A numerical model to predict laminar flows hydrodynamics and concentration
polarization of salt aqueous solutions in a slit is proposed and experiment
ally validated. Physical modeling for the flow and for the mass transfer pr
ocess is incorporated, in association with the osmotic pressure constitutiv
e equation and a variation law for the membrane intrinsic rejection coeffic
ient. The finite volume formulation is used with the SIMPLE algorithm to so
lve the discretized equations derived from the partial nonlinear differenti
al equations of the mathematical model. The convection terms of the transpo
rt equations are discretized by the second-order hybrid central differences
/upwind scheme. The experimental cell is a slit 200 mm x 30 mm x 2 mm that
simulates the two-dimensional hydrodynamic flow conditions of the open feed
channel of a spiral wound module. The predicted values at the hydrodynamic
; entrance region for different permeation velocities and rejection coeffic
ients for sodium sulfate solutions, and for a single Schmidt number of 850,
are compared against the corresponding experimental values and exhibit an
excellent agreement. A new mass transfer correlation St(p) = 1 + 3.68 x 10(
-4)(x/ h)(-1.11)Re(0.95)Rep(-1.79) is proposed.