An on-face central composite design was used to investigate
the interactive effects of Vgs1 and Vgs2 on hydrodynamic and mass
transfer properties. Thirteen experiments were designed and conducted
using response surface methodology (RSM) with a central
composite design. The range of Vgs1 and Vgs2, as key operating
parameters,were 0.0005–0.0069 m/s (central value = 0.0037 m/s)
and 0.0040–0.0238 m/s (central value = 0.0139 m/s), respectively.
The experimental design for X1 (Vgs1) and X2 (Vgs2) is shown in
Table 2. This table also lists the results of all responses under thedifferent operating conditions. A stepwise regression analysis was
conducted by generating a second-order polynomial equation:
Y = ˛0 + ˛1 · X1 + ˛2 · X2 + ˛11 · X2 1 + ˛22 · X2 2 + ˛12 · X1 · X2 (6)
in which Y is the expected response value predicted by RSM; ˛i, ˛j
and ˛ij are the parameters estimated from the regression results
(i = 1,2; and j = 1,2). Ten performance indices were used to assess
the influence of these variants on hydrodynamic and mass transfer
properties.