Question

The the species continuity equation for the axial dispersion model is ____

(a) u$\frac{∂C_A}{∂z} = \frac{∂D_a}{∂z}\frac{∂C_A}{∂z}$ + (rA)C

(b) u$\frac{∂C_A}{∂z} = \frac{∂D_a}{∂z}\frac{∂C_A}{∂z}$ + C

(c) $\frac{∂C_A}{∂z} = \frac{∂D_a}{∂z}\frac{∂C_A}{∂z}$ + (rA)C

(d) u$\frac{∂C_A}{∂z} = \frac{∂D_a}{∂z}\frac{∂C_A}{∂z}$ + (rA)

This question was posed to me in examination.

The question is from Solid Catalysed Reactions topic in division Solid Catalysed Reactions & Transport Processes with Reactions Catalyzed by Solids of Chemical Reaction Engineering

Answer 1

Right option is (a) u$\frac{∂C_A}{∂z} = \frac{∂D_a}{∂z}\frac{∂C_A}{∂z}$ + (rA)C

Best explanation: For statistically stationary flow, the species continuity equation for the axial dispersion model is u $\frac{∂C_A}{∂z} = \frac{∂D_a}{∂z}\frac{∂C_A}{∂z}$ + (rA)C

u is taken to be the mean (plug flow) velocity through the vessel, and Da is an axial dispersion coefficient to be obtained by means of experiments.