Search

In this study, the flow of Cu/oil nanofluids over an impermeable semi‐infinite plate was investigated. A complete single‐phase modeling of nanofluids flowing over a semi‐infinite plate was performed, bringing into account, real experimental data of oil‐based nanofluids. The empirical correlations revealed that the viscosity and thermal conductivity of the pure oil and oil‐based nanofluids strongly depend on temperature. The similarity transformation method was utilized to transform governing partial differential equations into coupled nonlinear ordinary differential equations solved by employing the standard Runge–Kutta. The results showed that even low volumetric fraction of copper/oil nanofluids noticeably enhanced the heat transfer; however, such behavior was not predicted accounting the classic modeling of nanofluids. Furthermore, both hydrodynamics and thermal characteristics were reliant on the thermal boundary conditions, which this seems to have received a marginal focus in the existing literature. [ABSTRACT FROM AUTHOR]

Thermal oils due to their high ability in cooling and lubricating have many applications in high-tech industries such as automotive industry. Dispersing nanoparticles in a thermal oil (which the resulted new liquid is called nanofluid) can modify further the cooling and lubrication efficiencies. This review paper aims to present the recent advances in the preparation methods and thermophysical properties measurements of oil-based nanofluids. Effects of various parameters such as nanoparticle concentration, size, and temperature on the values of properties including thermal conductivity, viscosity, density, and specific heat are reviewed. The correlations available for the properties of oil-based nanofluids are gathered from the literature that could be a worthy source for those who aim to work on oil-based nanofluids. Unlabelled Image [ABSTRACT FROM AUTHOR]

This study aims to experimentally investigate and introduce a new model for enhancing convective heat transfer in the presence of Ag/ oil nanofluid. An annular tube was designed with a turbine element attached to the inner tube. The inner tube was a bearing shaft which could rotate with the rotation of turbine element. As the previous works by authors, the setup was conducted with a fully developed laminar flow regime with the Reynolds numbers less than 160. The outer surface of the annular tube was heated by an element with constant heat flux of 204 W. Ag/ oil nanofluid was used in different volume concentrations of 0.011%, 0.044% and 0.171%. The new model could enhance the convective heat transfer coefficient up to 54% (compared to the simple annular tube in the case of base fluid) for the best studied case (nanofluid with the volume concentration of 0.171%) while the friction factor remained low. The new model can be applied for related applications regarding Ag/ oil nanofluid as a new step in enhancing the convective heat transfer coefficient. [ABSTRACT FROM AUTHOR]

In this work, an experimental study on nanofluid preparation stability, thermo-physical properties, heat transfer performance and friction factor of Al/ Oil nanofluids has been carried out. Electrical Explosion Wire (E.E.W) which is one of the most reliable one-step techniques for nanofluids preparation has been used. An annular tube has been considered as the test section in which the outer tube was subject to a uniform heat flux boundary condition of about 204 W. The utilized nanofluids were prepared in three different volume concentrations of 0.011%, 0.044% and 0.171%. A wide range of parameters such as Reynolds number Prandtl number, viscosity, thermal conductivity, density, specific heat, convective heat transfer coefficient, Nusselt number and the friction factor have been studied. The experiment was conducted in relatively low Reynolds numbers of less than 160 and within a hydrodynamically fully-developed regime. According to the results, thermal conductivity, density and viscosity increased depending on the volume concentrations and working temperatures while the specific heat declined. More importantly, it was observed that convective heat transfer coefficient and Nusselt number enhanced by 28.6% and 16.4%, respectively, for the highest volume concentration. Finally, the friction factor (which plays an important role in the pumping power) was found to be increased around 18% in the volume fraction of 0.171%. [ABSTRACT FROM AUTHOR]

This investigation has been carried out to study on preparation, thermal conductivity and dielectric strength of Ag- WO 3 hybrid nanofluid while the base fluid was transformer oil. The reasons of selecting silver and WO 3 as nanoparticles have been completely discussed. Applied nanofluids have been prepared by a one-step method known as Electrical Explosion of Wire (E.E.W). Measuring zeta potential of utilized hybrid nanofluids in three different weight fractions of 1%, 2% and 4% has been experimentally carried out. Thermal conductivity of applied nanofluids in temperature range of 40–100 °C has been measured by a KD2 pro thermal properties analyzer. The results showed that thermal conductivity of applied hybrid nanofluids increased by 41% in higher weight fraction and 100 °C. Finally, it has been observed that electrical conductivity of hybrid nanofluids decreased to 35 kV in 4% wt. [ABSTRACT FROM AUTHOR]

In this study, thermo-physical properties including thermal conductivity, viscosity, density and specific heat capacity of an oil based nanofluid including silver as to be nanoparticles have been experimentally studied. The results indicate an enhancement in thermal conductivity which was depended on bulk temperature and volume fraction of utilized nanofluids. Viscosity data show a significant increment through volume fraction increasing. In addition, the specific heat capacity and density of nanofluids were studied experimentally and it was found that, all measured rheological properties of these nanofluids, were not in agreement to published correlations. [ABSTRACT FROM AUTHOR]

In this study, a colloidal suspension consists of Cu nanoparticles and engine oil has been made by a one- step method known as Electrical Explosion of Wire (E.E.W) in three different weight concentrations of 0.2%, 0.5% and 1%. After studying physical properties of the applied nanofluids via high resolution transmission electron microscopy and measuring zeta potential for the stability analysis, thermo-physical properties such as thermal conductivity and viscosity, have been experimentally studied. Measured data of thermal conductivity and viscosity of applied nanofluids have been compared to the predicted ones through the proposed correlations for thermal conductivity and viscosity of oil based nanofluids and acceptable agreements between the two have been achieved. The range of thermal conductivity of higher weight concentration was measured to be from 0.153 to 0.17 (W/m. K) in the temperature range from 40 C to 100 C, while pure engine oil exhibits a decreasing trend in contradictory. Secondly, viscosity variations through capturing Newtonian or non- Newtonian behavior of utilized nanofluids has been investigated. The viscosity range for higher weight concentration nanofluid was observed from 235 cP to 35 cP in the applied temperature range. Finally, thermal conductivity and viscosity enhancements of 49% and 37% were observed for 1% weight fraction of utilized nanofluids. [ABSTRACT FROM AUTHOR]

• A novel highly stable and well-oxidized EGO/ vanadium electrolyte based nanofluid was prepared. • Rheological evaluation showed an optimum mass fraction of 0.05% to be applicable in VRFBs. • A model to predict the viscosity of the utilized nanofluid was developed accurately. • Electrical conductivity assessment confirmed 0.05% as the optimum concentration. • Thermal conductivity reached a maximum enhancement of 4% for the optimum 0.05 wt% The use of electrolyte-based nanofluid is a new approach for enhancing the performance of Vanadium Redox Flow Batteries (VRFBs). This paper, for the first time in the literature, presents an experimental study to comprehensively investigate the rheological behaviour, electrical conductivity, and thermal conductivity of a newly prepared electrochemical graphene oxide (EGO)/ vanadium (IV) electrolyte-based nanofluid in different weight concentration and bulk temperatures. SEM, FT-IR and X-ray Diffraction (XRD) characterizations were performed and different functional groups, smooth 2D layered structures, and low crystallinity were detected in our tailored oxidation EGO which are amongst the enhancing features for VRFBs electrode materials. It was observed that the optimum weight concentration of nanoparticles in the electrolyte-based nanofluid is 0.05 wt% with strong colloidal stability, enhanced electrical and thermal conductivities, and an optimal viscosity. The maximum feasible enhancements in electrical and thermal conductivities that were achieved were 12%, and 4%, respectively, which can positively affect the performance of flow battery in terms of electrochemical activity on the electrode surface and thermal management of the flow battery system. In addition, the rheological evaluation showed that the behaviour of the electrolyte-based nanofluid tends to change from Newtonian to non-Newtonian for weight concentrations higher than 0.05%. The results obtained from rheological behaviour can provide useful insights in choosing an optimum pumping system of the flow batteries working with electrolyte-based nanofluid. [ABSTRACT FROM AUTHOR]

The present work aims to study heat transfer performance and pumping power of MgO–MWCNT/ thermal oil hybrid nanofluid. Using a KD2 Pro thermal analyzer, the thermal conductivity of the samples has been measured. The results showed an increasing trend for the thermal conductivity of the nanofluid by increasing the mass concentration and temperature, in which the maximum enhancement of thermal conductivity was approximately 65%. Predicting the thermal conductivity of the nanofluid, a highly accurate correlation in terms of solid concentration and temperature has been proposed. Moreover, the heat transfer efficiency and pumping power in all the studied range of solid concentrations and temperatures have been theoretically investigated, based on the experimental data of dynamic viscosity and thermal conductivity, for both the internal laminar and turbulent flow regimes. It was observed that the studied nanofluid is highly efficient in heat transfer applications as a coolant fluid in both the laminar and turbulent flow regimes, although it causes a certain penalty in the pumping power. [ABSTRACT FROM AUTHOR]