understanding Direct Transfer Mass Flux Links

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    Rick Kossik

    Ashley,

    As you pointed out, the equation for the mass transfer rate is DM/dt = M * Fractional Transfer Rate (where M is the mass in the Cell).  

    This is the equation for first-order decay and the solution to this is an exponential. It is not linear. In order to be linear, the transfer rate would not be a function of the mass in the Cell (i.e., it would be DM/dt = Absolute Transfer Rate).

    If you plot the mass versus time, you will see the exponential behavior.

    I hope this helps.

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    Ashley R

    Thanks Rick.  I am able to replicate the results now in excel.    Is there an "Absolute Transfer Rate" option in goldsim? 

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    Rick Kossik

    What physical process are you trying to represent?

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    Ashley R

    For example, degradation of a species by sunlight at a rate of 10 mg/m2-d.   With the area = surface area of a pond.

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    Rick Kossik

    Hmm. So this rate is completely independent of the concentration in the water?  That seems a bit odd to me.

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    Ashley R

    here is a little blurb from the report i`m reading:

    Is it possible to simulate this type of mass transport for a single species in goldsim?

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    Rick Kossik

    Well, this does not say where those rates came from or how they were calculated.  I simply cannot understand how the removal rate would not be a function of the concentration. Chemical reactions are generally a function of the concentration of the reactants.  I have a hard time understanding how a reaction could be unrelated to the concentration.  In fact, this blurb does in fact say that the removal rate is a function of phosphorus concentration.  So there must be some ammonia concentration assumed.

    Nevertheless, if you must do this, I have sent a model to your email that closely approximates this.

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