Some Problems in Winding Geometry

The efficiency of wound, hollow-fiber separation modules used to remove dissolved salts from water by the process of reverse osmosis may be improved by alterations in module geometry. Normally, the hollow-fiber membranes composing the module are helically wound about a cylindrical core. Flow rate through the module may be increased, however, if the cross-sectional density of wound fibers varies uniformly along the module axis. This paper explores the analytical requirements for the helical winding of a conical mandrel with filamentary material in a manner that eventually produces a cylindrically shaped package. The effect of specifying either a constant yarn feed rate or a constant spindle speed during winding is considered in relation to restrictions on the length of material added per circuit.