Synergistic mechanism of thermal conductivity enhancement and economic analysis of hybrid nanofluids

Synergistic mechanism of enhanced thermal conductivity and the corresponding economic analysis are analyzed to select a reasonable nanofluid. To this end, effects of nanoparticles (NP) and base fluids (BF) mixture ratios on thermal conductivity enhancement (Al2O3-TiO2/EG-W, Al2O3-CuO/EG-W and Al2O3-Cu/EG-W) are carried out at 1.0 vol% and temperature of 20 °C to 60 °C. Results show that the maximum thermal conductivity for Al2O3-TiO2/EG-W nanofluid increases from 0.482 (20 °C) to 0.543 W/(m.K) (60 °C). Moreover, synergistic mechanism of thermal conductivity enhancement is caused by dispersing different sizes of nanoparticles to form order arrangement of liquid molecules around nanoparticles, results in more compact solid-liquid interface and reasonable heat transfer network. Then, sensitivity analysis indicates that NP mixture ratio is a more important factor to determine the alignment of nanoparticles. Finally, Al2O3-CuO/EG-W nanofluid is an efficient fluid in laminar flow, while Al2O3-EG/W single nanofluid is the best choice for turbulent flow from economic analysis.