The suitability of polypropylene‐graphite composites as materials for corrugated heat exchanger plates is investigated, as the associated materials have low density (<2.3 g/cm3) and excellent corrosion resistance at a comparatively low price. Therefore, custom‐made polymer composite plates with a thickness of 1–2 mm and a filling degree of up to 80 wt% were evaluated for their thermal and mechanical suitability with regard to their use in plate heat exchangers. Three‐point flexural tests show that the loading of polypropylene with graphite leads to mechanical properties that are suitable for the application of heat exchanger plates. The simulated maximum overpressure is greater than 7 bar. The thermal conductivity of the composites was increased by a factor of 20 compared to pure polypropylene, resulting in thermal conductivities of up to 2.74 W/mK. Considering the density differences between the developed composites and stainless steel, similar thermal performances over a wide range of process conditions are obtained. Moreover, the composites investigated have lower crystallization fouling susceptibility compared to stainless steel, which is attributed to the low surface free energies of approximately 25 mN/m. For calcium sulfate fouling, the fouling resistance on stainless steel exceeds that on the composite by 1.5 m2K/kW after 60 h.
The fouling kinetics and amount of calcium sulfate and calcium carbonate, respectively, on different polypropylene/graphite composites in a flat plate heat exchanger are determined and compared to the reference material stainless-steel. For a straight evaluation of the fouling susceptibility of the materials the formation of bubbles on the materials is considered by optical imaging or excluded by a degasser. The results are interpreted using surface free energy and roughness of the surfaces.The results show that when bubble formation is avoided, the polymer composites have a very low fouling tendency compared to stainless steel. This is particularly the case when turbulent flows are present or when sandblasted specimen are used. Sandblasting also continues to increase heat transfer compared to untreated samples by increasing thermal conductivity and creating local turbulences. Depending on the test conditions, the fouling resistance formed on the stainless-steel surface is an order of magnitude greater than on the polymer composites. In addition, the fouling layers adhere only weakly to the composites, which indicates an easy cleaning in place after the formation of deposits.
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