Spiral Wound Membranes are constructed in a number of parts
Firstly the permeate carrier layers are assembled and attached to the permeate tube. This allows the permeate to flow in a circular direction around the permeate tube from the outside of the membrane to the centre tube.
Inside each permeate carrier layer is a Membrane Envelope. The Membrane Envelope is made of the membrane enveloped around the feed channel spacer.
Product is fed in the feed channel spacer, the filtered product permeates the membrane and is then carried to the permeate tube, the retentate carries along the surface of the membrane in the feed channel and flows out the end of the membrane.
To learn more about the cross flow on the surface of the membrane click here.