A new method (improved shooting method) is used for effectiveness factor calculation by the diffusion-reaction approach.

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feed temperature, feed velocity, and solvent velocity is optimized according to synergistic effects. Simulation results show that, in the optimum operating conditions the removal percentage of H 2 S and CO 2 are 27 and 21 % respectively. List of symbolsI I-component (CO 2 and H 2 S) C 0 Inlet mixture concentration (mol/m 3 ) C Concentration (mol/m 3 ) C i-membrane Component i concentration in the membrane (mol/m 3 ) C i-shell Component i concentration in the shell (mol/ m 3 ) C i-tube Component i concentration in the tube (mol/ m 3 ) D Diffusion coefficient (m 2 /s) D i-membrane Diffusion coefficient of component i in the membrane (m 2 /s) D i-shell Diffusion coefficient of component i in the shell (m 2 /s) D i-tube Diffusion coefficient of component i in the tube (m 2 /s) F Body force (N) J i Diffusive flux of species i (mol/s) m Physical solubility (dimensionless) r Radial coordinate (m) r 1 Inner tube radius (m) r-2 Outer tube radius (m) r-3 Inner shell radius (m) R i Reaction rate of species i (mol/s) t Time (s) u Average velocity in the tube side (m/s) V Velocity vector (m/s) V z z Direction velocity in the contactor (m/s) V z-shell z Direction velocity in the shell (m/s) AbstractIn this paper a 3-dimensional modeling of simultaneous stripping of carbon dioxide (CO 2 ) and hydrogen sulfide (H 2 S) from water using hollow fiber membrane made of polyvinylidene fluoride is developed. The water, containing CO 2 and H 2 S enters to the membrane as feed. At the same time, pure nitrogen flow in the shell side of a shell and tube hollow fiber as the solvent. In the previous methods of modeling hollow fiber membranes just one of the membranes was modeled and the results expand to whole shell and tube system. In this research the whole hollow fiber shell and tube module is modeled to reduce the errors. Simulation results showed that increasing the velocity of solvent flow and decreasing the velocity of the feed are leads to increase in the system yield. However the effect of the feed velocity on the process is likely more than the influence of changing the velocity of the gaseous solvent. In addition H 2 S stripping has higher yield in comparison with CO 2 stripping. This model is compared to the previous modeling methods and shows that the new model is more accurate. Finally, the effect of feed temperature is studied using response surface method and the operating conditions of * Bahram Dabir Heat Mass Transfer 1 3 Greek symbols ∇ Gradient (dimensionless) ρ Density (kg/m 3 ) η Dynamic viscosity (m 2 /s) Subscripts in Inlet out Outlet V z-tube z Direction velocity in the tube (m/s) V inlet Inlet velocity to the contactor (m/s) z Axial distance (m)