# Souders-Brown Equation

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

Souders-Brown equation is used to find the maximum allowable vapor velocity in vapor-liquid seperation vessels.

## Souders-Brown Equation formula

$$\large{ v = K \; \sqrt{ \frac{\rho_l \;-\; \rho_v}{\rho_v} } }$$
Symbol English Metric
$$\large{ v }$$ = maximum allowable vapor velocity $$\large{\frac{ft}{sec}}$$ $$\large{\frac{m}{s}}$$
$$\large{ \rho_l }$$   (Greek symbol rho) = density of liquid $$\large{\frac{lbm}{ft^3}}$$ $$\large{\frac{kg}{m^3}}$$
$$\large{ \rho_v }$$   (Greek symbol rho) = density of vapor $$\large{\frac{lbm}{ft^3}}$$ $$\large{\frac{kg}{m^3}}$$
$$\large{ K }$$ = vapor velocity factor $$\large{dimensionless}$$

K Factors for maximum allowable superficial velocity (API Spec 12J)

• Vertical separator  -  5 ft. high  -  K = 0.12 to 0.24
• Vertical separator  -  10 ft. high  -  K = 0.18 to 0.35
• Horizontal separator  -  10 ft. long  -  K = 0.40 to 0.50
• Horizontal separator  -  Other lengths L ft. long  -  K = 0.40 to 0.50 $$\left( \frac{L}{10}\right)^{0.56}$$
• Spherical separator  -  All  -  K = 0.2 to 0.35
$$\large{dimensionless}$$