EXAMPLE 18.2. Substitute Gempak 230 A2T packing, manufactured by Glitsch, for
the 1-in. Intalox saddles in the tower of Example 18.1. What increase in gas mass
velocity is expected?
Solution
Use Fig. 18.8. From Example 18.1, $G_x/G_y = 1$ and
$\frac{G_x}{G_y} \left(\frac{\rho_y}{\rho_x}\right)^{0.5} = 1.25 \left(\frac{0.07465}{62.3}\right)^{0.5} = 0.0433$
From Fig. 18.8, $u_{o,f} \sqrt{\rho_y/(\rho_x - \rho_y)} = 0.11$. The superficial vapor velocity at flooding
is therefore
$u_{o,f} = 0.11\sqrt{\frac{62.3 - 0.07}{0.07465}} = 3.175 \text{ m/s}$
The allowable vapor velocity, at 60 percent of flooding, is
$u_o = 3.175 \times 0.6 = 1.905 \text{ m/s or 6.25 ft/s}$
The corresponding mass velocity is
$G = 6.25 \times 0.7465 \times 3,600 = 1,680 \text{ lb/ft}^2 \cdot \text{h}$
The increase in gas mass velocity is $(1,680/1,000) - 1 = 0.68 \text{ or } 68 \text{ percent}$.
