The dispersion stability and thermal conductivity of propylene glycol basednanofluids containing Al2O3 and TiO2 nanoparticles were studied in thetemperature range of 20 to 80 {\deg}C. Nanofluids with different concentrationsof nanoparticles were formulated by the two-step method without use ofdispersants. In contrast to the common belief the average particle size ofnanofluids was observed to decrease with increasing temperature. The nanofluidsshowed excellent stability over the temperature range of interest. Thermalconductivity enhancement for both of studied nanofluids was a non-linearfunction of concentration while was temperature independent. Theoreticalanalyses were performed using existing models and comparisons were made withexperimental results. The model based on the aggregation theory appears toyield the best fit. Keywords: Nanofluids, Propylene glycol, Alumina nanoparticles, Titaniananoparticles, Thermal conductivity, Dispersion stability.
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