Thermal performance of fouling-resistant polymer nanocomposite coatings in heat exchangers

Abstract

This paper presents an experimental study on the thermal performance of novel polymer nanocomposite coatings under the fouling environments with particular emphasis on their ability to exhibit anti-fouling and anti-wetting behaviour. Two different weight fractions at 0.3%, and 0.5% of the reduced graphene oxide/Epoxy (rGO-ER7004) and reduced graphene oxide/polyurethane (rGO-UR9002) coatings were applied to stainless steel substrates by a facile spray coating technique. To evaluate the anti-fouling performance of the coatings, the specimens were immersed in the Modified Baar's Medium for 672 h. The antifouling performance was evaluated by comparing the overall heat transfer effectiveness of the nano coated and bare specimens at different immersion intervals. Three different flow rates, viz. 4 lpm, 6 lpm and 8 lpm were used to compare the heat transfer effectiveness. The incorporation of rGO lead to a significant reduction in the wettability and surface roughness of coatings. amongst all the investigated coatings, the heat exchange with rGO/UR9002 0.5 wt.% coatings showed the highest heat transfer effectiveness. A small reduction (∼10%) in the heat transfer effectiveness after an immersion in the fouling media for 672 h was noticed. This can be attributed to the accumulation of salt particles on the coatings, observed visually. Finally, the 1-D heat transfer analysis is performed using finite element method based approach to evaluate the effect of the nano coatings and foulants on the temperature drop. It is deduced that a small foulant layer can significantly impede the heat transfer across the substrate. A strong correlation (∼0.99) between the heat transfer effectiveness and temperature drop is observed.