Polymeric hollow fiber heat exchangers

Metallic heat exchangers have a number of well-known shortcomings such as high weight and cost and low resistance to corrosion. Polymeric hollow fiber heat exchangers were proposed about a decade ago as an alternative for low temperature applications. Although experimental results have been published for liquid-to-liquid applications, there is no data for liquid-to-gas applications. To overcome this lack of data, two liquid-to-air cross-flow heat exchangers were prepared and tested. Two types of polypropylene hollow fibers (wall thickness 50 mu m, outside diameter 800 mu m and 600 mu m) were used to create heat exchangers with a heat exchange area of approximately 0.6 m(2). An original approach (fiber fabrics were woven) was utilized to achieve a uniform distribution of fibers. The heat transfer performance was studied with hot liquids (60-90 degrees C ethyleneglycol-water brine or water) flowing inside the fibers and cooling air flowing across the fibers. Experiments showed that hollow fiber cross-flow heat exchangers can achieve high values of overall heat-transfer coefficients (200-450 W/m(2) K) and can compete to ordinary finned-tube heat exchangers.