Use of perfluoropolyether coatings to prevent fouling on heat exchanger metal surfaces

Fouling on heat-transfer surface in heat exchanger is a hard problem to solve and several methods have been suggested to inhibit the deposition of scale on heat exchangers surfaces ( Malayeri et al., 2009; Müller-Steinhagen et al., 2011). One possibility to reduce or to avoid fouling is the modification of the heat transfer solid surface properties. The scope of this work is to create a coating on metallic surface in order to avoid any interaction of the metallic surface with harmful precipitates, thus preventing the fouling in heat exchangers. Perfluoropolyethers are used to obtain thin fluorinated layer able to preserve the properties of heat exchanger and, at the same time, make metallic surface hydrophobic. To demonstrate the ability of the hydrophobic coating to prevent fouling, a pilot plant with two identical heat exchangers AEW TEMA TYPE working in parallel at the same operating condition was built. One of them was characterized by the polymeric coating either on internal and external tubes surfaces. A simultaneously monitoring of the heat exchangers made possible to compare the performance of the coated heat exchanger respect to the not coated one. After a six months operation period , obtained experimental results demonstrate a significant increase of heat transfer resistance due to the fouling on the uncoated heat exchanger, respect to the coated one.