ABSTRACT
A permeate spacer is sandwiched between two membranes, the porous support side of the membrane being faced to the permeate spacer. Three edges of the membranes are sealed with glue to form a membrane envelope, the open end being connected to a central tube with holes. The membrane leaf so produced is wound spirally around the central tube together with a feed spacer. In order to make the leaf length shorter, several membrane leaves are wound simultaneously. The feed liquid flows inside the tube, and the permeate flows from the inside to the outside of the membrane tube and is collected at the permeate outlet. There are also tubular modules in which the feed is supplied to the outside of the membrane tube. When model equations are developed to describe the module performance, pressure, solute concentration, and flow rate of the feed solution are considered to be the functions of the radial coordinate, r, alone.
