Hatta number

The Hatta number (Ha) was developed by Shirôji Hatta, who taught at Tohoku University. It is a dimensionless parameter that compares the rate of reaction in a liquid film to the rate of diffusion through the film. For a second order reaction (r_A = k₂C_BC_A), the maximum rate of reaction assumes that the liquid film is saturated with gas at the interfacial concentration (C_A,i); thus, the maximum rate of reaction is k₂C_B,bulkC_A,iδ_L.

$Ha^2 = {{k_{2} C_{A,i} C_{B,bulk} \delta_L} \over {\frac{D_A}{\delta_L}\ C_{A,i}}} = {{k_2 C_{B,bulk} D_A} \over ({\frac{D_A}{\delta_L}}) ^2} = {{k_2 C_{B,bulk} D_A} \over {{k_L} ^2}}$

For a reaction m^th order in A and n^th order in B:

$Ha = {{ \sqrt{{\frac{2}{{m} + 1}}k_{m,n} {C_{A,i}}^{m - 1} C_{B,bulk}^n {D}_A}} \over {{k}_L}}$

It is an important parameter used in Chemical Reaction Engineering.

See also

• Dimensionless quantity
• Dimensional analysis