This Small Business Innovation Research (SBIR) Phase II project will further develop and commercialize an innovative coating which minimizes the accumulation of mineral fouling on industrial heat exchanger surfaces. Heat exchangers are used to heat or cool fluids in industrial processes, such as chemical manufacturing, oil refining, power generation, food processing, electronics manufacturing, and many more. Air conditioning for factories and large commercial buildings also represents a significant use of heat exchangers. Fouling occurs when naturally dissolved minerals in water, often called "hard" water, precipitate out of the water when it contacts a hot surface. This fouling can be seen in a typical home on the surface of a teakettle or showerhead. The resulting mineral crystals adhere strongly, and form an insulating layer that materially reduces the thermal efficiency of industrial heat exchangers. Mineral fouling is estimated to cost U.S. industry $40 Billion per year, and waste $3 Billion of energy, representing upwards of 1% of U.S. greenhouse gas emissions. In addition to wasting energy, this worldwide, never-ending problem increases factory downtime and maintenance costs, causes industry to spend large amounts on chemical treatment of water supplies, and decreases the useful life of heat exchanger systems. An effective coating will result in substantial environmental benefits including the elimination of greenhouse gas emissions resulting from the wasted energy, and a reduction of the water treatment chemicals, which eventually enter community wastewater streams.
The coating material is a low surface energy, self-assembling hydrophobic material which is a composite of a host polymer and a nanoparticle. The low surface energy of the coating impedes the attachment of the minerals to the coated heat transfer surface. Phase I results showed that any fouling accumulation on a coated surface exhibits low adhesion strength, which allows any fouling that does occur to predominantly be dislodged by the force of the water flowing over it - a phenomenon call "self-cleaning." The coating is very thin - less than 500 nm - which minimizes impedance of heat transfer due to the presence of the coating itself. Phase II research will focus on optimizing the properties of the coating, including substrate adhesion, surface energy, and toughness to ensure a useful life under industrial conditions. This will be accomplished by changing the host polymer chemistry to facilitate self-assembly, and also by changing the chemistry of the nanoparticle to obtain a covalent bond between the host polymer and nanoparticle. Work will also be performed to design the application process for industrial scale, and validate lab results with field trials at industrial sites.
