Polymeric hollow fiber heat exchangers

Polymeric hollow fiber heat exchangers were first proposed in 2004 by New Jersey Institute of Technology as an alternative to metal exchangers for low temperature application. The first study of this type of heat transfer surface started at Brno University of Technology in 2008. This paper presents a brief survey of activities of Heat Transfer and Fluid Flow Laboratory in the field. The heat exchangers presented use a polymeric capillary with an outer diameter of 0.5mm – 1.3mm and a wall thickness of about 10% of the outer diameter. The typical material is polypropylene and this material was used in the initial years of development. Tiny polypropylene fibers can withstand a burst pressure of 50 bar at room temperature. Heat exchangers using hollow fibers can in principle either have a rigid structure or be a bundle with a chaotic structure. These heat exchangers are effective even in natural convection application where the advantage of high heat transfer coefficient on micro surfaces is utilized. The use of plastic and non-corrosive materials is advantageous in applications where the weight of the heat exchanger is important (about 50% reduction in weight in comparison to classical metal products) and in difficult chemical environments. Flexible polymeric hollow fiber heat exchangers were developed and prototypes were prepared and tested for liquid / air and liquid / liquid conditions. The paper presents a survey of the materials used for hollow fibers, a description of the production of fibers by extrusion, the basic physical principles of heat transfer on micro-surfaces, and prototyping of the number of heat exchangers both with rigid and chaotic structures.