Sub-micron sized metal oxides based organic thermic fluids with enhanced thermo-physical properties

Abstract

Organic thermic fluids containing metal oxides as additives exhibiting good thermal stability, low freezing point, and high thermal conductivity, that can be used as heat transfer fluids in concentrated solar power (CSP) plants have been formulated. This work focus on the development of novel organic based sub-micron thermic fluids in which metal oxide particles viz. alumina (Al2O3) and titania (TiO2) with a particle size in the range of 0.5–0.6 μm have been incorporated in the base fluids to enhance the thermo-physical properties. Thus prepared thermic fluids have exhibited an enhancement in the thermo-physical properties, such as thermal conductivity, specific heat capacity, and cycle stability. In addition, the detailed rheological studies at various temperatures have been conducted for these fluids, containing 100–500 ppm of metal oxide sub-micron sized particles. Formulated sub-micron thermic fluids (SMTFs) have also been characterized for other properties such as flash point, no-flow point, density, viscosity index, and thermal and particle suspension stabilities. Among various samples prepared, the SMTF containing TiO2 sub-micron particles (200 ppm) has shown a maximum enhancement of thermal conductivity (~75 %) at 200 °C. The cycle stability studies of SMTFs were conducted by using in-house designed and fabricated solar test loop. The thermal conductivity before and after ten cycles of heating and cooling between ambient temperature to 300 °C were measured and the results indicate the developed SMTFs are highly stable.