Antifouling and anticorrosion behaviors of modified heat transfer surfaces with coatings in simulated hot-dry-rock geothermal water

Fouling and corrosion of heat exchanger and pipeline caused by geothermal water is one of the bottlenecks that restrict the efficient utilization of geothermal energy. To mitigate fouling and corrosion of heat transfer surfaces in hot-dry-rock geothermal water with the temperature of 423.15 K, SiO2, SiO2-FPS and TiO2 coatings on AISI304 stainless steel substrates were respectively prepared by sol-gel and liquid phase deposition methods. The effects of surface morphology, roughness and surface free energy on fouling deposition rate were studied. Based on the characteristics of two-dimension roughness profiles of surfaces, surfaces were classified into rough surface and microscopic rough surface. For microscopic rough surface, roughness coefficient was defined, which could preferably describe the characteristic of the microscopic roughness degree. The fouling and corrosion behaviors of different coatings and AISI304 stainless steel substrate in simulated hot-dry-rock geothermal water at about 423.15 K were investigated systematically under forced convection heat transfer. The results showed that the liquid phase deposition TiO2 and sol-gel TiO2 coatings had favorable antifouling property in the calcium bicarbonate type simulated geothermal water. The sol-gel SiO2 and SiO2-FPS coatings had better performances of antifouling and anticorrosion in moderately corrosive hot-dry-rock geothermal water with total dissolved solids (TDS) of about 7000 mg/L.