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*To*: "Stephan Kohler" <skohler@xxxxxxxxxxxxxxxx>*Subject*: Re: modelling a stirred tank reactor*From*: "David L Parkhurst" <dlpark@xxxxxxxx>*Date*: Fri, 29 Nov 2002 09:55:13 -0700*Bcc*: "David L Parkhurst" <dlpark@xxxxxxxx>*In-reply-to*: <NFBBJJDGMKMNCIJGJPOJOEEDCFAA.skohler@lmtg.ups-tlse.fr>

> Now are there more elegant ways to do it ? I've included an input file that performs a mixing calculation. I think it is close to what you want to do if you add the kinetic reaction. In the setup, solution 3 mixes with solution 1 in a two-cell transport calculation. It uses two cells because the minimum number of cells in a column for TRANSPORT is two, but calculations for cell 2 are ignored. For the transport calculation, there is no flow (flow_direction diffusion_only) and boundary conditions closed. A single stagnant cell is defined for each cell of the column; this allows explicit mixing factors to be defined for each cell. The mixing characteristics of cell 1 are defined explicitly by MIX 1, in this case .9 of solution 1 remains and .1 of solution 3 is added at each shift (mix). The composition of solution 3 does not change. The number of mixes is determined by the number of "shifts" in the transport calculation. You can run a transport calculation for a number of shifts, then redefine solution 3, and define another transport calculation to simulate a change in the feed to the reactor. Adding a definition for KINETICS 1 (and RATES and appropriate time_step in TRANSPORT) will include a kinetic reaction for cell 1. Similarly, you can add EQUILIBRIUM_PHASES 1, SURFACE 1, EXCHANGE 1, or SOLID_SOLUTIONS 1 to include those processes in the reactor. The example runs two mixes and the amount of bromide initially present in cell 1 decreases from 1 to .9 to .81 in the successive shifts in accordance with the mixing fraction of .9 of the solution remains and no additional Br is added. > How can I define a new solution from previously stored parameters OUTSIDE a rate function ? Hopefully you do not have to do this. It is probably possible to use clever definitions of another stagnant cell to save a solution. It is probably also possible to define a series of kinetic reactions, each of which adds back a saved quantity for a single element. > Can one make a DO LOOP to group a MIX and RATE function No, I've thought about it, but never got around to coding it. David solution 0-4 Na 1 Cl 1 end solution 1-2 K 1 Br 1 end MIX 1 3 .1 1 .9 END KINETICS 1 .... TRANSPORT -cells 2 -shifts 2 -time_step 1 # seconds -flow_direction diffusion_only -boundary_conditions closed closed -stagnant 1 0 0 0 -print_cells 1 -punch_cells 1 -warnings true END David Parkhurst (dlpark@xxxxxxxx) U.S. Geological Survey Box 25046, MS 413 Denver Federal Center Denver, CO 80225 Project web page: https://wwwbrr.cr.usgs.gov/projects/GWC_coupled

**References**:**modelling a stirred tank reactor***From:*Stephan Kohler

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