MASS-TRANSFER IMPROVEMENT BY SECONDARY FLOWS - DEAN VORTICES IN COILED TUBULAR MEMBRANES

A helically wound hollow-fibre (or tubular) membrane module was studie d in an oxygenation operation with water flowing in the laminar regime inside the tube. Data are compared with a conventional module where s traight hollow-fibre membranes are in parallel alignment. In the forme r design, the results are analyzed taking into account the formation o f secondary flow (Dean vortices) and a new mass transfer correlation i s presented. In the latter design, results are consistent with the Lev eque equation. It is shown that the presence of vortices gives better performance in terms of oxygen transfer. Improvement factors were in t he range of 2 to 4.