Rate-Based Columns

Multicomponent mass transfer via Onda (random packing) and Bravo-Rocha-Fair (structured packing) film coefficients feed gas/liquid transfer units per segment — a true rate-based alternative to the equilibrium-stage MESH assumption.

rate-basedmass-transferpacking

Concept

MESH assumes every stage reaches full vapor-liquid equilibrium — a real tray or packed bed only approaches it. Rate-based columns instead compute actual mass-transfer rates from film coefficients and interfacial area, then integrate transfer units up the column.

The math

Show the governing equations

\frac{a_w}{a_t} = 1-\exp\!\left[-1.45\left(\frac{\sigma_c}{\sigma}\right)^{0.75}\!Re_L^{0.1}Fr_L^{-0.05}We_L^{0.2}\right]\ \text{(Onda wetted area)}

N_G = \frac{k_G\,P\,a_w\,h}{G}, \quad N_L = \frac{k_L\,a_w\,h}{u_L}

Onda for random packing; Bravo-Rocha-Fair for structured packing (a Sherwood correlation on the crimp side for the gas film, penetration theory for the liquid film).

Execution

Selected via the rate_based_distillation / nonequilibrium_distillation unit-op types instead of distillation — same feed/product port shape, so swapping the model doesn't change the surrounding flowsheet.