The flow models you are going to learn about are all used by engineers, and they are all based upon performing a mass balance on a fixed control volume. This means that the flow models are based on the idea that within a fixed volume we observe that
Rate of Accumulation | = | Rate going in | - | Rate going out | +/- | Reaction within the Volume |
Where we have the following:
M | Mass of substance being monitored |
t | Time |
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Influent: the total volumetric flow rate going into the control volume (in units of volume per time) |
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Total concentration in the influent of the substance being monitored (in units of mass per volume) |
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Effluent: total volumetric flow rate going out of the control volume (in units of volume per time) |
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Total concentration in the effluent of the substance being monitored (in units of mass per volume) |
k | Reaction constant: not always actually constant, but often a function of the concentration of the mass being monitored (units in this equation are 1/time) |
In this way, the units in each of the products turn out to be in
terms of mass per time.