ADIABATIC LAMINAR FLOW WITH RADIAL AND AXIAL DIFFUSION

Mass and energy balance

Solving the previous problem, we assumed that the diffusivity was zero. Now, let us assume that that the diffusivity is no longer zero. To solve this problem the simplified general forms of the mass and energy balance are used, i.e. Eqn (5) and (11).

                                                (5)

                                       (11)

Boundary conditions

The boundary conditions are identical as for the previous case and can be expressed as:

                         Mass/Mole condition       Energy condition

at z = 0                                 

   at r = 0                                  

   at r = R                                 

We added the radial mass transport effects to the problem by giving the diffusivity a value other than zero. The value used in this case is about 100 times larger than the value of the diffusivity stated earlier in the introduction. This exaggeration was done to make the effect of the diffusivity clear.

Do you expect the diffusion to make a great change?