This feature simulates the fractionation of components across a semi-permeable membrane.
For symmetric membranes, this model only applies to crossflow pattern.
Model Description
This model is controlled by the permeation parameters supplied by user input. Only components that have a permeation constant with a value greater than zero cross the membrane. At least one component must have a user-supplied positive-valued permeation constant.
The controlling equation for the model is:
Fi = Ki x Area x (Pi, residue - Pi, surface)
where:
Fi = Permeation flow of component i through the membrane (std volume / time)
Ki = Permeability constant of component i (volume / [area*time*pressure])
Area = Effective permeable area of the membrane
Pi = Partial pressure of component i
The unit supports between 1 and 10 feeds. Multiple feeds are combined into a single feed at the lowest pressure among all the feed streams.
Permeation proceeds from the feed side across the membrane to the permeate side. All component flows that do not permeate across the membrane constitute the residue on the feed side.
The unit requires at least 2 products; the first declared product is the permeate and the second product is the feed-side residue. A two-product model represents a single-stage separator.
Multi-stage Component Separation
When 3 or more products are declared, the model acts as a multi-stage series separator to simulate progressive component fractionation. The number of products determines the number of stages in series. For example, declaring 5 product streams results in 4 stages. The permeates of the stages exit in the first 4 product streams. The final residue from the feed side exits as the last (fifth) product.
The most permeating components cross the membrane most readily, and form the bulk of the first product. The residue of the first stage serves as the feed to the second stage. The second product contains the permeate of the second stage. In turn, the residue of the second stage feeds the third stage, and so on. The last product stream always contains the final residue from the feed side.
The maximum number of products is 10, which defines a model of 9 stages in series. The permeate products from the 9 stages exit in the first 9 product streams. The final feed-side residue exits as the last (tenth) product.
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