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ABSTRACT
The main goal of the present study was to prepare and also to investigate the effects of both temperature and weight concentration on the thermo-physical properties of γ-Fe2O3/water nanofluids. The γ-Fe2O3 nanoparticles were synthesized by laser pyrolysis technique and characterized using TEM, XRD, and EDX techniques. Thermal conductivity, viscosity and surface tension of γ-Fe2O3/water nanofluids were investigated within the range of the temperature of 20°C to 70°C for various weight concentrations of nanoparticles (0.5, 1.0, 2.0, and 4.0 wt%). The experimental results show that the thermal conductivity ratio is much higher than of thermal conductivity of base fluid. Thus, the relative thermal conductivity was 59% for a concentration of 4.0 wt% and a temperature of 50°C. Also, it has been observed that the influence of weight concentration of nanoparticles on viscosity was lower at temperatures over 55°C. At standard temperature of 25°C and 2.0 wt.% concentration of nanoparticles, the relative dynamic viscosity was 5.61%. Experimental results show that the surface tension increases with increase of weight concentrations and decreases with increase of temperatures. For a temperature of 70°C and 2.0 wt.% concentration of nanoparticles, the relative surface tension was 46%. The experimental results were compared with data available in literature.
Acknowledgments
This work was supported by a grant of the Romanian National Authority for Scientific Research, CNCS – UEFISCDI, Project Number PN-II-ID-PCE-2011-3-0275.
Nomenclature
| cp | = | specific heat, (J/kg K) |
| d | = | equivalent diameter of a base fluid molecule, (m) |
| EDX | = | energy dispersive X-ray |
| FWHM | = | full-width at half-maximum |
| k | = | thermal conductivity, (W/m K) |
| KB | = | Boltzmann's constant,(1.38 · 10− 23J/K) |
| M | = | molar mass of the base fluid, (kg/kmol) |
| N | = | Avogadro number, (6.022 · 1023mol− 1) |
| r | = | radius, (nm). |
| rc | = | cluster radius, (m) |
| T | = | temperature, (K) |
| TEM | = | transmission electron microscopy |
| XRD | = | X-Ray Diffraction |
| Greek symbols | ||
| β | = | ratio of nanolayer thickness to nanoparticles radius |
| γ | = | nanolayer thickness (m) |
| 2θ | = | scattering angle |
| λ | = | wavelength (μm) |
| µ | = | dynamic viscosity, (Pa s) |
| ρ | = | density of nanoparticle, (kg/m3) |
| φ | = | concentration of nanoparticles |
| Subscripts | ||
| bf | = | base fluid |
| eff | = | effective |
| nf | = | nanofluid |
| np | = | nanoparticle |
| p | = | particle |
| s | = | solid |
Additional information
Notes on contributors
Gabriela Huminic
Gabriela Huminic received her MSc and PhD (cum laude) in Mechanical Engineering from Transilvania University of Brasov, Romania, in 2001 and 2005, respectively. Currently, she is Associate Professor with Transilvania University, Mechanical Engineering Department, where she is in charge of the Applied Thermodynamic Laboratory. Hers academic and research interests include heat transfer, heat pipes, heat exchangers, nanofluids for cooling applications and computational fluid dynamics.
Angel Huminic
Angel Huminic received his MSc and PhD in Mechanical Engineering from Transilvania University of Brasov, Romania, in 1996 and 2005, respectively. During 1996–2000 he was a Project Engineer at Design and Research Department of IAR Brasov, Romanian Company of Helicopters and Aircrafts. Currently, he is Professor with Transilvania University, Mechanical Engineering Department, where he is in charge of the Aerodynamics Laboratory. His academic and research interests include fluid mechanics, vehicle aerodynamics, nanofluids for cooling applications and computational fluid dynamics. He is a member of SAE International USA.
Florian Dumitrache
Florian Dumitrache received his MSc and PhD in Physics from University of Bucharest, Romania, in 1993 and 2013, respectively. Currently, he is Scientific Researcher at National Institute for Lasers, Plasma and Radiation Physics, Magurele, Romania. Romania. His research interests include nanomaterials, the synthesis of nanometric powders by laser pyrolysis technique, nanotechnologies, stable dispersion using nanoparticles, nanoparticle analysis and interpretation as well as biological applications of nanoparticles (drug delivery and contrast agents).
Claudiu Fleaca
Claudiu Fleaca received his BEng in 1973 at Petroleum, Gas and Geology Institute Ploiesti, Romania and his PhD in 1988 in Physics at the Institute for Atomic Physics, Magurele, Romania. From 1973 until 1990, he was Scientific Researcher at the Institute for Atomic Physics, Magurele, after which he was appointed Scientific Director of the National Institute for Lasers, Plasma and Radiation Physics, Magurele, Romania, from 1994 until 2009. At present he is General Director at the same Institute. He has experience in laser photochemistry, laser thermochemistry of inorganic salts, SO2 oxidation and reactions with NH3 CO, the synthesis of TiO2/anion-doped TiO2 nanoparticles and Fe2O3 nanopowders, laser Assisted CVD of thin coatings, metal films from metalorganic precursors and the lasers synthesis of Si-based nanopowders from gaseous precursors.
Ion Morjan
Ion Morjan received two MSc degrees in Chemical Engineering from ”Politehnica” University of Bucharest, Romania and a PhD in Physics from University of Bucharest, Romania in 1996, 1998, and 2012, respectively. Currently, he is Scientific Researcher at National Institute for Lasers, Plasma and Radiation Physics, Magurele, Romania. He has experience in characterization of carbon-based materials (using Raman Spectroscopy and Electronic Microscopy), in the synthesis of nanoparticles by laser pyrolysis, of carbon nanotubes by plasma/hot-filament-assisted CVD, sol-gel or combustion-assisted synthesis of nanoparticles, nanowires and polymer- nanoparticles composites.