Fine-Tuned Polymer Nano-Composite Coatings for Use in Geothermal Plants

Often times erosion, corrosion, and fouling by scale deposition are primary issues for geothermal-fluid-wetted process equipment. In particular, wet heat exchangers used in geothermal power plants must deal with scale deposition. Previously, a surface-coating of polytetrafluoroethylene (PTFE) was considered to provide a non-stick surface. However, intrinsically poor thermal conductivity of PTFE, along with its poor abrasion resistance and weak adhesion to metal substrate, turns out to be a serious concern for engineering use. In this paper, we report a fine-tuned nano-composite by incorporating PTFE/Carbon-nanotube (CNT) into the polyphenylene surfide (PPS) host matrix. PPS is a thermoplastic polymer exhibiting outstanding high-temperature stability, excellent flame resistance, and good chemical resistance. By adding PTFE/CNTs into a PPS matrix, a superhydrophobic surface can also be created by contemplating the chemical composition of the surface material and the cooperative effect of nano-micro structures at the surface. Furthermore, carefully engineered superhydrophobic surfaces can create so-called “dropwise condensation [1]” which can dramatically enhance steam condensation heat transfer. We report the performance results of such nanocomposites regarding steam condensation, along with other surface characteristics. It is our anticipation that, with proper treatment, PTFE/CNT blended PPS can be widely adopted for use in high performance heat exchangers in geothermal industries.