersed in turbulent pure water:

a. For radial diffusion only.

b. Diffusion occurs radially and axially