Silica fouling of heat transfer equipment in geothermal energy systems is studied. The effects of temperature, pH, and salinity on silica solubility and silica polymerization are reviewed. Experimental fouling data are presented for geothermal brines with different pH values, chemical compositions, and thermal-hydraulic conditions. The effects of supersaturation, pH, Reynolds number, and the concentration of ions in the brine solution on the formation of silica scale in the heat exchanger tube are discussed. A silica deposition model is proposed that accounts for supersaturation, pH factor, salinity, and thermal-hydraulic effects. Results based on the analytical model are compared with silica fouling data obtained in the laboratory as well as from two geothermal fields.

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