Polymer Composite Heat Exchangers

The innovative development of polymer composite tubes exhibiting high thermal conductivities for use in heat exchangers, various aspects for implementing these tubes and designing polymer composite heat exchangers are presented. Polymer composite grades based on polypropylene and polyphenylene sulphide filled with graphite have been developed by Technoform Kunststoffprofile GmbH (Lohfelden, Germany). A special extrusion process allows high filler loadings of up to 60 vol% and the orientation of filler particles in the polymer matrix to reach enhanced thermal conductivities in the radial direction. Thermal and mechanical properties, chemical resistance to various acids and alkaline media, lifetime behaviour, heat transfer performance and fouling behaviour were studied for composites with 50 vol% graphite. The extruded polymer composite tubes have a thermal conductivity of about 13–20 W/(m K) which is around 50–100 times higher than that of standard polymers and is comparable to stainless steel grades. The excellent chemical resistance, low weight, good processability as well as highly promising initial test rig results in fouling studies compared to corrosion-resistant metals open up cost-efficient opportunities for heat exchangers in various industries such as chemical, petrochemical, oil and gas, food and beverage, and seawater desalination industries. Important design aspects such as various possibilities of mounting the polymer composite tubes in the tube plates and the maximum unsupported tube span for avoiding tube failures by flow-induced vibrations are discussed. A potential enhancement of heat transfer by shaping polymer composite tubes other than circular plain tubes and the construction of fully polymer-based heat exchangers will be in the focus of future development.