Polymeric Hollow-Fiber Heat Exchangers for Thermal Desalination Processes

Abstract

Metallic shell-and-tube heat exchangers used in thermal desalination require huge capital investments, suffer from corrosion/erosion, create heavy metal pollution, and display a large footprint. This paper has explored their potential replacement by polymeric solid hollow fiber-based heat exchangers. Using solid hollow-fibers of polypropylene (PP) (wall thickness 75 μm, outside diameter 575 μm) a number of heat exchangers were fabricated in the laboratory (heat exchange area, 195−960 cm2) and at a commercial manufacturing facility (heat exchange area, 0.15−0.44 m2). The heat transfer performances of these devices were studied for a hot brine (4% NaCl, ca. 80−98 °C)−cold water (8−25 °C) system as well as for a steam (101−113 °C)−cold water (8−25 °C) system; these systems are typically encountered in thermal desalination plants. Overall heat transfer coefficient values of as much as 2000 W/(m2 K) were achieved. This is close to the limiting value imposed by the PP wall thickness, namely, 2660 W/(m2 K). Heat...