STUDY OF THE EFFECT OF ADDING AL2O3 NANOPARTICLES ON THE THERMAL PROPERTIES OF POLYPROPYLENE GLYCOL WITH DIFFERENT CONCENTRATIONS

Abstract

In this study, a comparison between thermal conductivity and dynamic viscosity of a pure propylene glycol liquid as a solar thermal fluid and its nanofluid has been carried out using different concentrations of nanoparticles. Aluminum oxide nanoparticles (α phase - size 50-90 nm) were added to the pure propylene glycol liquid at three different concentrations (0.2%, 0.4%, and 0.6%). The different thermal fluids (pure and nano-propylene glycol) were tested at different temperatures (20, 60, 100, 140, 180°C) on five different days. Regarding pure liquid, as temperature increases the thermal conductivity and viscosity drop for all experiment days. The minimum value for thermal conductivity and viscosity were recorded on the first day test at 180°C temperature with (k=0.13 W/m.K and µ=13.2 centipoise). However, adding the nanoparticles has reversed the temperature effect on the resulting nanofluids thermal conductivity. Where k reached its maximum value (0.307 W/m.K) at 180 °C for 0.6% concentration nanofluid on day (60) recording an improvement of (136.14%). Viscosity in contrast kept decreasing with temperature rise for each nanoparticles concentration. Yet the nanoparticles concentration proportional directly with dynamic viscosity at constant temperature. In this contest, on day (60) test, the viscosity at 20°C for both pure PG and 0.6% nano-PG were 58 and 64 centipoises, respectively. While at 180°C, µ= 14.9 and 21 centipoises respectively. The behaviour of PG nanofluid dynamic viscosity in different concentrations and different temperatures has almost the same response to concentration and temperature for ethylene glycol based nanofluid. Finally, SEM images showed homogeneity and distribution of the nanofluid at a concentration of 0.4%, and some aggregates were detected at a concentration of 0.6%.