Selective Salt Recovery from Reverse Osmosis Brine - University of ...

guess. This field feeds fsolve, the non-linear solver, an initial guess for solution phase
ion amounts (total meq). Since this number can vary greatly depending on the size of a
particular element and the initial solution concentrations, this approach is better than hard
coding a “one size fits all” guess into the function. It will not converge if the guess is too
far from the actual value. The input guess is only used for the first time step in the first
element. For all subsequent equations, the equilibrium concentration in the previous time
step in the previous element is used a guess.
Figure 9: Graphical User Interface for MATLAB model
The GUI also allows for graphing of solution and resin phase ion equivalents over
time and space. This feature was added to allow the user to confirm that the calculations
were successful and to get a quick overview of the system. Users can export the solution
or resin phase ion equivalents at a specific time for all segments as text file that can be
imported to any graphing program and can be plotted to shows the distribution of ions
within the column for any time (see Figure 10). The arrays can also be accessed directly
from the MATLAB environment by using the functions employed by the GUI graphing
feature. The function entitled get_segment_data allows the user to retrieve resin or
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