Effect of the Freeze-Thaw on the Suspension Stability and Thermal Conductivity of EG/Water-Based Al 2 O 3 Nanofluids

This paper reports the effect of the freeze-thaw on the suspension stability, particle size distribution, and thermal conductivity of EG/water-based nanofluids containing Al 2 O 3 nanoparticles that can be used as improved working fluid for cooling systems. The EG/water-based Al 2 O 3 nanofluids were prepared using a two-step method with a nanodisperser and decanting processes. To investigate the effect of freeze-thaw on the suspension stability and thermal conductivity of nanofluids, the prepared nanofluids were frozen at -32°C for 24 hours using a refrigerating chamber, and then they were completely thawed at room temperature for 24 hours. The suspension stability of the thawed nanofluids was quantitatively analysed for over a day using a Turbiscan. In addition, the particle size distributions and deformation of nanoparticles dispersed in the nanofluids were measured using a particle size analyzer (PSA) and TEM. Also, the thermal conductivity of the nanofluids was measured using a transient hot wire (THW) method in temperature from -10 to 70°C. Based on the results, we show that the suspension stability, thermal conductivity, and particle size of EG/water-based Al 2 O 3 nanofluids were not affected by low temperature.