Abstract
Over many years, great efforts have been made to develop new fluids for heat transfer applications. In this paper, the thermal conductivity (TC) and viscosity of SiO2–P25 TiO2 (SiO2–P25) hybrid nanofluids were investigated for different nanoparticle volume concentrations (0.5, 1.0 and 1.5 vol%) at five various temperatures (20, 30, 40, 50 and 60 °C). The mixture ratio (SiO2:P25) in all prepared hybrid nanofluids was 1:1. Besides, pure SiO2, P25 nanofluids were prepared with the same concentrations for comparison with the hybrid nanofluids. The base fluid used for the preparation of nanofluids was a mixture of deionized water and ethylene glycol at a ratio of 5:1. Before preparing the nanofluids, the nanoparticles were analyzed with energy-dispersive X-ray analysis, scanning electron microscope, X-ray powder diffraction, and Fourier transform infrared spectroscopy. The zeta potentials of the prepared nanofluids except SiO2 nanofluids were above 30 mV. These nanofluids were visually observed for stability in many days. The TC enhancement of the hybrid nanofluid was higher than the pure nanofluid. In particular, with 1.0 vol% concentration, the maximum enhancement of SiO2, P25 and SiO2–P25 nanofluids were 7.5%, 9.9% and 10.5%, respectively. The rheology of the nanofluids was Newtonian. The viscosity increment of SiO2, P25 and hybrid nanofluids were 19%, 32% and 24% with 0.5 vol% concentration. A new correlation was developed for the TC and dynamic viscosity of SiO2–P25 hybrid nanofluid.
Highlights
Masuda et al [1] and Choi [2] started working with nanofluids as an effective heat transfer fluid
Hybrid nanofluid with carbon nanotubes grafted to alumina/iron oxide spheres dispersed in poly-alpha-olefin was studied by Han et al [20]
Bahrami et al [28] and Nabil et al [38] found the Fe–CuO nanofluids and T iO2-SiO2 nanofluids owned Newtonian rheological behavior for different temperatures and concentrations. These results indicate that the properties of nanoparticles and temperature are important factors in the rheological properties of nanofluids
Summary
Masuda et al [1] and Choi [2] started working with nanofluids as an effective heat transfer fluid. HNs have been investigated with different nanoparticles, BFs, temperatures and concentrations. The A l2O3–Cu/water HNs with volume concentrations from 0.1 to 2% were investigated by Suresh et al [21]. The TC of the fluid increased by 48.4% compared to the BF of water up to 0.7 vol% of the hybrid nanocomposite. A numerical study on hybrid nanocomposite of T iO2, Al2O3 and SiO2 nanoparticles dispersed in water was performed [27]. Sundar et al and Zakaria et al [29, 30] investigated the TC of nanofluids with the BF of DW and EG mixture They found that the enhancement of TC was affected by volume concentration and temperature. It was found that the combination of nanofluids has higher TC and lower dynamic viscosity [33,34,35]
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